Fat

What is Fat?

Within the fields of nutrition, biology, and chemistry, “fat” refers to any ester of fatty acids or a combination of these substances, with the most prominent examples being those found in food or living things.

Triglycerides, or triple esters of glycerol, are the primary constituents of vegetable oils and animal fatty tissue.

The term is commonly used to refer only to these specific triglycerides, or, even more narrowly, to triglycerides that are solid or semisolid at room temperature, thereby eliminating oils.

The word can also be used more widely as a synonym for lipid, which is any biologically significant material made of carbon, hydrogen, or oxygen that is soluble in non-polar solvents but insoluble in water.

In this sense, the phrase would encompass a variety of additional molecules in addition to triglycerides, such as mono- and diglycerides, phospholipids (like lecithin), sterols (like cholesterol), waxes (like beeswax), and free fatty acids, all of which are often found in smaller amounts in the diet of humans.

Together with carbs and proteins, fats make up the majority of popular food items like milk, butter, tallow, lard, salt pork, and cooking oils. Fats are one of the three primary macronutrient groups in the human diet.

In most living organisms, they provide essential structural and metabolic tasks such as energy storage, waterproofing, and thermal insulation.

They constitute a significant and dense source of dietary energy for many animals. With the exception of a few essential fatty acids that must be consumed through food, the human body can create the necessary amount of fat from other food elements.

Certain vitamins flavoring and fragrance compounds that are not soluble in water are also transported by dietary lipids.

Biological Importance

Fats function as both energy sources and storage for more energy than the body requires at any given time in humans and many other animals.

Approximately nine food calories are released per gram of fat during burning or metabolism (37 kJ = 8.8 kcal).

Additionally, fats contain vital fatty acids, which are a crucial component of diets.

Fats are necessary for the digestion, absorption, and transportation of fat-soluble vitamins A, D, E, and K.

Fats are essential for sustaining good skin and hair, protecting internal organs from shock, regulating body temperature, and encouraging normal cell activity. Additionally, fat acts as a helpful defense against a variety of illnesses.

The body can store an irritating component in new fat tissue in order to effectively dilute it, or at least maintain homeostasis, when it reaches dangerous levels in the bloodstream, whether it be biotic or chemical.

This aids in the protection of important organs until the offending compounds are metabolized or eliminated from the body through processes like excretion, urine, unintentional or deliberate bleeding, sebum excretion, and hair growth.

Recent research has demonstrated that unsaturated fatty acid desaturases not only regulate the content of polyunsaturated fatty acids (PUFAs) but also have a significant impact on the recycling of NAD+ during glycolysis in the cell.

As a result, they may serve as a substitute pathway for the flow of reducing equivalents produced during glycolysis.

Anaerobic glycolysis and unsaturated fatty acid desaturases can both oxidize the reduced form of nicotinamide adenine dinucleotide (NADH) in anaerobic conditions when mitochondrial respiration is compromised.

This regenerates the NAD+ pool, which glyceraldehyde 3-phosphate dehydrogenase can use during glycolysis.

Changes in the expression or activity of fatty acid desaturases may have significant effects on the regulation of numerous bodily processes, including those connected to basic metabolism and the emergence of various pathological conditions.

Given the complex roles played by PUFAs and unsaturated fatty acid desaturases (regardless of their products).

In this review, we mainly address unsaturated fatty acid desaturases; we go over the function of these enzymes, their impact on human health, recently suggested therapeutic uses and potential avenues for future investigation.

Adipose Tissue

Animals’ bodies use their adipose, or fatty, tissue to store metabolic energy for long periods of time.

Dietary fat and fat produced by liver metabolism are stored in adipocytes or fat cells. These cells may break down their fat reserves in order to release glycerol and fatty acids into the bloodstream when they are under energy stress.

Numerous hormones, including insulin, glucagon, and adrenaline, control these metabolic processes. The hormone leptin is also secreted by adipose tissue.

Adipocytes make up the majority of the loose connective tissue which is referred to as adipose tissue, body fat, or just fat.

Apart from adipocytes, preadipocytes, fibroblasts, vascular endothelial cells, and a range of immune cells including adipose tissue macrophages are among the cells that make up the stromal vascular fraction (SVF) of adipose tissue.

Preadidipocytes are the source of adipose tissue. In addition to cushioning and insulating the body, its primary function is to store energy in the form of lipids.

Adipose tissue is not hormonally inactive; rather, in recent times, it has come to be acknowledged as a significant endocrine organ since it produces hormones like resistin, leptin, estrogen, and cytokines, particularly TNFa.

Adipokines, a group of pro-inflammatory indicators, are released chronically from adipose tissue in obesity and are linked to the development of metabolic syndrome, a group of illnesses that includes atherosclerosis, cardiovascular disease, and type 2 diabetes.

Adipose tissue comes in two varieties: brown adipose tissue (BAT), which produces body heat, and white adipose tissue (WAT), which stores energy.

The adipose gene appears to play a role in the development of adipose tissue. Conrad Gessner, a Swiss scientist, made the initial identification of adipose tissue—more precisely, brown adipose tissue—in 1551.

Production and Processing

Fats are produced and processed using a range of chemical and physical methods, both in industrial and residential settings. Among them are:

• pressing to remove liquid lipids, such as olive oil from olives, fruits, seeds, or algae
• extraction of solvents using supercritical carbon dioxide or hexane as solvents
• Rendering is the process of melting fat from adipose tissue to create
• products like lard, tallow, whale, and fish oil.
• Whirling milk to make butter
• Increasing the degree of fatty acid saturation through hydrogenation
• Interesterification is the process by which fatty acids are rearranged among various triglycerides.
• Using winterization, oil components with higher melting points are removed.
• Butter clarification

Metabolism

By hydrolyzing the ester bond and “releasing” the fatty acid, pancreatic lipase operates at the ester bond. Lipids in triglyceride form are indigestible by the duodenum.

After the triglycerides are broken down, the duodenum absorbs fatty acids, monoglycerides (one glycerol, one fatty acid), and some diglycerides.

Triglycerides undergo a process in the intestine known as lipolysis that splits them into monoacylglycerol and free fatty acids when lipases and bile are secreted. After that, they are transferred to the intestinal lining’s absorptive enterocyte cells.

In the enterocytes, the triglycerides are reassembled from their fragments and combined with proteins and cholesterol to form chylomicrons.

Before being combined with blood, they are removed from the cells, gathered by the lymphatic system, and delivered to the major vessels close to the heart. Chylomicrons can be taken up by a variety of tissues, which release triglycerides for use as an energy source.

Liver tissue can create and preserve triglycerides. The hormone glucagon causes hormone-sensitive lipase to break down triglycerides and release free fatty acids when the body needs fatty acids as an energy source.

The glycerol component of triglycerides can be broken down into glucose via gluconeogenesis, which first converts it into dihydroxyacetone phosphate and then into glyceraldehyde 3-phosphate.

This is because the brain cannot use fatty acids as an energy source unless they are converted to a ketone.

If the demands of the brain ever exceed those of the body, fat cells might also be broken down for that reason. Triglycerides are unable to readily flow across cell membranes.

Triglycerides need to be broken down into free fatty acids and glycerol by unique enzymes called lipoprotein lipases that are found on the walls of blood vessels.

Fatty acid transport proteins (FATPs) are then responsible for the uptake of fatty acids by cells. Triglycerides are essential for metabolism as energy sources and dietary fat transporters since they are the main constituents of chylomicrons and very low-density lipoprotein (VLDL).

Compared to carbs, which have about 4 kcal/g or 17 kJ/g of energy, they have more than twice as much energy (about 9 kcal/g or 38 kJ/g).

Nutritional and Health Aspects

Triglycerides are the most prevalent kind of fat found in the diets of humans and other living things.

They are an ester of three fatty acids and the triple alcohol glycerol H(–CHOH–) 3H. A triglyceride molecule is the product of a condensation reaction, or more precisely, esterification, between the –OH groups of each glycerol and the HO– part of the carboxyl group HO(O=)C- of each fatty acid.

This process forms an ester bridge -O-(O=)C- and eliminates a water molecule, H 2O.Diglycerides, and monoglycerides are other less prevalent forms of fats in which only one or two of the –OH groups in glycerol are esterified.

Glycerol may be substituted with other alcohols, like cetyl alcohol, which is the main alcohol in spermaceti.

Phosphoric acid or a monoester thereof takes the place of one of the fatty acids in the phospholipids.

Many studies have been conducted on the advantages and disadvantages of different types and amounts of dietary fats, and these issues are still quite contentious.

Essential Fatty Acids

Alpha-linolenic acid, an omega-3 fatty acid, and linoleic acid, an omega-6 fatty acid, are the two essential fatty acids (EFAs) in the human diet.

From these two, the adult body may synthesize additional lipids as needed. The body cannot generate essential fatty acids (EFAs), which means that humans and other animals must consume them in order to maintain good health.

Humans are known to require only two fatty acids: linoleic acid (an omega-6 fatty acid) and alpha-linolenic acid (an omega-3 fatty acid).

The body receives them either as free fatty acids or, more frequently, as derivatives of glycerides.

It is rare to be deficient in these fatty acids. Because they are building blocks for vitamins, cofactors, and derivatives such as lipoxins, thromboxanes, prostaglandins, and leukotrienes, these fatty acids are vital.

The two EFAs were named “vitamin F” when they were discovered in 1923, but rat studies in 1929 indicated that they are actually better categorized as fats than as vitamins.

Type	Processing treatment	Saturated fatty acids	Monounsaturated fatty acids Total	Monounsaturated fatty acids Oleic acid(ω-9)	Polyunsaturated fatty acids Total	Polyunsaturated fatty acids α Linolenic acid(ω-3)	Polyunsaturated fatty acids Linolenic acid(ω-6)	Polyunsaturated fatty acids ω-6:3 ratio	Smoke point
Avocado		11.6	70.6	52–66	13.5	1	12.5	12.5:1	250 °C (482°F)
Brazil nut		24.8	32.7	31.3	42.0	0.1	41.9	419:1	208 °C (406°F)
Canola		7.4	63.3	61.8	28.1	9.1	18.6	2:1	204 °C (400°F)
Coconut		82.5	6.3	6	1.7				175 °C (347°F)
Corn		12.9	27.6	27.3	54.7	1	58	58:1	232 °C (450°F)
Cottonseed		25.9	17.8	19	51.9	1	54	54:1	216 °C (420°F)
Cottonseed	hydrogenated	93.6	1.5		0.6	0.2	0.3	1.5:1
Flaxseed/linseed		9.0	18.4	18	67.8	53	13	0.2:1	107 °C (225°F)
Grape seed		10.4	14.8	14.3	74.9	0.15	74.7	very high	216 °C (421°F)
Hemp seed		7.0	9.0	9.0	82.0	22.0	54.0	2.5:1	166 °C (330°F)
High-oleic safflower oil		7.5	75.2	75.2	12.8	0	12.8	very high	212 °C (414°F)
Olive, Extra Virgin		13.8	73.0	71.3	10.5	0.7	9.8	14:1	193 °C (380°F)
Palm		49.3	37.0	40	9.3	0.2	9.1	45.5:1	235 °C (455°F)
Palm	hydrogenated	88.2	5.7		0
Peanut		16.2	57.1	55.4	19.9	0.318	19.6	61.6:1	232 °C (450°F)
Rice bran oil		25	38.4	38.4	36.6	2.2	34.4	15.6:1	232 °C (450°F)
Sesame		14.2	39.7	39.3	41.7	0.3	41.3	138:1
Soybean		15.6	22.8	22.6	57.7	7	51	7.3:1	238 °C (460°F)
Soybean	partially hydrogenated	14.9	43.0	42.5	37.6	2.6	34.9	13.4:1
Sunflower		8.99	63.4	62.9	20.7	0.16	20.5	128:1	227 °C (440°F)
Walnut oil	unrefined	9.1	22.8	22.2	63.3	10.4	52.9	5:1	160 °C (320°F)

Dietary sources

Saturated vs. Unsaturated Fats

Foods vary in their fat content and the ratios of saturated and unsaturated fatty acids they contain.

Saturated fatty acids predominate in some animal products, such as beef, and dairy products, such as yogurt, ice cream, cheese, and butter, that are manufactured with whole or reduced-fat milk (and some have large levels of dietary cholesterol).

The majority of the fats in other animal products, such as pig, chicken, eggs, and shellfish, are unsaturated.

Deep-fried processed foods with hydrogenated oil have a high saturated fat content, and industrialized baked goods may also use fats with high unsaturated fat concentrations, particularly those that contain partially hydrogenated oils.

With a few notable exceptions, such as coconut and palm kernel oil, unsaturated acids are often found in higher concentrations in plant and fish oils. Unsaturated fat-containing foods include avocado, almonds, walnuts, and vegetable oils like canola.

Numerous meticulous investigations have revealed that substituting cis-unsaturated fats for saturated fats in the diet lowers the risk of diabetes, heart disease, and death.

The World Health Organization (WHO) and other medical associations and public health agencies were prompted by this research to formally recommend that course of action. Among the nations that have such suggestions are:

• United Kingdom
• USA
• India
• Canada
• Australia
• Singapore
• New Zealand
• Hong  kong

A review published in 2004 came to the conclusion that “no lower safe limit of specific saturated fatty acid intakes has been identified” and suggested that future research should concentrate on the effects of varying saturated fatty acid intakes against a backdrop of diverse individual lifestyles and genetic backgrounds.

The designation of the two types of fats as “good” and “bad” fats, respectively, oversimplifies this advice.

However, it is unrealistic and even foolish to completely exclude saturated fat because the majority of naturally occurring and conventionally processed foods contain both unsaturated and saturated fatty acids in their fats and oils.

For example, for a significant portion of the populace in underdeveloped nations, certain foods high in saturated fat, including coconut and palm oil, provide a cheap source of calories.

At a 2010 American Dietetic Association conference, concerns were also raised about how a general recommendation to avoid saturated fats might encourage people to cut back on polyunsaturated fats, which may also have health benefits, or swap out fats for refined carbohydrates, which increase the risk of obesity and heart disease.

For these reasons, the U.S. Food and Drug Administration, for instance, suggests consuming an average of 30% (or less) of total calories from all fat, with at least 10% (7% for high-risk groups) of calories coming from saturated fat.

The American Heart Association (AHA) also suggested a global 7% limit in 2006.
Additionally, the WHO/FAO report suggested substituting fats in order to specifically lower the amount of myristic and palmitic acids.

The so-called Mediterranean diet, which is common in many Mediterranean Sea region countries, contains more total fat than the diets of Northern European countries, but the majority of this fat is in the form of unsaturated fatty acids (monounsaturated and omega-3) from fish, vegetables, and some meats, like lamb.

Saturated fat consumption is relatively low. According to a 2017 analysis, there is evidence that a diet based on the Mediterranean diet may lower the risk of death, neurological disorders, cardiovascular disease, and cancer incidence overall.

According to a 2018 assessment, adopting a diet similar to the Mediterranean may enhance general health, including a lower risk of non-communicable diseases.

Additionally, it might lower the financial and social toll that diet-related diseases take. Only a few recent assessments have contested this unfavorable perception of saturated fats.

For instance, substituting dietary saturated fat with linoleic acid was shown to have a negative influence on health from 1966 to 1973, as seen by an increase in the prevalence of cardiovascular disease, coronary heart disease, and death from all causes.

Numerous scientists have contested these findings, but the medical community as a whole agrees that there is a strong correlation between saturated fat and cardiovascular disease.

Despite this, conflicting research continued to feed discussion on the benefits of replacing saturated fats with polyunsaturated fats.

Cardiovascular Disease

Many studies have been conducted on the impact of saturated fat on cardiovascular disease.

Most people agree that there is moderately good evidence of a significant, reliable, and graded association between blood cholesterol levels, the incidence of cardiovascular disease, and the consumption of saturated fat.

Numerous governmental and medical institutions agree that the linkages are causal. According to a 2017 AHA assessment, switching to polyunsaturated fat from saturated fat in the American diet could lower the risk of cardiovascular illnesses by 30%.

Saturated fat intake is typically regarded as a risk factor for dyslipidemia, which is defined as abnormal blood lipid levels, such as high triglyceride, high total cholesterol, high low-density lipoprotein (LDL, “bad”), or low high-density lipoprotein (HDL, “good” cholesterol).

It is therefore thought that these measures serve as risk markers for specific forms of cardiovascular disease. Children were also seen to experience these impacts.

Multiple reviews and consolidations of previously published experimental studies, known as meta-analyses, have confirmed a significant correlation between high serum cholesterol levels and saturated fat.

This correlation has been linked to an increased risk of cardiovascular disease, a theory known as the “lipid hypothesis.” Nonetheless, a variety of circumstances may contribute to elevated cholesterol.

It has been shown that other markers, like a high LDL/HDL ratio, are more predictive.52 countries participated in a study on myocardial infarction, and the ApoB/ApoA1 (associated with LDL and HDL, out of all the risk factors, the ratio (respectively) was the most reliable indicator of CVD.

Other pathways that contribute to CVD include obesity, triglyceride levels, insulin sensitivity, endothelial function, and thrombogenicity, among others.

However, it appears that these other known risk factors have only a minor atherogenic effect when there is no negative blood lipid profile. The effects of distinct saturated fatty acids vary depending on the lipid levels.

Cancer

There isn’t much data to support the theory that eating saturated fat causes cancer, and there’s also no clear consensus among doctors on this point.

• Saturated fat and breast cancer had a strong positive correlation, according to a 2003 meta-analysis. Two more evaluations, however, have underlined the presence of confounding factors and found weak or insignificant relationships.
• Limited evidence was discovered in another review to support a link between eating animal fat and a lower risk of colorectal cancer.
• High consumption of saturated fat has been linked to an increased risk of ovarian cancer, according to several meta-analyses.
• According to certain research, there is a dose-dependent relationship between elevated risk of prostate cancer and serum myristic and palmitic acid, dietary myristic and palmitic saturated fatty acids, and serum palmitic paired with alpha-tocopherol supplementation. However, rather than actually being a cause, these relationships might just be the result of variations in the precancer cases’ and controls’ intake or metabolism of these fatty acids.

Bones

Saturated fat consumption has been shown in several animal studies to have a detrimental impact on bone mineral density. According to one study, men might be especially at risk.

Disposition and Overall Health

Research has indicated that replacing saturated fatty acids with monounsaturated fatty acids is linked to higher levels of resting energy expenditure and daily physical activity.

A higher oleic acid diet was linked to reduced irritation, anger, and physical activity compared to a diet high in palmitic acid.

Monounsaturated vs. Polyunsaturated Fat

Unsaturated or mono-unsaturated fatty acids are the most prevalent types of fats in human diets.

High-fat foods like avocados and olives, whole milk products, nuts, and animal flesh like red meat are good sources of monounsaturated fats.

About 75% of the fat in olive oil is monounsaturated.At least 70% of the fat in sunflower oil that is high in oleic acid is monounsaturated.

About 58% of the fat in cashews and canola oil is monounsaturated. Tallow Lard has roughly 40% monounsaturated fat and (beef fat) contains roughly 50%.

Additional sources are avocado, macadamia, hazelnut, grapeseed, sesame, popcorn, groundnut (peanut) oil, popcorn, whole grain wheat, cereal, oatmeal, almond, hemp, and tea-oil camellia.

The main sources of polyunsaturated fatty acids may guard against insulin resistance, but certain MUFAs—like the SFAs—may actually increase it.

Food source (100g)	Polyunsaturated fat (g)
Walnuts	47
Canola oil	34
Sunflower seeds	33
Sesame seeds	26
Chia seeds	23.7
Unsalted peanuts	16
Peanut butter	14.2
Avocado oil	13.5
Olive oil	11
Safflower oil	12.82
Seaweed	11
Sardines	5
Soybeans	7
Tuna	14
Wild salmon	17.3
Whole grain wheat	9.7

Insulin Resistance and Sensitivity

It has been discovered that MUFAs, particularly oleic acid, reduce the prevalence of insulin resistance, but PUFAs, particularly high concentrations of arachidonic acid, and SFAs, such as arachidic acid, increase it.

The phospholipids in human skeletal muscle and other tissues can also be used as indexes for these ratios.

The link between insulin resistance and inflammation is assumed to be secondary to the relationship between dietary fats and insulin resistance.

Dietary fat ratios (omega−3/6/9) partially regulate this relationship, with omega−3 and −9 being thought to be anti-inflammatory and omega−6 being pro-inflammatory (as well as by a variety of other dietary elements (polyphenols and exercise, in instance, both of which have anti-inflammatory properties).

The majority of US diets have dietary fat ratios that are skewed towards omega-6, which leads to disinhibition of inflammation and intensification of insulin resistance, despite the biological necessity of both pro- and anti-inflammatory kinds of fat.

The idea that polyunsaturated fats have been demonstrated to be beneficial against insulin resistance is at odds with this.

The large-scale KANWU study discovered that insulin sensitivity might be improved by increasing MUFA and lowering SFA intake, but only in situations when total dietary fat intake was low.

On the other hand, whereas PUFAs may guard against insulin resistance, certain MUFAs—like the SFAs—may actually increase it.

Cancer

In red blood cell membranes, the presence of oleic acid and other MUFAs was positively correlated with the risk of breast cancer.

The incidence of breast cancer was inversely correlated with the saturation index of the same membranes. Breast cancer that develops after menopause is predicted by MUFAs and low SI in erythrocyte membranes.

Dependent on the activity of the enzyme delta-9 desaturase (?9-d), are both of these variables. Gender and genetic risk are two of the many variables influencing cancer incidence that have affected the conflicting results of observational clinical trials on PUFA intake and cancer.

Certain malignancies, such as colorectal and breast cancer, have been linked to higher blood levels and/or intakes of omega-3 polyunsaturated fatty acids (PUFAs). However, other studies have not established any correlation between PUFA levels and cancer risk.

Pregnancy Disorders

Supplementing with polyunsaturated fat was found to have no effect on the incidence of pregnancy-related conditions like hypertension or preeclampsia, although it may slightly lengthen gestation and reduce the number of premature deliveries that occur too soon.

To improve the fetus’s and the newborn’s DHA status, expert committees in the US and Europe advise pregnant and nursing women to consume more polyunsaturated fats than the general population.

“Cis Fat” vs. “Trans Fat”

Rather than having double bonds in a trans configuration, unsaturated fatty acids typically have them in a cis configuration, where the neighboring C-C bonds are on the same side.

Food type	Trans fat content
butter	2 to 7 g
whole milk	0.07 to 0.1 g
animal fat	0 to 5 g
ground beef	1 g

However, ruminant meat and milk (cattle, sheep, and goats) contain trace levels of trans fatty acids (TFAs), usually 2–5% of total fat.

These animals’ rumen is the source of natural TFAs like conjugated linoleic acid (CLA) and vaccenic acid. Due to its two double bonds—one in the trans and one in the cis configuration—CLA functions as both a trans and a cis fatty acid at the same time.

When it was discovered that trans fatty acids were an inadvertent consequence of the partial hydrogenation of vegetable and fish oils, questions concerning their presence in the human diet were raised.

Even though these so-called “trans fats” are edible, they have been linked to a number of health issues.

Wilhelm Normann created and patented the hydrogenation process in 1902, which allowed for the conversion of relatively inexpensive liquid fats, like fish or whale oil, into more solid fats and the extension of their shelf life by preventing acidification.

At first, the source fat and the manufacturing method were kept under wraps to prevent consumer resentment.

In the early 1900s, the food industry widely adopted this technique; first, it was used to produce margarine, which replaced butter and shortening, and later, it was used to produce various additional fats that were used in snack food, packaged baked goods, and deep-fried products.

A fat or oil that has undergone complete hydrogenation becomes totally saturated. However, in order to produce a fat product with a particular melting point, hardness, and other characteristics, hydrogenation was typically stopped before it was fully completed.

Through an isomerization process, partial hydrogenation converts a portion of the cis-double bonds to trans bonds.

Since the trans configuration has a lower energy form, it is preferred [citation needed].

By far the majority of trans fatty acids eaten today can be attributed to this adverse reaction. Up to 30% “trans fats” were discovered in artificial shortening, 10% in bread and cake products, 8% in cookies and crackers, 4% in salty snacks, 7% in cake frostings and sweets, and 26% in margarine and other processed spreads, according to a 2006 study of a few industrialized foods.

However, a 2010 investigation discovered that margarine and other processed spreads contained just 0.2% trans fat.

As much as 45 percent of the fat in foods containing artificial Trans fats can be produced by partially hydrogenating plant-based fats. Unless they are reformed, baking shortenings have about 30% more trans fats than total fat.

Dairy products with high-fat content, like butter, have roughly 4%. While some reformulated margarines have less than 1% trans fat, un-reformulated margarines can have up to 15% trans fat by weight.

Popular “fast food” meals have been shown to have high levels of TFAs. The amount of trans fat in McDonald’s french fries offered in New York City was found to be twice as high as in Hungary and 28 times higher than in Denmark.

Where trans fat consumption is regulated, according to an analysis of samples taken in 2004 and 2005. The pattern was different for Kentucky Fried Chicken products: the Hungarian product had twice as much trans fat as the New York product.

There was diversity even within the United States, with New York fries having 30% higher trans fat than Atlanta fries.

Cardiovascular Disease

TFA consumption has been linked to an increased risk of cardiovascular disease, according to numerous studies.

According to the Harvard School of Public Health, it is better for your health to substitute cis-monounsaturated and polyunsaturated fats for trans fats and saturated fats.

By increasing levels of low-density lipoprotein (LDL, often known as “bad cholesterol”), lowering levels of high-density lipoprotein (HDL, often known as “good cholesterol”), raising blood triglyceride levels, and encouraging systemic inflammation, consuming trans fats has been demonstrated to increase the risk of coronary artery disease.

An increased risk of coronary artery disease (CAD) has been recognized as the main health risk associated with trans fat consumption.

According to a 1994 study, eating trans fats is thought to be the cause of approximately 30,000 cardiac deaths annually in the US. Higher estimates of 100,000 deaths were proposed by 2006.”

On a per-calorie basis, trans fats appear to increase the risk of CAD more than any other macronutrient, conferring a substantially increased risk at low levels of consumption (1 to 3% of total energy intake)”.

This is the conclusion drawn from a thorough review of trans fat studies published in the New England Journal of Medicine in 2006.

The review reveals a strong and consistent correlation between trans fat consumption and CAD.

The Nurses’ Health Research, a cohort research that has been tracking 120,000 female nurses since its start in 1976, provides the majority of the evidence about the impact of trans fat on CAD.

Hu and associates examined data from 900 coronary events that occurred within the research group over a 14-year follow-up period.

He discovered that for every 2% increase in trans fat calories (as opposed to carbohydrate calories) ingested, a nurse’s chance of developing CAD nearly quadrupled (relative risk of 1.93, CI: 1.43 to 2.61).

Conversely, for every 5% increase in calories from saturated fat (instead, there was a 17% increase in risk (relative risk of 1.17, CI: 0.97 to 1.41) with regard to calories from carbohydrates.

The replacement of saturated fat or trans unsaturated fat by cis (nonhydrogenated) unsaturated fats was associated with larger reductions in risk than an isocaloric replacement by carbohydrates.

Hu also discusses the advantages of consuming less trans fat. The risk of CAD is more than halved (53%) when 2% of meal energy from trans fat is substituted with non-trans unsaturated fats.

In contrast, the risk of CAD is reduced by 43% when non-trans unsaturated fats are substituted for a higher 5% of meal energy that comes from saturated fat.

The consumption of trans fats was associated with an increase in mortality, while the consumption of polyunsaturated fats was linked to a decrease in mortality, according to another study that looked at fatalities from CAD.

Trans fat functions similarly to saturated fat in that it raises blood levels of LDL (commonly known as “bad cholesterol”), but it also lowers HDL (also known as “good cholesterol”), in contrast to saturated fat.

Trans fat causes a net increase in the LDL/HDL ratio that is roughly twice as large as that caused by saturated fat, which is a commonly used risk factor for coronary artery disease.

Choleryl ester transfer (CET) was 28% higher after the trans meal than after the cis meal, and lipoprotein concentrations were enriched in apolipoprotein(a) after the trans meals.

According to a 2003 randomized crossover study comparing the effects of eating a meal on blood lipids of (relatively) cis and trans-fat-rich meals.

The cytokine test is currently being investigated, but it may be a more accurate predictor of CAD risk.

C-reactive protein (CRP) levels in the blood were 73% higher in individuals in the highest quartile of trans fat consumption than in those in the lowest quartile, according to a study including over 700 nurses.

Breast Feeding

It is known that the amount of trans fats in human breast milk varies according to the amount consumed by the mother and that the amount of trans fats in breastfed infants’ bloodstream varies according to the amount detected in their milk.

Trans fat levels in human milk (as a percentage of total fats) were reported in 1999 to be 1% in Spain, 2% in France, 4% in Germany, and 7% in both Canada and the US.

Other Health Risks

There are suggestions that the negative consequences of trans fat consumption go beyond the cardiovascular risk. In general, there is much less scientific consensus asserting that eating trans fat specifically increases the risk of other chronic health problems:

1. Alzheimer’s disease: Although not supported by evidence from an animal model, a study published in the February 2003 issue of Archives of Neurology claimed that consuming both trans and saturated fats may accelerate the onset of Alzheimer’s disease.
   • Trans fats have been shown to impair learning and memory in middle-aged rats. Rats that consumed trans fats had brains with reduced levels of some proteins necessary for normal neurological function. inflammation in and around the hippocampal region, the brain region in charge of memory and learning. Even though the rats were still young, these are the identical kinds of alterations that are often shown at the outset of Alzheimer’s disease, but they were noticed six weeks later.
2. Cancer: There is conflicting scientific evidence regarding the overall large increase in cancer risk associated with trans fat consumption.Trans fats and cancer: According to the American Cancer Society, the connection “has not been determined.”Trans fat has been positively associated with prostate cancer, according to one study. Nonetheless, a more extensive investigation discovered a link between trans fats and a notable decline in high-grade prostate cancer. The findings from the French portion of the European Prospective Investigation into Cancer and Nutrition imply that a higher diet of trans fatty acids may increase the risk of breast cancer by 75%.
3. Diabetes: There is growing worry that consuming trans fats raises the risk of type 2 diabetes. Still, no agreement has been achieved. According to one study, people who consume trans fat in the top quartile are at a higher risk. After controlling for other variables including BMI and total fat intake, another study revealed no diabetes risk.
4. Obesity: Despite consuming identical amounts of calories, research suggests that trans fat may exacerbate weight growth and abdominal fat. Monkeys fed a meal high in trans fat acquired 7.2% of their body weight over the course of a 6-year experiment, while those fed a diet high in mono-unsaturated fat gained 1.8%. There is not a strong scientific consensus linking trans fat and obesity, although the 6-year experiment did find a link and concluded that “under controlled feeding conditions, long-term TFA consumption was an independent factor in weight gain.” Although trans fat and obesity are frequently linked in the popular media, this is usually in the context of eating too many calories. Even in the absence of calorie excess, TFAs increased the deposition of fat intra-abdominally and were linked to insulin resistance, with evidence that signal transduction following insulin receptor engagement is compromised.”
5. Women’s infertility: According to a 2007 study, there is a 73% increased risk of ovulatory infertility for every 2% increase in energy consumption from trans unsaturated fats compared to carbs.
6. Major depressive disorder: After analyzing 12,059 people’s diets over a six-year period, Spanish researchers discovered that individuals who consumed the highest amounts of trans fats had a 48% higher chance of developing depression than those who did not. A plausible explanation could be the replacement of docosahexaenoic acid (DHA) levels in the orbitofrontal cortex (OFC) by trans-fats. Reduced DHA levels in the brain were linked to extremely high trans-fatty acid consumption (43% of total fat) in mice from 2 to 16 months of age (p=0.001). Upon post-mortem examination, the brains of fifteen major depressive people who had committed suicide were compared to twenty-seven age-matched controls. It was discovered that the suicidal brains had, on average, 16% less DHA in them than the controls of the OFC. The OFC regulates the limbic system and controls reward, reward expectancy, and empathy—all of which are diminished in depressive mood disorders.
7. Aggression and behavioral irritability: A 2012 observational review of participants in a previous study discovered a substantial correlation between self-reported behavioral aggression and irritability and dietary trans fat acids, implying but not proving causation.
8. Diminished memory: “Greater dietary trans fatty acid consumption is linked to worse word memory in adults during years of high productivity, adults age <45,” according to a 2015 study that reanalyzed data from the 1999–2005 UCSD Statin Study.
9. Acne: A 2015 study found that trans fats, along with high-glycemic carbohydrates like refined sugars and starches, milk and dairy products, and saturated fats, are among the elements of Western pattern diets that contribute to acne. Conversely, Western pattern diets are deficient in omega-3 fatty acids, which help to prevent acne.

Biochemical Mechanisms

Research on the precise molecular mechanism by which trans fats cause certain health issues is still ongoing.

Consuming trans fat in food causes disruptions to the body’s metabolism of essential fatty acids (EFAs), such as omega-3, which alters the phospholipid fatty acid composition of arterial walls and increases the risk of coronary heart disease.

It is suggested that trans double bonds cause the molecule to adopt a linear shape that favors its rigid packing, as in the creation of plaques.

Contrarily, it is asserted that the cis double bond’s shape causes the molecule to bend, preventing stiff forms.

The processes by which trans fatty acids cause coronary artery disease are largely known, while the mechanisms by which they affect diabetes are still being studied. They might hinder the way long-chain polyunsaturated fatty acids (LCPUFAs) are metabolized.

The favorable correlation between nursing and IQ may, however, be explained by the inverse relationship between the trans fatty acid intake of pregnant mothers and the levels of long-chain polyunsaturated fatty acids (LCPUFAs) in newborns.

The liver handles trans fats differently than it does other types of fats.

By interfering with delta 6 desaturase, an enzyme involved in converting essential fatty acids to prostaglandins and arachidonic acid, both of which are crucial for cellular function, they may cause liver damage.

Natural “trans fats” in Dairy products

Naturally occurring lipids and conventionally processed foods contain some trans fatty acids. In addition to various isomers of conjugated linoleic acid (CLA) present in meat and dairy products from ruminants, breast milk contains vaccenic acid.

For instance, butter has roughly 3% trans fat. According to the U.S. National Dairy Council, trans fats found in animal foods are not the same kind as those found in partially hydrogenated oils and don’t seem to have the same detrimental consequences.

Although a review notes that the conclusion—that “the sum of the current evidence suggests that the Public health implications of consuming trans fats from ruminant products are relatively limited”—agrees with it, it also raises the possibility that this is because artificial trans fats are more commonly consumed than those derived from animals.

All trans fats, whether they come from natural or artificial sources, equally raise LDL and lower HDL levels, according to a 2008 meta-analysis.

However, when it comes to trans fats derived from animals, such as conjugated linoleic acid (CLA), other studies revealed conflicting findings.

The cis-9, trans-11 form of CLA has been shown by studies to have anti-inflammatory and anti-cancer effects, in addition to lowering the risk of cardiovascular disease.

By reducing total LDL and triglyceride levels, two Canadian studies have demonstrated that vaccenic acid, a TFA found naturally in dairy products, may be advantageous over hydrogenated vegetable shortening or a combination of pig lard and soy fat.

According to a US Department of Agriculture study, industrial trans fats only elevate LDL cholesterol and have no positive effect on HDL, but vaccenic acid raises both LDL and HDL cholesterol.

Official Recommendations

Nutritional specialists urge reducing trans fat consumption to trace levels due to the overwhelming body of research supporting their equally detrimental health effects.

The World Health Organization advised in 2003 that trans fats should not account for more than 0.9% of a person’s diet. In 2018, the organization unveiled a 6-step plan to remove trans-fatty acids manufactured in factories from the world’s food supply.

For use in public policy and product labeling initiatives, the National Academy of Sciences (NAS) provides nutritional scientific advice to the governments of the United States and Canada.

Their results and suggestions about trans fat consumption are included in their 2002 Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids.

Two important facts form the basis of their recommendations. First, whether they come from plants or animals, “trans fatty acids are not essential and provide no known benefit to human health”.

Second, the NAS came to the conclusion “that dietary trans fatty acids are more deleterious with respect to coronary artery disease than saturated fatty acids” based on their effects on the LDL/HDL ratio that have been observed.

According to a 2006 review that appeared in the New England Journal of Medicine (NEJM), consuming trans fatty acids has significant potential negative effects but no discernible positive effects from a nutritional standpoint.

The NAS has determined that there is no safe level of trans fat consumption in light of these findings and concerns.

Trans fats have no acceptable maximum limit, suggested daily intake, or appropriate level.

This is due to the fact that consuming more trans fat raises the risk of coronary heart disease by a small amount. The NAS dietary guidelines do not advocate removing trans fat from the diet, despite this worry.

This is due to the fact that trans fat is found in trace amounts in many animal foods naturally, thus eliminating it from a regular diet could have unfavorable consequences and produce nutritional imbalances.

Therefore, the National Academy of Sciences “recommended that trans fatty acid consumption be as low as possible while consuming a nutritionally adequate diet”.

Similar to the NAS, the WHO has attempted to strike a compromise between the practical amount of trans fat consumption and public health objectives. In 2003, the WHO recommended limiting trans fat intake to less than 1% of total caloric intake.

Regulatory Action

Many nations have implemented strict regulations in the past few decades that have limited the amount of trans fat that may be found in commercial and processed food products.

Alternatives to Hydrogenation

Interest in substituting partial hydrogenation has increased due to the unfavorable public perception and stringent legislation.

Triglycerides are mixed with fatty acids during fat interesterification.

This process could theoretically achieve results similar to partial hydrogenation without affecting the fatty acids themselves; specifically, without creating any new “trans fat”.

When applied to an appropriate blend of oils and saturated fats, possibly followed by the separation of unwanted solid or liquid triglycerides.

Trans fat can be produced in modest amounts while still achieving hydrogenation. Five to six percent trans fat was created in margarine using high-pressure procedures.

As per the present U.S. labeling regulations (see below), the producer has the ability to declare the product devoid of trans fat. Alterations to the temperature and hydrogenation time can also change the amount of trans fat present.

A “cooking fat” that functions similarly to trans and saturated fats can be created by combining oils (such as olive, soybean, and canola), water, monoglycerides, and fatty acids.

Omega-Three and Omega-Six Fatty Acids

Considerable study has been paid to the? -3 fatty acids. Among the omega-3 fatty acids, the risk of breast cancer was not consistently linked to either the long-chain or short-chain versions.

However, the most prevalent omega-3 polyunsaturated fatty acid in erythrocyte (red blood cell) membranes, docosahexaenoic acid (DHA), has been linked to a lower risk of breast cancer.

A polyunsaturated fatty acid diet provides DHA, which has a good correlation with both behavioral and cognitive function.DHA is also essential for retinal stimulation, neurotransmission, and the human brain’s grey matter formation.

Interesterification

By contrasting diets including interesterified (IE) and non-IE fats with the same overall fatty acid composition, some studies have examined the potential health implications of IE fats.

A diet high in IE fat (25–40% C16:0 or C18:0 on the 2-position) did not significantly vary from a diet high in non-IE fat (3–9% C16:0 or C18:0 on the 2-position) in a number of human experimental tests conducted on fasting blood lipid levels.

Another study comparing the effects of an IE fat product that mimicked cocoa butter and the actual non-IE product on blood cholesterol levels yielded a negative outcome.

According to a 2007 study supported by the Malaysian Palm Oil Board, substituting interesterified or partially hydrogenated fats for natural palm oil resulted in negative health outcomes like elevated plasma glucose and the LDL/HDL ratio.

Nevertheless, rather than the IE process itself, these effects might be linked to the larger context of partially hydrogenated fats and saturated acids in the IE.

Role in Disease

Elevated blood triglyceride levels have been associated with atherosclerosis, heart disease, and stroke in humans.

Nevertheless, it is currently unknown how much of a harm elevated triglyceride levels do in comparison to LDL: HDL ratios.

The danger may be partially explained by the significant inverse correlation between HDL cholesterol and triglyceride levels.

However, elevated triglyceride levels also contribute to the risk by increasing the number of dense, tiny LDL particles.

Guidelines

For triglyceride levels, the National Cholesterol Education Program has established guidelines:
Eight to twelve hours following the fast, these levels are measured. After eating, triglyceride levels continue to rise momentarily.

To promote heart health, the American Heart Association suggests maintaining triglyceride levels at 100 mg/dL (1.1 mmol/L) or below.

Level (mg/dL)	Level (mmol/L)	Interpretation
< 150	< 1.70	Normal range – low risk
150–199	1.70–2.25	Slightly above normal
200–499	2.26–5.65	Some risk
500 or higher	5.65	Very high – high risk

Reducing Triglyceride Levels

The first-line lifestyle modification therapy for hypertriglyceridemia that works well are weight loss and dietary changes.

Modest exercise, weight loss, and dietary adjustments are advised for those with mildly or moderately elevated triglyceride levels.

This could entail eating less fat and carbs overall, especially fructose, and increasing your intake of omega-3 fatty acids from foods like algae, nuts, fish, and seeds.

If the aforementioned lifestyle changes do not result in reduced triglyceride levels, medication is advised; fibrates are the first choice in this regard.

A prescription medication called omega-3-carboxylic acids is also used to treat extremely high blood triglyceride levels.

The choice to use medication to treat hypertriglyceridemia is based on the levels as well as the existence of additional cardiovascular disease risk factors.

A medication belonging to the fibrate class is used to treat extremely high levels that could raise the risk of pancreatitis.

When lowering cardiovascular risk is necessary for moderate hypertriglyceridemia, statins are the primary treatment of choice. Niacin and omega-3 fatty acids may also be taken in combination with statins.

Fat Digestion and Metabolism

In a healthy body, fats are broken down to liberate their constituents, fatty acids and glycerol. The liver can transform glycerol into glucose, which can then be used as an energy source.

The pancreas produces lipases, which are enzymes that aid in the breakdown of fats and other lipids in the body.

Both glucose and fatty acids can be used by a variety of cell types as a source of energy for metabolism.

Fatty acids are particularly preferred by the heart and skeletal muscle.[Reference required] Contrary to popular belief, fatty acids can also be utilized by brain cells as a fuel source through mitochondrial oxidation.