GUIDE TO DIETARY FATS: REVIEW OF NON-ESSENTIAL FATS (PART 3)
Medically Reviewed by Dr. Rosmy Barrios - September 18, 2024
The following article forms part 3 of a guide to dietary fats, covering essential dietary fats.
Part 1 covers fat classifications and the role fat plays in the body, part 2 covers essential dietary fats and part 4 offers useful tips for optimizing fat metabolism.
Non-Essential Dietary Fats
The following fats are non-essential, either unrequired by the body or endogenously produced. Despite their non-essentiality, many of them have benefits when consumed in moderation in the context of a healthy diet plan.
Monounsaturated Fats
Monounsaturated fats are often able to substitute a portion of saturated fats in the diet, with more favorable effects on health and well-being. The body metabolizes fats through various processes; however, it does not primarily convert long-chain saturated fats into monounsaturated fats. Increasing monounsaturated fat intake and lowering long-chain saturated fat intake help to enhance the efficiency of fat metabolism in the body as a whole.
Oleic Acid
Oleic acid is one of the most ubiquitous long-chain MUFAs found in nature[1]. In the human body, it is one of the main fats found stored in fatty tissue and is used as a precursor for the production of phospholipids and cholesterol. Oleic acid is made from stearic acid in the liver and is as poorly absorbed from the diet as palmitic acid. Nonetheless, it is a much healthier dietary fat than palmitic acid, associated with positive health benefits and optimal fat metabolism.
Food sources
- Olive oil (55-83%)
- Macadamia oil (57-67%)[2]
- Fish, especially freshwater fish[3]
- Shea Butter (37-45%)
- Cocoa butter (34%)
- Sunflower oil (14-43%)
- Canola oil (27-65%)
- Soybean oil (24%)
- Corn oil (35%)
- Palm oil (39-40%)
- Lard (42%)
- Butter (22%)
- Sesame oil (28-29%)
- Almond oil (62-76%)
- Avocado oil (40-65%)
Benefits
- Reduces inflammation and blood pressure[4]
- Improves insulin sensitivity
- Suppresses VLDL cholesterol production in the liver through hypothalamic signaling
- Promotes optimal liver fat metabolism[5]
- Lowers risk for heart diseases, atherosclerosis, blood clotting disorders and diabetes
- Serves to counter the deleterious effects of excessive palmitic acid[6]
- Promotes healthy cellular turnover through regulating cellular growth pathways
- May protect against female infertility[7] [8]
Side Effects
- Average dietary consumption of oleic acid is not associated with any known side effects
- Pure extracts of oleic acid may cause skin irritation[9] and may impair fertility[10] in high concentrations
Isomers
- Elaidic acid (a trans-fat isomer of oleic acid) is linked with an increased risk for coronary heart disease and obesity[11] when consumed in quantities higher than 1%.
- Vaccenic acid (conjugated oleic acid trans-fat), associated with neutral or positive health benefits, is found stored in animal products, particularly dairy. Vaccenic acid is a precursor to conjugated linoleic acid. Proven to reduce triglyceride levels and fat mass in rats. In most human studies, it is inversely associated with insulin resistance and type 2 diabetes risk; however, there have been conflicting results.[12]
Palmitoleic Acid
Palmitoleic acid (also known as trans-palmitoleate) is a minor monounsaturated fatty acid found in dairy and meat products and is classified as a cis-fatty acid. Second to oleic acid, it is one of the most common monounsaturated fats in the human diet; however, it is present in very low quantities.
The human body also produces its own palmitoleic acid (from palmitic and stearic acid[13]) in the liver and in fat tissue. While relatively little is known about it, studies suggest it acts as a lipid hormone required for optimal functioning of insulin in fat, muscle and liver tissues. As the body produces its own supply, consuming food sources is entirely unnecessary for health.
Food sources
- Macadamia oil (14-24%)
- Palm oil (19-29%)
- Dairy and meat products
- Algae
Benefits
- Moderate intake is linked with lower diabetes risk and healthier blood profiles regarding inflammation, cholesterol, and insulin.[14]
- May be beneficial for those with autoimmune conditions as it has the potential to inhibit lymphocyte proliferation.
- Associated with liver disease prevention.
- Serves to regulate insulin in muscle tissue.
Side Effects
- High concentrations may inhibit the proliferation of lymphocytes, which would block inflammation as well as the adaptive immune response.[15]
- Frequent consumption is contraindicated for hypercholesterolemia.[16]
Saturated Fats
Saturated fats traditionally have a bad reputation for unbalancing cholesterol production and fat metabolism. However, this only truly applies to certain types of saturated fats when they’re consumed in excessive quantities. The worst offenders are typically industrially produced trans-fats, which are largely unable to be processed by the body. Most natural saturated fats are not nearly as detrimental to health as trans fats[17].
The following section highlights how most saturated fats (excluding trans fats) are not bad for the body when consumed in moderation.
Palmitic Acid
Also known as Hexadecanoic acid, palmitic acid is a long-chain fat and the most common saturated fat found in the cells of animals, plants and microbes.[18] The human body is able to synthesize its own palmitic acid for discrete purposes and maintains it at a very specific concentration in all tissues. Elevated tissue concentrations are associated with deleterious health effects. Dietary palmitic acid reduces endogenous production of the fat in order to keep its levels regulated.
However, factors that impair fat metabolism are able to promote excessive palmitic acid production in the body (lipogenesis), both of which lead to many metabolic problems. Excessive palmitic acid consumption is one prime factor that is able to disrupt fat metabolism, particularly when coupled with a sedentary lifestyle and a non-nutritious, high-calorie diet.
Fortunately, dietary palmitic acid is known to be poorly absorbed and metabolized[19]. Furthermore, in a healthy context, its consumption is balanced with appropriate omega-3 and omega-6 intake, both of which serve to regulate fat metabolism in the body. Oleic acid also appears to offset its negative effects, along with many other healthful unsaturated fats.[20]
Therefore, the deleterious effects only truly apply when consumed in excessive quantities in the absence of regulating nutrients and for a prolonged period of time. Foods containing palmitic acid ought to be assessed for their nutritional value, and if found to be low, they ought to be consumed in moderation or avoided entirely.
Food sources
- Palm oil (44%)
- Palm kernel oil
- Cocoa butter (25%)
- Canola oil (4-16%)
- Butter (18-28%)
- Meat and dairy products (50-60%)
- Olive oil (7.5-20%)
- Found in small quantities in other saturated plant fats
Benefits
- Serves as a substrate for palmitoleic acid (see ‘Monounsaturated Fats’ above).
- At the right concentrations, it fulfills important physiologic functions in most cells and tissues, including regulating membrane integrity.
- Provides the building block for sapienic acid, the main lipid found in sebum on the skin’s surface[21]. Sebum seals moisture into the skin, prevents skin dehydration and provides a suitable habitat for friendly skin bacteria, which protect the skin from pathogens.
Side Effects
- Promotes mitochondrial dysfunction, generalized inflammation, impaired fat metabolism and problems with cellular protein assembly.
- Associated with cardiovascular inflammation and an elevated risk for cardiovascular diseases[22].
- Excessive levels are linked with increased risks of developing metabolic syndrome, obesity, type 2 diabetes, atherosclerosis and blood clotting disorders.
- Noted to promote viral replication in fish cells[23].
Stearic acid
Stearic acid is a long-chain saturated fat found in many plant and animal fats[24]. The human body is able to produce its own stearic acid from palmitic acid as a substrate.[25] Stearic acid goes on to form part of important enzymes that are involved in fat metabolism and also serves as a substrate for oleic acid production.[26]
Food sources
- Cocoa butter (33-37%)
- Shea butter (42-49%)[27]
- Animal-based cooking fats (12-19%)
- Meat and dairy products (11-16%)[28]
Benefits
- Short-term consumption of a diet high in stearic acid proved to lower total cholesterol levels[29]
- Associated with improved blood platelet markers and a lower risk for blood clotting disorders and atherosclerosis[30]
- Proven to regulate mitochondrial function and potentially enhance cellular fat metabolism[31]
Side Effects
- Long-term consumption of a high stearic acid diet increases total cholesterol (similar effect seen for any long-term diet too high in saturated fat[32])
Myristic acid
Myristic acid is a minor saturated long-chain fat found in a variety of plant sources and milk. The human body does not produce its own myristic acid. Dietary sources are associated with health benefits when consumed in low quantities.
Food sources
- Nutmeg oil (75%)
- Coconut Oil (8-19%)
- Palm Kernel Oil (16%)
- Cow’s Milk (10%)
- Butter (10%)
Benefits
- Moderate dietary amounts (less than 1.5%) are associated with a healthy lipid and cardiovascular profile when balanced with other fatty acids[33]
- Enhances omega-3 content in cells when consumed in low to moderate amounts
- Test-tube studies indicate that myristic acid may lower skin inflammation and pain perception[34]
Side Effects
- High concentrations of myristic acid are known to promote hypercholesterolemia[35] (similarly to palmitic acid[36]) and are associated with an increased risk of cardiovascular disease[37]
- Associated with promoting inflammation and damage in liver cells in high quantities[38]
- Direct exposure to pure extracts can irritate the skin and eyes[39]
Lauric acid
Lauric acid is a medium-chain saturated fat that is often used as an ingredient in cosmetic products. It is secreted onto the skin as part of human sebum[40]. However, it is unknown whether the body produces lauric acid endogenously or not.
While proven to be non-toxic, studies regarding lauric acid reveal that it is capable of enhancing the effects of other fats. As part of coconut and MCT oil, lauric acid is usually beneficial, while as part of palm kernel oil, it can be detrimental.
Food sources
Benefits
- Increases HDL cholesterol while having little to no effect on LDL cholesterol.[44]
- Slower release of energy by comparison to other components of MCT oil, thereby extending the benefit (see ‘Capric and Caprylic Acid’).
- Shown to induce apoptosis (cell death) in breast cancer cells.[45]
- Confers antimicrobial properties to skin sebum, coconut oil and other cosmetic preparations.
- May reduce the risk of developing obesity at low dietary concentrations.
- Moderate amounts of lauric acid served to protect against irregular metabolism, thermoregulation, and menstrual disruption in female mice fed a high-fat diet[46].
Side Effects
- Promotes weight gain in excessive quantities and is associated with a greater risk for obesity compared to palmitic acid.
- Associated with increasing inflammation to a lesser extent than palmitic acid.
- Excessive quantities may increase the risk for developing liver disease, insulin resistance and diabetes in the long term.[47]
- Test-tube studies highlight that excessive levels of lauric acid in the bloodstream can cause rapid dyslipidemia, promote the death of blood cells, increase blood clotting and raise the risk for cardiovascular disease.[48]
- Lauric acid is toxic to lymphocytes and, therefore, may suppress immune function if ingested in exceedingly high quantities.
- May increase mammary gland development during pregnancy and puberty.[49]
Capric and Caprylic Acids
Capric (8:0) and caprylic (10:0) acids are two medium-chain saturated fats not produced or required by the body. Together with caproic acid, they form the main components of MCT oil (medium-chain triglyceride oil)[50]. While they are two distinct fats, they are most commonly studied together or as part of MCT oil. As such, they have been included together in this review alongside MCT oil.
MCT oil is easy for the body to absorb and has been administered to those who battle to metabolize fat since the 1950s as an energy substitute. By comparison to long-chain fats, MCTs yield a greater conversion into ketones (fat energy molecules) and are less problematic for those on a ketogenic diet.
Food sources
- Coconut Oil (11%)
- Milk (0.4-3%)
- MCT Oil (70-100%)
Benefits
- C810 is known to have several properties that inhibit the growth of Candida Albicans and prevent it from becoming resistant.[51] [52]
- Proven to be protective against listeriosis, E. Coli, Cholera, Salmonella, pathogenic Clostridium species and some strains of Malassezia (a pathogenic fungus problematic in hospitals).
- C810 is less likely to be stored in fat and is readily converted into ketones in the liver.
- Shown to promote weight loss in both animals and humans.
- C810 is able to bind to ghrelin, the ‘hunger hormone,’ and reduce appetite[53] [54].
- A beneficial energy source for those with pancreatic insufficiency, liver disease and other metabolic issues that impact fat metabolism.
- C810 readily crosses the blood-brain barrier and can be used as a viable energy source for the brain.
- May enhance mitochondrial function, mildly improve cognition and reduce neuro-excitotoxicity.
- MCT oil reduces an allergenic immune profile (Th2) and can lower specific types of inflammation (TLR4 and NFkB).[55]
- May influence the gut microbiome in a way that lowers gut inflammation and promotes better intestinal integrity.
- Shown to induce apoptosis (cell death) in breast cancer cells.
- Associated with reducing the risk for neurodegenerative diseases, epilepsy, cancer, atherosclerosis, cardiovascular disease, liver disease, diabetes, metabolic syndrome and obesity.
Side Effects
- No side effects have been associated with MCT oil, even in excessive dietary applications.[56]
- Promotes an inflammatory autoimmune profile (Th1 and Th17).
Butyric acid
Butyric acid is a short-chain fat that is produced locally by friendly bacteria in the gut microbiome. It is not classified officially as an essential nutrient, yet many researchers regard it as essential owing to the number of critical functions it helps to regulate in the body as a whole[57]. Butyrate (conjugate of butyric acid) forms a ratio with propionate and acetate in the gut of approximately 20:20:60, respectively. Acetate or amino acids can also be used by gut bacteria to produce butyrate.
Enteric cells in the gut (especially the colon) depend on butyric acid in order to meet metabolic requirements and renew themselves. As one of the most active cell types in the body, enteric cells in a healthy gut turnover completely within 3-5 days. This can only be achieved with an adequate supply of butyric acid.
Butyric acid also provides an essential substrate for the inhibitory neurotransmitter GABA (gamma-aminobutyric acid). GABA is required to tone down activity in most of the nervous system, as well as to enhance firing in the hippocampus and improve learning, memory and cognitive flexibility.
Food sources
- Milk
- Butter (2.5%)
- Fermented foods
Most of the butyric acid is produced endogenously through consuming a balanced diet with enough prebiotic fiber to feed the gut. Resistant starches[58] and lactate[59] were shown to provide an optimal substrate for butyrate production from relevant bacterial strains.
Benefits
- Substantially reduces the risk of colon cancer[60]
- Shown to be toxic to several types of cancer cells in vitro, as well as able to slow their growth[61]
- Has the potential to lower the risk of autoimmune digestive disorders (including IBS/IBD), depression, Alzheimer’s Disease, Parkinson’s Disease, type 2 diabetes, and obesity[62]
- Promotes optimal regeneration and metabolic functioning of the intestinal wall
- Enhances nervous transmission and smooth muscle contraction in the gut
- May reduce digestive pain and inflammation
- When used in combination with probiotics, butyric acid proved to be more effective than laxatives for treating constipation in an elderly group of patients
- May lessen diarrhea severity by promoting optimal water uptake and enteric cell function
- Can help regulate pancreatic beta cell function
- May contribute toward the integrity of the blood-brain barrier and the maturation of brain cells
- Butyrate is able to reduce neuroinflammation and regulate brain immune cells (through HDAC inhibition)
- Enhances brain and gut production of tryptophan hydroxylase[63], a required enzyme for serotonin, dopamine, noradrenaline and adrenaline production
- Contributes to the regulation of appetite, circadian rhythm, sleep, memory, learning and general cognition
Side Effects
- Excessive gut quantities are associated with gut dysbiosis and a shortage of other essential microbiome-derived nutrients (e.g. propionic acid)
- Excessive dietary quantities may promote dental inflammation, cavities[64] and obesity[65]
Isomers
- GABA. Butyrate is the precursor to GABA. GABA is associated with improving the quality of sleep, integration of information, focus, mental clarity, and relaxation (parasympathetic activity). It is the opposing neurotransmitter to glutamate, which is required for nerve activation and transmission. GABA protects against neuroinflammation and neurotoxicity induced by the over-excitability of neurons (a by-product of excessive glutamate levels).
Propionic acid
Alongside butyric and acetic acids, propionic acid is another short-chain fatty acid metabolite of friendly gut bacteria that serves to maintain bodily homeostasis. Gut bacteria often produce it in the form of indole-3-propionic acid, which confers different health effects depending on various factors (i.e. concentration, metabolism, diet, etc). Another form, propionate, is added to many foods as a preservative and is associated with negative effects on health.
Food sources
- Fermented foods
- Shellfish
- Added to many foods as a preservative in the form of propionate
Prebiotic fibers (e.g. inulin[66]) that feed the relevant gut bacteria promote the production of propionic acid.
Benefits
- Lowers markers of inflammation associated with fat metabolism and helps to regulate immune function[67] [68]
- Enhances fat metabolism through inhibiting lipogenesis, with noticeable reductions of fat observed in liver and blood plasma
- Promotes satiety
- May reduce the risk of developing diabetes, obesity, and some cancers[69]
- Shown to have antimicrobial actions[70] that could help to maintain beneficial populations of bacteria in the gut
- Increases colonic blood flow and improves intestinal integrity[71]
- May help to regulate insulin signaling and blood glucose levels
Side Effects
- Food preservative propionate is linked with increasing adrenaline, noradrenaline[72] and the risk for metabolic disorders[73]
- Shown to be elevated in those with autism[74] and associated with promoting some of the neurological aspects of the disease
- Can induce neuronal excitotoxicity in excessive quantities by stimulating glutamate and inhibiting GABA[75]
- May aggravate immune activity[76], increasing inflammation and allergic reactions
- Excesses are indicative of gut dysbiosis, as well as increased blood glucose and triglyceride concentrations[77]
5 Pro Tips for Making the Most of Fats
To be continued in part 4.
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