Lipids are fundamental to life itself. Without fat and its components, not only would the very cells within an organism fail, the individual working components within cells would cease to be. In other words, while a low-fat diet might have some value for some people and for certain conditions, a no-fat diet would be fatal.
When discussing healthful fats, it is more accurate to refer to the component fatty acids, the chains of carbon atoms that differ in both length and degree of saturation. (Saturation refers to the number of hydrogen atoms linked to each interconnected carbon in the chain.) It’s the unique fatty acid profile that gives individual fats their characteristics and functionalities.
Most fatty acids in foods are between four and 22 carbons in length. Terms such as “saturated,” “unsaturated,” and “omega” are used in describing the structure of individual fatty acids. A saturated fatty acid has only single hydrogen bonds between the carbons in the chain. An unsaturated fatty acid has at least one double bond between two of the carbons.
A fatty acid with one double bond is referred to as a monounsaturated fatty acid (MUFA), while a fatty acid with more than one double bond is termed a polyunsaturated fatty acid (PUFA).
The position of the double bonds determines the class of fatty acids. For example, an omega-3 fatty acid has its first double bond at the third carbon from the end (omega). It can (and does) have more double bonds in the chain, but all members of the omega-3 family have the first double bond in the number three position.
STRUCTURE GIVES FUNCTION
There are certain general properties among fatty acids that determine how they function in a formulation. Each double bond puts a kink in the fatty acid chain. The more double bonds, the more kinks or bends.
This changes the melting point of the fatty acid. Fatty acids with more bends have a greater tendency to stay liquid as the temperature drops. Moreover, the more double bonds, the less saturation, but the greater the tendency of the fat to oxidize and turn rancid.
A double bond that produces a kink in the fatty acid chain has what is called a “cis” configuration, whereas a double bond that doesn’t produce a kink has a “trans” configuration. Some trans-fatty acids occur naturally, while others are a byproduct of the process of hydrogenation, the conversion of unsaturated fatty acids to saturated fatty acids. The latter are associated with increased disease risk and now require labeling.
The diversity of fatty acids, and the fact that all naturally occurring fatty foods contain a variety of fatty acid types, makes determining the benefit of specific fats in the modern diet a complex question. Since fats always have been an important part of our diet (and always will be), the question becomes one of balance. For example, both omega-3 and omega-6 fatty acids are polyunsaturated and cannot be made in the body. These are, therefore, “essential” fats.
While both omega-3 and omega-6 fatty acids are essential, the proportion of omega-6 to omega-3 fatty acids in the modern diet has shifted, favoring the omega-6 class. The reason is simple: The majority of animals used for food are grain-fed. The germ of grains is a rich source of omega-6 fatty acids, whereas green plants are prime sources of omega-3 fatty acids.
Omega 3s are well known to have anti-inflammatory capacity, whereas some of the downstream products of omega-6 fatty acid metabolism tend to favor the inflammatory processes. It should be noted, though, that not all inflammation is bad. Inflammation is a necessary part of wound healing.
Two other omegas have been garnering attention of late, omega-9s, generically termed oleic acid, and omega-7s, the most common being palmitoleic acid. Omega-9s typically are monounsaturated, and the human body can make both omega-9s and omega-7s (along with saturated fatty acids). But this does not diminish the importance of these omegas in the diet.
Omega-9s are dominant in olive oil and avocados, and generally are associated with some of the benefits attributed to the Mediterranean diet. Omega-9 has been shown to lower LDL cholesterol, without decreasing HDL. The body can make it from stearic acid, the saturated fatty acid found in abundance in beef.
Omega-9 also is the main type of fatty acid in many of the nuts that can help prevent heart disease. These include not only tree nuts — including cashews, almonds, hazelnuts, pistachios, and pecans — but also peanuts. It is abundant in canola oil, as well as in high-oleic soybean and sunflower oils.
Normally rich in omega-6 fatty acids, these high-oleic oils are the result of croos-breeding efforts that boosted the oleic acid content to 70% of total fatty acids. These oils also are rapidly replacing hydrogenated oils in processing. MUFAs have a much lower tendency to spoil since they have only one double bond, which makes them attractive for modern food processing.
Studies show that the effect of MUFAs on blood profiles of lipoproteins and triglycerides compares favorably with that of saturated fatty acids. Moreover, they lack the health risk of trans-fatty acids that result from hydrogenation. In fact, a health claim was recently allowed for these two lipids.
Palmitoleic acid, an omega-7 fatty acid that occurs in both cis and trans forms, is a MUFA that has received much attention recently. This novel fatty acid has been associated with increased insulin sensitivity and decreased fat accumulation in the liver. In animal studies, the cis form of palmitoleic acid has been shown to lower levels of pro-inflammatory markers.
Palmitoleic acid is synthesized in humans, primarily in the liver and adipose tissue, using the same enzymes that create oleic acid from saturated fatty acids. Dietary sources of this fat include olive oil, macadamia nuts, chocolate, eggs, and fatty fish.
The highest concentration of palmitoleic acid in plants is found in oil extracted from sea buckthorn berries. The oil contains 32–42% palmitoleic acid. The trans form is found in dairy products and partially hydrogenated oils.
Conjugated linoleic acids (CLAs) are naturally occurring isomers (same formula, different shape) of linoleic acid, an omega-6 fatty acid. CLAs are produced by microbes in the rumen of cows and goats and therefore are found in meats and dairy products. Animal experiments have shown CLAs can help increase the uptake of glucose into the cell and increase fatty acid metabolism.
Gamma-linolenic acid (GLA) is an omega-6 fatty acid (PUFA) found in human breast milk and several botanical seed oils, such as borage oil and evening primrose oil. It’s typically consumed as a dietary supplement. There have been many promising in vitro and animal studies showing GLA can help control inflammatory responses.
While the results of all such clinical studies are encouraging, they also bring forward a variety of complicating factors. For example, genetic differences could affect the conversion of GLA to dihomo-gamma linolenic acid (DGLA) and arachidonic acid (AA), longer chain metabolites, which in turn affects the balance of downstream metabolites, some of which could have opposing effects. These factors can limit the efficacy of PUFAs for treating inflammatory conditions.
Alpha-linolenic acid (ALA) is the parent of the omega-3 family of fatty acids. It’s the omega-3 fatty acid found in flax, hempseed, chia, soybeans, walnuts, green vegetables, and algae, among many other plant sources. ALA is a precursor to the long-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the best-known sources of which are fish oils. Many small animals readily convert ALA to EPA and DHA. In humans, this ability is more limited.
EPA plays an important role in blood flow and control of inflammation, while DHA is essential for neurogenesis, photoreception, and synaptic signaling. There is growing interest in ALA on its own, as it has a role to play in brain health, vascular function, tissue elasticity, skin integrity, and hair condition.
Some primate studies showed that a deficiency of ALA can lead to fatty liver disease, loss of tissue elasticity, and severe behavior pathology. This is a cause of concern due the recent change in the ratio of omega-6s to omega-3s in modern diet, as previously noted.
• Vitamin A
Dietary fats play a critical role in the absorption of fat-soluble vitamins and fat-soluble phytochemicals. An excessively low-fat diet could risk deficiency by hindering the absorption of essential vitamins and of phytochemicals that, if not essential, certainly provide health benefits. These lipids we need in tiny amounts include the fat-soluble vitamins A, D, E, and K, as well as other vitamin A-like carotenoids, such as lutein, lycopene, xanthine, and astaxanthin.
Vitamin A has a multitude of functions, from growth and development to skin integrity, bone health, and eyesight. There are different forms of vitamin A: the acid form (retinoic acid), the aldehyde form (retinal), and the alcohol form (retinol). Its precursor, provitamin A, is found in plants as beta-carotene and converted to vitamin A in the body by enzymatic action.
The pre-formed vitamin A found in animals is highly toxic in large amounts, unlike the beta-carotene found in plants. The orange color of carrots, mangoes, sweet potatoes, pumpkins, and similar foods is due to beta-carotene content. Beta-carotene also is found in large amounts in green vegetables, though it is hidden by green chlorophyll.
• Vitamin D
There has been a resurgence in vitamin D interest, stimulated by a flood of research uncovering unexpected benefits beyond its role in bone growth. The hormone-like, fat-soluble vitamin has demonstrated abilities to influence or contribute to multiple metabolic functions. It has an impact on everything from heart health and immunity to weight management and cognitive well-being. Vitamin D has even been shown to help reduce the number of asthma attacks in children.
Vitamin D is found naturally in only a few foods, fatty fish being a main source. Humans depend mostly on the sun, particularly ultraviolet light, which in the skin triggers vitamin D synthesis from cholesterol in the body. In its best known role in maintaining healthy bones, vitamin D acts by promoting calcium absorption in the gut and thus maintains adequate serum calcium and phosphate levels in the blood. These are key minerals in bone growth and development.
In spite of all the excitement over vitamin D’s recently disclosed benefits, better-for-you product makers still haven’t focused on it as a nutraceutical to employ beyond its inclusion in dairy. That’s unfortunate, because in the US, vitamin D deficiency has been on the rise. This is partly a result of reduced sun exposure as people are less active, go outdoors less, and then cover up to reduce the chance of UV-stimulated skin cancer when they do venture outside. That, coupled with decreased consumption of D-fortified dairy products, leads many experts to consider the US population as being in the throes of epidemic deficiency.
For example, in a survey of US nursing facility residents, 60% were shown to be vitamin D-deficient. A survey of hospitalized patients found similar levels of deficiency (57%). This increases the risk of hip fractures in older adults, whose ability to produce vitamin D is reduced by age and lack of exposure to the sun, thus necessitating supplementation via foods, beverages, or other methods.
There are two primary forms of vitamin D, cholecalciferol (vitamin D3) — the form that is produced by sunlight — and ergocalciferol (vitamin D2), found in foods. Vitamin D3 is generally preferred in clinical practice. It is closer to the more natural form, more potent, and believed to pose less of a toxicity risk, as it binds more efficiently to receptors in human tissues.
However, recent research indicates that the D2 form is better absorbed and utilized than previously believed. That’s good news for vegetarians, since it turns out that mushrooms, especially UV light-treated mushrooms, are a good source of vitamin D2. In fact, they are the only significant source of the vitamin for those following vegan diets.
• Vitamin E
Vitamin E functions as a fat-soluble antioxidant to help protect membranes from damage. The vitamin exists in eight main forms, alpha-, beta-, gamma-, and delta-tocopherols and alpha-, beta-, gamma-, and delta-tocotrienols. The tocopherols are saturated chains, and the tocotrienols are unsaturated counterparts. In the body, alpha-tocopherol is generally regarded as the dominant form.
This natural phenomenon has contributed to the oversight of tocotrienols. Yet, recent studies have shown that tocotrienols have superior antioxidant and anti-inflammatory properties over alpha-tocopherol. Moreover, studies of tocotrienols have revealed impressive capacities to prevent certain cancers and even kill cancer cells. This form of vitamin E also has been shown to help to protect tissues against radiation damage during cancer therapy.
In light of the different bioactive properties of tocopherols and tocotrienols, future studies should consider all isoforms of the vitamin. To date, despite the extensive study of vitamin E, only a small number of studies have considered isoforms beyond alpha-tocopherol, a direct result of the assumption that it is always the most bioactive.
While tocopherols have been one of the foremost natural antioxidants used in the food industry, the recognition of tocotrienols as having upwards of 400 times the antioxidant capacity has some manufacturers looking at this powerful fat-soluble vitamin form as an alternative.
Annatto oil, red palm oil, and rice bran oil all are excellent sources of tocotrienol vitamin E, and dovetail nicely with the current culinary trends focusing on South Asian, South American, and African cuisines.
• Vitamin K
Vitamin K consists of several compounds with a common chemical structure reflecting their origin. These compounds include phylloquinone (vitamin K1) and a series of menaquinones (vitamin K2). The menaquinone forms have unsaturated side chains and are named MK-4 through MK-13, based on side-chain length.
Vitamin K functions as a coenzyme (that is, it works together with an enzyme) that is required for the synthesis of blood clotting proteins and bone metabolism. Vitamin K1 is the main dietary form of vitamin K and is found in virtually all of the green leafy vegetables. The various forms of Vitamin K2 are produced in humans by healthy gut bacteria. MK-4 is derived from phylloquinone by a non-bacterial process.
Two compounds with similar structure to beta-carotene are lutein and zeaxanthin. They tend to accumulate in the macula portion of the retina and protect eyes from age-related macular degeneration, one of the leading causes of blindness in the world.
Another popular carotenoid — one easy to include in food and beverage formulations — is lycopene. Responsible for the red color in many fruits and vegetables, it is most prevalent in tomatoes, and tomato paste is a good source of the carotenoid. Many studies have indicated that increased levels of circulating lycopene are associated with reduced risk of prostate cancer.
In marine animals harvested for EPA and DHA, the carotenoid astaxanthin is a pink-red pigment. It is responsible for the pink coloring in flamingos, salmon, and shrimp. As with many carotenoids, astaxanthin acts as a fat-soluble antioxidant.
While it is known primarily as an anti-aging compound that helps protect skin from UV damage and restores suppleness to skin, some studies suggest astaxanthin could help lower blood pressure and reduce LDL cholesterol. Many studies indicate that it can help prevent atherosclerosis because of its potential to reduce inflammation and enhance both lipid and glucose metabolism.
No discussion of lipids and lipid soluble nutrients would be complete without giving a nod to Coenzyme Q10, also known as ubiquinone. CoQ10 is a fat-soluble component necessary for cellular energy production. But after approximately 35 years of age, the body becomes less efficient at manufacturing CoQ10. Only recently have better-for-you product developers recognized its value and begun incorporating it into certain formulations, such as bars and beverages.
The fact that, at its peak, the human body generally makes 10 times the amount of CoQ10 necessary for energy production suggests another function for this critical element. That function is believed to be its activity as a fat-soluble antioxidant, one capable of regenerating vitamin E. Not only can CoQ10 strengthen the heart muscle, it can help protect the heart from oxidative damage to the vessels that feed it.
The variety and complexity of lipids and lipid-soluble nutrients, along with a wide spectrum of beneficial lipid- soluble components, make the issue of fats in the diet a complex one. The simple fact is that fats are healthy and necessary food components for too many reasons to count. The only real question is one of balance.
Fatty acids are the real workhorses of fats, serving both as a fuel source (yielding 9kcal/g) and as precursors to a number of bioactive lipids that act as hormones, controlling mechanisms like platelet aggregation, inflammation, and smooth muscle contraction, as well as playing critical roles in immunity.
Lipids are vital sources of energy. They rank above protein as a source of fuel because there is no nitrogen to eliminate, but below carbohydrates, since energy from lipids cannot be delivered to hard-working cells as fast when explosive energy is needed. Yet, dietary fats and related compounds also are essential to the function of every cell in the body. Although needed in small amounts, they perform big jobs and can add inimitable value to many formulations.
Mark Anthony, PhD, is an adjunct professor of nutrition science at St. Edwards University, Austin, Texas, and co-director of S/F/B Communications Group. A former lab director of The Institute for Biomedical Research at the University of Texas, Anthony also is the author of Gut Instinct: Diet’s Missing Link (Leap Forward Press, 2003), a book that presents a unique investigation into carbohydrates and the fundamental chemistry of nutrition and metabolics on maintaining health as people age.
He can be reached at firstname.lastname@example.org.
PS, I Love You
All biological membranes are composed of a double layer of specialized lipids called phospholipids. These allow an interface between water-soluble and fat-soluble components because they contain both hydrophobic (water-fearing) and hydrophilic (water-loving) regions.
This property allows phospholipids to naturally form membranes that wall off the outside of a cell and create a protected environment. In addition to membranes, phospholipids transport triglycerides and fat-soluble nutrients through the blood to tissues.
Food manufacturers have taken advantage of the natural property of phospholipids and their tendency toward self-assembly to create nutrient delivery systems within beverages. This is an outgrowth of drug-delivery systems that employ phospholipids to create a number of different specialized structures called liposomes. Liposomes can carry vitamins (both water- and fat-soluble), enzymes, antimicrobial polypeptides, essential oils, and phenolic compounds.
Phospholipids exist in a variety of forms, two of which, phosphatidylserine (PS) and phosphatidylcholine, have been gaining attention as functional supplements. Choline is a precursor molecule to the neurotransmitter acetylcholine. Phosphatidylcholine has been investigated for its potential to delay the onset and reduce the severity of cognitive decline in Alzheimer’s disease.
PS is being studied for a number of functions. They include improving function of nerve cells and enhancing memory. In addition, PS has a modulating effect on cholesterol metabolism, the inflammatory response, and the blood coagulation system, which could give it therapeutic value in preventing atherosclerosis.
Some studies suggest a role for PS in the cell cycle of life and death, naturally linking it to potential cancer treatments. PS has been used in infant formula and as a supplement for mood and cognitive support.
ABCs of CBD
While much attention goes to the potential of medical marijuana to relieve the negative side effects of chemotherapy, reduce symptoms of glaucoma, and ameliorate symptoms of other diseases and dysfunctions, many of the compounds in the cannabis plant are less known than the primary psychoactive component, a cannabinoid compound called tetrahydrocannabinol (THC), although they might have equally positive qualities.
Cannabinoids are a class of compounds with great therapeutic potential. Cannabidiol (CBD) is one of these and is found concentrated in the oils. Unlike THC, CBD is not psychoactive. Studies suggest that CBD can reduce inflammation and pain. Research also indicates some positive mood benefits from CBD oil, plus other functions, such as helping reduce withdrawal symptoms from nicotine and decreasing the severity of epileptic seizures. One of the most promising uses of CBD is its potential anti-cancer agent against certain tumors. Its actions include possibly inhibiting the invasive and metastatic tendencies of tumors by impeding the vascularization of invading tumors, reducing their energy supply.
In laboratory studies, CBD’s properties appear to be directed at cancer cells only, having no effect on normal cells. There is also the possibility that, in concert with standard chemotherapy, CBD can increase the effectiveness of treatment allowing for a less damaging application of the chemotherapy.
Another group of potentially beneficial compounds in cannabis include terpenes. These lipid-soluble, aromatic compounds are in virtually all plants and have demonstrated a number of health benefits. The recent legalization of cannabis products in many states is leading to a boom in the creation of foods and beverages containing cannabis ingredients. To find out more, check out the spring issue of Prepared Foods’ Cannabis Products supplement next month.