THE OMEGA FATS

Learn more about the various types of omegas and how they can contribute to overall health.

 

Many consumers have heard about the health benefits of omega-3 fatty acids, but most are unaware of the other omega fats that play various roles in improving overall health. We know there are several omegas found in foods and supplements, but it’s important to know exactly what they are, what role they play in the body, how they contribute to health.


Fatty Acids’ Many Roles
The length of the carbon chain, the degree of saturation, and the position of the double bonds affect the roles fatty acids play in the body. Dietary fats may be oxidized as energy or stored as triglycerides. In addition, dietary fats regulate gene expression, modulate ion channels, are incorporated into cell membranes where they affect membrane fluidity, and more.

Polyunsaturated Fatty Acids (PUFAs)

Omega-3 Fatty Acids
A 2008 review concluded that fish or fish oil providing approximately 250 mg of EPA + DHA daily significantly lowers the risk of coronary heart disease (CHD) death by 36% compared with not consuming EPA + DHA.

Other research shows that omega-3 fatty acids in fish may have health effects beyond the heart. Studies suggest that EPA and DHA intake is critical for the development of the fetal brain and retina. In fact, one small study found that mothers who took DHA supplements during pregnancy gave birth to children who demonstrated better problem-solving skills at 9 months old.

It’s been suggested that depressed patients and those with Alzheimer’s disease may have low levels of DHA. Recent studies have found that EPA and DHA supplementation may reduce symptoms of depression and improve cognitive functioning of patients with mild Alzheimer’s disease.  In addition, these fatty acids potentially have strong anti-inflammatory effects. Other areas of research include their role in the treatment or prevention of age-related macular degeneration, ADHD, rheumatoid arthritis, and asthma.

EPA and DHA often are the focus of research, but the shorter-chain omega-3 fatty acid ALA also provides health benefits. There is a growing evidence base demonstrating a beneficial role of ALA in the primary and secondary prevention of cardiovascular disease.  Based on the epidemiologic data, there are comparable CVD [cardiovascular disease] benefits for EPA + DHA vs. ALA. However, despite there being some clinical trial evidence about CVD benefits of ALA, there have been more studies conducted with EPA + DHA.  Other studies also support ALA’s potential benefits in chronic inflammation, the metabolic syndrome, inflammatory bowel disease, cancer, lupus, and rheumatoid arthritis.

Omega-6 Fatty Acids
Linoleic acid (LA), an omega-6 fat, is the most common PUFA in the diet. The appropriate intake of LA and other omega-6 fatty acids is controversial. LA is the precursor to arachidonic acid (AA), which can be metabolized into bioactive eicosanoids associated with inflammation and chronic disease.

Researchers have debated the merits of limiting omega-6 fatty acids in the diet to decrease the production of inflammatory compounds. There has been further concern that high LA intake will result in decreased production of omega-3 anti-inflammatory eicosanoids because of the competition of enzymes between the two classes of PUFAs. The Food and Agricultural Organization of the United Nations and the World Health Organization recommend that an intake of omega-6 fats should equal 2.5% to 9% of energy, or total calories.

Omega-6 fatty acids are not responsible for ill health.  Increasing LA in the diet doesn’t significantly increase AA in the tissues; thus only a small portion of LA contributes to inflammatory eicosanoids.  AA also is important for resolving inflammation.  Arachidonic acid is not just a bad guy; it also helps the body recover. The same proinflammatory compounds trigger resolution and bring tissues back to health.  Results of systematic reviews should reassure individuals that both omega-3 and omega-6 fatty acids are beneficial.

Monounsaturated Fatty Acids (MUFAs)

Omega-9 Fatty Acids
Omega-9 fatty acids can be synthesized in vivo; therefore, they aren’t essential to the diet. However, dietary omega-9 fats affect cardiovascular risk factors. When they replace saturated fatty acids in the diet, LDL cholesterol levels improve, HDL cholesterol levels remain stable, and insulin resistance improves.  When replacing carbohydrate in the diet, omega-9 fats increase HDL cholesterol levels and decrease triglyceride levels.

Oleic acid is the predominant omega-9 fatty acid in the diet. Researchers became interested in omega-9 fats because of the observed health benefits of consuming a Mediterranean-style diet, which is high in oleic acid mainly from olive oil.   Also, the omega-9 fatty acids may improve both cardiovascular risk and insulin resistance.

Omega-7 Fatty Acids
Because of the potential health benefits of omega-7 fats reported, you may hear about palmitoleic acid. It is purported to reduce inflammation, increase satiety, promote weight loss, lower cholesterol and triglyceride levels, and improve insulin resistance.

There are two forms of this fatty acid.   Unlike the metabolic effects of most trans fats, some research suggests that trans-palmitoleic acid has positive health effects, including improved insulin resistance and blood lipids.  However, don’t jump on the omega-7 bandwagon just yet,  because more research must be done. There are both positive and negative associations with omega-7 intakes. It’s not so clear-cut.

What is Best?
It’s common to have questions about which fats are the most healthful and which are the best cooking oils to use. Emphasize overall diet quality, with an emphasis on plant-based eating, including plant-based fats.

Consistent with the AHA’s recommendations, individuals can consume fatty fish such as salmon, tuna, mackerel, and lake trout twice per week to obtain EPA and DHA.  For convenience, buy tuna, salmon, and sardines in cans or pouches.

Consume nuts and seeds a few times each week. And if you love butter, try a trans fat–free  or a plant stanol/sterol–fortified spread such as Smart Balance or Earth Balance.

Most recipes can be adjusted for fat quality, but some beg for solid fat. For classic cookies such as chocolate chip, use one-half butter and one-half canola oil.  For cakes, replace 1/2 cup butter with 1/3 cup canola oil, and if the cake is too dense, whipping the egg whites can increase the airiness.

Take care not to over-consume healthful fats.  While they are good for you, all fat contains 9 calories per gram, so the total calories quickly add up.  Each unsaturated fatty acid offers something unique, so try to eat a variety of foods rich in unsaturated fats.

Jill Weisenberger, MS, RDN, CDE

 

Sources and Dietary Reference Intakes of Selected Fatty Acids


Fatty Acid

Major Food Sources

US Dietary Reference Intake (DRI)

Usual Daily Intake

Alpha-linolenic acid (18:3, n-3)

Flax, chia and hemp seeds, walnuts, canola and soybean oils

Adequate Intake (AI): 1.1 to 1.6 g, 0.6% to 1.2% of energy intake

1.4 to 1.8 g

Eicosapentaenoic acid (20:5, n-3)

Fish and seafood

No DRI established

30 to 40 mg

Docosahexaenoic acid (22:6, n-3)

Fish and seafood

No DRI established

60 to 80 mg

Linoleic acid
(18:2, n-6)

Soybean and corn oils, shortening

AI: 12 to 17 g, 5% to 10% of energy intake

13 to 18 g

Arachidonic acid
(20:4, n-6)

Meat, poultry, eggs

No DRI established

120 to 180 mg

Palmitoleic acid
(16:1, n-7)

Macadamia nuts, blue-green algae

No DRI established

1.2 g

Oleic acid
(18:1, n-9)

Olive and canola oils, avocado, beef tallow, lard

No DRI established

27 g

— Source: Vannice G, Rasmussen H. Position of the Academy of Nutrition and Dietetics: dietary fatty acids for healthy adults. J Acad Nutr Diet. 2014;114(1):136