By Alisa G. Woods, PhD | May 22, 2009 1:15 pm
Maybe primitive humans had it better than we think. Sure, they had to forage and struggle just to eat, but what they ate was actually more nutritious than what many modern humans consume daily in industrialized countries like the United States. Even the food in many developing countries today, usually grown locally without advanced agricultural techniques, is more nutritious than the typical American diet. Improved food production in the West has replaced hunting and gathering and traditional farming with simply going to the supermarket. Thus for many, inexpensive food is readily available. Ironically, these advances in convenience and abundance have worsened the typical diet and caused setbacks in health.
Much recent research points toward a specific nutritional problem with modern man’s diet: a lack of essential fatty acids. According to Artemis Simopoulos, M.D., President of the Center for Genetics, Nutrition, and Health in Washington, DC, it is not an overall deficiency of these nutrients that is the problem, but an imbalance of different types of essential fatty acids, due to high amounts of omega-6 and very low amounts of omega-3 fatty acids in the typical modern diet.
According to Simopoulos, “Today’s Western diets are characterized by an increase of energy intake over energy expenditure, high amounts of saturated fat, high amounts of omega-6 fatty acids, high amounts of trans fatty acids, and very low amounts of omega-3 fatty acids. They are [also] very low in antioxidants, and the foods contain less vitamins and minerals than the foods human beings evolved to eat.”
Essential fatty acids are the focus of many current news stories about nutrition, but what are they exactly, and why is it so important to eat enough of them and to keep them in balance?
Essential fatty acids include two types: omega-3 and omega-6. They are called “essential” fatty acids because they cannot be naturally produced by the human body, so they have to be consumed as part of the diet. They are polyunsaturated, meaning they have two or more carbon—carbon double bonds in each molecule. Polyunsaturated fats are liquid at room temperature, when refrigerated, and even in the freezer.
Omega-3 fatty acids are named based on their chemical structure. A biochemist would tell you that this means they have their first carbon—carbon double bond between the third and fourth carbon atoms in the molecule. Three types of omega-3 fatty acids important to nutrition exist: Alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). ALA is produced by leafy green vegetables and can be converted into EPA and DHA by the body. One rich source of ALA that can be purchased in health-food stores or even some supermarkets is flaxseed oil. Canola oil, walnuts, and walnut oil also contain ALA. EPA and DHA can be consumed directly by eating fish and certain other sea creatures, or by taking fish oil supplements.
Omega-6 fatty acids are also named based on their chemical structure, with the first of their carbon—carbon double bonds between the sixth and seventh carbon atoms. They are formed from linoleic acid (LA), which can be consumed from cereals, eggs, poultry, vegetable oils, whole-grain breads, baked products, and margarine. The body can convert LA into gamma-linolenic acid (GLA) and then into arachidonic acid (AA). GLA can also be directly obtained from plant oils such as evening primrose oil, borage oil, black currant oil, and hempseed oil. It is also present in human breast milk. AA can be obtained from meat, some seaweeds, egg yolks, and shrimp. It is also found in small amounts in human breast milk and cow’s milk.
Essential fatty acids are vital for the body’s normal development. They are a necessary component of cell membranes throughout the body; they are also particularly important for development of the brain and the retina. Both omega-3 and omega-6 fatty acids are required for neurons, the information-processing cells of the brain and nervous system, to function properly. They are used to make brain cell membranes as well as neurotransmitters, the chemicals that neurons use to communicate. Deficiencies in essential fatty acids can also cause reduced growth, infertility, and an inability to heal wounds and fight infection.
Deficiencies in omega-3 fatty acids during pregnancy and in babies can cause developmental problems in the nervous system, including the visual system. Breast milk is a good source of essential fatty acids, including omega-3. DHA in particular is important for brain and eye development. For this reason, some baby formulas are now supplemented with essential fatty acids.
Today’s humans eat less of omega-3 and more of omega-6 fatty acids primarily because they eat less fish and fewer green, leafy vegetables. In addition, modern farming techniques that emphasize mass production of food tend to produce meat, fish, eggs, and vegetables that are lower in omega-3 and higher in omega-6 fatty acids than foods grown in the wild. One reason for this is that farm animals are fed grains, which are high in omega-6.
Too much of omega-6 fatty acids in the diet may lead to inflammation (although some studies indicate that one specific omega-6 fatty acid, GLA, can actually be anti-inflammatory). Inflammation is a response of the immune system that is designed to protect the body against injury or infection, but sometimes it can actually cause or worsen diseases.
Relative decreases in the consumption of omega-3 fatty acids may lead to a number of medical problems, including cardiovascular disease, cancer, osteoporosis, premature birth, cystic fibrosis, depression, asthma, and diabetes. Increasing consumption of omega-3 fatty acids usually reduces consumption of omega-6; this in turn can reduce inflammation and increase blood vessel dilation. These responses may help in the treatment or prevention of many diseases.
The most effective way to eliminate the imbalance of omega-6 and omega-3 is to change one’s diet. Simopoulos states, “The simplest recommendation that anyone can make at this point is to change vegetable oils. In other words, not to eat or cook with corn oil, sunflower, safflower, cottonseed, or soybean oils because they are very high in omega-6 and contain practically no omega-3. Instead, use a combination of olive and canola oils or flaxseed oil or walnut oil.” Simopoulos also recommends eating more green, leafy vegetables, fish, and servings of fruit. She has written a book called The Omega Diet: The Lifesaving Nutritional Program Based on the Diet of the Island of Crete, which describes her recommendations in greater detail. (Also check out “Omega Bites” for more information about how to replace omega-6 fatty acids in your diet with omega-3 fatty acids.)
Several studies have provided evidence that omega-3 fatty acids may be good for preventing or treating diabetes. The first piece of evidence comes from studies of people who eat large amounts of fish. These populations, which include residents of Greenland and Alaska, tend to have a lower incidence of diabetes. People who immigrate to India, a country in which fish is not regularly consumed, tend to acquire diabetes at a higher rate than their peers who remain in their native lands. Studies of rats have shown that omega-3 fatty acids suppress the development of insulin resistance in those rats given a high-fat diet.
Studies examining the effect of omega-3 fatty acids in healthy people have consistently shown a 20% to 50% reduction in triglyceride levels from consuming 2—3 grams of omega-3 per day. This effect is even greater in people with elevated triglycerides, including those with diabetes. Reductions in triglycerides and increases in HDL (high-density lipoprotein, or “good”) cholesterol have been reported in people with both Type 1 and Type 2 diabetes who consume omega-3 fatty acids, generally DHA and EPA together.
Reductions in LDL (low-density lipoprotein, or “bad”) cholesterol have also been shown in similar studies of people with both types of diabetes, although increases have also occurred. These increases are most likely offset by increases in HDL cholesterol and decreases in triglycerides. Furthermore, the type of LDL cholesterol that is produced in people who consume more omega-3 is less likely than others to cause heart disease. This is because it contains more omega-3 fatty acids, giving it a larger particle size. Ingestion of omega-3 fatty acids also reduces blood pressure in people with either Type 1 or Type 2 diabetes.
Recent research has not convincingly shown that omega-3 fatty acids improve blood glucose control in people with diabetes – but studies conducted so far may not have had enough subjects, so larger studies are still needed to examine this issue. So far, no studies of humans have looked at whether diabetic complications may be reduced by omega-3 fatty acids, but experiments with animals have suggested that omega-3 may prevent diabetic neuropathy (nerve damage).
Clinical trials in progress will further examine the effects of omega-3 fatty acids in people with diabetes. These include ASCEND (A Study of Cardiovascular Events in Diabetes), which will look at people with Type 1 and Type 2 diabetes, and the AFORRD (Atorvastatin in Factorial with Omega-3 fatty acids Risk Reduction in Diabetes) trial, which will examine people with Type 2 diabetes. Preliminary results from AFORRD have demonstrated reductions in triglycerides of 5.6% but no reduction in cardiovascular disease risk.
The ORIGIN (Outcome Reduction with Initial Glargine Intervention) trial will examine the use of diabetic insulin glargine – a synthetic, long-acting insulin – and omega-3 fatty acids in over 12,000 people with diabetes. This trial will be particularly important for understanding the use of omega-3 fatty acids in diabetes control, due to the large number of people enrolled in it.
People with diabetes have a risk of developing heart disease three to four times greater than the general population. Studies of omega-3 fatty acids and heart disease are therefore of particular interest to people with diabetes. The consumption of high levels of omega-3 fatty acids, both DHA and EPA, for heart health has been referred to as “the Eskimo diet,” based on several studies showing that Greenland Inuits (Eskimos) have a lower prevalence of coronary heart disease than Western Europeans, specifically Scandinavians. Other populations that consume high levels of fish, such as the Japanese and Alaskans, similarly have a decreased incidence of death from coronary heart disease. Several studies of omega-3 fatty acids in Western populations have found that a higher omega-3 fatty acid intake predicts a lower incidence of heart disease.
Eating omega-3—rich diets has been shown to prevent heart attacks, possibly because omega-3 fatty acids prevent blood clotting and heart irregularities in addition to lowering triglyceride levels and increasing HDL cholesterol. In fact, the American Heart Association recommends that people eat fish high in both EPA and DHA – particularly fatty fish such as mackerel, sardines, albacore tuna, and salmon – at least twice a week. It also recommends that people with documented coronary heart disease increase their intake of total DHA and EPA to about 1 gram per day, either in the form of fish or in a supplement. People with elevated triglycerides should consider consuming 2—4 grams per day, although according to the association, people who take over 3 grams daily should be monitored by a physician due to a theoretical increased risk of bleeding, despite the lack of firm clinical evidence of this. For more about these recommendations, visit www.americanheart.org/presenter.jhtml?identifier=4632.
Several studies have suggested that decreased intake of omega-3 fatty acids may increase the risk of depression, and that supplementing the diet with omega-3 fatty acids may help alleviate symptoms of depression. Essential fatty acids may help restore normal levels of neurotransmitters such as serotonin, which are believed to be lower in people with depression, and may also increase levels of molecules that benefit the brain, such as brain-derived neurotrophic factor.
People with diabetes are at higher risk for depression, and depression tends to worsen diabetes control. For this reason, awareness of factors that may contribute to the development of depression is particularly important for people with diabetes. (Read more about depression and diabetes at www.diabetesselfmanagement.com/articles/Emotional_Health.)
Although DHA is the predominant omega-3 fatty acid found in the brain, EPA may be a more effective treatment for depression. Some studies have shown that either EPA with DHA or EPA alone is effective at treating depression, but that DHA alone is not. More studies still need to be done to determine which essential fatty acid or combination of essential fatty acids is best for treating depression. Studies also need to help determine what dose of essential fatty acids should be used and for how long.
When deciding whether to supplement your diet with omega-3 fatty acids, there are several things to consider. As usual, it is best to consult your physician or dietitian, since a medical professional who knows you can make the best recommendation based on your personal health, lifestyle, and diet.
If you decide to increase your fish consumption or to use fish oil supplements, select fish and supplements that contain the lowest obtainable levels of polychlorinated biphenyls (PCBs), mercury, and dioxins. These are waterborne pollutants found in fish that may have harmful effects if consumed. To learn more about mercury levels in commercial fish, visit this site provided by the U.S. Department of Health and Human Services and the U.S. Environmental Protection Agency: www.cfsan.fda.gov/~frf/sea-mehg.html. To find out more about fish oil supplements and suppliers that have been United States Pharmacopeia (USP) verified (certified to contain the level of active ingredient listed on the label), go to www.usp.org/USPVerified/dietarySupplements.
Flaxseed oil is another potent source of omega-3 fatty acids. It is rich in ALA, the precursor of DHA and EPA. Not all ALA ingested is converted by the body, however, and the ability to convert ALA into DHA and EPA may be impaired in people with diabetes. Despite these limitations, flaxseed may be a good option for people who do not want to consume fish products.
Although further research is needed to more fully understand how essential fatty acids work, current evidence suggests that almost everyone would be better off with increased consumption of omega-3. It is important to note that essential fatty acids are, in fact, fats, so take care not to increase total intake of fat or calories when adding them to your diet. In nearly all respects, however, foods and supplements that contain omega-3 fatty acids seem to be a good catch.
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