by Bonnie Bruce, DrPH, MPH, RD
Have you ever considered the way your ancestors lived? Not your grandparents, but relatives who lived way back in time — such as 10,000 years ago, when humans were hunter-gatherers. Imagine what it must have been like to subsist only on what you could hunt, fish, or forage. The human diet consisted primarily of plant foods, with some wild meats when the hunting was good. Limited though it may seem to us, our ancestors’ diet met their bodies’ needs and allowed them to survive.
That kind of life is far from today’s reality. Most of us have easy access to all the food we want, and a wide variety at that. And we live much longer, on average, than our ancestors did. But we also have high rates of chronic diseases such as heart disease and diabetes, health problems that researchers think most of our ancestors didn’t have to contend with.
What accounts for the rise in these diseases? Some scientists and nutrition experts believe that we have essentially the same genetic makeup as when we were living in caves and off the land, so changes in our genes don’t seem to be the culprit. Our longer lifespan may have something to do with it, since many chronic diseases are associated with age. But many clues point to today’s Western diet and lifestyle. We exercise far less than our ancestors did, we eat far more refined, sugary, salty, and high-fat processed foods, and too many of us are overweight or obese. All this makes some researchers wonder if our lifestyles have changed too fast for our genes to keep up — and whether a diet closer to that of our ancestors might be better for our bodies.
For too many of us, the great majority of our calories come from processed meats and other foods, added sugar, and refined grains, none of which existed during our hunter-gatherer years. Today, many of us are becoming more aware of the ill effects of eating too many processed foods and are trying to make better choices. Those of us concerned about heart health may be aware of the need to cut down on foods high in saturated and trans fats, but few of us are aware of a dietary issue that some scientists believe may be a contributor to many of our current health problems: an imbalance in our dietary intake of certain types of fatty acids. This article explains what fatty acids are, what foods they are found in, and how you can achieve a better balance.
Fatty acids are the basic building blocks of the kind of fat that is found in food and that makes up our body fat. Three fatty acid molecules attach to a three-slot chemical backbone to form larger fat molecules called triglycerides. During digestion, the body splits up the triglyceride molecule and then absorbs the parts. The body uses the fatty acids as they are, or when it is able to, it changes some of them into different metabolic substances that perform a wide variety of functions.
Since the early days of nutrition research, chemists have identified a few hundred different fatty acids. In the early 20th century, scientists discovered that a few fatty acids are essential for life and normal growth and development. They found that the body is unable to manufacture these fatty acids, and thus we can get them only by eating foods that contain them. Originally, scientists called these essential fatty acids “vitamin F,” but they later reclassified them as fats rather than vitamins. (To this day, however, some companies sell fatty acid supplements erroneously promoted as “vitamin F.”)
Essential fatty acids are indispensable for numerous biological activities that affect growth, development, and overall health, and they are also a source of the body’s energy. They are used to produce hormonelike substances that regulate several body functions, including blood pressure, blood clotting, brain development, and immune system responses, including inflammation. They influence cell behavior, participate in genetic activities, and are a component of cell membranes. Simply put, we could not live without them.
There are two main fatty acids that are considered essential. These are linoleic acid and linolenic acid, both of which belong to a class of fats called polyunsaturated fats. Linoleic acid is the primary member of a family of polyunsaturated fats called omega-6 fatty acids. Linolenic acid is the primary member of the omega-3 fatty acid family. These two essential fatty acids are used to make other fatty acids important for health and growth. Without them, the body would be unable to manufacture certain other fatty acids and compounds. Examples of these beneficial products include other members of the omega-3 family called eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are best known for being found in fish oils.
Because our bodies cannot make linoleic acid or linolenic acid, we need to get both omega-6 and omega-3 fatty acids through foods that contain them.
Omega-6s. It is easy to get omega-6 fatty acids in our diet. They are abundant in both natural and man-made foods, and we get plenty of them. There are liberal amounts in vegetable and seed oils such as corn, safflower, soybean, sunflower, and cottonseed oils, as well as leafy greens, seeds, and nuts. (Coconut, cocoa, and palm oils are exceptions — they are saturated fats and not sources of omega-6s or omega-3s.) Omega-6 fatty acids frequently appear in junk foods, fast foods, and many processed foods, such as crackers, cookies, and sweets. Other sources include supermarket meat, eggs, farmed fish, and dairy foods that come from animals fed grains rich in omega-6 fatty acids. (This diet is typical for most farmed animals nowadays.)
Omega-3s. In comparison to omega-6 fatty acids, there are fewer naturally occurring sources of omega-3s. Saltwater fish usually have higher levels of omega-3s than freshwater fish. Fish rich in omega-3s include anchovies, salmon, sardines, herring, mackerel, albacore tuna, and lake trout. Omega-3s are also found in some plant foods, such as flaxseed, walnuts, walnut oil, hazelnuts, almonds, pecans, cashews, and macadamia nuts. Cod liver oil is another good source, and some less common foods, such as purslane, seaweed, and soybean sprouts, contain omega-3 fatty acids too. We can also get omega-3 fatty acids from dietary supplements, such as those made with fish oils.
Wild game, seafood, and farmed animals that feed on fresh pasture or dried grasses (“grass fed”) — as they were likely to have done in hunter-gatherer times — are richer in omega-3 fatty acids. Plants grown through modern agriculture tend to contain fewer omega-3 fatty acids than wild plants.
The good news is that getting enough of either essential fatty acid is rarely a problem. In modern times, the issue is whether we are getting them in a proper balance. Some scientific evidence suggests that our genetic makeup is geared to function best when we balance our intake of these two kinds of fatty acids. History suggests that before we embraced our Western style of eating, we consumed roughly equal amounts of omega-6s and omega-3s. According to some research estimates, we now consume 14–25 times more omega-6 than omega-3 fatty acids. In addition, some experts believe that we consume too few omega-3 fatty acids overall.
There is scientific evidence showing that when omega-6 and omega-3 fatty acid intake is balanced, the body is more likely to run like an efficient motor with all its workings in order. A high ratio of omega-6 to omega-3 fatty acids in the diet has been shown to upset the body’s normal metabolic routines and may explain — at least in part — the increase in some chronic health problems, such as heart disease.
Studies have shown that a diet high in omega-6s can increase the production of pro-inflammatory substances in the body. Inflammation is part of our body’s normal immune response — when a foreign substance enters the body, immune-system cells gather at the infection site to attack the invader. Such attacks can result in the heat, redness, and tenderness we know as inflammation. But when inflammation happens in the absence of an infection or becomes chronic, it can disrupt the body’s normal functioning. Inflammation is an underlying problem in conditions such as rheumatoid arthritis (RA) and has also been linked to chronic diseases such as heart disease and diabetes.
In contrast, omega-3s help the body make substances that help to quench inflammation. Many studies have reported that omega-3 fatty acids may help reduce inflammation in artery walls, joints (in RA), and other tissues. Some studies in which the ratio of omega-6 to omega-3 fatty acids has been decreased have demonstrated benefits to people affected by inflammatory conditions such as RA, as well as favorable changes in other metabolic activities. This includes helping keep the blood from forming clots, which are a risk factor for heart attack and stroke. Some preliminary research suggests that omega-3s may also help protect against other chronic conditions, such as Alzheimer disease, but more studies need to be done.
Although more research is needed to confirm benefits of balancing our intake of omega-6s to omega-3s, the known benefits of omega-3s suggest that increasing omega-3 intake relative to omega-6 intake is probably a good thing.
First, become aware of what you eat and identify where you might be able to make some shifts in your intake of these essential fatty acids. This could mean reducing your use of vegetable oils that are high in omega-6 fatty acids, minimizing your intake of processed, junk, and fast foods, or eating less grain-fed meat and fewer dairy foods. At the same time, replace these with foods that are high in omega-3 fatty acids. Increase your intake of omega-3–rich fish and use oils such as olive and canola oil. Current nutrition advice is to eat fish twice a week as part of a healthful diet that includes ample fruits and vegetables of different colors and types, whole grains, and some lean meat and poultry. Ideally, you’d work a variety of fish into your diet, with an emphasis on oily fish such as salmon and trout.
Of concern to many of us, though, is the potential for fish to be contaminated with mercury, polychlorinated biphenyls (PCBs), and other harmful chemicals. Because of the risk of contaminants, young children, nursing mothers, pregnant women, and women planning to become pregnant should avoid shark, swordfish, king mackerel, and tilefish and limit albacore tuna consumption. For the rest of us, eating a 3-ounce serving of oily fish twice a week is generally considered safe. Fish alternatives include omega-3–rich plant foods such as flaxseed and walnuts. One ounce of walnuts (about 1/4 cup and roughly 200 calories) contains roughly the same amount of omega-3s as 3 1/2 ounces of salmon. However, it is not quite clear whether the omega-3s from plant sources are as potent or have all the same health effects as those from fish oils.
Taking a fish-oil or other omega-3 dietary supplement can also help to increase intake, but be aware that there are concerns about their safety and benefit. Nutrition experts typically advise getting nutrients from food rather than supplements because different nutrients in foods often work together, and it’s unclear that getting more of an isolated individual nutrient provides the maximum health benefit. In addition, like fresh fish, fish-oil supplements may contain PCBs or other contaminants. Fish oil has anti–blood-clotting effects, and taking it in large doses (more than 3 grams a day) can increase the risk of bleeding, as can taking it with other medicines that have anti-clotting effects, such as aspirin. Some people have bad breath or a bad taste in their mouth when taking fish-oil supplements. The best advice is to take these supplements only under the guidance of a physician.
An important consideration with all dietary supplements is that they are not regulated by the Food and Drug Administration. Supplement manufacturers do not have to prove safety or effectiveness before they sell a product, and there’s no guarantee that they are free of contaminants or contain the amount of the active ingredient they say they contain. If you decide to try a fish-oil supplement, look for one with a “USP Verified” seal given by United States Pharmacopeia, an independent, nonprofit organization that tests supplements and certifies those that meet its purity and potency standards.
Not all nutrition experts agree that eating like a caveman would take care of at least some of our modern ills, but some share the view that we are living in an environment that may be in conflict with our genetic constitution. Getting closer to balancing our intake of omega-6 and omega-3 fatty acids, in addition to eating more fruits and vegetables and fewer processed foods, could be one way of helping to get our diet back into sync with how our body operates best.
Last Reviewed March 7, 2013
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