Omega-3 Fatty Acids Transcend the Heart

he Inuit people who live in the Arctic probably consume more dietary fat than any other culture on earth. Add to this the fact that fruits and vegetables rarely pass their lips (plants don’t grow too well in ice—even iceberg lettuce likes a warm, sunny climate), and a bleak nutritional picture begins to emerge. To put it bluntly, their diet isn’t going to win any awards for being especially healthy.

But if their diet is so poor, why do the Inuit have such a low incidence of heart disease and certain types of cancer? Nutritionists and medical researchers were perplexed by this apparent contradiction, so they investigated the matter and found that a fish-rich diet was the Inuit’s saving grace. Coldwater fish, as it turns out, are a particularly rich source of health-promoting omega-3 fatty acids. The researchers concluded that the high intake of these beneficial compounds, regardless of other nutritional deficits, protected the Inuit from many chronic diseases. But why are omega-3 fatty acids so good for us?

A High Proportion of Omega-3s Is Better

Omega-3 fatty acids affect certain cellular metabolic processes involving a variety of hormones that play important roles in inflammation, cell proliferation, cell death, and the immune response. High levels of long-chain omega-3 fatty acids, especially EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), affect these processes in beneficial ways that favor improved health.* By contrast, diets that are rich in related compounds called omega-6 fatty acids (typically found in cooking oils such as safflower, corn, and soybean oil) may increase the risk of many chronic diseases, even though they, like the omega-3s, are vital to your health—but in lesser amounts than the omega-3s.

*EPA and DHA are called “conditionally essential” fatty acids: your body can make them, but only to a very limited extent. Dietary intake through food or supplements is required to provide adequate amounts of these vital compounds. And they’re called fatty acids because, like many other long-chain organic acids, they are chemical precursors to fats.

It’s a matter of proportion. Many researchers believe that the total amounts of omega-3 and omega-6 fatty acids in your body are not as important as the ratio of omega-3s to omega-6s. A higher ratio (more omega-3s than omega-6s) is believed to decrease the risk of chronic disease and to promote improved health. This ratio appears to be especially important in cancer, observes Dr. Elaine Hardman from Louisiana State University in Baton Rouge.¹ She notes that “Both animal and epidemiologic studies indicate that the ratio of n-3 to n-6 fatty acids in the diet is particularly important to the reduction of cancer risk.” (In the nomenclature of these compounds, the letter n is sometimes used instead of omega.)

What is the best way to optimize this ratio? Simple: it is to increase your dietary omega-3 fatty acid intake, preferably while simultaneously decreasing your consumption of omega-6 fatty acids. And what is the best source of omega-3 fatty acids such as EPA and DHA? It’s coldwater fish, such as salmon, tuna, mackerel, halibut, and herring. For those who may not be too keen on fish, a more convenient way to obtain these compounds is by taking fish-oil supplements.

Omega-3-Rich Diets Reduce Cancer Risk

A number of epidemiologic studies (scientific studies that examine large populations for correlations between disease and some measurable factor, such as diet) suggest that people who consume foods that are rich in omega-3 fatty acids have reduced incidences of certain types of cancer. Current research suggests that these compounds (and the fats that are made from them in the body) are particularly protective against breast and colon cancer.

Researchers at the University of Nevada recently published a paper in Cancer Letters demonstrating that omega-3 fatty acids reduce the growth of human colon carcinoma cells.² Their method, which was fairly complex, relied on transplanting human tumor cells into mice whose immune systems had been compromised so that they would be particularly susceptible to cancer. After the transplant, the mice were divided into different groups: two groups were fed a diet supplemented with omega-3 fatty acids, while the other groups were fed either a low-fat (8% corn oil) or high-fat (24% corn oil) diet that lacked omega-3 fatty acids (recall that corn oil is rich in omega-6 fatty acids).

Omega-3s Suppress Tumors

In all the mice, the size of the cancerous tumor was measured at the beginning of the study and again at the end, 54 days later. Mice in the two groups receiving the omega-3 fatty acid-supplemented diet had significantly smaller tumors—up to 90% smaller—than the mice on the omega-6-rich/omega-3-deficient diets. The authors concluded that “These findings indicate that dietary omega-3 fatty acids possess significant tumor-suppressing properties and that the primary tumor-suppressing fatty acid is docosahexaenoic acid [DHA].”

Another important finding was that the low-fat diet (8% corn oil) significantly reduced the growth of tumor cells compared to the high-fat diet (24% corn oil). Together, these results suggest that a good way to inhibit tumor cell growth is to decrease total fat intake while increasing the consumption of omega-3 fatty acids. Indeed, this view is shared by Dr. Hardman, who suggests that “. . . increasing the consumption of n-3 fatty acids may be a nontoxic way to augment cancer therapy and to significantly increase life span.”

How Do Omega-3 Fatty Acids Work?

Beyond the study just mentioned, why do researchers think that omega-3 fatty acids are a good addition to conventional cancer therapy and may also help prevent the occurrence of cancer in the first place? The answer is complex, because omega-3 fatty acids have many beneficial functions. For example, they help regulate the expression (the “on-or-off” status) of certain genes in cancer cells. As a result, they may tell cancer cells to die—a process called programmed cell death, or apoptosis, in medical jargon.

Another possibility is that they may instruct cancer cells to stop dividing by inhibiting mitosis—the process by which one cell becomes two cells with all the same genetic material—which is almost as good as telling them to die. Alternatively, omega-3 fatty acids may encourage cancer cells to differentiate into a cell type that is no longer capable of replicating itself without limit and that is thus no longer cancerous.

Cancer cells need a steady supply of nutrients to survive and proliferate. Omega-3 fatty acids, which are important nutrients in their own right, may limit the access of other nutrients to cancer cells by inhibiting the growth of blood vessels to tumors. They may also stall cancer-cell growth in certain cell types by interrupting the normal biochemical processes that govern the production and release of essential hormones. No matter the mechanism, the important thing to remember is that all these changes have the same result—stopping the growth of cancer cells.

Not only may they slow cancer growth, but omega-3 fatty acids may provide a useful adjunct for conventional chemotherapy. For example, animal experiments have shown that concomitant administration of omega-3 fatty acids increases the efficacy of chemotherapy while reducing its side effects. You can think of all these effects of omega-3 fatty acids as a “multiple whammy” against cancer.

Omega-3s Are for Heart Health Too

The health benefits of omega-3 fatty acids extend well beyond the role they play in reducing the risk of cancer. Extensive research on their role in heart health (see the sidebar) has shown that dietary omega-3 fatty acids greatly improve heart health and significantly reduce the risk of death from coronary heart disease.³

One of the most important roles that omega-3 fatty acids play in maintaining heart health is to help regulate cardiac rhythm. As a result, they reduce the risk of ventricular fibrillation, one of the leading causes of cardiac mortality. Other important roles are to: reduce the risk of thrombosis (blood clots, which can lead to heart attack or stroke); retard the growth of atherosclerotic plaque; mildly decrease blood pressure; help reduce triglycerides (fats) in the blood; and promote vasodilation, the relaxation of blood-vessel walls. When you combine all these benefits, it is clear that omega-3 fatty acids are an important factor in helping to reduce the risk of heart disease.

Omega-3s Are Vital for Cognition

Additional research indicates that omega-3 fatty acids such as DHA play an important role in cognition. This is especially true in the developing brains and eyes of infants, where the omega-3s are essential for proper cognitive and visual functions. These organs have high levels of DHA in their cell membranes and rely on adequate dietary intake to maintain those levels and thus to ensure optimal function. Indeed, several studies have shown that infants who are fed breast milk, which is rich in DHA, have improved cognitive and visual skills compared to those who are fed formula that lacks DHA.

Other research points to the benefits of omega-3 fatty acids in adult cognition as well. While high intakes of total fat, saturated fat, and cholesterol all lead to an increased risk of dementia, a high consumption of fish that are rich in omega-3 fatty acids reduces that risk.⁴ In fact, many studies indicate that there is a relationship between fish consumption and enhanced cognitive abilities.

It has been proposed that omega-3 fatty acids may reduce injury to the brain by reducing the likelihood of thrombosis, atherosclerosis, and inflammation that may damage the lining of blood vessels in the brain. Whatever the mechanism, it is clear that a diet rich in omega-3 fatty acids benefits your noggin and may limit the deterioration of your cognitive skills as you age.

Omega-3 Benefits Are Easy to Obtain

Happily, you don’t have to live on an iceberg to enjoy the same health benefits that were long the norm for the Inuit (at least before they began to adopt our ways, including our generally unhealthy diet). Omega-3 fatty acids are widely available in supplements and have much scientific evidence to support their health benefits. So if you don’t have a harpoon handy, don’t despair—you can still get the health benefits of omega-3 fatty acids without putting on a parka and braving the Arctic elements.

References

1. Hardman WE. Omega-3 fatty acids to augment cancer therapy. J Nutr 2002;132:3508S-12S.
2. Kato T, Hancock RL, Mohammadpour H, et al. Influence of omega-3 fatty acids on the growth of human colon carcinoma in nude mice. Cancer Lett 2002;187:169-77.
3. Kris-Etherton PM, Harris WS, Appel LJ. Fish consumption, fish oil, omega-3 fatty acids and cardiovascular disease. Circulation 2000;106:2747-57.
4. Kalmijn S. Fatty acid intake and the risk of dementia and cognitive decline: a review of clinical epidemiological studies. J Nutr Health Aging 2000;4:202-7.

Dr. Jensen is a cell biologist who has conducted research in England, Germany, and the United States. He has taught college courses in biology and nutrition and has written extensively on medical and scientific topics.