Many of us probably know that eating a very-high-fat diet will not only make us gain weight, but it will also increase our risk of heart disease. But surprisingly, there are 2 disparate population groups that, notably, consume very high quantities of dietary fats, yet have a very low incidence of cardiovascular disease, polar bears and traditional Alaskan Eskimos. How is that possible? Does it have to do with the types of fats they eat, or to specific physiological adaptations? The answer is yes, to both of these questions.
A recent study published in the highly touted scientific journal Cell (Polar Bear Study), showed that polar bears and brown bears diverged in evolutionary history less than 500,000 years ago. This is a surprisingly short time, in evolutionary terms. During this time, polar bears moved north, subsisted on a blubber-rich diet of primarily marine mammals and fish, and became profoundly obese. Interestingly though, these bears do not develop fatty deposits in blood vessels (atherosclerotic plaques) or suffer from cardiovascular diseases (CVDs) that afflict most humans with diets rich in fat. How can that be? The answer to this seemingly paradoxical question was revealed by the gene studies in this publication, and was discussed recently in Science Daily (Researcher Interviews). The researchers found that polar bears had evolved several gene variants that helped them adapt to the high-fat diet. These variants were in genes which related to fatty acid metabolism and cardiovascular function. The researchers concluded that this study may provide insight into how to protect humans from the ill effects of consuming too much dietary fat.
The second group mentioned above, arctic Eskimos called the Intuits, also eat high-fat diets and have traditionally had very low incidence of CVD. This has been referred to as the ‘Intuit Paradox’ (Discover Magazine). The Intuits historically ate a high-fat diet consisting of seal and walrus meat and other blubbery marine mammals. Although we don’t know about specific gene variants in this population relating to heart disease, we do know that the composition of fat they consumed is very different from fat consumed today by most Americans. The Intuit diet was traditionally high in mono- and polyunsaturated fatty acids (and protective omega-3 fatty acids), and low in saturated and trans fats. This seems rather unexpected since most of us know that animal fats are high in saturated fat. It had to do with the source of the fats. It turns out the wild-animal fats are different (less saturated fat; higher in monounsaturated fats, like in olive oil) from farm-animal fats and processed fats (which also contain damaging trans fats). Moreover, cold water fishes and marine animal fats are particularly rich in polyunsaturated fats and omega-3 fatty acids.
So this then leaves us with 3 options if we choose to consume lots of dietary fats and still want to be healthy: 1) hope that we rapidly evolve like the polar bears; 2) consume more fat from wild-caught animals; or 3) focus on fats derived from plant foods like seeds, nuts and whole grains. What will your choice be?
You have probably heard that we all should eat more fish and seafood, right? What you probably haven’t heard as much about is how the source and the type of fish you eat can influence not only nutrient intake levels but also the levels of certain contaminants you consume. This is a particular concern as some fish contain antibiotics, pesticides, or other chemicals, including mercury, polychlorinated biphenyls (PCBs) and dioxins. For some individuals, for example pregnant women, this is an issue of real importance as these substances can cause harm to the developing fetus.
Despite these potential risks, it is generally accepted in the nutrition community that fish is a healthy dietary choice and regular consumption can have a positive impact on overall health. For example, the American Heart Association recommends eating fatty fish at least two times a week (AHA Omega-3 FAs), and diets such as the Mediterranean and DASH diet also promote fish consumption. Certain fish (e.g. salmon) contain high levels of omega-3 fatty acids which have anti-inflammatory properties, and may decrease risk of heart arrhythmias and blood clotting, and thus be protective against heart disease. Fish is also high in protein yet low in saturated fats.
This then leaves us in a quandary. How are we to eat more fish and other seafood, yet avoid exposing ourselves to dangerous environmental contaminants? The answer lies in the type of fish we consume, whether it was farm raised or caught in the wild and the frequency with which we consume the fish. Let’s look at species first. Contaminants are most likely to be present in older, larger predatory fish, such as shark, swordfish, king Mackerel and tilefish (Mayo Clinic Fish Info). The U.S. Food and Drug Administration (FDA) thus recommends that young children and pregnant and lactating women avoid eating these fish. It is also important to keep in mind, that not all fish and other seafood are high in omega-3 fatty acids. Some however, contain significant levels of omega-3 fatty acids and also have lower levels of environmental contaminants. These include salmon, canned light tuna, shrimp, pollock and catfish, which then are the best choice for consumers.
Two other issues to consider are the source of the fish and whether taking fish oil supplements is a good alternative. As you may or may not know, many fish such as tilapia are raised in “fish farms”. These aquaculture facilities raise large numbers of fish in relatively tight quarters. This leads to an increase in the risk for infection and other illnesses; antibiotics are thus routinely used in this setting. It is also important to consider whether the fish was imported into the U.S. from another country, as the inspection process may not be so robust. Moreover, there is some evidence that the nutrient content of wild caught fish is higher, but the price may also be higher. And lastly, there is emerging evidence in the nutritional sciences world that fish oil supplements do NOT provide the same health benefits that regular consumption of certain fish.
In summary, eating fish is good for us, but we have to be educated to realize the greatest health benefits. This general rationale also applies to many other aspects of healthy eating, such as choosing fruits and vegetables with the lowest levels of contaminating pesticides. So, learn, procure, cook and enjoy!
(written with the creative assistance of Avery Bramnik and Nicole Solomon, both University of Florida undergraduate students)
You may have heard about the purported benefits of the Mediterranean diet (MD). Media outlets, which may sensationalize scientific studies, often report the benefits of such a dietary pattern. From the perspective of a scientist, are these reports accurate? Have studies that examined the Mediterranean dietary pattern been in agreement on the health benefits? Where did this idea originate? Let’s take a closer look at these issues.
It was first reported in the 1940s in the landmark Seven Countries study that men living on the island of Crete in the Mediterranean Sea, which is part of Greece, had long life spans and low rates of heart disease. This observation piqued the interest of nutritional science researchers, who proceeded to analyze the lifestyles and dietary patterns of these individuals. It was noted that the indigenous people of Crete lived lives that were low in stress that included daily exercise, often in the form of walking. Moreover, their diets were high in olive oil and nuts, which contain abundant mono- and polyunsaturated fat, and in carbohydrates. They also consumed fish often and regularly had wine with meals.
Over the past several decades, these observations have morphed into what we now refer to as the “Mediterranean diet”, which only partially reflects the dietary patterns of the people of Crete at that time. The modern MD is high in beans, whole grains, fruit and vegetables, fish and nuts, and low in red and processed meats, added sugars and saturated fats with moderate alcohol consumption. Studies have consistently shown that this dietary pattern is associated with a lower incidence of cardiovascular disease (CVD) and may also decrease the risk of cancer and other chronic diseases.
What is it about the MD that offers these health benefits? What are the beneficial nutrients in the MD that promote good health? For starters, higher mono- and polyunsaturated fat intake, which typifies the MD, has been associated with decreased risk of CVD. The MD also contains high potassium and low sodium, supporting blood pressure control. Fruits, vegetables and nuts are high in fiber and also contain abundant phytochemicals, some of which are known to have positive health benefits. High fiber intake is associated with reduced risk of some cancers (e.g. colon cancer) and it also decreases blood cholesterol levels. Fish contains omega-3 fatty acids, which have anti-inflammatory properties. Moreover, the MD limits red and processed meats, which are typically high in saturated fat, cholesterol and sodium. Moderate alcohol consumption has also been linked to a lower incidence of CVD, particularly red wine, which contains a powerful antioxidant phytochemical.
The MD diet thus promotes good health. If this dietary pattern is combined with regular exercise and one works at decreasing daily stress, it can certainly reduce risk for developing a host of chronic diseases. Can you think of other health benefits of the MD? How can you alter your diet so it more closely reflects this dietary pattern? Why might the MD be more beneficial than the typical American diet?