By Patti Wade, Registered Dietitian and Manager of Food Services, Columbus Regional Health

It seems that every month a new study is heralded suggesting that we can now eat a formerly forbidden food. Or, a food we thought would cure all turns out to be nothing more than a mere food. When studies seem contradictory and recommendations turn around 180 degrees, it is hard to know what to eat. It is also hard to trust the distinguished organizations which make the recommendations.

To help understand how we got where we are, it is beneficial to look at how scientists and nutritionists determine dietary guidelines. It often starts with the realization that a certain group of people has a lower occurrence of a particular disease. For example, the observation was made in the 1960s of a very low incidence of heart disease in native Alaskans. This group was ‘protected’ from heart disease despite consumption of large amounts of fat and very few fruits and vegetables. Looking at what foods the ‘protected’ group consumed differently than the groups with higher incidences of the disease, recommendations can be made based on associations. We do not necessarily understand the cause and effect relationship. In this case, scientists understood that fatty fish contain some beneficial oils and made recommendations to include these in our diets.

In continuing to try to determine dietary influences on heart disease, scientists looked at fat consumption patterns of different groups of people, the incidence of heart disease, and at levels of blood cholesterol, which was felt to be the blood level indicator for risk of heart disease. Looking both at fat structure and the factors above, they determined that health is impacted by differences in fat saturation. Nutritionists felt comfortable recommending reductions in total fat and saturated fats (firm fats primarily from animal sources) and replacing saturated fat with polyunsaturated and monounsaturated fats (liquid fats, primarily oils from vegetables, nuts, and seeds).

As the research has continued, scientists have become aware that fats contain blends of different fatty acids (components of fats). The structure of fatty acids that make up a fat dictates the fat’s role in our bodies. Some polyunsaturated fatty acids help our blood vessels to open up and some promote blood vessel tightening. Some saturated fatty acids raise blood cholesterol levels and some do not impact blood cholesterol. The role of a particular fat changes based on interactions with other compounds in the body. Some fatty acids compete with others for enzyme activity, which means that the presence of one will impact the effectiveness of another.

Because of the very complex interactions and roles of fatty acids, a study may report on one aspect of the entire picture and contradict what we have been told previously. For example, there was a recent report that full-fat dairy products are no longer found to raise blood cholesterol. Full-fat dairy products contain primarily saturated fatty acids. Some saturated fatty acids do not raise cholesterol. But many saturated fatty acids do raise cholesterol. At this stage in dietary fat research, organizations such as the American Heart Association, the Institute of Medicine, the Academy of Nutrition and Dietetics, and the World Health Organization do not have enough conclusive data to recommend a turn-around on full-fat dairy products.