According to researchers, a healthy diet can include "a lot of fat." A review of available evidence suggests that a Mediterranean diet with no restrictions on fat intake may reduce a person's risk for breast cancer diabetes, and cardiovascular events compared to other diets. The findings are published in Annals of Internal Medicine.

Despite advances in diagnosis and treatment, cardiovascular disease, diabetes, and cancer continue to be among the leading causes of morbidity and mortality in developed countries. Typical Western diets, which are high in saturated fats, sugar, and refined grains, have been linked to the development of these chronic diseases. Limited evidence has suggested that a Mediterranean diet, which is essentially plant-based, may be a healthier option.

Researchers reviewed available evidence to summarize the effect of a Mediterranean diet on health outcomes and to assess whether North American populations would be likely to adhere to such a diet. Since not everyone defines the Mediterranean diet in the same way, the researchers defined it as a diet that placed no restriction on total fat intake and included two or more of seven components: high monounsaturated-to-saturated fat ratio (for example, using olive oil as a main cooking ingredient), high fruit and vegetable intake, high consumption of legumes, high grain and cereal intake, moderate red wine consumption, moderate consumption of dairy products, and low consumption of meat and meat products with increased intake of fish. Few randomized, controlled trials compared this type of diet to all others, but the few that did suggest that a Mediterranean diet with no restriction on fat intake may be associated with reduced incidence of cardiovascular events, breast cancer, and type 2 diabetes but does not affect all-cause mortality.

The researchers found no studies that met their inclusion criteria to assess adherence outcomes, however, observational data reveal that total cancer incidence and mortality and colorectal and lung cancer incidence were lower in persons with the highest adherence to the Mediterranean diet compared to those with the lowest but show no association between Mediterranean diet adherence and breast cancer risk.