The Pursuit of Optimal Diets: A Progress Report

During the twentieth century, enormous progress was achieved in the identification of essential nutrients and the elmination of diseases specifivally related to their deficiencies. Partly a result of these successes, chronic diseases such as cardiovascular diseases, cancer, and neurodegenerative conditions have become the dominant health cocerns of most countries. International comparisons and studies of migrants indicate that these conditions are to a great extent preventable, and the identification of diets that could provide optimal health has become a major goal. Current dietary advice, represented by the US food Guide Pyrmid and WHO guidelines, has emphasized restricting all forms of fat and consuming large amounts of starch. Intake of fruits and vegetables and dairy product has been encouraged, and no distinction has been made among red meat, fish, poultry, nuts, and legumes as sources of protein. These recommendations appear inconsistent with metabolic studies that have shown important distinction among various types of fat and forms of carbohydrates. During the last decade, large epidemiologic studies of diet and health have provided additional evidence that the type of dietary fat is extremely important: trans fatty acids are related to elevated riskks of coronary heart disease and diabetes, and unsturated fats are related to reduced risk when compared to carbohydrate. Also higher intakes of refined starch and sugar (in particular as beverages) predict greater risk of these disease whereas high-fiber cereal products are associated with lower riskd. High intakes of fruits and vegetables have important benefits, but these appear greater for cardiovacular disease than for cancer. Recently, evidence has emerged that inadequate vitamin D status in likely to be a major contributor to cancer mortality as well as risk of fractures.