Welcome to The Nutrition MD. Nutrition is the main determinant of health and the backbone of preventive medicine, which is recognized as the highest form of healing. The purpose of this web site is to serve as the source for authoritative, unbiased, and evenhanded information on achieving the optimal diet.
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Disclaimer: The educational material herein is presented as a public service and is intended for an educated readership. Questions of a general nature are most welcome. However, I cannot give personal medical advice and none of the information contained on this web site should be construed as personal medical or dietary advice or as a substitute for such advice.
The most consistent recommendation derived from studies exploring the relationship between nutrition and chronic disease is to consume more fruits and vegetables. Whether we're talking about heart disease, stroke, diabetes, cancer, cataract, or Alzheimer's disease, we come to the same conclusion: a plant-based diet has powerful preventive effects. The educational program designed to persuade people to consume at least five servings of fruits and vegetables a day soon advanced to eight a day. Our expanding knowledge of preventive nutrition has made it clear that we should try to maximize our plant food consumption while minimizing animal product consumption. Unfortunately, the feeble educational effort conducted so far has been a failure. To see what we have been up against, we need only examine the data from the Food and Agricultural Organization (FAO) of the United Nations for the year 1988. Of the 22 higher income countries studied, only Iceland showed a lower per capita vegetable consumption than the U.S.
From a practical standpoint, it is not necessary to know why plant food consumption is so beneficial. The "mad scientist" approach of trying to identify beneficial compounds in plants so they can be injected into foods or administered as supplements is unlikely to succeed. The beneficial effects of plant foods appear to be due to the synergistic effect of dozens or perhaps even hundreds of compounds present in the whole plant. The remedy for unhealthful eating is education, not more pills.
However, for the scientifically curious, some explanation is in order. First and foremost, plants contain phytochemicals. Technically, these chemical compounds are not nutrients because they are not required for growth and maintenance of the body the way vitamins are. However, they do nourish the body by means of their health-promoting properties. Many are antioxidants, which we believe help resist aging and degenerative changes in the tissues of our body. Phytochemicals are thought to inhibit the development and progression of cancers through a variety of mechanisms. They have anti-inflammatory activity, a property of great importance with the emergence of evidence that inflammation plays an important role in the development of many of our most common chronic diseases. An inflammatory tendency is related both to the kinds of food we eat as well as the quantity. For example, animal products are the main source of the fatty acid (building block of fat) called arachidonic acid, which is transformed by our bodies to inflammatory substances called eicosanoids. As will be discussed elsewhere, overeating produces a marked inflammatory tendency as well. Some phytochemicals prevent the platelets in our blood from becoming too "sticky." Platelets are the cellular fragments that are involved in the first step leading to blood clot formation. Another important property of some phytochemicals is their effect on hormones. For example, some have antiestrogenic effects, countering high estrogen levels caused by a low fiber diet. High estrogen levels are thought to play a role in the development of certain hormonally-dependent cancers, such as breast cancer.
Plant foods owe some of their beneficial properties to their fiber content. "Fiber" refers to complex substances, mostly in the carbohydrate category, that cannot be digested in our stomachs and small intestines, although they may be broken down to some degree by the bacteria residing in our large intestines. Fiber helps keep food moving through our digestive tracts and helps reduce the risk of constipation, diverticulosis, and hemorrhoids. It also helps reduce cholesterol absorption while increasing its excretion, and, in a related way, affects hormone levels, as mentioned earlier. Fiber also has an effect on the kinds of bacteria that populate the large intestine, and this in turn has effects on the immune system.
Fruits and vegetables tend to be rich in vitamin C, which is virtually absent from animal products, and vitamin E, whereas animal products contain relatively small amounts of the latter. These important antioxidants have been under study for many years in terms of their ability to prevent chronic disease. Vitamin E from foods is quite different from that in most supplements. There are actually eight main types of vitamin E in foods, four tocopherols and four tocotrienols. Alpha-tocopherol, the type found in supplements, is the best known, but the average diet actually provides more gamma-tocopherol than alpha-tocopherol. Studies have shown that gamma-tocopherol may help prevent heart disease and prostate cancer. The lesser known tocotrienols may be even more powerful antioxidants than the tocopherols. Here again, we see evidence of the advantages of a plant-based diet over supplement use.
Plant foods are the best sources of several important minerals, including magnesium, which is abundantly present in whole grains, green vegetables, legumes, nuts, and seeds. Magnesium may, in fact, be the most important mineral for disease prevention. It plays a major role in the quality of bone and may be just as important, if not more important, than calcium in preventing osteoporosis. Higher intakes of magnesium are associated with a lower risk of several chronic diseases: diabetes, high blood pressure, kidney stones, and heart problems. Magnesium helps prevent arrhythmias (irregular heart rhythms), both in the upper chambers of the heart (atria) and in the lower (ventricles).
In summary, consuming a wide variety of vegetables, fruits, whole grains, and nuts and seeds in moderation is the key; the rest is only commentary. To quote the late Ernst Wynder, M.D., "It should be the function of medicine to help people die young -- as late in life as possible."
The ideal diet, as described above, is extremely simple. What is not so simple is breaking a lifetime of inappropriate dietary patterns shaped by family and cultural influences and by inaccurate nutritional information emanating from unreliable sources. In this section, I will discuss many of today's controversial issues in nutrition and, in so doing, I will help you understand how the ideal dietary recommendations were derived. Be advised, however, that nutrition is a science, and nutritional concepts are subject to change as the results of new studies emerge.
This may surprise you, but how much you eat may be just as important as what you eat. A growing body of evidence from so-called dietary restriction or caloric restriction studies has shown that cutting calories by 20-30%, while maintaining nutritional adequacy, can dramatically lower cholesterol and triglyceride levels, blood pressure, blood sugar and insulin levels (thereby lowering the risk of diabetes or even reversing the disease) and C-reactive protein levels (a measure of inflammation in the body). It may also retard aging changes in the heart and elsewhere. In virtually all animals studied, dietary restriction causes a dramatic extension of life span and a decrease in chronic, degenerative diseases. Read more about this major breakthrough in nutritional understanding: Dietary Restriction
"Raw foods" advocates make claims that the nutrition establishment considers unscientific, but clearly there are differences between cooked and uncooked foods. The debate revolves around nutrients, enzymes, chemicals produced by the cooking process, and other issues. Is a diet consisting mainly of uncooked foods beneficial or harmful to health? Should we be consuming more raw vegetable products or at least cooking foods at lower temperatures and for shorter periods of time? Click on this link for an objective discussion of the effects of cooking on foods and the implications for health: Raw Foods
Recent reports have given some people the impression that nutrition scientists have changed their minds about low-fat diets. The fat content of the diet may have a bearing on weight control and on the risk of diabetes, heart disease, cancer, and other chronic diseases. Take a look at the evidence: Low-Fat Diets
Some people think that taking a multivitamin/multimineral supplement will provide "insurance" against nutritional deficiencies. Others feel that it will give them renewed energy. And still others feel that the same beneficial nutrients and phytochemicals found in plant foods can be obtained from any of a number of supplements. Do the nutrients in supplements generally assume the same form as those found in food? Is there a downside to taking supplements? The question is explored in an evenhanded way, free of supplement industry bias: Supplements
The United States Department of Agriculture's Food Guidance System now recommends that half of all grains consumed be whole grains. In the face of an avalanche of studies exploring the relationship between whole grain consumption and disease, learn about the protective effects of whole grains, how whole grains differ from refined grains, and why the USDA should have concluded that there is no place at all for refined grains in a healthful diet: Whole Grains
Many people are considering cutting down on or eliminating meat consumption but feel they will need to compensate for nutrients like protein, iron, and zinc. On the other hand, few people would worry about nutrient deficiencies if they were to increase their meat consumption. The essentiality of meat in the diet is something that has been drummed into most people's heads from the time they were born. Any poorly planned diet can have deficiencies, but what are the risks in a meat-based diet vs. a plant-based diet? See the subject in a new light: Meat
Only tiny amounts of this animal product-containing B-vitamin are needed, but, without it, irreversible damage can occur to the central nervous system. Even if it is provided in the diet, some people lose the ability to absorb it. Learn the ins and outs of vitamin B-12 and what you can do to safeguard against deficiency: Vitamin B12
The news media frequently carry stories describing fish as a health food and recommending that people increase their fish consumption. But what does an evenhanded review of the scientific literature have to say? Should vegetarians be adding fish to their diet? Is there any good evidence that fish consumption lowers the risk of heart disease? Read about the pros and cons of fish as part of a healthful diet: Fish
Although eggs have become synonymous with cholesterol in recent years, some groups seem to imply that inclusion of eggs in the diet in limited amounts is acceptable, especially if used in place of other high-fat foods. Learn about the nutrient contribution of eggs, their effects on health, and whether they can be part of an optimal diet: Eggs
Dairy products are heavily promoted as a source of calcium, protein, riboflavin, and other nutrients. Numerous claims have been made over the years: that increased intake will help prevent osteoporosis, lower blood pressure, reduce the risk of colon cancer, and, most recently, promote weight loss in overweight people. Learn about the nutritional attributes of dairy products, their effects on health, and the role they should be playing in the context of the ideal diet: Dairy
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