Nutrition Overview
Nutrition is often considered to be complementary or alternative since medications offered by the physician are seen as the primary treatment strategy and preventive medicine, such as nutrition lifestyle changes, does not have a large share of the practice of medicine at this time. Consider that only 25% of the US medical schools have a required course of nutrition in their medical curriculum (Tufts has a required course of 27 hours). Few medical care systems have the dietitian/nutritionist as an integral part of their medical team. This often results in nutrition evaluation, advice and counseling being offered outside of the medical office and it is not necessarily coordinated with the medical care given by the allopathic physician.
Nutrition is the science that interprets the
relationship of food to the functioning of the living organism.
In humans it involves the intake of food, the liberation of energy,
the impact of food and the compounds in food on all biochemical
and hormonal pathways, elimination of wastes and the syntheses
of all organic molecules for the maintenance, growth and reproduction
of the species. Nutrients essential to health are generally divided
into macronutrients (proteins, carbohydrates and fats) and micronutrients
(vitamins and minerals). However, foods contain hundreds or even
thousands of other compounds that may also facilitate health
and are designated as phytochemicals. Their role in the maintenance
of health is currently an active area of research.
Nutritional standards have been developed to evaluate the nutritional status
of a food, a diet or a person. Some of the current standards include:
- Dietary Reference Intake (DRIs) according to age and gender for over 26 micronutrients
- Upper limits of intake recommended for these 26 micronutrients
- Nutriton and Your Health: Dietary Guidelines for Americans, a set of recommendations on macronutrients, general nutrition recommendations to achieve balance of intake and use of exercise to maintain a healthy weight
- US Food Guide Pyramid, a graphic representation of foods grouped into 5 categories with recommended daily servings. These standards do not include information on the “ideal” intake of food or nutrients which is in the process of being researched.
Research in nutrition generally begins with the testing of hypotheses in animals and use animal models that most closely represent human characteristics of health or disease. Information from these studies usually results in the design of human studies that investigate the association between dietary factors and specific functioning or disease. These types of studies include:
- international epidemiological studies comparing dietary intake and nutritional status and disease prevalence or mortality
- migrant studies that investigate the effect of environment versus genetics on functioning and disease prevalence,
- case-control studies to compare persons with disease to an age and gender matched control group free of disease or symptoms, to discern the difference between the two groups,
- cohort studies which document dietary factors and nutritional status in a large group of healthy people and follow them for a number of years to determine if there is an association between the baseline nutritional status of those who develop disease compared to those who do not develop disease. All four of these type of studies can only determine an association between nutritional factors and health and/or disease. In order to prove causation a nutrition intervention trial or a randomized clinical trial (RCT) is required . However, these types of studies are difficult to carry out, require large numbers of subjects and are very expensive and time consuming. In addition, they cannot be easily blinded if the intervention cannot be put into a pill with a matching placebo pill. Many questions in nutrition relate to eating patterns of foods and not to one simple nutrient. In these cases, subjects need to be taught to develop a new eating pattern that is easily distinguished from the control group or the usual food intake pattern. Additional biases can then be presented in these intervention trials that make interpretation more difficult. In many cases where the role of foods or nutrients on the development of chronic disease are being investigated, intervention trials are done in patients who already have the disease (secondary prevention) rather than in healthy people (primary prevention) and conclusions cannot be extrapolated to the other group. Most nutritional factors are considered to be important in primary prevention rather than in secondary prevention (treatment of disease).
NCCAM