USANA Nutritionals

THE "AVERAGE DIET" THEORY

It would be nice to offer a solution to the problem of good nutrition by drawing up diets that would be right for everyone. Unfortunately, this is not as easy as it sounds, for several reasons.

First, foods mat are commonly found in one area of the country or in the diet of one ethnic or economic group may be uncommon in another. People's eating habits also vary widely, even within ethnic groups and regions of the country.

Second, a diet evaluation must include only food that is actually eaten. If considerations are based only on what is bought or prepared, the resulting nutritional picture will be distorted.

Third, the way you prepare and cook raw and processed foods at home may affect their vitamin content. For example, paring certain vegetables before cooking often results in the loss of most of their water-soluble vitamins. Baking and other cooking methods can also lead to vitamin loss.

When estimating the vitamin losses from your food during preparation, remember that it is unreasonable to expect that the preparation conditions of test foods will be identical to those being prepared in your home. Therefore, individual diets can be evaluated only by analyzing the final food product.

Fourth, your dietary or body level of one vitamin or mineral may influence your requirement for another. For example, many of the water-soluble vitamins' functions are interrelated because they all participate in the series of chemical reactions known as the Krebs cycle, which is involved in energy generation. Thus, a deficiency in one vitamin may affect the ability of the other vitamins to function. The nutrients that are interrelated in this way are niacin, thiamin, pyridoxine, riboflavin, biotin, pantothenic acid, choline, and cyanocobalamin.

Vitamin needs can also be related to the nature of your dietary intake. More thiamin, niacin, riboflavin, and other water-soluble vitamin requirements are needed in a high-carbohydrate diet. In contrast, a high-protein diet calls for increased pyridoxine and has an effect on the amount of riboflavin the body stores. Zinc seems to play a role in the action of vitamin A, so that vitamin A deficiencies can be more easily corrected if there is a sufficient amount of zinc in the diet And vitamin C (ascorbic acid) is a factor in the efficient absorption of iron from the gastrointestinal tract. Thus it is possible that you are taking enough iron but don't have enough ascorbic acid in the diet to get the full value of that iron. Usually, however, the situation is reversed, with more than enough C and too little iron in the diet.

Fifth, it is difficult and time consuming to translate information from nutrition value tables to our daily diet. For example, to determine the vitamin content of a simple ham sandwich on white bread, we must find the listing for "Ham: piece, approx. 4 1/8 in. long, 2 1/4 in. wide, 1/4 in. thick; wt 1 1/2 oz." Assuming that three such slices are used in our sandwich, we can determine that, from the ham alone, we will gain no vitamin A, 7.2 mg of niacin, 0.37 mg of riboflavin, 0.81 mg of thiamin, and no vita¬min C. Similar steps must be followed for every part of the sandwich, and then for total food intake.

Interestingly, the technology explosion has led to the introduction of a number of programs and services that will analyze your diet for vitamin and mineral content—as well as for fat, cholesterol, sodium, and other nutritive components—using a computerized listing of the information contained in the United Stales Department of Agriculture (USDA) tables on the nutritive value of American foods.

These computer programs can help you find an optimal diet by pointing out where your diet is lacking and making suggestions as to how to improve your eating patterns.

THE DIETARY GUIDELINES FOR AMERICANS

Over the years, nutrition and food researchers have developed a set of standard recommendations for the kinds of foods we should eat to maintain a healthy nutritional state.The Dietary Guidelines for Americans are the official policy of the United States Department of Agriculture and are updated every five years. The guidelines describe food choices that will help you meet the RDA/DRIs. They also intersect with the nutrition labeling that now appears on all packaged food products.

Here are the basic recommendations contained in the latest edition of the Dietary Guidelines for Americans:

• Eat a variety of foods. No one food can supply all of the vitamins, minerals, and other nutrients your body needs. By varying the foods you eat, you have the greatest chance of obtaining the full range of nutrients. The Food Guide Pyramid offers information on the number of servings and amounts of various foods that are most healthful to consume.

• Balance the food you eat with physical activity and maintain or improve your weight. Being overweight dramatically increases the risk for many diseases, such as high blood pressure, heart disease, stroke, diabetes, cancer, arthritis, and breathing disorders. Since many adults have a tendency to gain weight with age, this guideline encourages weight maintanance or loss as a goal of good health.

• Choose a diet with plenty of grain products, vegetables, and fruits. These foods are the basis of a varied and healthy diet. They contain vitamins, minerals, complex carbohydrates, and other compounds that are healthful, and they are usually low in fat.

• Choose a diet low in fat, saturated fat, and cholesterol. Although some dietary fat is needed to ensure good health, most Americans consume way too much fat and cholesterol. Such high-fat diets raise the risk of obesity, heart disease, and cancer.
 
• Choose a diet moderate in sugars. As with fat, Americans tend to go overboard with sugar, which is high in calories.

• Choose a diet moderate in sodium. Sodium has been associaed with high blood pressure. Sodium and sodium chloride (salt) are found in large amounts in processed and prepared foods.

• If you drink alcoholic beverages, do so in moderation. Alcohol is high in calories and typically devoid of nutrients and can cause a number of illnesses if consumed to excess. Moderation is defined as no more than one drink per day for women and two drinks a day for men.

Technical Background

• Vitamin D is a fat-soluble nutrient that plays a central role in bone growth and health.1 It can be acquired either through the diet or through exposure to sunlight, when ultraviolet light reacts with a form of cholesterol and converts it to vitamin D. Cholecalciferol is the form of vitamin D normally found in humans and the form typically found in nutritional supplements.
• A unique property of vitamin D is that it functions very much like a hormone. Its target tissues in the human body include the kidneys, intestines, and bones, where it acts to regulate calcium and phosphorus homeostasis.
• In the intestines, vitamin D plays an important role in the absorption of calcium. In bone tissue, vitamin D plays a role in regulating calcium deposition (bone mineralization) and mobilization.
• Given the above functions, vitamin D is essential for normal bone development, particularly in children. Without it, bones do not calcify properly, leading to the condition known as “rickets”. Vitamin D also plays an important role in tooth development. It is necessary for proper tooth eruption, growth, and ultimate strength.
• Research is currently being done to examine the role of vitamin D and its analogues in inhibiting prostate cancer2 and breast cancer.3 Recently, a research team reviewed 63 studies on the relationship between vitamin D and certain types of cancer. In addition to prostate and breast cancer, the majority of studies found a relationship between vitamin D status and lower risk of colon and ovarian cancers as well.4 In another recent study, women taking a calcium and vitamin D supplement had a 60 percent lower incidence of all cancers than women not taking the supplement.
• Vitamin D intake is especially important for women. In addition to its possible role in breast cancer and osteoporosis prevention,6 recent studies have found that vitamin D and calcium supplementation in pre-menopausal women may also decrease in the incidence of premenstrual syndrome (PMS).
• A recent study found that over half of the women in North America receiving treatment for osteoporosis had an inadequate intake of vitamin D.8 New research indicates that vitamin D deficiencies are widespread among pregnant women and infants despite prenatal vitamin usage.
• Vitamin D is also being researched for its role as an immune system regulator and modulator,10,11 for its role in reducing insulin resistance and type-2 diabetes,12,13 and for its role in healthy heart and lung function.

Sources and Recommended Intake

• The Recommended Dietary Allowance (RDA) for vitamin D is 5 micrograms (200 IU) per day for children, and 5-15 micrograms (200-600 IU) per day for adults.16 These amounts can be obtained with 15-30 minutes of exposure to sunlight on the hands, arms, and face. The use of sunscreens interferes with vitamin D synthesis. Dark skin (i.e. having a high melanin content) requires longer exposure than lighter skin to achieve the same degree of vitamin D synthesis17. Furthermore, the capacity of skin to synthesize vitamin D decreases with age.
• The only significant dietary source of vitamin D is fortified milk. Other sources include fish and fish liver oils.
• Although the upper limit established by the Food and Nutrition Board is 2,000 IU (or 50 mcg), many prominent researchers view this a being too restrictive. Human clinical trial data published after the establishment of the UL support a significantly higher UL. Absence of toxicity in trials conducted in healthy adults support the level of 10,000 IU as a more reasonable UL.
• Importantly, the benefits of vitamin D supplementation are achieved only if adequate calcium and phosphorus are provided in the diet.

Abstracts

Augier P and Gandini S. Vitamin D Supplementation and Total Mortality: A Meta-analysis of Randomized Controlled Trials. Arch Intern Med 2007 Sep 10;167(16):1730-7. Ecological and observational studies suggest that low vitamin D status could be associated with higher mortality from life-threatening conditions including cancer,
cardiovascular disease, and diabetes mellitus that account for 60% to 70% of total mortality in high-income countries. We examined the risk of dying from any cause in subjects who participated in randomized trials testing the impact of vitamin D supplementation (ergocalciferol [vitamin D(2)] or cholecalciferol [vitamin D(3)]) on any health
condition. METHODS: The literature up to November 2006 was searched without language restriction using the following databases: PubMed, ISI Web of Science (Science Citation Index Expanded), EMBASE, and the Cochrane Library. RESULTS: We identified 18 independent randomized controlled trials, including 57 311 participants. A total of 4777 deaths from any cause occurred during a trial size-adjusted mean of 5.7 years. Daily doses of vitamin D supplements varied from 300 to 2000 IU. The trial size-adjusted mean daily vitamin D dose was 528 IU. In 9 trials, there was a 1.4- to 5.2-fold difference in serum 25-hydroxyvitamin D between the intervention and control groups. The summary relative risk for mortality from any cause was 0.93 (95% confidence interval, 0.87-0.99). There was neither indication for heterogeneity nor indication for publication biases. The summary relative risk did not change according to the addition of calcium supplements in the intervention. CONCLUSIONS: Intake of ordinary doses of vitamin D supplements seems to be associated with decreases in total mortality rates. The relationship between baseline vitamin D status, dose of vitamin D supplements, and total mortality rates remains to be investigated. Population-based, placebo-controlled randomized trials with total mortality as the main end point should be organized for confirming these findings.