Water Soluble Vitamins

Eight of the water-soluble vitamins are known as the B-complex group: thiamin (vitamin B₁), riboflavin (vitamin B₂), niacin, vitamin B₆, folate, vitamin B₁₂, biotin and pantothenic acid. These vitamins are widely distributed in foods. (See Table 2.) Their influence is felt in many parts of the body. They function as coenzymes that help the body obtain energy from food. They also are important for normal appetite, good vision, healthy skin, healthy nervous system and red blood cell formation.

Beriberi, pellagra and pernicious anemia are three well-known B-vitamin deficiencies. These diseases are not a problem in the United States, but occasionally they occur when people omit certain foods or overeat certain foods at the expense of others. Alcoholics are especially prone to thiamin deficiency because alcohol replaces food.

When grains and grain products are refined, essential nutrients lost during processing are put back into these foods through a process called enrichment. Among the nutrients added during the enrichment process are thiamin, niacin, riboflavin, folate and iron. Some examples of enriched grain products are white rice, many breakfast cereals, white flour, breads, and pasta.

For some populations, rice is the main dietary staple. When "polishing" rice (removing its outer layers) became popular, thiamin deficiency, or beriberi, increased significantly.

In the early 1900s, the most widespread vitamin deficiency disease in the United States was pellagra, or niacin deficiency. At that time, pellagra caused thousands of deaths and many cases of mental and physical illness among the poor in the Southeast. The enrichment of flour, rice, and wheat products helped to eliminate the deficiency problems found in people who depended on these food items for most of their daily calories.

Table 3 summarizes the new standards for nutrient recommendations: The Dietary Reference Intake (DRI). The recommendations meet the average daily nutritional needs of all healthy people. To ensure the needs of all in the population, the DRI usually exceeds the requirements for most people. They do not cover requirements for illness and special health disorders.

Vitamin C

Why do we need vitamin C? Like the other vitamins, the body needs vitamin C to keep it in good working order. Also known as ascorbic acid, vitamin C helps hold body cells together, aids in wound healing, assists in bone and tooth formation, strengthens the blood vessel walls, is vital for the function of the immune system, and improves absorption and utilization of iron. It also helps prevent nutritional ailments such as scurvy, the disease that did the most to bring public attention to vitamin deficiency diseases.

Our bodies cannot make vitamin C. Therefore, every day we must eat foods containing this vitamin. Although the body has a constant need for vitamin C, it has a limited storage capacity. A regular and adequate intake is essential.

Eating vitamin C-rich foods is the best method to ensure an adequate intake of this vitamin. While many common foods contain vitamin C, the best food sources are citrus fruits. One orange, a kiwi fruit, 6 oz. of grapefruit juice or 1/3 cup of chopped sweet red pepper each supply enough vitamin C for one day.

Some conditions have been shown to increase vitamin C requirements. They are:

The controversy over megadoses of vitamin C to prevent or cure the common cold and other disorders has not been resolved. Vitamin supplements will not necessarily provide extra energy, clear up skin problems, or prevent and cure the common cold, heart disease, and cancer. Unlike pellagra, beriberi, or scurvy, these problems are not the result of a vitamin deficiency. What is known is that the only disease a vitamin will cure is the one caused by a deficiency of that vitamin.

Vitamin C also serves as an antioxidant. It works with vitamin E as a free-radical scavenger. Studies suggest that vitamin C may reduce the risk of certain cancers, heart disease and cataracts. Research continues to document the degree of these effects.

Definitions

Dietary Reference Intake (DRI): The new standards for nutrient recommendations that can be used to plan and assess diets for healthy people. Think of Dietary Reference Intakes as the umbrella term that includes the following values.

Estimated Average Requirement (EAR): A nutrient intake value that is estimated to meet the requirement of half the healthy individuals in the group. It is used to assess nutritional adequacy of intakes of population groups. In addition, EARs are used to calculate RDAs.

Recommended Dietary Allowance (RDA): This value is a goal for individuals and is based on the EAR. It is the daily dietary intake level that is sufficient to meet the nutrient requirement of 97 to 98 percent of all healthy individuals in a group. If an EAR cannot be set, no RDA value can be proposed.

Adequate Intake (AI): This is used when an RDA cannot be determined. A recommended daily intake level based on an observed or experimentally determined approximation of nutrient intake for a group (or groups) of healthy people.

Tolerable Upper Intake Level (UL): The highest level of daily nutrient intake that is likely to pose no risks of adverse health effects to almost all individuals in the general population. As intake increases above the UL, the risk of adverse effects increases.

Source: Food Insight, September/October 1998.

References

¹J. Anderson, Colorado State University Cooperative Extension foods and nutrition specialist and professor; and L. Young, M.S., former graduate student. 3/02. Reviewed 2/05.
 

Water Soluble Vitamins

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* These statements have not been evaluated by the FDA. These products are not intended to diagnose, treat, cure or prevent any disease.