Information About Vitamins A & B

Vitamin A belongs to the group of nutrients called fat-soluble vitamins, while the B vitamins are classified as water-soluble. When originally discovered, researchers thought that vitamin B was a single compound. Upon further investigation, however, scientists realized that what was once named water-soluble B was actually a family of eight different vitamin compounds: thiamin, riboflavin, folate, niacin, vitamin B-6, vitamin B-12, pantothenic acid and biotin.

Vitamin A

The term vitamin A refers to a family of substances called retinoids, which include retinol, retinal and retinoic acid. Collectively, these substances are called preformed vitamin A. Retinol is the most usable form of the retinoids and can be converted to retinal and retinoic acid in your body. Preformed vitamin A is only found in animal food sources, such as milk, eggs and organ meats like liver.

Plant foods contain a substances called provitamin A carotenoids, which your body converts into retinol. The carotenoids are responsible for the yellow-red pigments that provide foods such as carrots and butternut squash with their color. There are more than 600 carotenoids, but only three of them, beta-carotene, beta-cryptoxanthin and alpha carotene, are converted to vitamin A, according to "Nutrition and You" by Joan Salge Blake.

Functions of Vitamin A

Vitamin A allows your retina to convert light into images. Vitamin A is also essential for cell regulation, gene expression and immune health. Consuming adequate amounts of vitamin A when you are pregnant ensures that the limbs, heart, eyes and ears of the developing fetus form correctly.

B Vitamin Functions

Vitamins do not contain calories, so they do not provide a direct source of energy. You do require the B vitamins to turn the protein, fat and carbohydrates you eat into energy, however. Specific B vitamins also play independent roles in your body. Thiamin keeps your nerves healthy and helps break down alcohol in your body. Niacin helps you synthesize fat and cholesterol in your body. Vitamin B-6 and vitamin B-12 play essential roles in the creation of red blood cells. Folate helps make the DNA in your cells and prevents birth defects in a developing fetus.

Sources of B Vitamins

Most of the B vitamins in your diet come from enriched breads and grains and fortified cereals. Milk and yogurt are good sources of riboflavin and meat, fish and poultry contain significant amounts of niacin and vitamin B-12. Nuts, peanut butter and legumes provide vitamin B-6, pantothenic acid and biotin. Leafy green vegetables, such as spinach and lettuce, broccoli and asparagus are good sources of folate.