Healthy Eating: Valuable Vitamins
Unlike the fat-soluble vitamins, water-soluble vitamins dissolve in water. These vitamins are carried in the bloodstream and, for the most part, are not stored in the body. In general, your body uses what it needs and excretes the rest through urine. For this reason, it is important to regularly replenish these vitamins by eating a healthy and varied diet each day. Because water-soluble vitamins dissolve in water, they are much more easily destroyed in cooking and storing than the fat-soluble vitamins are.
The water-soluble vitamins consist of the B-complex vitamins and vitamin C. The B vitamins work together in converting carbohydrates, protein, and fats to energy, and many are found in the same foods. For this reason, poor intake of one B vitamin is usually associated with poor intake of other B vitamins.
Thiamine (Vitamin B1)
Thiamine is needed to help produce energy from the carbohydrates that you eat. It also is required for normal functioning of all body cells, especially nerves.
A deficiency of thiamine can lead to beriberi, fatigue, mental confusion, loss of energy, nerve damage, muscle weakness, and impaired growth. Thiamine deficiency is very rare in the United States because most people consume plenty of grain products. Since thiamine is a water-soluble vitamin, the body excretes excess amounts that you consume. There are no known benefits to taking megadoses of thiamine, including the popular belief that it will help boost energy. Thiamine has no established UL.
Foods rich in thiamine (vitamin B1) include whole-grain foods, enriched-grain foods, fortified cereals, beef liver, pork, and wheat germ.
Fact: When whole grains are refined, certain vitamins, including the B vitamins, are lost during the milling process. Refined grains are therefore enriched, meaning that nutrients—including B vitamins—are added back to the grain.
Riboflavin (Vitamin B2)
Just like thiamine, riboflavin plays a key role in releasing energy from the macronutrients to all cells of the body. Riboflavin also helps change the amino acid (building blocks of protein) tryptophan into niacin, another B vitamin. Riboflavin is important in normal growth, production of certain hormones, formation of red blood cells, and in vision and skin health.
A deficiency of riboflavin is unlikely, but can cause eye disorders, dry and flaky skin, and burning and dryness of the mouth and tongue. There are no reported problems from consuming too much, but again, moderation is the best policy. Riboflavin has no established UL.
Foods rich in riboflavin (vitamin B2) include beef liver, milk, low-fat yogurt, cheese, enriched-grain foods, whole-grain foods, eggs, and green leafy vegetables.
Fact: Riboflavin is easily destroyed by light. For this reason, milk is packaged in opaque plastic or cardboard containers. Riboflavin-rich foods should be stored in darker places and not in transparent containers such as glass.
Niacin (Vitamin B3)
This B vitamin, like its counterparts, is also involved in releasing energy from foods. Niacin specifically helps your body use sugars and fatty acids. In addition, niacin helps enzymes function normally in the body and promotes the health of nerves, skin, and the digestive system.
Although niacin deficiency is rare among populations that eat adequate amounts of protein-rich foods, it can cause pellagra. Symptoms include diarrhea, mental confusion, and skin problems. Niacin, in large doses, has been used as a cholesterol-lowering supplement. Because large doses can cause symptoms such as flushed skin, rashes, and even liver damage, this should only be done under doctors' supervision. Niacin has a UL set at 35 mg per day for adults over eighteen.
Niacin is usually measured in niacin equivalents ONE) because it comes from two sources: niacin itself and from the amino acid tryptophan. Tryptophan can be converted to niacin in the presence of riboflavin and of vitamin B6. Foods rich in niacin include meat, poultry, fish, legumes, peanut butter, enriched and fortified grain products, and yogurt.
Pyridoxine (Vitamin B6)
Vitamin B6 is necessary in helping your body to make nonessential amino acids (the building blocks of protein). These nonessential amino acids are used to make necessary body cells. Vitamin B6 also helps to turn the amino acid tryptophan into niacin and serotonin (a messenger in the brain). This vitamin also helps produce insulin, hemoglobin, and antibodies that help fight infection.
Deficiency symptoms of vitamin B6 include depression, nausea, and greasy and flaky skin. In infants, a deficiency can cause irritability and mental convulsions in severe cases. Proper amounts of breast milk and properly prepared infant formulas contain enough of this vitamin to protect against deficiencies. Vitamin B6 is one of the few water-soluble vitamins that can cause harm if taken in megadoses. Large doses taken over a long period can damage the nervous system. Vitamin B6 has a UL set at 100 mg per day for adults over eighteen.
Foods rich in vitamin B6 include protein-rich foods such as chicken, fish, pork, liver, peanut butter, whole grains, nuts, and legumes.