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Nutrient Series: Vitamins
When parents worry that their child is getting good nutrition, they're often concerned about vitamins. But if your little one is getting a balanced diet of protein, carbohydrates and fats, most likely he's receiving all the vitamins required for his age.

Vitamins and minerals are called micronutrients because unlike the macronutrients—protein, fat and carbohydrates—which are measured in grams, vitamins and minerals are measured in micro-units, such as milligrams. Vitamins are not sources of energy but work to enhance the metabolism of the macronutrients. We are not going to discuss minerals in this article because, with the exception of iron, mineral deficiency is rare.

There are two categories of vitamins: fat-soluble and water-soluble. The fat-soluble vitamins A, D, E and K are stored in body fat and tend to stay in the body for longer periods of time. The water-soluble vitamins B and C are transported through the body in the water component of our fluids and are passed out mostly through the urine.

Vitamins have different roles: Vitamins C and E are antioxidants, D and K are important for bone health, Vitamin A helps with vision and Vitamin K with blood clotting. The B vitamins are coenzymes, substances that work with your body's enzymes to cause metabolic reactions. Vitamin C, although not a coenzyme, works like one for some metabolic processes. Understanding the function of vitamins is an important part of understanding nutrition.

The Fat-Soluble Vitamins:

Vitamin A is most important for maintaining healthy eyesight and allows you to see colors. It combines with a protein called opsin to allow you to see at night, helping the eye to dilate and adjust to light changes. Beta-carotene is the best source of Vitamin A and is found in dark orange and leafy green vegetables. Try sweet potatoes, carrots, spinach and broccoli for lots of this vitamin.

Vitamin D is also known as the sunshine vitamin. It's best known function is to work with calcium for bone health. Vitamin D can be made in your body from sunlight, but sunscreens and less outdoor activity has caused some concern about vitamin D deficiency, also known as rickets. Current recommendations are to expose your skin, at least your face, to 30 minutes of sunlight each day. If this is not possible, the best food sources are pasteurized milk and fortified cereals.

Vitamins A and D are stored in the body for a very long time, so supplementing is never recommended unless a physician prescribes it. Too much of either vitamin can be toxic and cause damage to the body. You cannot become toxic from food sources, although you might turn orange from too much beta-carotene.

Vitamin E is an antioxidant and protects various organs and membranes from damage. Vitamin E is nontoxic, but too much can interfere with blood clotting. Good food sources are nuts, safflower oil, strawberries and wheat germ.

Vitamin Khelps your blood clot, protects you from bleeding profusely and helps to form bone. Obviously, Vitamin K deficiency, which is very rare, would cause bleeding and bone fractures. It is excreted faster than the other fat-soluble vitamins, so toxicity from food is not often seen. The best food sources are raw turnip greens and spinach, raw cauliflower and raw cabbage. You can also get Vitamin K from green beans, broccoli, liver and eggs.

Water-soluble vitamins:

There are eight B vitamins: thiamin, riboflavin, niacin, B6, folate, B12, pantothenic acid and biotin. They are found throughout a wide variety of foods, so eating a balanced diet should keep you covered.

Thiamin works with reactions that produce energy, so a deficiency will impact those body systems that have high-energy needs like the central nervous system (brain and nerves). Alcohol interferes with thiamin absorption, so deficiencies in industrialized countries are most often seen in alcoholics. Wheat germ, pork, enriched grains and rice, legumes and nuts are your best food sources.

Riboflavin is also necessary for reactions that cause energy. Beef liver is the best source; milk and milk products are excellent foods for this vitamin as well.

Niacin is a coenzyme involved in hundreds of metabolic reactions, many of them providing energy, and also in the synthesizing of fatty acids. Excellent sources are chicken, tuna, salmon, ground beef and peanut butter.

Vitamin B6 helps make non-essential amino acids within the body and supports the immune system. It's found in bananas, watermelon, meat, fish and poultry. Starchy vegetables, like potatoes, and also good sources. Too much B6 over time can cause painful nerve damage, which is unusual for a water-soluble vitamin. Such mega-doses are obtained from supplements.

Folate is most important to DNA synthesis and cell division, and a lack of folate in a woman's diet can cause neural tube disorders (spina bifida) in babies. Since women should have good folate levels before becoming pregnant, foods are now fortified with this vitamin. Folate also appears to lower a woman's colon cancer risk. Fortified cereals provide the best supply, but you can also find folate in spinach, lentils, romaine lettuce, asparagus and liver.

Vitamin B12 is the only B vitamin not found in plant-based foods. However, B12 can store in the liver for up to two years. It is essential to activate folate for DNA synthesis and maintains the covering of the nerves, protecting them from damage. Vitamin B12 is easy to get from meat and fish. Only vegans are at risk for B12 deficiency and must supplement to keep their stores adequate.

Pantothenic acid, like biotin, riboflavin and thiamin, is involved with many basic metabolic pathways. Pantothenic acid is pretty fragile but is so available in foods that a deficiency is close to impossible.

Biotin is similar in function to pantothenic acid. Food sources are cauliflower, cheese, peanuts and cooked eggs. Deficiency is rare.

So, vitamins are tiny little substances that deliver big returns when it comes to body metabolism. The human body is very efficient in extracting, storing and using vitamins. In most cases, very little supplementation is necessary if a variety of food is eaten. If you are still concerned about the vitamin status of your little ones, a simple generic child's vitamin every few days will fill in any gaps.

I will write about Vitamin C, probably the best known of the water-soluble vitamins, in a separate article.

Susan M. Leisner RD, IBCLC, RLC Nutritionist & Lactation Consultant