Function: As well as being necessary to new cell growth, vitamin A helps fight infections, and is essential for healthy skin, blood, bones and teeth. It also plays essential roles in the kidneys, bladder, lungs and membranes, as well as helping maintain good eyesight. Vitamin A also helps eyes adjust to changes in levels of light.
Sources: Fish liver oils, liver, dairy products, carrots, cantaloupe, peaches, squash, tomatoes, and all green and yellow fruits and vegetables can fuel the body with vitamin A. Note: Many plants contain beta carotene, which the body converts into vitamin A. Dark, green, leafy vegetables and yellow and orange vegetables and fruits are excellent sources of beta carotene.
Recommended daily intake: It is recommended that women consume 800 mcg and men consume 1000 mcg of vitamin A daily. Like other fat-soluble vitamins, vitamin A can be harmful when too much is consumed. Too much can lead to toxicity and other health problems, including an increased risk of fractures in postmenopausal women, nausea, blurred vision and irritation. In more severe forms of overconsumption, it can lead to hair loss, growth retardation and an enlarged spleen and liver. Too little vitamin A (though rare in the United States) can lead to night blindness, eye inflammation and diarrhea.
Function: Vitamin B-6 helps the brain function at its peak and helps the body convert protein to usable energy. It is also needed for the production of red blood cells and antibodies.
Source: Meats, whole grain products, bananas, green leafy vegetables, pecans, eggs and milk are excellent sources of B-6.
Recommended daily intake: Women require 1.6 mg of B-6 daily, while men need 2 mg. Daily intake of over 250 mg can lead to nerve damage. Pregnant women should not take more than the recommended amount, as it could harm a developing fetus. As a water-soluble vitamin, B-6 must be replenished each day. Any B-6 not used is eliminated in urine, thus new sources are always needed.
Function: Vitamin B-12 works with folic acid to produce healthy red blood cells. Also, it plays key roles in maintaining health of the nervous system, absorption of foods, protein synthesis, carbohydrate and fat metabolism, and normal digestion.
Sources: Liver, kidneys, muscle meats, fish, dairy products, meat and eggs are all good sources of B-12.
Recommended daily intake: Both men and women need 2.0 mcg of B-12 daily. Because B-12 is water-soluble, it is constantly lost in urine when not used and a steady supply is needed. B-12 deficiency can lead to a type of anemia, walking and balance problems, sore tongue, weakness, confusion, and in advanced cases, dementia. Pregnant or breastfeeding women should not take more than 2.6 mcg and 2.8 mcg of B-12, respectively. People over the age of 50 may need B-12 supplementation as the body's ability to absorb vitamin B-12 from food sources diminishes.
Function: Vitamin C helps to heal wounds, prevent cell damage, promote healthy gums and teeth, strengthen the immune system and absorb iron. It also helps to neutralize free radicals in cells that promote aging, fight bacterial infections and aid in the production of red blood cells.
Sources: Fresh fruit and berries (especially citrus fruits), green vegetables, onions, tomatoes, radishes and rose hips are all excellent vitamin C sources.
Recommended daily intake: Men and women should each consume at least 60 mg of vitamin C daily. Many things can increase the need for vitamin C in the body, including stress and smoking. For smokers, recommended intake increases to 110 mg for women and 125 mg for men. While not getting enough vitamin C can lead to scurvy, consuming more than 2000 mg on a daily basis can lead to headaches, increased urination, mild diarrhea, nausea and vomiting. Pregnant and breastfeeding women should not take more than the recommended amounts of Vitamin C.
Function: Vitamin D is important in helping the body use and absorb calcium. It is also necessary in the utilization of phosphorous. Also known as Calciferol, it promotes strong bones and teeth, prevents rickets, supports muscle and nerve function and, some studies have shown, helps prevent osteoporosis.
Sources: Fortified milk and cereals, eggs, tuna, fish-liver oils and sun exposure all help the body obtain vitamin D.
Recommended daily intake: Men and women aged 19-50 should consume at least 200 IU of vitamin D on a daily basis. People over the age of 50 should consume at least 400 IU daily, as the body's ability to convert sunlight to vitamin D decreases with age. While too little vitamin D can lead to weakened bones and an increased risk of fractures, too much vitamin D can cause nausea, vomiting, poor appetite, constipation, weakness and weight loss. Prolonged exposure to too much vitamin D can lead to health problems and toxicity. If you take antacids, some cholesterol-lowering drugs, some anti-seizure medications or steroids, know that they all interfere with the absorption of vitamin D.
Function: Vitamin E acts as an antioxidant that prevents premature reaction to oxygen in the body and the breakdown of many substances in the body. It neutralizes free radicals in the body that would otherwise cause damage to cells and tissue, while aiding in circulation, clotting and healing. Some studies have even shown that vitamin E decreases symptoms of premenstrual syndrome and certain types of breast disease. Other studies have shown that taking large doses of vitamin E has decreased the risk of coronary artery disease.
Sources: Most vegetable oils, wheat germ, soybean oil, raw seeds and nuts, egg yolk, whole-grain products, beef liver, peanut butter and unrefined cereal products are good sources of vitamin E.
Recommended daily intake: Women need 8 mg and men require 10 mg of vitamin E on a daily basis. Though it's almost impossible to have a vitamin E deficiency, too much can cause nausea and digestive tract problems. Prolonged overexposure can lead to toxicity and other health problems.