Too much of a good thing can be dangerous -- and vitamins are no exception. In the case of vitamin A, overdosing can lead to serious health consequences such as liver damage and decreased bone density. Several other nutrients, such as zinc, impact your body's ability to absorb vitamin A. However, researchers don't currently connect zinc to increased risk of vitamin A toxicity. On the other hand, getting enough zinc might help prevent a deficiency in vitamin A.
Vitamin A Benefits
Among the potential advantages of taking the recommended amount of vitamin A is improved immunity through the creation of white blood cells that fight off bacteria and viral infections. While too much vitamin A can lead to birth defects, doctors also link adequate vitamin A intake to a decreased risk of birth defects, notes the National Institute of Health's Office of Dietary Supplements, or ODS. The nutrient additionally aids healthy vision. In particular, vitamin A's promotion of a healthy retina, the nerve located at the back of the eye, improves your ability to see at night.
Overdose Risks
Hypervitaminosis A, or vitamin A toxicity, is more likely to result from vitamin supplements or animal-based foods than from plant-based sources of vitamin A, notes ODS. Severe cases can lead to liver damage, birth defects from too much of the nutrient taken by expectant mothers, osteoporosis and damage to the central nervous system. Signs of potential hypervitaminosis A include headaches, blurred vision, vomiting, nausea and impaired muscle function. Most known cases come from abusing vitamin supplements, but some people have developed vitamin A toxicity after eating excessive amounts of liver. Alcoholics, older people and those with a family history of high cholesterol might be more prone to hypervitaminosis A than the general population, notes the Linus Pauling Institute.
Recommended Amounts
Teen and adult females need about 2,310 IUs of vitamin A each day, while teen and adult males need 3,000 IUs of the nutrient. Teens of both genders should not take in more than 9,240 IUs of vitamin A daily. The tolerable upper limit for men and women is 10,000 IUs. Animal-based forms of the nutrient include chicken or beef liver, milk and cheese. Orange, red, yellow and dark green fruits and vegetables offer plant-based forms of vitamin A.
The Zinc Link
Zinc is more likely to be connected with vitamin A through deficiencies in both nutrients than as a cause of vitamin A overdose, says ODS. You need an adequate amount of zinc to produce retinol-binding protein, a substance that allows your body to absorb and use the vitamin A you consume. Not taking in enough iron, protein or calories also might interfere with proper processing of vitamin A.
Adequate Zinc Amounts
Like vitamin A, zinc is an antioxidant nutrient. It helps bolster your immune system and might reduce the incidence or severity of colds, canker sores and gastric ulcers. To prevent a deficiency in zinc that robs you of the mineral's benefits, as well as its beneficial role in delivering vitamin A, make sure to get adequate zinc through diet and, if needed, from supplements. Teen and adult women need a minimum of between 8 and 9 mg zinc daily, while teen and adult men need at least 11 mg zinc. Do not take more than 40 mg of zinc daily without talking to a physician. Foods high in zinc include red meat, shellfish, cheese, legumes, brewer's yeast and sunflower seeds.
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