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http://www.aolhealth.com/healthy-living/nutrition/vitamin-safety?icid=100214839x1204715369x1200190215
Your Vitamins Could Kill You
By Caroline Howard
About half of us take dietary supplements, mostly vitamins and minerals, according to the American Dietetic Association. But if you're eating a healthy diet and taking vitamins, you may be getting more than you bargained for. And, with so many fortified foods and drinks available — even if you tend to skimp on the healthy stuff — many medical experts are concerned that you may be at risk for vitamin overload. Here, 10 vitamins and minerals to watch.
1. Vitamin A (retinol)
Recommended Dietary Allowance (RDA): 3,000 International Units (IU) for men; 2,330 IU for women. Limit: 5,000 IU
This vitamin helps maintain healthy teeth, bones, skin, vision and mucous membranes. But too much can work in the opposite direction, causing reduced bone density and osteoporosis, hair loss and liver problems. Excessive amounts of vitamin A during early pregnancy (over 10,000 IU) was linked to birth defects in Boston University School of Medicine study. Ironically, vitamin A deficiency also causes birth defects.
Foods: Red, yellow and orange fruits and vegetables.
2. Vitamin B6
RDA: 1.3 mg. Limit: 100 mg
Your nervous and immune systems depend on vitamin B6, also known as pyridoxine. And if you're a big meat eater, listen up: The more protein you consume, the more B6 you need to use that protein. (Sidenote: Higher doses of B6 also benefit those who abuse alcohol). Studies suggest that excessive amounts may cause damage to the nervous system, specifically to the arms and legs. It is, however, reversible when dosage drops, according to the National Institutes of Health.
Foods: Baked potato for the vegetarians, pork loin or roast beef for the omnivores.
3. Vitamin B9 (folic acid)
RDA: 400 mcg. Limit: 1,000 mcg
Folate occurs naturally in food; folic acid is found in vitamins and fortified food. The specific role of both, among many benefits, is to make and maintain healthy blood. Nausea, insomnia and abdominal distension are typical symptoms of overdose. Excess folic acid can also mask signs of B12 deficiency, including anemia.
Foods: Fortified breakfast cereals, blackeye peas and spinach.
4. Vitamin C
RDA: 90 mg for men; 75 mg for women. Limit: 2,000 mg
Can there be too much of a good thing? According to some, including Nobel Prize winner Linus Pauling, no. His eponymous institute recommends at least 400 mg of vitamin C each day in order to best to take advantage of its antioxidant and common cold-fighting properties, among others. However much you decide to take, toxicity is very rare; the body cannot store the vitamin. However, amounts greater than 2,000 mg daily are not recommended by the National Academy of Sciences because it can can lead to indigestion, diarrhea and GI discomfort. Diabetics, pregnant women and others who are testing for blood sugar levels should also be wary of ingesting high doses.
Foods: Kiwifruit, parsley and blackcurrant all have more vitamin C than oranges
5. Vitamin D
RDA: 400 IU. Limit: 2,000 IU
It's claimed that as little as 10 minutes of UV-B sunlight daily offers the recommended level of vitamin D. But for many of us, including black people and those with darker skin pigments, a little dietary help is in order. Unfortunately, this vitamin best known for building strong bones and fighting rickets and osteoporosis, is naturally found in few foods. So it's really all about balancing any supplements with fortified foods and drinks. Unlike water soluble vitamins like vitamin C, that simple pass through the urine, vitamin D is fat soluble and isn't removed as easily. More than 2,000 IU daily can lead to too much calcium in the blood or hypercalcemia, which can lead to kidney stones and kidney damage.
Food: Fatty fish such as salmon and tuna, plus fortified milk and energy bars.
6. Vitamin E
RDA: 15 IU. Limit: 400 IU
An antioxidant, vitamin E has long enjoyed a reputation for benefits to cardiovascular health, cancer and hot flashes due to low estrogen. Recently, though, it has come under suspicion and attack as having “no proven clinical benefits,” according to the Annals of Internal Medicine. Separate studies have linked excessive vitamin E intake to an increased risk of all-cause mortality, congestive heart failure and increased bleeding. The Centers for Disease Control and Prevention (CDC) has reported that over 11 percent of Americans consume in excess of 400 IU.
Food sources: Vegetables oils, including wheat germ, safflower and corn oil.
7. Beta-Carotene
RDA: None. Limit: None (not enough studies)
Although research is still underway, beta-carotene is thought to help boost the immune system and prevent heart disease and a number of cancers, and is especially powerful against leukemia. Consuming toxic levels of beta-carotene only occurs in very rare circumstances, but can lead to increased risk for heart disease and a temporary yellowing of the skin. Research shows that people who smoke and take high levels of beta-carotene supplements may be more susceptible to lung cancer.
Foods: Spinach and carrots for the veggie lovers; for those with a sweet tooth, go for apricots or cantaloupes.
8. Calcium
RDA: 1,000 mg. Limit: 2,500 mg
Calcium has one of the most important job in your body. Ninety-nine percent of our body's calcium is stored in our bones and teeth to support and maintain their structure. The remainder is found in the blood, muscles and fluid between cells. While calcium is obviously important, too much can impair kidney function and decrease absorption of other minerals in the body. Excessive intake of calcium or vitamin-D (50,000 IU or higher) overtime can result in hypercalcemia (elevated levels of calcium in the blood).
Foods: Milk, yogurt and cheese are the main suppliers, but don't overlook leafy greens.
9. Iron
RDA: 18 mg. Limit: 45 mg
Iron is one essential mineral that must be consumed in careful moderation. An adequate amount of iron is essential for cell growth regulation and specialization. Too much, however, can be even more dangerous than an inadequate amount. Studies show that high iron levels may be a risk factor for heart disease. Iron also competes with important minerals, like copper, for absorption in the body. The scariest possibility? Too much iron can result in iron toxicity, which can progressively damage the liver, heart and endocrine glands. Without proper care, the damage done to these organs can ultimately result in premature death.
Foods: Beans, dried fruits, eggs and fortified breads.
10. Zinc
RDA: 11 mg for men; 8 mg for women. Limit: 40 mg
Zinc is found in almost every cell of your body, and is key to keeping a healthy immune system. While it supports growth and development, overexposure can lead to hair loss, ovarian cysts and muscle spasms. It's a balancing act. Not enough zinc can cause diarrhea, delayed sexual maturation and impotence and growth retardation. And it isn't hard to max out when using zinc lozenges for cold relief. ConsumerLab.com, an independent firm that evaluates health and nutrition products, found that lozenge label requirements suggest a dose every two hours to be effective. This results in zinc intake several times more than needed.
Foods: Oysters, beef, pork, and yogurt all contain zinc.
Final Word of Advice
When tallying up your daily dosage, always remember to add up the dosage you're getting from the natural foods and fortified foods you eat and the vitamins you take. Also, unless your doctor specifically prescribes vitamin supplements for a medical condition, it's generally a good idea to talk to your health provider before taking anything more than a basic multivitamin.
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