Vitamins are molecules your body needs in small amounts for optimal functioning of your cells, tissues and organs. You can consume your daily allotment of vitamins through a well-balanced diet or with supplements. In the correct dosage, vitamins benefit your health. However, taking too many vitamin supplements might render certain vitamins harmful. Seek the advice of a dietitian or your health care provider before including vitamin supplements in your nutrition plan.
Vitamin A
Vitamin A is one of four fat-soluble vitamins -- vitamins A, D, E and K. Vitamin K toxicity is very rare in Western countries. Because your body stores them in your fat tissues, fat-soluble vitamins are more likely to accumulate and potentially cause negative effects than water-soluble vitamins. In recommended amounts, vitamin A promotes good vision, supports your immune system and helps synthesize red blood cells. Food sources of vitamin A, such as carrots and sweet potatoes, contain beta-carotene, a precursor molecule that converts to vitamin A only as your body needs it. Therefore, foods pose little risk of causing vitamin A toxicity. However, pre-formed vitamin A, contained in some supplements, can be harmful if you consume more than 3,000 micrograms, or mcg, per day over an extended period of time, according to the Linus Pauling Institute. Vitamin A toxicity symptoms include dry or itchy skin, bone pain, cerebral edema and headache.
Vitamin D
Vitamin D, another fat-soluble vitamin, assists your body in absorbing dietary calcium. Your skin can synthesize vitamin D upon exposure to ultraviolet radiation from sunlight, or you can consume this vitamin from fortified milk, fortified cereal or canned fish. Vitamin D toxicity is unlikely to occur from sun exposure, but excess dietary intake -- more than 4,000 international units, or IU, every day -- might lead to excess calcium in your blood. Elevated blood calcium might, in turn, cause calcium to deposit in soft tissues, such as your heart or kidneys. You might also experience loss of bone mass and the formation of kidney stones if you regularly consume vitamin D at unsafe levels.
Vitamin E
Fat-soluble vitamin E, in addition to its role as an antioxidant, functions to prevent your platelets from aggregating as they normally do during blood clotting. While inhibition of platelet aggregation might be helpful under certain medical conditions, excess vitamin E can increase your risk of hemorrhage. Foods rich in vitamin E, such as plant-based oils, nuts and seeds, are safe to consume, but supplementing with more than 1,000 mg daily might affect the ability of your platelets to clot your blood during surgery or in the event of an injury.
Vitamin C
Vitamin C is a water-soluble vitamin abundant in citrus fruits, strawberries, peppers and tomatoes, among other fresh produce. Similar to vitamin E, vitamin C serves as an antioxidant. It also assists in wound healing and helps your body absorb iron. Regularly ingesting more than 2,000 mg of vitamin C each day might be harmful to your body, as it might lead to gastrointestinal upset, kidney stones and accumulation of iron in your blood and tissues.
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