Excess Of Fat Soluble Vitamins

Fat-soluble vitamins, which include vitamins A, D, E and K, are found in the lipid-rich tissues of both animals and plants. These vitamins can be stored in your body tissues for longer periods of time than water-soluble vitamins, such as the B vitamins and ascorbic acid. Because they can remain in your body, some of the fat-soluble vitamins can reach toxic levels if you regularly take more than you need. Dr. Elson Haas, author of "Staying Healthy with Nutrition," states that the range between effectiveness and toxicity for fat-soluble vitamins, especially for vitamins A and D, is much narrower than it is for most other essential nutrients.

Vitamin A Toxicity

The recommended intake for vitamin A ranges from 1,000 to 3,000 IU daily, depending on your age. Upper limits, or ULs, range from 2,000 to 10,000 IU. Toxicity can occur in adults with daily doses of 25,000 IU for one to two months or with higher doses -- 500,000 to 750,000 IU -- for several days. Symptoms of toxicity include headaches due to brain swelling, dizziness, irritability, nausea, vomiting, abdominal pain, hair loss, itchy and flaky skin, loss of appetite, weight loss, liver enlargement, menstrual irregularities and stunted growth in children. According to a 1999 report in "Annual Review of Pharmacology and Toxicology," adequate vitamin A intake during pregnancy is vital, but excessive intake can increase the risk for birth defects.

Vitamin D Toxicity

The synthesis and metabolism of vitamin D in the human body is complex. Your skin produces vitamin D every time you are exposed to sunshine, and you also absorb it from your diet. Recommended daily intake varies from 200 to 600 IU daily, depending on your age and gender. ULs vary from 1,000 to 2,000 IU daily, although some experts, such as Dr. Reinhold Vieth at Mount Sinai Hospital in Toronto, believes that the UL should be as high as 10,000. Prolonged consumption of high doses -- tens of thousands of IU daily -- can lead to high blood calcium levels and calcification of your muscles and other soft tissues. Excessive thirst, diarrhea, nausea, weakness and headaches are additional symptoms of vitamin D toxicity.

Vitamin K Toxicity

Vitamin K is actually a combination of three related compounds. Food sources of vitamin K are slightly different from the form produced by bacteria in your gut, and a synthetic form of vitamin K is also available. Recommended daily intakes vary from 2 mcg for infants to 120 mcg for adult males. According to Haas, toxicity from natural sources -- food and intestinal production -- is rare, but supplemental intake or medical treatment with vitamin K can lead to toxic symptoms, including flushing, sweating, chest pressure or pain and hemolytic anemia, a condition caused by the destruction of your red blood cells.

Vitamin E Toxicity

Vitamin E is not stored as readily as the other fat-soluble vitamins, so toxicity is uncommon. Excess vitamin E is fairly rapidly eliminated in your urine and feces, and most surpluses clear your body within several days. Recommended daily intakes vary from 6 IU in infants to 28 IU in lactating women. Most people tolerate 400 to 600 IU daily. Doses of 1,200 to 1,500 IU daily for several weeks or months can lead to immune suppression, increased blood pressure and increased bleeding tendencies. Additional symptoms of toxicity include nausea, diarrhea and flatulence.

Considerations

Toxicity from natural sources of fat-soluble vitamins is unlikely. However, unlike water-soluble vitamins, which have a wide margin of safety, excessive doses of supplemental fat-soluble vitamins, particularly vitamins A and D, can lead to toxicity. If you feel you need additional nutritional support with these vitamins, ask your doctor.