There are four fat-soluble vitamins, which are stored for long periods by the body. This means that they can build up to toxic levels, but this problem is much rarer than the many illnesses that can be caused by failing to take adequate levels.
Vitamin A Vitamin A facilitates the formation and maintenance of teeth, bones, soft tissue, mucous membranes, and skin. The recommended daily allowance is 900 µg (micrograms). Levels below this can result in night-blindness and keratomalacia (dry cornea). Levels above 3,000 µg can be toxic. Some animal livers, such as that of the polar bear, contain so much Vitamin A that they are poisonous to humans, but the vast majority of toxic events are related to vitamin pills. Hypervitaminosis A can cause bone and skin problems, hair loss, and birth defects. Extra care must be taken with pregnant women and with small children. Vitamin A can be found in the following common foods:
- Halibut fish oil
Vitamin D helps the body use calcium. It can be produced by the body with the help of ultraviolet radiation from the sun. Thus, anyone concerned about vitamin deficiency may want to regularly schedule time outdoors. One warning: while the skin has a built in brake to stop it from producing too much Vitamin D, other health risks, such as cancer, will continue to rise with sun exposure.
The recommended daily allowance is 5.0 µg-10 µg. Levels below this can result in rickets, which softens the bones and raises the risk of breakages.
The safe upper limit for Vitamin D has not been pinned down, but recorded cases of overdose are almost all at over 1000 µg. Some of the symptoms of toxic exposure are excessive thirst, itch, urine production, blood-pressure, and abnormal calcium absorption.
In addition to sunlight, Vitamin D can be obtained from the following common foods:
- Fortified milk
Vitamin E (Tocopherol)
Vitamin E is an antioxidant that facilitates the formation of red blood cells and the exploitation of Vitamin K. The recommended daily allowance is 15 milligrams. It is extremely rare to suffer any serious health problems because of deficient Vitamin E, but there have been some cases of newborns developing anemia through a lack of Vitamin E.
The dangers of excessive Vitamin E are not fully established. Investigation is ongoing, and points to some possible risks associated with blood clotting.
Vitamin E can be obtained from the following common foods:
- Wheat germ
- Spinach and other green leafy vegetables
- Vegetable oils and products made from vegetable oils, such as margarine
Vitamin K is crucial for healthy blood clotting. The recommended daily allowance is 120 µg. Deficiencies can cause excessive bleeding and bruising, but this problem is very rare because bacteria in the intestine is usually capable of producing sufficient amounts.
No dangerous upper dosage limit has yet been established.
Vitamin K can be obtained from the following common foods: