Toxicity of Vitamins
~ April 2000 No.100 ~
When people start to look around for supplements they naturally are looking to get the most for their money. That is only natural. And of course the companies that sell vitamins try to get your attention by printing in large print how much each capsule or pill contains: this one has 100 IU´s, another 200, and a third 300 IU´s. The use of supplements is increasing and so is the number of fortified foods. The question that arises, is whether we need to worry about getting too much of a good thing. And the answer is yes and no.
Vitamins are grouped into two broad categories: water soluble vitamins (thiamine, niacin, riboflavin, pantothenate, vitamin B12, folic acid, ascorbic acid) and fat soluble vitamins (vitamin E (tocopherols), vitamin D, vitamin A, vitamin K). It is a general rule that there is very little danger of consuming toxic levels of water soluble vitamins; because they are soluble in water, their elimination from the body is very efficient. So when the body recognizes that the intake of water soluble vitamins exceeds daily needs, the elimination process becomes more efficient and the excess is voided from the body in the urine.
With fat soluble vitamins there is more danger. Fat soluble vitamins are not as quickly eliminated from the body, but rather are stored in fat tissues and in various organs throughout the body. The regulation of the body levels of these vitamins is therefore not as precise as for the water soluble vitamins and long term consumption at levels above those required can mean the build up of toxic levels of fat soluble vitamins in the body. Toxic symptoms have been recorded but for some fat soluble vitamins such as vitamin E and vitamin K it has been difficult to establish the effects of chronic (long term) consumption levels.
For some people supplements may be a way of making up for inadequate or improper nutrition, but attention should be paid to the total intake of all nutrients from all sources (diet plus supplements) to avoid over nutrition and toxic results.
|vitamin A:||100,000 units/day||irritability, fatigue, insomnia, painful bones and joints, abnormal bone growth, loss of hair, itchy skin, anorexia, decreased blood clotting time, birth defects, abortions. In children: malaise and fatigue, desquamation of the skin and mucous membranes, abnormal growth, and pain an tenderness in the long bones. Pseudotumour cerebri, manifesting as headache and irritab|
|vitamin E:|| Not established|
|possible increase in blood pressure|
|vitamin D:||4000-10,000IU /day||anorexia, nausea, diarrhea, muscular weakness, joint pains, calcification of soft tissues, resorption of bone. In children: weakness, lethargy, anorexia and constipation, and chronic overdosage results in hypercalcemia, nephrocalcinosis and eventually azotemia|
|vitamin K3 (menadione):||Not established||possible thrombosis, vomiting, porphynuria in pregnancy can cause jaundice in the newborn, block the effects of oral anticoagulants.|
|vitamin K1 (phytonadione:|| Not considered|
|vitamin K2 (menaquinone):|| Not considered|
|Handbook of Vitamins and Hormones R.J. Kutsky, New York: Van Nostrand-Reinbold, 1973|
J Nutr. 1998,128:2023-7