Vitamin A: The Bear Had The Last Laugh
30 Mar 2003
I’ve always liked bears. So I find it hard to understand how hunters can slaughter them. That’s why I like this medical story of how the bear, although killed, had the last laugh.
Hunters tracked down a bear and shot it. After the kill they were looking forward to a meal. They all loved liver and consumed large quantities. But although great hunters, they were obviously babes in the wood when it came to bear’s livers. They didn’t know that bear livers contains massive amounts of vitamin A. And so I shed few tears to learn that they all suffered from vitamin A poisoning. Maybe they’ll spare the next bear!
Today there’s a national mania to pop vitamins. There’s no doubt that some help to fight disease and aging. But it’s been aptly said that, "Too much of a good thing is worse than none at all." So think twice before you swallow vitamin A. It’s a two-edged sword, hazardous when taken to excess.
The recommended daily allowance (RDA) for adults is 3,000 international units (IU) with the upper safe limit at 10,000 IU. For children the RDA is from 1,000 to 2,000 IU. In the past it’s been easy to exceed these amounts. A recent report showed that one company had to recall it’s energy bars because they contained 32,500 IU.
So what happens if you consume too much vitamin A? One little girl developed increasing fatigue, loss of appetite and finally kidney failure. Her grandmother owned a health food store and was gradually killing her with excessive vitamin A. Another child developed extreme agitation, fever and pains in her bones. The diagnosis? Vitamin A poisoning.
Consumers who are getting too much Vitamin A complain of coarsening of the hair or hair loss, nausea, dry, scaly skin, fatigue, headaches and blurry vision.
Overdosing during early pregnancy can cause serious birth defects such as skull and facial deformities as well as abnormalities of the central nervous system.
A report from Boston also has disquieting news about vitamin A. The Harvard Health Study has followed 120,000 nurses for the last 26 years. Researchers report that postmenopausal nurses who consumed the most vitamin A had a 48 percent greater risk of hip fracture.
It’s not certain how vitamin A increases hip fractures. We know that bone isn’t like steel, but is constantly undergoing revision. Cells called osteoblasts manufacture bone while at the same time osteoclasts are breaking it down. It’s believed that too much vitamin A increases the activity of osteoclasts and may interfere with the metabolism of Vitamin D which is essential for healthy bone.
Just as too much vitamin A can cause birth defects the right amount is vital for embryonic growth of the fetus. It’s also required for gene and cell function. Without sufficient vitamin A the number of immune cells that fight infection and disease decreases. A is also required for healthy eyes and prevents night blindness. It’s tragic that in under-developed countries 500,000 children every year lose their sight from lack of this vitamin.
In North America most people get adequate amounts of vitamin A . There are several ways to obtain it. Animal foods are the richest source. For instance, three ounces of cooked beef liver provides 30,000 IU and one ounce of cooked chicken liver 14,000 IU!
Vitamin A content in milk varies. A cup of whole milk is about 300 IU. But since vitamin A is added to low fat and skim they can end up containing more A than whole milk. An ounce of cheddar cheese provides another 300 IU. Breakfast cereals are also fortified with A. And if you like carrots they are a good source of A.
The Harvard Study revealed that some nurses obtained 40 percent of their vitamin A from multivitamin tablets. But if you’re getting Vitamin A this way read the amount on the vitamin bottle and make sure it’s not more than 5,000IU. Just remember "the more the merrier" proposition simply does not apply to vitamin A. Like other things in life it must be handled with respect, including bears.
