By Dr. Joseph Mercola,
with Rachael Droege.
Dr. Joseph Mercola,
Author of The No-Grain Diet.
Vitamin A is an important nutrient yet there is much confusion surrounding its appropriate form, dosage and source. Many people do not receive enough of this nutrient, particularly those in developing countries, however, many people are afraid of taking too much due to the commonly heard warnings that too much vitamin A is toxic and can result in birth defects, liver abnormalities, and reduced bone mineral density, which could result in osteoporosis.
Unfortunately, what is rarely addressed along with these warnings is the TYPE of vitamin A. There is a big difference between synthetic vitamin A and vitamin A from natural sources. Most cases of vitamin A toxicity result from an excess intake of synthetic vitamin A in supplements, NOT the natural form of retinol (vitamin A) found in liver or cod liver oil.
In fact, vitamin A, an anti-infective vitamin, is useful for many conditions including vision problems, poor thyroid function, a weakened immune system, and fighting off infections, especially those that involve mucous membranes as vitamin A is used to form the cells lining the digestive, respiratory, reproductive and urinary tracts and all tissue linings of the body. It is also required for the digestion of protein, lactation, reproduction, healthy skin and eyes, and the formation of steroid hormones. Vitamin A deficiency can result in a number of problems including night blindness, dry eyes, eye infections and skin problems.
There are no plant sources of vitamin A (carrots and other yellow/orange vegetables and dark-green leafy vegetables such as spinach and lettuce contain beta-carotene, not vitamin A); it is only present in animal products. If you follow my newsletter then you’ll know that I recommend cod liver oil as the best source of vitamin D (other than the sun, of course), but what you may not know is that it is also one of the best sources of vitamin A.
There is no need to worry about vitamin A toxicity if you take it in cod liver oil, and there are several reasons for this. First of all, as I mentioned earlier the main toxicity that can result from vitamin A is due to SYNTHETIC vitamin A, NOT the natural form found in cod liver oil.
Secondly, cod liver oil has vitamin D in it, and it is virtually impossible to become toxic on vitamin A if you take it along with vitamin D. As you can see in a study published in the December 2003 American Journal of Clinical Nutrition, vitamin D is associated with reduced vitamin A toxicity, and the vitamin D appears to protect against retinal toxicity.
This study also found that the safe upper single dose of retinol IN OIL seems to be 12,000 to 18,000 units of vitamin A per kilogram of body weight. The cod liver oil that I recommend has 1,000 to 1,250 units in a one-teaspoon serving, which means that you will be way under this limit if you follow my recommended dose (one teaspoon for every 50 pounds of body weight per day).
Relying on plant foods containing beta-carotene as your sole source of vitamin A is not a wise choice, and vitamin A deficiency is a major concern for people who choose to have a strictly vegetarian diet. Beta-carotene is the metabolic precursor of vitamin A, which means that it must be converted into vitamin A in the body. However, it takes bile salts, thyroid hormone and dietary fat to facilitate this conversion, and even then the conversion of beta-carotene into vitamin A is poor (it takes about six units of beta-carotene to make one unit of vitamin A).
Further, people with liver or gall bladder problems, hypothyroidism, alcoholism (heavy alcohol intake can impair storage of vitamin A in the liver), or diabetes, and infants, cannot adequately convert beta-carotene to vitamin A, so it is especially important for this large group of the population to consume animal sources of vitamin A like cod liver oil.
If you are consuming a healthy diet, there is no need to supplement with vitamin A. Some excellent sources of natural and beneficial vitamin A include:
Cod liver oil (this will also give you beneficial omega-3 fats and vitamin D).
Raw, whole milk.
Liver (beef, chicken).
Including these foods in your diet should give you adequate vitamin A with no need for supplementation and little to no risk of overdosing. Vitamin A is a fat-soluble vitamin, which means that it needs to be eaten with fat in order to be optimally absorbed. One of the great things about natural foods is that they almost always account for these types of conditions. You’ll notice that all of the foods above also contain fats, so the environment is automatically right for the vitamin A to be utilized by your body.
©Copyright 2003 Dr. Joseph Mercola. All Rights Reserved. This content may be copied in full, with copyright, contact, creation and information intact, without specific permission, when used only in a not-for-profit format. If any other use is desired, permission in writing from Dr. Mercola is required.
Go to ...
Top of Page.
List of Categories.
Blind World Website
Designed and Maintained by:
All Rights Reserved.