Rabu, 13 April 2011


By Grattan Woodson, MD FACP


image A Daily Multiple Vitamin is probably the only way to obtain all the vitamins and micro-nutrients you need over the long run.   While all necessary vitamins and nutrients are found in foods, it is simply impractical to obtain what is needed from what most of us eat every day.  For instance, to obtain the Recommended Daily Allowance (RDA) of the same mix of vitamins and trace minerals found in my preferred brand name multiple vitamin products, Centrum®, would require the daily consumption of an impossible variety and quantity of food.   Even a trained dietician would find it just about impossible to do this.  Study after study now shows the benefit of maintaining an adequate daily intake of these essential nutrients.  No one is too young or too old to benefit either.  For children or adults who can’t swallow large tablets, try chewable Centrum Jr®.  Another way of obtaining a regular daily dose of vitamins, especially for children who won’t take a pill, is by eating a bowel of cold breakfast cereal each day.  Many of these products have been enriched with the equivalent of a multiple vitamin with each serving.  For pre-menopausal women, Centrum A to Zinc® is recommended as it includes iron, an important mineral for menstruating women. For all men and post-menopausal women, Centrum Silver® is the best choice.  It has the same components as Centrum A to Zinc® except iron which is not usually needed for these groups. 

Mega-Doses of Anti-oxidant Vitamins

Mega-doses of anti-oxidant vitamins are no longer recommended.  These new recommendations are for Vitamin C, Vitamin E, and beta-carotene.  Despite the hope that there would be benefit from their use, several very large well designed scientific studies failed to show any cancer or cerebrovascular disease benefit with the use of these vitamins.  Since the best quality long term studies of prevention of chronic degenerative disease with these vitamins failed to show any benefit, routine use of these vitamins in anti-oxidant dose levels can not be advocated. 

Vitamin E
Vitamin E is a fat-soluble vitamin.  It is found naturally in vegetable oils.  The US RDA is 30 iu.  There are anecdotal reports that vitamin E may reduce breast nodules and pain due to fibrocystic breast disease. 

Vitamin C
Vitamin C, ascorbic acid, is a water-soluble vitamin found naturally in fruits and vegetables.  The US RDA is 50 mg.  When used at bedtime, this can lower risk for urinary tract infections in women prone to get them.  Vitamin C is actually ascorbic acid.  Most of the daily dose above 50 mg is passed into the urine.  Ascorbic acid colors the urine yellow and causes it to become acidic which is a difficult environment for bacteria to cause an infection.  Use of more than a 1000 mg of vitamin C per day can lead to kidney stones.  There is no evidence that vitamin C reduces risk or speeds recovery from common colds despite the belief of many. 

Beta-carotene and Vitamin A
Beta-carotene is a chemical precursor of vitamin A.  It is found in yellow and green vegetables like carrots, sweet potatoes, and spinach.  The US RDA for vitamin A is 5000 iu.  The body converts beta-carotene into vitamin A as it is needed for metabolism.  While beta-carotene does not appear to represent any health threats consumption of high quantities vitamin A can cause toxic skin rashes and lead to osteoporosis. 

The Folic Acid Story
For years, nutrition scientists defined the minimum daily requirement for folic acid based upon the amount needed to prevent anemia.  This is because this medical condition was the only one we knew was due to folic acid deficiency and was easy to measure with a simple blood test. In the 1980s scientists and public health officers at the CDC first came to understand that the crippling and sometimes fatal birth defect, spina bifida, was caused by maternal folic acid deficiency. Then came the realization that a low intake of folic acid caused a high serum homocystine level.  Homocystine is a blood substance that damages the artery wall in a way that contributes to the development of cardiovascular disease.   Homocystine levels can be lowered dramatically by folic acid and vitamin B12 supplementation.  When used for this purpose, I recommend supplementation with two 400 mcg tablets daily plus two 100 mcg vitamin B12 tablets daily.  Folic acid deficiency has also been linked to colon cancer.  In the long running Nurses Study, women who had the highest daily intake of folic acid had the lowest risk for colon cancer.  In fact, the risk can be reduced by two thirds after 15 years of use of a daily multiple vitamins.  Unless you have a special need for higher doses, a daily intake of 400 mcg of folic acid appears to be sufficient to obtain the important health benefits of the necessary nutrient.  This is the amount found today in multiple vitamin preparations.  Most diets have some folic acid in them.  Foods especially rich in folic acid include white beans like soy and navy beans.  The US FDA now requires food producers to add folic acid to flour and cereal products so consumption of these complex carbohydrate foods will increase your folic acid intake.

Vitamin D
Vitamin D is a fat soluble vitamin that can be made in the skin when exposed to ultraviolet light.  It is also added to bread and milk products.  Vitamin D is necessary for the proper absorption of calcium from the diet and its lack causes weak fracture prone bones.  A number of studies indicate that vitamin D deficiency is more common in the US than previously thought.  Adults after age 70 are at especially high risk and African Americans have higher rates of vitamin D deficiency than other Americans.  Anyone who consumes a limited diet and doesn’t get out in the sunshine often is at risk.  The US RDA for vitamin D is 400 iu which is the amount contained in all multiple vitamin tablets.  This is fine for young folks but after age 60 studies show that 800 iu is best to prevent osteoporosis.  In fact, some patients with osteoporosis may require even higher doses of this vitamin.  Beware of taking too much vitamin D unless specifically directed to by your doctor as too much can be quite toxic. 

Calcium is important for preventing osteoporosis, colon polyps and possibly cancer, and may help lower blood pressure.  While all multiple vitamins include some calcium, the amount is much too small to matter much. Pre-menopausal and young adult men need about 1000 mg of elemental calcium daily with postmenopausal women and men over age 50 needing about 1500 mg each day.  Daily calcium requirements are the same whether you are getting your calcium from the diet, a supplement, or a combination of both.  Studies show that except for calcium citrate (Citracal®) there is not much difference in how well these different sources of calcium are absorbed from the intestine.  Calcium carbonate, the most common supplement used, is absorbed into the body better if it is taken with meals or a snack than on an empty stomach.  The reason for this is that acid released from the food during digestion helps break up the calcium carbonate molecule, which is necessary for calcium absorption.  As some people get older their stomachs fail to make as much acid as in the past.  Without acid, the calcium stays in a form that cannot be absorbed.   Citracal® can be absorbed in patients whose stomach lacks acid or who take certain medications (Zantac®, Tagamet®, Pepsid®, Prilosec®, Nexium®, etc.) that reduce stomach acid.  In these patients, Citracal® may be the preferred option.

Recommended Daily Calcium Allowance

Infants, Children, & Teens

  • Birth to 6 months = 400mg
  • 6 to 12 months = 600mg
  • 1 to 5 years = 800mg
  • 6 to 12 years = 800mg to 1200mg
  • 12 to 19 years = 200mg to 1500mg


  • 21 to 30 = 1200mg to 1500mg
  • 31 to 50 = 1000mg
  • 50 + = 1500mg
  • Pregnant and lactating women = 1500mg

Optimal Calcium Intake. NIH Consensus Statement 1994 Jun 6-8; 12(4): 1-31.


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