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Vitamin A and Hip Fractures in Postmenopausal Women
31 January 2002
by Wyn Snow, Managing Editor

Hip fractures in elderly women often lead to significant declines in health and mobility. Recent research finds that high intakes of vitamin A in postmenopausal women are associated with the highest risk of hip fractures. Does this mean that such women should stop taking vitamin A?

New research analyzed data from 72,000 nurses

This analysis of data from the Nurses' Health Study was published in the January 2 issue of the Journal of the American Medical Association (JAMA 287,1:47-54,2002). The study collected a wide range of dietary and health information from nurses in 11 states over two decades. The analysis looked at 72,337 postmenopausal women aged 34 to 77.

Increased risk of fractures was found with both dietary and supplemental intake of retinol (the technical name for vitamin A). Women with the highest levels of intake experienced approximately 50% more hip fractures than those with the least intake. However, no correlation between intake and fractures was found with beta-carotene, which the body converts into vitamin A. Also, for women taking estrogen replacement therapy, the increase in risk was not as great.

Results of other research in humans and animals

In contrast to this NHS research, the National Health and Nutrition Examination Survey III (which surveyed hundreds of thousands of people) found no association between vitamin A intake and bone density. A study of postmenopausal women in Iowa also found no correlation between vitamin A supplementation and either bone loss or fractures. However, animal studies have found a relationship between very high levels of vitamin A intake and loss of bone mineral density.

Response from dietary supplement trade organizations

The Consumer Healthcare Products Association (CHPA) and the Council for Responsible Nutrition (CRN) both responded that scientific conclusions are based on the totality of the evidence. The Institute of Medicine's current tolerable upper intake level (more familiarly known as a safe upper limit) is set at 3,000 mcg (equivalent to 10,000 IU). The highest level of intake in the NHS study was roughly 4,000 mcg from food and supplements combined. If the Institute of Medicine decides the upper intake level should be lowered, CHPA and CRN said that supplement manufacturers would follow the new guideline for maximum dosage levels.

Vitamin A is an important nutrient

As its place in the vitamin alphabet suggests, vitamin A was the first to be named and one of the first to be discovered. Research has established that vitamin A is essential for growth, immune function, reproduction and vision, and may also reduce the risk of some cancers.

Vitamin A occurs in two forms:

  1. Retinol, the "already formed" variety, is a fat soluble vitamin. Good sources include liver, fish liver oil, egg yolks and milk products.

  2. Beta-carotene is the main form of provitamin A (the body converts beta-carotene into vitamin A). Beta-carotene is found in a wide variety of yellow- and orange-colored fruits and vegetables, as well as leafy green vegetables.

How much vitamin A do people need?

There is no simple answer to this question. The Institute of Medicine set the recommended dietary allowance (RDA) at 900 mcg for men and 700 for women (equivalent to 3,000 IU for men and 2,333 for women). RDAs are a minimalist approach to nutritional needs. They are designed to prevent deficiency diseases in 95% of the healthy population.

However, some doctors believe the official RDA may not be enough to maintain optimal health. Dr. Elson Haas (medical director of the Preventative Medical Center of Marin in San Rafael CA, author of many books and a leading practitioner of integrative medicine) says, "Vitamin A is needed at a level of at least 5,000 IUs per day, though this may vary due to many factors. . . . Analysis of the average American diet reveals that it provides only about 4,000 units of vitamin A daily, so the many problems of vitamin A deficiency, such as visual changes, skin dryness, and increased infections, are more common than most people realize."

As pointed out in SupplementQuality.com's article on RDAs and Safe Upper Limits: Solid Science Versus Bureaucratic Bias, the data used to establish RDAs are not always solid or extensive. Also, the recommended dietary allowance (RDA) is designed to meet the needs of 95% of healthy people -- and does not apply to anyone who is ill. In that article, Dr. Jonathan Wright (Medical Director of the Tahoma Clinic in Kent WA, author of many books and a leading practitioner of nutritional medicine) describes the case of a woman who needed ten times the tolerable upper intake level of vitamin A -- and suffered ulcerating corneas when she didn't get it.

The prudent course

Avoiding hip fractures and ensuring an optimal intake of vitamin A are both vitally important to maintaining wellness. Also, vitamin A (as retinol) is a fat soluble vitamin and can be toxic at high levels in other ways as well. The human body stores any "extra" that it receives, so a diet with too much retinol -- whether from foods or supplements or both -- can create a toxic buildup over time.

What does this mean for consumers who are watching their vitamin intake? Since beta-carotene does not pose any heightened risk of bone density problems or hip fractures (or other negative side effects), people who supplement their diets with vitamin A would be wise to choose beta-carotene supplements.

Clearly, in vitamin A as in shoes, one size does not fit all. To be sure of getting both enough and not too much, the most prudent course is to consult a doctor who is knowledgeable about nutrition and can assess individual needs.

Sources

Diane Feskanich, ScD, et al. "Vitamin A Intake and Hip Fractures Among Postmenopausal Women." Journal of the American Medical Association, Vol 287, No 1, pages 47-54, 2002. ama.ama-assn.org/cgi/content/abstract/287/1/47 (abstract available to public; full text subscribers only).

Elson M. Haas, MD. "Vitamin A -- Betacarotene." Excerpted from Staying Healthy with Nutrition: The Complete Guide to Diet and Nutritional Medicine. www.healthy.net/asp/templates/article.asp?PageType=article&ID=1923.

Natural Products Industry Insider. "Dietary Vitamin A May Increase Postmenopausal Fracture Risk." News story posted 2 January 2002. www.naturalproductsinsider.com/hotnews/21h21339.html.

Reuters Health. "Too Much Vitamin A Can Up Risk of Hip Fracture." Yahoo health news, 2 January 2002.

Tammy Webber. "Study: Vitamin Linked to Fractures." Associated Press health news on Yahoo.com, 2 January 2002.end-of-story

 

 

   
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