have recently heard that Vitamin A may be linked to osteoporosis. I
see Vitamin A in nearly everything on food labels, even my soymilk.
What is the connection and how much should I be consuming?
Read the new information regarding this same concern for men at the end of this article.
This study examined the relationship between intake of Vitamin A (from foods and vitamin supplements) and hip fractures in 72,000 postmenopausal women as part of the Nurses' Health Study in the US. Higher levels of Vitamin A intake nearly doubled the risk of hip fractures in those women whose intakes were 10,000 IU vs. those who consumed less than 4,125 IU. This was particularly noticeable in those women not using HRT.
The increased risk was only associated with the pre-formed or animal form of vitamin A (called retinol/retinoic acid or Vitamin A palmitate on food labels). Intake of the form of vitamin A that comes from plant sources, carotenoids such as beta-carotene, did not increase the fracture risk.
Vitamin A is found in some animal foods naturally like fatty fish, liver, and egg yolks. However, the animal form of vitamin A is also added to many other foods like low-fat milks (including soymilk), margarine, cereal, and energy bars. It is also in many vitamin and mineral dietary supplements. Cod liver fish oil is an exceptionally high source of Vitamin A. Become an avid label reader and look for vitamin A content.
What is significant and worrisome about this study is that the increased risk of hip fracture came with dietary vitamin A intake levels previously considered non-toxic. This same relationship has also been shown in some previous Swedish research, too.
The percentages of Daily Value (DV) of Vitamin A listed on food and dietary supplement labels are still based on the 1968 RDA of 5000 IU per day. This RDA is approximately twice as high as the most recent Recommended Dietary Intakes (RDI) for vitamin A by the National Academy of Sciences (3000 IU for men and 2330 IU for women). The recently established safe Upper Limit (UL) for the pre-formed or animal form of Vitamin A is 10,000 IU (the same as 3000 mcg) per day for adults.
Thus, it is easy to see that obtaining an intake at or above the UL would be fairly easy to do when consuming a vitamin supplement with 100% DV for Vitamin A and several fortified foods on a daily basis containing the pre-formed or animal form of Vitamin A. This is the level that was associated with the increased risk of hip fracture.
It is important to note that there are no toxicity concerns regarding the plant form of Vitamin A, beta carotene and other carotenoids, thus no DV, RDI, or UL have been established.
My bottom line recommendations at this time:
The biological mechanisms are still being studied to fully understand the observed connection between higher vitamin A intake and increased risk of hip fractures. This study shows both how complicated nutrition is and also how young the science is.
Certainly, none of us want to unwittingly undermine one aspect of our health while trying to optimize another. I have always treated my osteoporosis very vigorously, not wanting to find myself having beat my cancer only to die from complications of a broken hip. Thus, I am now paying more attention to my sources and amounts of vitamin A, in addition to calcium, vitamin D, magnesium, strength training, and impact exercise!
This is the first study to show that increased fracture risk also exists in men and also the first study to use a biological marker in addition to reported dietary intakes to assess the intake of vitamin A. Confirming previous dietary intake studies, no relationship was found between the serum level of beta-carotene (the plant form of vitamin A) and increased fracture risk.
that men also review this new information and compare their intake of
pre-formed vitamin A from foods and dietary supplements with my bottom
faq posted 05/02, updated 02/03
These questions and answers are intended to be of a general informative nature. Please consult with the Registered Dietitian in your cancer center or your health care provider for nutritional advice that can be individualized to your specific medical condition.
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