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Greens for bones ... researchers say vitamin K may improve bone health.

It is well known that green leafy vegetables such as cabbage, cauliflower, spinach, kale and broccoli are healthy foods. But did you know that these vegetables may help keep bones strong? And this isn't merely because some of them contain calcium, but because they are the best sources of vitamin K.

Until recently, vitamin K has been most well known as a fat soluble vitamin that plays an important role in blood clotting. However, researchers have also found that circulating vitamin K blood levels are often low in patients with osteoporosis and osteoporotic fractures.

According to a study that appeared in the American Journal of Clinical Nutrition in 1999, Vitamin K is needed to make a protein that's essential for bone formation.

In the great majority of people, beneficial intestinal bacteria make much of the K needed for this purpose, which is why you hear so little about this vitamin. But to get enough K, especially to keep bones strong, you need to eat K-rich vegetables. Studies examining vitamin K supplementation have also shown promising results for increasing bone mineral density.

In the U.S., the ongoing Nurses' Health Study followed 72,000 middle-aged women for 10 years. It found that those who consumed moderate or high amounts of vitamin K (nearly all from vegetables) had a 30 percent lower risk of hip fractures than women consuming little or no K. This held true even when other factors affecting bone health, such as calcium and vitamin D, were factored in. It didn't take much vitamin K -- about 100 to 150 micrograms a day -- to achieve this protective effect.

Worldwide, only a handful of researchers study vitamin K. But with the aging of the population, this vitamin may command a bigger following as its importance to the integrity of bones becomes increasingly clear. Sarah Booth, of the Vitamin K Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston, says that it has become apparent that Vitamin K isn't as abundant in the diet as once thought.

A recent survey Booth conducted in collaboration with the Proctor & Gamble Company supported what she had seen in an earlier study of U.S. diets by the vitamin K lab. If you're between the ages of 18 and 44, there's a good chance you don't get enough vitamin K. Booth and her colleagues have found that people over age 65 consume more K than those in the 20 to 40 age bracket.

However, before vitamin K can be considered truly effective in decreasing fracture risk, randomized placebo-controlled trials need to be performed. The only such trials that have been published to date have been conducted in Japan. All these trials showed vitamin K to have a beneficial effect on bone mineral density (bone mineral density is the parameter doctors measure to determine if an individual has osteoporosis).

The University of Toronto is currently conducting the first Canadian research study to test the effects of vitamin K against a placebo. This study will also be the largest study of its kind ever performed in postmenopausal women with low bone mass.

Vitamin K supplements are currently not available in Canada unless by prescription for blood coagulation treatment. Multivitamins bought in the U.S. may contain some vitamin K. Because of vitamin K's role in blood coagulation, individuals on blood thinners should check with their doctor before attempting to increase their intake.

Vitamin K-Rich Foods

* 1/2 cup of cooked broccoli (90 micrograms of vitamin K)

* 1/2 cup of cooked Brussel sprouts (230 micrograms of vitamin K)

* 1 cup of coleslaw (120 micrograms of vitamin K)

* 1/2 cup of cooked collards (370 micrograms of vitamin K)

* 1 and 1/2 cups of iceberg lettuce (30 micrograms of vitamin K)

* 1 and 1/2 cups of romaine lettuce (190 micrograms of vitamin K)

* 1/2 cup of cooked spinach (320 micrograms of vitamin K)

* Some types of oil also have small amounts of vitamin K

Vitamin K Research Needs Participants

The University of Toronto study is called ECKO (Evaluation of the Clinical Use of Vitamin K in Postmenopausal Women with Osteopenia). Researchers are currently looking for postmenopausal participants of any age.

The main goal of the ECKO trial is to evaluate the clinical use of Vitamin K supplementation on bone mineral density. This is a two year study and requires four visits to the University Health Network Osteoporosis Program, Toronto, Canada, in the first year, and two additional visits in the second year.

A postmenopausal woman may qualify if she is not taking: Hormone Replacement Therapy, Bisphosphonates, Selective Estrogen Receptor Modulators, Anti-coagulants, and high doses of vitamin A and/or E.

Participants must have a condition called osteopenia, or low bone mass. Low bone mass is often a symptomless condition that can progress undetected for many years without a bone mineral density scan. If you do not know your bone mineral density scan results or you have not had a bone mineral density scan, one will be performed for screening purposes to see if you qualify.

Participants can expect:

* To take calcium, vitamin D and perhaps vitamin K (depending on the treatment group) supplementation for 2 years. Supplements are provided free of charge.

* To complete questionnaires about nutrition, lifestyle and health status.

* To provide small samples of blood for tests.

* To have 3 bone mineral density scans.

For more ECKO information, contact: Osteoporosis Program, Toronto General Hospital, University Health Network, Toronto, Ontario, (416) 340-4843

Other Vitamin K studies in the U.S. are:

Boston (Tufts University) - Recruiting men and women aged 60 to 80; women cannot be on estrogen replacement therapy. Contact Molly Damon at (617) 556-3154 or vitamink@hnrc.tufts.edu

Upper Midwest (University of Wisconsin) - Recruiting women who are at least 5 years post menopausal (natural or surgical); women cannot be on estrogen replacement therapy. Contact Judy Harke at (608) 265-6410 or jmharke@facstaff.wisc.edu
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Article Details
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Author:Forrester, H.J.
Publication:Natural Life
Article Type:Brief Article
Geographic Code:1USA
Date:May 1, 2002
Words:989
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