Can Omega-3 Fatty Acids Prevent Osteoporosis?

Summarized by Robert W. Griffith, MD
May 17, 2007

Summary

Among listings of the benefits of increased omega-3 intake, osteoporosis is often mentioned. The available but sparse data for this benefit have recently been reported in a review in the American Journal of Clinical Nutrition, summarized here.

Introduction

Increased omega-3 fatty acid intake is associated with improvements in coronary heart diseases, stroke risk, autoimmune disorders, inflammatory bowel disease, psoriasis, and the risk of cancers of the breast, colon, and prostate. And a recent study indicates it can improve bone mineral density in healthy young men.¹ So a natural question is whether increased intake can prevent the occurrence of osteoporosis. An editorial in the American Journal of Clinical Nutrition has tried to answer this. Here's a summary of the experts' view.

What are the PUFAs?

There are two main classes of polyunsaturated fatty acids (PUFAs): omega-3 and omega-6 fatty acids (often written as n-3 and n-6 fatty acids, respectively). And there are two important omega-3s: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These are found chiefly in fish and fish oils.

Both omega-3 and omega-6 fatty acids are forerunners of eicosanoids - prostaglandins, leukotrienes, and thromboxanes - so their importance is clear. The eicosanoids derived from omega-3 fatty acids are more effective in this respect than those from omega-6 fatty acids.

A Bone Mineral Density (BMD) Study

This Swedish study examined the fatty acid composition of the serum of 78 healthy young men, and measured their spine, hip, and whole-body BMD. They found a clear link between the omega-3 content of the serum and the BMD levels. On the other hand, higher ratios of omega-6 to omega-3 fatty acids were linked to lower spinal BMD. (A similar finding has been reported for elderly men and women, using food frequency questionnaires rather than serum fatty acid measurements).

Omega-3 Fatty Acids and Bone Loss

Several pointers suggest a role for omega-3 fatty acids in healthy bone metabolism. Mice that are made menopausal (by removing their ovaries) have significantly less bone loss if they are fed a diet high in fish oil. Another clue: taking one of the glitazone antidiabetic drugs (e.g. rosiglitazone, troglitazone) is associated with increased lumbar spine bone loss in elderly women than in women not taking them; these drugs work by activating a chemical (PPAR-gamma) that is also activated by omega-6. This suggests that omega-6 is 'pro-osteoporotic', as indicated in the recent Swedish study above.

Clinical studies

A few studies of this aspect of osteoporosis causation have been done, with contradictory results. One report described separate studies performed in 43 pre-menopausal and 42 post-menopausal women. No effect of evening primrose oil (4 grams) plus marine fish oil (440 mg) daily, given for 12 months, was seen in either population.²

In another study, 65 elderly women (average age 79) took a mixture of EPA and gamma-linolenic acid or placebo for up to 18 months; bone mineral density in the lumbar spine decreased 3.2% with the placebo, but remained the same with the treatment, and femoral bone density decreased with the placebo (-2.1%), but increased with the EPA and gamma-linolenic acid (1.3%).³

In a Japanese study of 995 women of average age 45, different amounts of fish or soybean in the diet had no significant effect on bone mineral density in the 2nd metacarpal (hand) bone.⁴

Conclusions

While there are no well-conducted clinical studies to show that omega-3 fatty acids have a role to play in preventing or slowing osteoporosis, the Swedish study relating blood levels of fatty acids to bone mineral density in men is persuasive. Omega-3s are important in many diseases, and there's good reason to believe they may be helpful in preventing osteoporosis. Ensuring adequate intake of omega-3s, or a lowered ratio of omega-6 to omega-3 fatty acids, should not be difficult for most people: eat more fish (anchovy, halibut, herring, mackerel, salmon, tuna), and fish oils. If necessary, one can take supplements - up to 1 gram daily of EPA plus DHA.

Source

• Do n-3 fatty acids prevent osteoporosis? Editorial. C. Vanek, WE. Connor, Am J Clin Nutr, 2007, vol. 85, pp. 647--648

Footnotes
1. n-3 Fatty acids are positively associated with peak bone mineral density and bone accrual in healthy men: the NO2 Study. M. Hogstrom , P. Nordstrom , A. Nordstrom, Am J Clin Nutr, 2007, vol. 85, pp. 803--807
2. Lack of effect of supplementation with essential fatty acids on bone mineral density in healthy pre- and postmenopausal women: two randomized controlled trials of Efacal v.calcium alone. E. Bassey, J. Littlewood, M. Rothwell, D. Pye, British Journal of Nutrition, 2000, vol. 83, pp. 629--635
3. Calcium, gamma -linolenic acid and eicosapentaenoic acid supplementation in senile osteoporosis. M. Kruger, H. Coetzer, R. de Winter,  et al., Aging (Milano) , 1998, vol. 10, pp. 385--394
4. Dietary soybeans intake and bone mineral density among 995 middle-aged women in Yokohama. K. Tsuchida, S. Mizushima, M. Toba, K. Soda, Journal of Epidemiology, 1999, vol. 9, pp. 14--19

Related Links
The Latest View on Omega-3 Fatty Acids
University of Maryland: Omega-3 Fatty Acids
Fats and Health: FAQs

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