Researchers found that three months of strength training helped increase muscle strength among 45 healthy women in their 60s. But those who used fish oil at the same time had somewhat greater gains.

Whether older women should run out to buy fish oil for the sake of their muscles remains to be seen.

It's not clear whether the extra strength gain would be meaningful in a woman's life -- and, therefore, worth the cost and potential side effects of fish oil pills.

The findings are "intriguing" and deserve further study, said Catherine Jackson, a professor of kinesiology at California State University in Fresno who was not involved in the study.

But, she told Reuters Health in an email, "I would be a bit cautious about over-interpretation."

The researchers themselves echoed that thought. The findings "should be viewed with caution," according to Luiz Claudio Fernandes and colleagues at Parana Federal University in Brazil.

"Other studies involving a larger sample and other combinations of training and supplementation period are required," they write in the American Journal of Clinical Nutrition.

WHAT DOES FISH OIL DO?

Fish oil, which is rich in omega-3 fatty acids, is probably best known for its link to heart health. Fish oil supplements can lower triglycerides (a type of blood fat), and people who get more omega-3 have been found to have a lower risk of heart disease.

But there's also evidence that fish oil can improve nerve function and the ability of heart muscle to contract. So it's "reasonable to hypothesize" that fish oil could boost muscles' response to strengthening exercises, according to Fernandes' team.

To study the question, the researchers randomly assigned 45 older women to one of three exercise groups: In one, the women performed strengthening exercise three times a week for three months; the other two groups followed the same regimen, but also took fish oil -- 2 grams per day, either starting on the same day as their exercise program, or starting two months beforehand.

On average, all three groups increased their muscle strength, which was measured in tests where the women contracted their leg muscles. But the change was greater in the two fish-oil groups.

On top of that, only women who used fish oil showed changes in nerve activity in the muscles.

Exactly what that all means for women's well-being is not clear.

One issue, Jackson said, is that "strength measurement is difficult at best and shows huge differences among subjects."

The study participants did take four "functional" tests that gauged strength, balance, agility and how far they could walk in 6 minutes. And women using fish oil did slightly better on one of those tests -- where they had to sit down and rise up from a chair several times in a row, as fast as they could.

Whether any of that could translate into better fitness, a lower risk of falls or other health benefits is unknown for now.

A question with any supplement study, Jackson noted, is whether users were "deficient" in a nutrient -- omega-3 fats, in this case -- to begin with. If so, the supplement might have brought them to a more "normal" level, and the benefit of a supplement beyond a healthful, balanced diet would be unclear.

In the U.S., a monthly supply of one-gram fish oil capsules can run well over $15.

And while fish oil is generally considered safe at recommended doses, it can have side effects; the more common side effects include bad breath, heartburn, nausea and loose stools.

At higher doses -- more than 3 grams per day -- fish oil might interfere with blood clotting and raise the risk of internal bleeding, according to the National Institutes of Health.

People using medications -- as most older adults are -- should also check with their doctor about possible interactions. Fish oil can, for example, boost the effects of blood pressure drugs, which could send your blood pressure too low.

SOURCE: bit.ly/AnRGII American Journal of Clinical Nutrition, January 4, 2012.

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