Whole flaxseed, but not oil, may cut cholesterol

NEW YORK (Reuters Health) - Adding whole flaxseed to your diet, but not flaxseed oil, may help lower your cholesterol levels, hint the combined results of multiple studies.

Flaxseed is seen as a heart-healthy food as it contains high amounts of omega-3 fatty acids, fiber, digestion-aiding compounds called lignans, and alpha linolenic acid, which is linked to heart health.

However, individual studies on flaxseed's impact on blood cholesterol levels have yielded mixed results.

This led Dr. Xu Lin, at the Chinese Academy of Sciences in Shanghai, and colleagues, to pool results from 28 studies involving more than 1,500 men and women to try to clarify the impact whole flaxseed and its derivatives have on cholesterol levels. Average whole flaxseed or flaxseed oil intake was about one tablespoon daily.

The findings, reported in the American Journal of Clinical Nutrition, link whole flaxseed with reductions in total cholesterol and "bad" LDL cholesterol.

Total and LDL cholesterol reductions with whole flaxseed intake were stronger in women, particularly postmenopausal women, than men, and in people with higher cholesterol concentrations at the outset, the researchers note.

Whole flaxseed, however, did not appear to significantly alter levels of harmful triglycerides or "good" HDL cholesterol.

Lin's group also noted declines in total and LDL cholesterol, but not HDL cholesterol or triglycerides, associated with taking supplements of flaxseed lignans (about 430 milligrams on average), but no reductions associated with flaxseed oil supplements.

The investigators suggest, based on their findings, that eating whole flaxseed may be a "worthwhile dietary approach" for preventing high cholesterol.

They call for further large-scale investigations to assess the impact flaxseed and flaxseed compounds have among men and women at risk for heart disease.

SOURCE: American Journal of Clinical Nutrition, August 2009