Flaxseed significantly reduced total cholesterol and LDL or “bad” cholesterol levels but did not substantially affect HDL or “good” cholesterol levels or triglycerides, a new study says.
The meta-analysis, which combines results from multiple studies, was reported in the August issue of the American Journal of Clinical Nutrition.
A number of foods including soy protein, plant sterols, nuts and fish have shown in epidemiological and research studies to reduce cholesterol levels.
Researchers at the Chinese Academy of Sciences in Shanghai wanted to determine if flaxseed or is derivatives (lignan supplement or flaxseed oil) would also help to lower cholesterol levels. Until now, study results have yielded mixed results.
Flaxseed is an excellent source of fiber (28% by weight) of which 25 percent is in the soluble form. Clinical studies have demonstrated the beneficial effect that soluble fiber intake has on lowering total and LDL cholesterol levels.
Although each of the twenty-eight studies included in the analysis used flaxseed or its derivatives, their study design, methods and criteria varied considerably. Of the more than 1,500 men and women participating, 6 trials involved just women, 10 trials involved just men and another 10 trials involved both sexes. Flaxseed dosing varied from 20 to 50 grams per day, with a median of 38 grams. Control regimens included wheat, wheat bran/germ, manioc flour, sunflower seed or psyllium. Flaxseed oil dosing ranged from 200 mg to 600 mg per day, with a median of 430 mg. The trials varied in length, from 2 to 52 weeks, with a median of 8.5 weeks.
Further analysis revealed that the cholesterol-lowering effects varied among study groups. A significant reduction in total cholesterol was seen in studies using whole flaxseed and lignan supplements but not flaxseed oil. In general, reduction in total cholesterol was greater in women, especially postmenopausal women, than in men. Greater reduction in total and LDL cholesterol levels were seen in higher-quality studies (e.g., studies using randomization, blinding). Significant reductions were found in studies where subjects had higher initial total cholesterol levels.
In the studies that used whole flaxseed, in women or individuals with high initial cholesterol levels, the reduction in total and LDL levels results in an estimated 3 percent reduction in all case mortality and of 6 percent in both coronary heart-disease mortality and total events.
Based on the clinical significance of the meta-analysis, study authors concluded, “Flaxseed consumption may be a worthwhile dietary approach for preventing hypercholesterolemia, particularly in specific patient subgroups”.
†Total cholesterol decreased by 0.10 mmol/L; LDL cholesterol levels decreased by 0.08 mmol/L. Normal adult levels of total blood cholesterol are 150 to 200 mg/dL or 3.9 to 5.2 mmol/L.
The Bottom Line
For over a decade, we’ve recommended that our patients supplement their diet with both ground flaxseed and flaxseed oil. While the ground flaxseed is a good source of fiber (soluble and insoluble fiber) and lignans, the oil provides an excellent source of the essential fatty acid, alpha-linolenic acid.
This study provides another reason to consume this beneficial seed – to help lower total cholesterol and LDL cholesterol levels.
Finding flaxseed products is easier than ever. Not only health food stores but many conventional supermarkets now offer whole and ground flax seeds. In addition, a number of websites offer a variety of flax seed products.
Flaxseed is easy to incorporate into the diet – it can be added to yogurt, smoothies and other foods. Make it a point to include this important nutritional seed into your diet.