Flaxseed - more protective than soy protein against heart disease?

Adding flaxseed meal to the diet may help reduce high triglyceride levels and build-up of fats in the liver, both risk factors for heart disease and diabetes, report US researchers.

A team from the Beltsville Human Nutrition Research Center in Maryland, US, studied both flaxseed meal and soy protein in an animal model for a six-month period. Flaxseed meal decreased blood levels of trigylcerides and fat deposition in the liver to a significantly greater extent than soy protein.

The researchers said they were as yet unable to explain how the flaxseed had this effect but that further study in humans was needed.

The study was carried out on both lean and obese rat models. They were fed diets containing 20 per cent of energy from casein (control), soy protein concentrate or flaxseed meal for six months. Plasma was analysed for total cholesterol, LDL cholesterol, triglyceride and total protein. Livers were analysed for steatosis - deposits of fat in the liver, which reflects a high circulation of fat in the bloodstream.

In lean rats, soy protein and flaxseed meal significantly decreased total cholesterol (26 per cent and 20.3 per cent respectively) compared to casein. However as this included both LDL and HDL-cholesterol ('good' cholesterol), this was not considered an important benefit.

In obese rats, the two foods had different effects. Flaxseed meal significantly lowered plasma triglyceride in both lean and obese rats compared to casein fed rats (33.7 per cent and 37 per cent respectively).

There was significantly greater fat accumulation in livers of obese rats than lean rats (200 per cent) regardless of dietary protein type but flaxseed meal significantly lowered fat deposition in livers of both lean and obese rats compared to rats fed casein or soy protein.

The team concluded that flaxseed meal supplementation may provide a new therapeutic strategy to reduce hypertriglyceridemia and fatty liver.