Cholesterol reduction: A look at the evidence

Improved heart health relates to reducing the risk of developing cardiovascular disease (CVD), coronary heart disease (CHD), and stroke. The major risk factors for these diseases are numerous, but include smoking habits, body weight, blood pressure, cholesterol levels, and physical exercise levels.

Cholesterol link​

Cholesterol is a steroid metabolite, and an essential structural component of mammalian cell membranes.

However, high blood cholesterol levels (known as hypercholesterolemia) are strongly associated with cardiovascular disease (CVD), due to the increased risk of atherosclerotic plaque formation – which can lead to an increased risk of myocardial infarction (heart attack), stroke, and vascular disease.

High blood levels of ‘bad’ LDL cholesterol are known to contribute to this process of plaque formation, whilst ‘good’ HDL cholesterol has been found to offer protection against heart disease.

A number of dietary ingredients have been suggested to reduce the levels of LDL cholesterol, and according to Frost and Sullivan, the heart health market is dominated by four main ingredients: phytosterols, omega-3s, beta-glucan, and soy protein.

Phytosterols​

Numerous clinical trials in controlled settings have reported that daily consumption of 1.5 to 3 grams of phytosterols/-stanols from foods can reduce total cholesterol levels by between eight and 17 per cent, representing a significant reduction in the risk of cardiovascular disease.

A review of 84 clinical trials in the Journal of Nutrition, authored by researchers from Unilever R&D and Wageningen University – neither of which are strangers to the world of plant sterols – concluded that phytosterol-enriched foods are effective for reducing levels of LDL cholesterol, with no differences between stanols and sterols, or delivery in fat or non fat foods.

“For the recommended intake of two grams per day, the expected LDL-C–lowering effect of phytosterols is ​[about] 9 percent,”​ wrote the authors, led by Isabelle Demonty. “A reduction in LDL-C of about 10 percent would reduce the incidence of CHD by about 10-20 percent.​

“Although no direct evidence is available yet for the ability of phytosterols to lower CHD incidence, the well-documented cholesterol-lowering effect of phytosterols is the basis for recommendations to include phytosterols into strategies to lower LDL-C concentrations,”​ they added.

Overall the research suggests that doesn’t seem to matter whether we consume the ingredients in their sterol or stanol form, neither does it diminish the benefits if fat or non-fat-based foods are used. Getting your sterols from dairy or non-dairy formats also doesn’t affect the results.

Omega-3 ​

Omega-3 has been identified as one of the super-nutrients, taking the food and supplements industry by storm, and much of its reputation is based on evidence that it can help to protect the heart against cardiovascular disease.

The first reports of the heart health benefits of omega-3 fatty acids were reported in the early 1970s by Jørn Dyerberg and his co-workers in The Lancet​ and The American Journal of Clinical Nutrition​. The Danes sought to understand how the Greenland Eskimos, or Inuit, could eat a high fat diet and still have one of the lowest death rates from cardiovascular disease on the planet.

Since then omega-3s have been studied extensively for their potential to decrease the risk of cardiovascular disease, however according to a recent Cochrane review “dietary omega-3 polyunsaturated fatty acids (PUFAs) are known to reduce triglyceride levels, but their impact on cholesterol levels … and vascular outcomes are ​[still] not well known.”​

However a recent study in the academic journal Clinical Nutrition suggested that three grams of omega-3 per day was associated with improvements in a wide range of cardiovascular risk factors, including cholesterol levels, and triacylglyceride levels.

Beta-glucan​

Beta-glucan is a type of soluble fiber that is found predominantly in cereal grains. Oats and barley are said to contain the highest level of beta-glucan, with barley containing the highest levels of up to 11 percent.

Previous research has shown consumption of oats to significantly lower serum total cholesterol concentrations, and there is emerging data to support the belief that barley may have similar health benefits.

A meta-analysis of 11 clinical trails published in European Journal of Clinical Nutrition recently suggested that a daily consumption of three grams of beta-glucan can significantly reduce both total and LDL cholesterol concentrations.

The authors of the meta-analysis also noted that beta-glucan characteristics, including its solubility and molecular weight, are important determinants of its cholesterol-lowering action.

They said that highly water-soluble beta-glucan with moderate to high molecular weight may reduce serum LDL cholesterol levels better than beta-glucan with a low water solubility and low molecular weight.

Soy protein​

The Food and Drug Administration (FDA) heart health claim for soy protein established in 1999 states that "25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease."​

Currently, 11 other countries have approved health claims for soy protein's potential to lower blood cholesterol and lower the risk of coronary heart disease. However, recently the European Food Safety Authority (EFSA) issued a negative opinion to a health claim submission linking soy protein and reduced cholesterol – stating that there was not enough evidence of causation to approve a claim in Europe.

A 2008 study suggested that the cholesterol-lowering effects of soy protein may by located in the liver. The study, published in the Journal of Agricultural and Food Chemistry, reported that soybean protein was found to stimulate the low-density lipoprotein receptor (LDL-R) transcription in liver cells.

A recent study from Solae backs up these claims for soy protein’s cholesterol lowering effect, but says the mechanism behind benefits is ‘yet to be determined’. The study published in the Journal of Clinical Lipidology, suggests that soy protein lowers total cholesterol and non-HDL cholesterol, in patients with moderately high cholesterol levels, but said that a mechanism for such benefits could not be determined.