Plant-based eating and cholesterol

This is a review of the latest scientific evidence for the impact of healthful plant-based eating on serum cholesterol. Elevated levels of cholesterol are a primary modifiable risk factor for cardiovascular disease (CVD) and in particular, coronary heart disease (CHD). The evidence strongly demonstrates that healthful plant-based eating patterns and specific plant foods have a significant cholesterol-lowering effect.

There is wide acceptance among scientists that one of the important ways plant-based eating improves heart health is by its action on blood lipids. According to the World Health Organization (WHO), raised cholesterol is a leading cause of CHD and stroke and is responsible for 2.6 million deaths and 29.7 million Daily Adjusted Life Years (DALYS) globally.(1)

In particular, there is a huge body of evidence to demonstrate that prolonged exposure to high levels of low-density lipoprotein (LDL) cholesterol is associated with a higher risk of atherosclerotic heart disease. This finding has been observed consistently in a large volume of high-quality peer-reviewed studies, including epidemiological studies, Mendelian randomisation studies and randomised control trials (RCT).(2)

Plant-based diets and cholesterol

Several recent RCT have demonstrated the benefits of plant-based dietary patterns for lowering cholesterol levels. Firstly, the BROAD study demonstrated that over a 12-month period, participants adhering to a whole food plant-based diet experienced a reduction of 0.55 mmol/L (±0.54, P = 0.05) total cholesterol and a 4.2 (±0.8) kg/m2 reduction in BMI.(3) The diet included whole grains, legumes, vegetables and fruits with no restriction of energy intake.

Another two studies (total 376 participants) assessed the impact of dietary interventions based on the Mediterranean diet principles.(4,5) Participants reduced their meat, dairy and refined grain intake and increased consumption of healthy plant-based foods including fruits, vegetables, legumes, nuts, wholegrains as well as seafood. In both studies, the group following the Mediterranean diet reduced LDL cholesterol levels. In the 6-month intervention LDL cholesterol was reduced by 6.1 mg/dL (3.7%)

Plant-based diets have a beneficial fat profile

The cholesterol-lowering effect of plant-based diets is often attributed to their overall beneficial nutrition profile including their beneficial fat profile – lower saturated fat intakes and higher intakes of unsaturated fats. This is not surprising as plant-based diets will often displace the main food sources of saturated fats such as meat products and sometimes dairy.

It is now well established that saturated fat intakes are linearly correlated to serum LDL cholesterol.(2,6-10) Overall conclusions:

• Saturated fat intakes are the dietary factor that has the greatest impact on raising LDL cholesterol levels and CVD risk

• Reducing intakes of saturated fat will result in reductions in total and LDL cholesterol and is associated with 7-17% reduced incidence of CVD and CHD(9)

• What replaces saturated fat in the diet is a critical factor for lipid lowering:

  • Replacing saturated fats with polyunsaturated (PUFA) and/or monounsaturated fats (MUFA) will provide the optimum cholesterol-lowering and cardioprotective effect

  • Replacing with PUFA has been associated with a 27% reduced risk of CVD events and does not adversely affect high-density lipoprotein (HDL) cholesterol. A number of plant foods provide this ideal cardioprotective fat profile e.g. nuts, seeds, legumes and wholegrains

  • Replacing with refined carbohydrates is unlikely to have any cholesterol-lowering or CVD benefit, and instead has the potential to increase serum triglycerides, LDL cholesterol and CVD risk

    This highlights the importance of promoting healthful plant-based diets which are low in high fat, sugar and salt foods, and rich in wholegrains, fruit, vegetables and plant proteins

  • Replacing with trans fat will exacerbate elevated LDL cholesterol levels (potentially to a greater level than saturated fat) and significantly increase CVD risk

Plant-based foods and cholesterol

Researchers have also reviewed the impact of specific plant foods on LDL cholesterol levels.(11,12) Four groups of foods have been noted to have a moderate to large LDL cholesterol lowering effect:

• Tree nuts and peanuts

  28-30g daily intakes are associated with LDL cholesterol reductions of 7%.(13) This is often attributed to their favourable nutritional profile: dietary fibre, unsaturated fatty acids, vitamin E, naturally-occurring sterols/stanols, minerals and other bioactive compounds.

• Foods containing soluble fibre, in particular beta glucans found in oats and barley

  A 3g daily intake of the viscous fibre beta-glucan, has been proven to lower serum LDL cholesterol by anything from 4-7%.(14,15) Beta-glucan is thought to interfere with the entero-hepatic circulation of cholesterol.

• Foods with added plant sterols or stanols

  Although naturally found in nature in small quantities, fortification is needed to provide the effective daily dose of 1.5-3g. In the gut, sterols and stanols interfere with the transporter-mediated process for dietary and endogenous cholesterol uptake to produce a 7-12% LDL cholesterol.(16)

• Soya foods (see below)

Additionally, a small to moderate reduction in LDL cholesterol was observed with consumption of other plant-based foods including flaxseeds, avocadoes, pulses and tomatoes.(12) Plant-based diets encouraging consumption of these foods may therefore be beneficial in reducing and maintaining healthy cholesterol levels.

The Portfolio dietary pattern has been developed with these cholesterol lowering foods in mind. This diet includes daily intake of 42g nuts, 50g protein from soya foods or pulses, 20g soluble fibre and 2g plant sterols from fortified plant-based margarine. A systematic review and meta-analysis demonstrated that a Portfolio dietary pattern, in combination with the NCEP (National Cholesterol Education Program) Step II diet significantly reduced LDL cholesterol by approximately 17% in 7 interventions >3 weeks duration.(17)

Plant-based protein and cholesterol

A meta-analysis was carried out on behalf of the American Heart Foundation in 2017 to analyse the impact of replacing animal-based protein in the diet with protein from plant-based sources.(18) Li et al. reviewed 112 randomised control trial (RCT) with a total of 5,774 participants. The main plant-based protein used in the intervention was soya protein (94 trials), other sources included pulses, nuts, oat and seeds.

The review indicated that replacing 1 to 2 servings of animal proteins with plant-based proteins on a daily basis resulted in a modest reduction (<5%) of LDL, non-HDL and ApoB, an important component of many of the most atherogenic lipoprotein particles. The authors further suggest that the health benefits could be even greater if people combined plant proteins with other cholesterol-lowering plant foods such as viscous, water soluble fibre from oats or barley and plant sterols.

This dietary intervention (replacing animal-based proteins with plant-based sources) may have a clinically meaningful benefit in helping people to achieve lipid targets and reduce cardiovascular risk.

Soya protein and cholesterol

Soya protein has long been associated with heart-health benefits. In 1999, the FDA approved the health claim: “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."(19)

Since then, a 2019 meta-analysis of 46 peer-reviewed studies (total 2,607 participants) has confirmed that consumption of 25 g per day of protein from soya-based foods over a median follow-up period of 6-weeks, significantly decreased LDL cholesterol by 4.76 mg/dL (3.2%) and total cholesterol by 6.41 mg/dL (2.8%) compared to the control group.(20)

Although the reduction is mild, the authors note that the magnitude of reduction in cholesterol depends on which foods soya displaces in the diet. A previous study estimated that a 7.9-10.3% reduction in LDL cholesterol is possible when 13-58g animal-based foods high in saturated fat and cholesterol in the diet are replaced with the equivalent quantity of soya foods.(21)

Conclusion

Healthful plant-based dietary patterns, which include sources of plant food sources of protein, can significantly reduce cholesterol levels and improve cardiovascular health outcomes.