Maintaining a vegetarian or vegan diet lowers the risk of developing high cholesterol and fats in the blood, a new study has shown.
Researchers at Rigshospitalet in Copenhagen, Denmark, analysed 30 randomised trials published between 1982 and 2022, which quantified the effect of vegetarian or vegan diets compared with omnivorous diets on levels of all types of cholesterol, low-density lipoprotein cholesterol (LDL), triglycerides and the protein apoliprotein B (apoB).
Although previous meta-analyses have investigated this, none has been published since 2017, none addressed the impact of age, body mass index, and health status, and none focused on the effect of diet on concentrations of apoB, the researchers say.
This study, published in the European Heart Journal, is claimed as the largest systematic review of the topic, and the first to include apoB.
Professor Ruth Frikke-Schmidt, chief physician at the Rigshospitalet, and her team found vegetarian and vegan diets were associated with a 14% reduction in all lipoproteins as indicated by apoliprotein B.
“This corresponds to a third of the effect of taking cholesterol-lowering medications such as statins and would result in a 7% reduction in the risk of cardiovascular disease in someone who maintained a plant-based diet for five years,” she said.
“Statin treatment is superior to plant-based diets in reducing fats and cholesterol levels. However, one regimen does not exclude the other, and combining statins with plant-based diets is likely to have a synergistic effect, resulting in an even larger beneficial effect.
“If people start eating vegetarian or vegan diets from an early age, the potential for reducing the risk of cardiovascular disease caused by blocked arteries is substantial. Importantly, we found similar results across continents, ages, different ranges of body mass index, and among people in different states of health.”
The 2,372 participants in the 30 studies were randomised to follow either a vegetarian or vegan diet or to continue with an omnivorous diet.
The length of time on the diets ranged from ten days to five years, with an average of 29 weeks.
Analysis found that compared to people eating an omnivorous diet, those following a plant-based diet experienced an average reduction in total cholesterol levels of 7% from levels measured at the start of the studies, a 10% reduction in LDL cholesterol levels and a 14% reduction in apoB levels.
“We saw significant effects from both vegetarian and vegan diets and people ranging from a normal weight to obese,” said Prof Frikke-Schmidt.
“Recent systematic reviews have shown that if the populations of high-income countries shift to plant-based diets, this can reduce net emissions of greenhouse gases by between 35% to 49%. Our study provides robust evidence that plant-based diets are good for our health for people of different sizes, ages and health conditions.
“Furthermore, populations globally are aging and, as a consequence, the cost of treating age-related diseases such as atherosclerotic cardiovascular disease is increasing. Plant-based diets are key instruments for changing food production to more environmentally sustainable forms, while at the same time reducing the burden of cardiovascular disease. We should be eating a varied, plant-rich diet, not too much, and quenching our thirst with water.”
While there are strengths to the study, Prof Frikke-Schmidt said limitations included the fact that individual randomised controlled trials were relatively small, some of the studies were short and it was not possible to blind the participants to which diet they were placed on.
The researchers call for further larger studies with longer duration, and which include apoB and other biomarkers for conditions such as inflammation and insulin resistance.
Vegetarian or vegan diets and blood lipids: a meta-analysis of randomized trials. European Heart Journal25 May 2023; doi:10.1093/eurheartj/ehad211
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