Plant-Based Diet Tied to Healthier Blood Lipid Levels

Marlene Busko

May 26, 2023

People who followed a vegan or vegetarian diet had lower blood levels of low-density lipoprotein cholesterol (LDL-C), total cholesterol, and apolipoprotein B (apoB) than people who followed an omnivore diet, in a new meta-analysis of 30 trials.

The findings suggest that "plant-based diets have the potential to lessen the atherosclerotic burden from atherogenic lipoproteins and thereby reduce the risk of cardiovascular disease," write Caroline Amelie Koch, a medical student at the University of Copenhagen, Denmark, and colleagues. Their findings were published online May 24 in the European Heart Journal.

"Vegetarian and vegan diets were associated with a 14% reduction in all artery-clogging lipoproteins as indicated by apoB," senior author Ruth Frikke-Schmidt, DMSc, PhD, Rigshospitalet, and professor, University of Copenhagen, said in a press release from her university.

"This corresponds to a third of the effect of taking cholesterol-lowering medications such as statins," she added, "and would result in a 7% reduction in the risk of cardiovascular disease in someone who maintained a plant-based diet for 5 years."

"Importantly, we found similar results, across continents, ages, different ranges of body mass index (BMI), and among people in different states of health," Frikke-Schmidt stressed.

And combining statins with plant-based diets would likely produce a synergistic effect, she speculated.

"If people start eating vegetarian or vegan diets from an early age," she said, "the potential for reducing the risk of cardiovascular disease caused by blocked arteries is substantial."

In addition, the researchers conclude: "Shifting to plant-based diets at a populational level will reduce emissions of greenhouse gases considerably — together making these diets efficient means towards a more sustainable development, while at the same time reducing the growing burden of atherosclerotic cardiovascular disease (ASCVD)." 

More Support for Vegan, Vegetarian Diets

These new findings "add to the body of evidence supporting favorable effects of healthy vegan and vegetarian dietary patterns on circulating levels of LDL-C and atherogenic lipoproteins, which would be expected to reduce ASCVD risk," Kevin C. Maki, PhD, and Carol Kirkpatrick, PhD, MPH, write in an accompanying editorial.

"While it is not necessary to entirely omit foods such as meat, poultry, and fish/seafood to follow a recommended dietary pattern, reducing consumption of such foods is a reasonable option for those who prefer to do so," note Maki, of Indiana University School of Public Health, and Kirkpatrick, of Idaho State University.

Plant-Based Diet Needs to Be 'Well-Planned'

Several experts who were not involved in this meta-analysis shed light on the study and its implications in comments to the UK Science Media Center.

"Although a vegetarian and vegan diet can be very healthy and beneficial with respect to cardiovascular risk, it is important that it is well planned so that nutrients it can be low in are included including iron, iodine, vitamin B12, and vitamin D," said Duane Mellor, PhD, a registered dietitian and senior lecturer, Aston Medical School, Aston University, Birmingham, UK.

Some people "may find it easier to follow a Mediterranean-style diet that features plenty of fruit, vegetables, pulses, wholegrains, fish, eggs and low-fat dairy, with only small amounts of meat," Tracy Parker, senior dietitian at the British Heart Foundation, London, UK, suggested.

"There is considerable evidence that this type of diet can help lower your risk of developing heart and circulatory diseases by improving cholesterol and blood pressure levels, reducing inflammation, and controlling blood glucose levels," she added.

And Aedin Cassidy, PhD, chair in nutrition & preventative medicine, Queen's University Belfast, noted that "not all plant-based diets are equal. Healthy plant-based diets, characterized by fruits, vegetables, and wholegrains improve health, but other plant diets (eg, those including refined carbohydrates, processed foods high in fat/salt, etc) do not."  

This new study shows that plant-based diets have the potential to improve health by improving blood lipids, "but this is one of many potential mechanisms including impact on blood pressure, weight maintenance, and blood sugars," she added.

"This work represents a well-conducted analysis of 30 clinical trials involving over two thousand participants and highlights the value of a vegetarian diet in reducing the risk of heart attack or stroke through reduction in blood cholesterol levels," said Robert Storey, BM, DM, professor of cardiology, University of Sheffield, UK.

However, it also demonstrates that the impact of diet on an individual's cholesterol level is relatively limited, he added.

"This is because people inherit the tendency for their livers to produce too much cholesterol, meaning that high cholesterol is more strongly influenced by our genes (DNA) than by our diet," he explained.

This is "why statins are needed to block cholesterol production in people who are at higher risk of or have already suffered from a heart attack, stroke, or other illness related to cholesterol build-up in blood vessels."

Beneficial Effect on ApoB, LDL-C, and Total Cholesterol

ApoB is the main apolipoprotein in LDL-C ("bad" cholesterol), the researchers note. Previous studies have shown that LDL-C and apoB-containing particles are associated with increased risk of ASCVD.

They aimed to estimate the effect of vegetarian or vegan diets on blood levels of total cholesterol, LDL-C, triglycerides, and apoB in people randomized to a vegetarian or vegan diet versus an omnivorous diet (ie, including meat and dairy).

They identified 30 studies published between 1982 and 2022 and conducted in the United States (18 studies), Sweden (2), Finland (2), South Korea (2), Australia (1), Brazil (1), Czech Republic (1), Italy (1), Iran (1), and New Zealand (1).

The diet interventions lasted from 10 days to 5 years with a mean of 29 weeks (15 studies ≤ 3 months; 12 studies 3-12 months; and three studies > 1 year). Nine studies used a crossover design, and the rest used a parallel design whereby participants followed only one diet.

The studies had 11 to 291 participants (mean, 79 participants) with a mean BMI of 21.5-35.1 kg/m2 and a mean age of 20-67 years. Thirteen studies included participants treated with lipid-lowering therapy at baseline.

The dietary intervention was vegetarian in 15 trials (three lacto-vegetarian and 12 lacto-ovo-vegetarian) and vegan in the other 15 trials.

On average, compared to people eating an omnivore diet, people eating a plant-based diet had a 7% reduction in total cholesterol from baseline (–0.34 mmol/L), a 10% reduction in LDL-C from baseline (–0.30 mmol/L), and a 14% reduction in apoB from baseline (–12.9 mg/dL) (all P < .01).

The effects were similar across age, continent, study duration, health status, intervention diet, intervention program, and study design subgroups.

There was no significant difference in triglyceride levels in patients in the omnivore versus plant-based diet groups.

Such Diets Could Considerably Reduce Greenhouse Gases

Senior author Frikke-Schmidt noted: "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%."

"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" in an aging population, she said.

"We should be eating a varied, plant-rich diet, not too much, and quenching our thirst with water," she concluded.

The study was funded by the Lundbeck Foundation, the Danish Heart Foundation, and the Leducq Foundation. The authors, editorialists, Parker, Cassidy, and Storey have reported no relevant financial relationships. Mellor has disclosed that he is a vegetarian.

Eur Heart J. Published online May 24, 2023. Article, Editorial

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