Compared with an omnivorous diet, following a vegetarian diet was associated with significantly lower TC and low-density lipoprotein ‘bad’ cholesterol (LDLC) in observational studies. The vegetarian diet also induced significantly lower TC and LDLC in clinical interventions reported the meta-analysis led by George Washington University, in association with the Physicians Committee for Responsible Medicine, Washington DC.
High-density lipoprotein ‘good’ cholesterol (HDLC) was also lower for vegetarians in both types of study, but there were no significant differences in triglyceride levels in either type of trial. Sub-group analysis also found that a vegan diet had an even larger effect on blood lipid levels than a lacto-ovo vegetarian diet.
“Consumption of vegetarian diets, particularly vegan diets, is associated with lower levels of plasma lipids, which could offer individuals and healthcare professionals an effective option for reducing the risk of heart disease or other chronic conditions,” concluded the authors.
The researchers also recommended that referral to registered dieticians, who would advise on transitioning to a vegetable rich diet, would relieve time pressure on clinicians, while improving heart health in individuals with elevated cholesterol.
Main results
The meta-analysis included 49 studies of which 30 were observational and 19 clinical trials.
In observational studies, following a vegetarian diet was associated with 29.2 milligrams/ decilitre (mg/dL), (0.76 millimoles/litre (mmol/l)) lower TC than an omnivorous diet. In clinical trials, vegetarian diets reduced TC by 12.5 mg/dL (0.32 mmol/l).
Vegetarian diets were correlated with a 12.5 mg/dL (0.32 mmol/l) lower LDLC level in observational studies. In clinical trials, vegetarian diet induced a 12.2 mg/dL (0.32 mmol/l) LDLC reduction.
The findings of the current meta-analysis are consistent with earlier reviews. The researchers emphasised the importance of also including observational data in the study to highlight long-term benefits of a plant-based vegetarian diet.
"The immediate health benefits of a plant-based diet, like weight loss, lower blood pressure, and improved cholesterol, are well documented in controlled studies," said study author Susan Levin.
“While observational studies present a higher risk of bias compared with clinical trials, they also reflect long-term effects of vegetarian diets on plasma lipids that are not apparent in most clinical trials,” she explained.
“Those who have followed vegetarian dietary patterns for longer periods may have healthier body compositions as well as better adherence to a vegetarian diet, both of which may have an effect on blood lipids.
“Our goal with studying plasma lipids throughout the lifespan is to capture the net risk reduction of using a vegetarian diet to control lipid levels. We hope to empower patients with new research about the long-term cardiovascular health benefits of a vegetarian diet, which include a reduced risk of a heart attack, stroke, and premature death," she concluded.
Source: Nutrition Reviews
Published online. DOI: 10.1093/nutrit/nux030
“Association between plant-based diets and plasma lipids: a systematic review and meta-analysis”
Authors: Yoko Yokoyama, Susan M. Levin, Neal D. Barnard