Sir, please step away from the barbecue.
Bad week if you’re looking for evidence to support a meat-heavy diet.
A new systematic review and meta-analysis is the first, it claims, to synthesise evidence on the effects of vegetarian and vegan diets on not just cholesterol, but apolipoprotein B (apoB), a major risk factor for atherosclerosis, the main driver of cardiovascular disease, the single biggest killer of humans on the planet.
The team dug up 30 intervention studies published over the past 40 years, with a variety of designs, durations, sizes and study populations, but all comparing omnivorous diets with either vegan or lacto-ovo-vegetarian diets. None, obviously, were participant blinded.
Nearly all studies showed a decrease in total and LDL cholesterol, though not all of them reached significance. On triglycerides, most studies found no change.
The six studies that compared apoB before and after mostly showed large decreases, though again some studies were too small to reach significance.
They attribute the difference to plant-based diets being usually higher in poly-unsaturated fatty acids (PUFAs) and lower in saturated fatty acids, cholesterol, and total fat, leading to lower intestinal absorption of triglycerides and cholesterol and thence to lower levels of cholesterol-containing lipoprotein particles in the blood.
A subgroup analysis – handle with care – on obese subjects found a smaller decrease in total cholesterol, thanks to the adverse effects of obesity on cholesterol metabolism. There was also a smaller effect on those being treated with lipid-lowering drugs.
The authors acknowledge the difficulty some people would have in cutting out meat, and note that a fairly large study using the non-meat-free but plant-heavy Mediterranean diet also saw a large reduction in recurrence of CVD events.
Co-author Professor Ruth Frikke-Schmidt of the Rigshospitalet in Copenhagen told media that while the effect of a plant-based diet was only a third as large as that of taking statins, combining the two was likely to have a synergistic effect. She noted that recent systematic reviews had shown that shifting high-income populations on to plant-based diets could reduce greenhouse gas emissions by up to 49%, and that this study meant that could come without a cost to health but rather the reverse.Â
In the same week, two archaeologists writing in The Conversation note the complete absence of clinical evidence to support the Paleo Diet, which they say is unsurprising given its flawed rationale.
The now 20-year-old fad proclaims that eating lots of meat and less dairy and grains leads to weight loss and general healthyfulness, since we evolved as hunter-gatherers and agriculture is a relatively recent invention.
Life expectancy of cavemen aside, the authors point out that mutations to support dietary changes don’t take 10,000 years to become prevalent, using lactase persistence (5000 years) and alcohol metabolism in African populations (2000 years) as examples.
Time to consign that expensive and high-emissions indulgence to the Bin of Failed Diet Fads.
Emitting story tips to penny@medicalrepublic.com.au is good for you and our habitat.
