Red meat no worse, no better than soy protein

Red meat no worse, no better than soy protein for heart disease risk

Three weekly servings of fresh, unprocessed red meat over eight weeks neither lowers nor raises heart disease risk in already at-risk men, findings from a novel New Zealand study suggest.

And here’s the kicker: soy protein has equal – that is, neutral – effects on heart disease risk in this population group, at least over the study period.

Researcher Dr Amber Milan from the University of Auckland-based Liggins Institute and AgResearch is presenting the yet-to-be-published findings at an international conference in Rotorua, New Zealand this week.

The study was co-funded by a programme grant from New Zealand’s High-Value Nutrition National Science Challenge and by New Zealand Wagyu beef producer First Light Foods to AgResearch, and led by Liggins Institute Professor David Cameron-Smith, Research Fellow Dr Amber Milan and AgResearch Senior Scientist Dr Emma Bermingham.

The participants were 50 men aged 35-55 years who were already at risk of heart disease. They were randomly split into three groups, receiving three servings (total 500g) a week for eight weeks of either grass-fed Wagyu beef, grain-finished Angus beef, or soy-based meat alternative.

They were asked to eat an otherwise normal diet, except for the exclusion of other red or processed meat, oily fish and omega-3 supplements to avoid confounding results.

New Zealand pasture-raised Wagyu beef is from specially bred and fed cows, and prior analyses by the team confirmed it has a markedly different fat profile to grain-fed beef. It is rich in a fat called conjugated linoleic acid, or CLA, and several other so-called ‘good fats’, including omega-3 fats, and contains on average less than half the saturated fat in ribeye, striploin and tenderloin cuts compared to grain-fed beef.

A saturated fat-heavy diet raises cholesterol and heart disease risk, while CLA and omega-3 are anti-inflammatory and help protect against heart disease. Researchers wanted to see whether the fats in Wagyu beef could lower heart disease risk when eaten in moderation.

The findings were unexpected: all three food conditions had the same neutral effect on heart disease risk. Analyses of blood samples showed reduced levels of ‘bad’ LDL cholesterol and total cholesterol, and of fatty acids circulating in the blood across all participants. Total body fat percentage and waist circumference also dropped across the board. However, specific biomarkers for heart disease risk normally used in research, such as the density and size of LDL cholesterol particles, remained unchanged.

“What is clear is that at 500g a week – the level of intake recommended by dietary guidelines in New Zealand and Australia and by the World Cancer Research Fund – we don’t see a detrimental impact to heart health in an eight week period,” says Dr Milan.

“A couple of things may have been at play in our study: often, just being in a dietary study makes people eat healthier because they’re thinking more about what they’re eating and they know they’re being watched.

"Also, because they had to exclude other red meat, including processed meat like sausages and ham, their diet during the study may have been different from their normal diet, and some of the foods they stopped eating may have partly led to some of the observed changes.”

Red meat has been linked to an increased risk for heart disease and colon cancer, but almost all of the evidence comes from large population or ‘epidemiological’ studies that identify patterns between people’s self-reported diet and their health status years later. These studies are subject to errors in people’s recall of what they ate, and often not very good at teasing out the influence of other diet and lifestyle factors, nor the effects of fresh versus processed meat.

Dr Milan is presenting the findings at the Food Structures, Digestion and Health International Conference in Rotorua.

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