Animal protein-rich diets raise risk of death, research shows

It’s not just how much protein you eat, but where it comes from that matters.

A new study from Harvard University shows that animal protein-rich diets are associated with higher mortality, while the opposite is true for diets enriched in plant proteins.

Substituting protein of animal origin with plant protein can reduce the risk of death, the researchers say.

Diets with high protein and low carbohydrate content can promote weight loss. However, the source of the protein is important, as it is associated with other nutrients that can have an adverse effect on a person’s health.

The study analysed two large groups of patients in the US - totalling 131,342 individuals - who were followed for up to 32 years and provided detailed information about their diets and lifestyle. The average age of participants was 49.

The results show that high consumption of animal protein was associated with increased risk of death, while high intake of plant protein resulted in the opposite trend.

Taking into account other risk factors such as smoking, obesity, diabetes and physical activity, high animal protein intake was associated with a 2 per cent increase in the risk of death by any cause, and an 8 per cent increase in the risk of death by cardiovascular disease.

Processed red meat

High consumption of protein from processed red meat was strongly associated with risk of death, whereas no association was found for protein from fish or poultry.

The authors suggest that as well as the proteins, other components in animal protein-rich foods - such as chemicals used in processed red meat - may be responsible for the effect.

On the other hand, a diet rich in plant proteins was associated with decreased risk of death.

Both the damaging (for animal protein) and beneficial (for plant protein) effects of the diet were only observed in participants who presented at least one other risk factor, such as obesity or heavy alcohol consumption.

This suggests that diet may worsen or compensate for other lifestyle choices.

When 3 per cent of total calories in the diet coming from animal protein were substituted for plant protein, the risk of death decreased dramatically, especially when the substituted animal protein came from processed red meat.

Overall, the study shows that substituting protein of animal origin for plant protein can be highly beneficial, the authors say.

Vanesa Martinez is on placement at The Irish Times under the BSA/SFI media fellowship programme