Is red meat bad for you? The evidence is far from clear

Eating red meat may raise the risk of dying from heart disease, cancer, Alzheimer’s and diabetes, a study in the British Medical Journal has suggested. (However, see our analysis below.)

Researchers from the National Cancer Institute in Maryland looked at data gathered from over half a million Americans aged between 50 and 71. Their diets were tracked over a 16-year period.

It was found that those who ate the most red meat (beef, lamb, and pork) were 26 per cent more likely to die prematurely, compared with those who ate the least.

However, the study also found that those who ate the most white meat (poultry and fish) were 25 per cent less likely to die prematurely.

The findings seem to suggest that meat eaters should swap red for white to live a longer life, particularly if it is unprocessed.

The study is the first to find an association between the intake of heme iron (which makes up about 40 per cent of the iron in meat) and mortality from almost all causes.

Writing in the BMJ, the researchers said: ‘The results show increased risks of all-cause mortality and death due to nine different causes associated with both processed and unprocessed red meat. They also show reduced risks associated with substituting white meat, particularly unprocessed white meat.

‘The effects of meat on human health may be due to ingredients such as heme iron, nitrates, and nitrites. High intakes of heme iron have been shown to be associated with cancer and cardiovascular disease.

‘Nitrates and nitrites are added to meat during the curing process. Some investigators believe that nitrates from vegetable sources may have potential benefits, particularly for cardiovascular health, but nitrate/nitrite from drinking water and processed meat has been associated with increased risks of different cancers.’

Instant analysis
This is a prospective cohort study, useful for delineating risk factors for predetermined outcomes, but subject to significant bias. This strongly limits the conclusions we can draw from the results.

An increase of 26 per cent in all-cause mortality at first sight seems significant, but when looked at in context is marginal, especially as there are so many other risk factors not accounted for.

The true significance of observed phenomena are found in their explanation — and here the paper is lacking. Higher meat intake in this study was a marker of diabetes, less physical activity and lower socioeconomic status, all major risk factors for poor health and, by extension, higher mortality. So it is possible that meat consumption is not a causal factor at all.

US agricultural practices differ in certain respects from those in Europe — this includes the use of antibiotics, growth hormone and other growth attenuators that are banned in the EU. These differences not only lower the quality of the meat in the US but may have an effect on human health too.

Overall, there are too many factors at play for any definitive conclusion to be made. The literature, too, is steeped in controversy.

Take-home message: a focus on overall health and prevention, including by eating the highest quality food, is the one intervention everyone can agree on.
TSA
Research score: 3/5