People who have been vegetarian for a large chunk of their lives live nearly four years longer than meat eaters, according to research published in the Journal of the American Osteopathic Association.
The authors, from the Mayo Clinic in Arizona, looked at data from six studies involving 1.5 million people, whose meat consumption was recorded over periods ranging from five to 28 years. They found that all-cause mortality was higher among those who eat meat.
They also found that the steepest rise in mortality occurred at the smallest increases of total red meat intake. An increase in life expectancy of 3.6 years was observed in those who eat a long-term vegetarian diet (for more than 17 years).
A review carried out in 2003 of more than 500,000 participants found a decreased risk of 25 per cent (to nearly 50 per cent) of all-cause mortality for those with very low meat intake compared with higher meat intake.
And a 2014 study looked at associations between meat consumption and death from cardiovascular disease heart disease. In that study of over 1.5 million people, researchers found that it was only processed meat that significantly increased the risk of early death.
The researchers behind the study say that, when combined, these findings are ‘statistically significant in their similarity’.
Brookshield Laurent, the study’s lead author, said: ‘This data reinforces what we have known for so long — your diet has great potential to harm or heal. This clinical-based evidence can assist physicians in counselling patients about the important role diet plays, leading to improved preventive care, a key consideration in the osteopathic philosophy of medicine.’
Existing evidence suggests that higher consumption of meat is associated with higher mortality rates from all causes.
We have to remember, though, that this data is mostly from non-randomised, retrospective, epidemiological data. There are many factors that affect studies like this that cannot always be taken into account — some other, unforeseen reason that makes meat eaters more likely to die earlier.
Some contrasting data is also available, for example evidence suggesting that white meat may lower risks of mortality.
A large study, or studies that are consistent in their results, suggest that an issue has been resolved definitively, as is the case with meat consumption.
One problem, though, is that most of the studies have been carried out in the US and agricultural practices there can be very different to those in other countries. The data may not give an accurate picture of the results of eating meat in different parts of the world.
Evidence is available that cattle fed on grain have higher markers of inflammation in their meat than grass-fed cattle; this is important as cardiovascular disease can, at a simple level, be considered essentially a disease of inflammation.
This might explain why excessive meat consumption has been associated with higher rates of heart disease and death — although admittedly this is speculation, as research in this area has not yet been carried out.