How to live longer: eat less red meat and more nuts. And be optimistic.

Will eating more red meat kill you? It just might–but there's something you can do about it.

Red meat has long been implicated in some very bad health outcomes, especially heart disease and colon cancer. And yet people keep eating it, for the simple reason that it tastes good (though not to everyone, of course).

A recent study out of Harvard and Fudan University, published in the BMJ, put some numbers on the risk of eating red meat. The authors used two very large studies, one of men and one of women, to ask a simple question: does eating red meat make it more likely that a person will die?

The answer is yes: in the study, men and women who ate more red meat–half a serving more per day–had about a 9% greater risk of death (from any cause), over the course of an 8-year followup period. Processed meats were worse: an increase of half a serving per day led to a 17% higher risk of death.

In case you're wondering, "processed" meats are foods like hot dogs, bacon, and sausages. And if half a serving per day sounds like a lot, it's not: the scientists defined a serving as just 85 grams of beef, pork, or lamb, or a single 45-gram hot dog, or 2 slices of bacon. By comparison, a quarter-pound hamburger is 115 grams. So an extra half-serving isn't very much.

(But smoked salmon lovers needn't worry: as I wrote back in August, smoked salmon is not processed meat. It's fish, which is far healthier than red meat.)

Can you lower our risk of death by reducing red meat consumption? The study looked at this question too, and the answer was, again, yes: if you replace one serving of red meat per day with whole grains, vegetables, or nuts, your risk of dying goes down, as much as 19%.

Even better is to replace one serving per day of processed meat (bacon, sausages, etc) with nuts:

"A decrease in processed meat and a simultaneous increase in whole grains, vegetables, or other protein sources was even more strongly associated with lower total mortality, with the largest reductions in risk seen with increases in nuts."

That led to a 26% reduction in the risk of death over eight years. The authors found similar results when they looked at benefits over different time spans.

The conclusion is pretty clear: replace some of the red meat in your diet with vegetables, whole grains, or nuts, and you'll probably live longer.

There's another thing you can do to avoid dying of a heart attack: be optimistic. In a completely independent study published just last week in JAMA, scientists conducted a meta-analysis of 15 earlier studies, asking whether optimism is associated with better heart health. They found that over a 14-year period, optimistic people had a 35% lower (relative) risk of cardiovascular problems and 14% lower (relative) risk of dying than pessimistic people.

There are many caveats about this study–first, it's a meta-analysis, meaning that it combines the data from many other studies. That can lead to biases, but the authors acknowledged this problem and seem to have been pretty careful to avoid it. Second, how do you measure optimism? Turns out there's a questionnaire for that, dating back 25 years, and it appears to be reliable and reproducible. Most of the studies used the same method for measuring optimism, and the benefits were quite consistent across all the studies. And it's possible that sicker people are more pessimistic, so the cause-and-effect could go either way here.

So there you have it: cut down on red meat, eat nuts instead, and stay positive. You'll live longer.