Have you been following your doctor's orders and limiting you red meat intake? If you're a meat lover, here's some nutrition news that might make you regret all those steaks you didn't eat.
Sometimes researchers begin a study expecting a certain outcome and end up with a different result. This is one of those studies. It was done by the Harvard School of Public Health to review the evidence that eating red meat can cause heart disease, strokes and diabetes.
The researchers looked over nearly 1,600 studies and were startled to find that even though the health risks of red meat seem well-established, the evidence for that is actually mixed.
"More surprising, we found that all of the studies had either looked at total red meats or processed red meats, but very few of the studies had looked at unprocessed red meats separately," said researcher Dariush Mozaffarian, an assistant professor at the Harvard School of Public Health and Harvard Medical School.
The consequence of eating processed meats is dramatic: a 42 percent higher risk of heart disease and almost a 20 percent higher risk of diabetes.Unprocessed red meat means beef, lamb or pork that hasn't been preserved with smoking, curing, salting or chemical additives. Processed meats include bacon, hot dogs, sausage and most cold cuts. When the researchers did distinguish between the two, what they discovered (PDF) seems to turn current nutritional advice on its head.
"We found that processed meats were associated with higher risk of heart disease and diabetes, and then unprocessed red meats were not," Mozaffarian explained.
Take a second to let that sink in: they found that unprocessed red meats are not associated with heart disease or diabetes. When it comes to strokes, there were too few studies to draw any strong conclusions. But the researchers also found that the consequence of eating processed meats is dramatic: a 42 percent higher risk of heart disease and almost a 20 percent higher risk of diabetes.
So what makes their health effects so different? It's not saturated fat and cholesterol; the researchers found the average amounts of those to be similar in both kinds of meat.
But Mozaffarian says there are two big distinctions: "Really what was different was salt, which was 400 percent higher in the processed meats, and nitrates and other preservatives, which were about 50 percent higher in the processed meats."
Salt, of course, is known to increase blood pressure, which can lead to heart disease. And nitrates and other preservatives are linked to both heart disease and diabetes.
Mozaffarian says this suggests that nutritionists should focus on getting people to reduce their intake of processed red meats, not all red meats. And he says this points the way for the food industry to make its products more healthy.
"Maybe we should try to be making our processed meats with less salt and nitrates, and that will minimize the health harms," he says.
Until then, though, the researchers stress that they didn't find that unprocessed red meat is good for you. It could cause other problems, according to Harvard research fellow Renata Micha, the study's lead author.
"Total meat intake has been associated with higher risk of some cancers, especially colorectal cancer," whereas alternatives to red meat, such as seafood and fresh produce, are known to have actual health benefits, Micha says.
"People should not use this finding as an excuse or license to eat at much unprocessed red meat as they like," she adds, "and they should increase intake in their diet of foods that have been shown to be protective, such as fruits, vegetables, whole grains, fish and nuts."
So the researchers say one lesson of this study is that when eating any kind of red meat, as with so many things in life, moderation is key.
And they say if we want to reduce the amount of preservatives in our foods, we'll have to go back to a time of eating the food you buy within just a few days — and what we lose in shelf-life, we may gain in good health.
The study appears in the journal Circulation, which is published by the American Heart Association. It was funded by the Bill & Melinda Gates Foundation; the National Heart, Lung, and Blood Foundation; the National Institutes of Health; and the Searle Scholars Program, which supports independent research in the biomedical sciences and chemistry.
This program aired on May 18, 2010.