- Studies often come to contradictory conclusions on how diet and fitness impact our odds of developing diseases.
- A new, independent statistical tool aims to cut through that noise.
Dr. Chris Murray isn't as shy as he used to be about adding a little red meat into his diet.
For several years, Murray and colleagues at the independent Institute for Health Metrics and Evaluation have been evaluating existing nutrition and health studies, endeavoring to understand the health risks of different diets and lifestyles. So far, Murray's been most shocked to find out that red meat may not necessarily be the cancer and heart health culprit he once thought it was.
"Probably a little more tolerance for eating red meat, on my part," he said, during a press conference.
The IHME's new collection of peer-reviewed studies, out Monday in Nature Medicine, aims to do for others what it did for Murray — cutting through the noise of "a big cloud of studies," he said, in order to determine, statistically speaking, which behaviors are inextricably linked to bad health outcomes like cancer or heart disease, and which need more evidence.
To that end, the IHME has developed a tool aimed at making it easier for doctors, the public, and policy-makers to make sense of scientific evidence. So far, they've weighed in on smoking, red meat eating, vegetable-eating, and high blood pressure.
The tool uses a "star" rating system. Five stars indicate very strong evidence linking a behavior or characteristic to a bad health outcome, while one star suggests there may not be any relationship between a given indicator and a health issue.
Smoking is clearly linked with cancer, but evidence on red meat is murkier
So far, IHME's data shows:
- Tobacco consumption is inextricably linked to cancers including throat, lung, pancreas, as well as other health issues at 4-star and 5-star levels.
- High blood pressure is clearly linked with heart disease at a 5-star level. The higher your blood pressure is, the more dangerous it is for your health. Concerningly, this is true even at some elevated blood pressure levels which are technically listed as "normal," the study authors noted.
- Low vegetable consumption is linked with more strokes and heart disease at 3-star and 2-star levels, suggesting a moderate, but consistent, association between non-starchy vegetable-eating and better health.
- Whether unprocessed red meat consumption really leads to more cancer and heart issues is up for debate, with only 1-star and 2-star levels of association.
"Red meat is a very controversial area," Murray said, adding that one's willingness to include red meat in a diet is "very much going to be depending on an individual's willingness to take risk." After all, the absence of evidence for harm doesn't necessarily mean a given action is perfectly safe.
Evidence against unprocessed red meat is 'weak' so far
Existing studies of red meat don't reliably show us whether eating animals is truly a health hazard, especially when done in moderation. Red meat has been shown in many studies to be linked with earlier deaths, and with cancers — especially colon cancer.
But so far, "all the evidence on red meat is in the weak category," Murray said.
His team's IHME evaluations aimed to "have the burden of proof be on the science to actually convince us that something is harmful," using statistical models.
The best evidence red meat is harmful is related to colorectal cancer risk — there is an association here, albeit a weak one.
"We should not be at all surprised if future studies change our understanding of the risks associated with red meat," Murray said. Particularly when it comes to eating small quantities of red meat, it's not clear whether there's a direct connection to disease risks.
There may even be a somewhat protective effect of eating red meat on your odds of developing a stroke or suffering a hemorrhage. That doesn't mean we should all load up on red meat. Instead, the takeaway is that existing studies don't show any strong conclusions on red meat one way or the other.
It's worth noting 2 big caveats before grabbing a hot dog
This study did not look at the relationship between disease and eating processed meats, like sausage, bacon, and hot dogs. Processed foods of all kinds are worse for our health than unprocessed, whole foods. It also didn't take into account the environmental impacts of eating more red meat, and we know those are substantial.
The team at IHME plans to update the 5-star tool regularly as more studies come out. They also plan to include alcohol, air pollution, BMI, whole grains, legumes, and dietary fiber in the rankings.