Meat and mortality: What does color have to do with it?

"High intakes of red or processed meat may increase your risk of mortality."  So conclude the authors of a ten-year study involving half a million people, published in this week's Archives of Internal Medicine.

The authors found that those who ate the most red meat were about 20% more likely to die of cancer than those who ate the least. The risk of cardiovascular disease was also elevated in those who ate more red meat. (Eating more white meat appeared to have a protective effect.) You can access the entire article here: "Meat Intake and Mortality." 

Whenever you have big studies like this, there are always questions about whether the results are skewed by confounding variables.  In this study, the researchers attempted to "adjust" for as many variables as they could. They took into account the subjects' age, race, physical activity, vegetable intake, vitamin supplements, alcohol use, body weight, smoking habits, and family health history.   

But you can never account for everything. For example, they did NOT account for things like sugar, sodium, monounsaturated fat, or trans fat intake--dietary factors that all have a strong link to either cancer, heart disease, or both.  I wish we could see how adjusting for those factors affected the findings.

Seeing Red

But my main complaint with this study is not whether they accounted for enough (or the right) confounders but with the most basic aspect of the study's design. The division of meat into "red" and "white" categories seems completely arbitrary to me.

In this study, "red" meat included anything made with beef or pork, including steaks, bacon, liver, cold cuts, burgers, ham, sausage, and hot dogs.   "White" meat included anything made from chicken, turkey, or fish.   Although these categories have some cultural significance, they make absolutely no sense from a nutritional, or even a zoological, perspective.  How is canned tuna more nutritionally similar to turkey sausage than it is to a filet of beef?

In other words, someone who ate grass-fed beef five times a week would be in the same category as someone who ate a fast food hamburger every day.  Someone who ate wild-caught salmon three times a week would be in the same category as someone who ate chicken nuggets just as often. Even if you controlled for things like saturated fat content (which they did), how much could comparing these dietary "patterns" possibly reveal about human health and disease?

I can think of several ways to analyze meat consumption that would have shed more light on connections between meat consumption, cancer, and heart disease.  For example, how about categorizing meat based on the percentage of monounsaturated fat it contains?  What would these groups look like?

Some meats containing more than 40% of total fat as monounsaturated fat
Beef tenderloin
Pork Roast
Sablefish

Some meats containing less than 40% of total fat as monounsaturated fat
Skinless roasted chicken breast
Canned white tuna
Steamed shrimp

Intake of omega-3 and omega-6 fats is also linked to both heart disease and cancer; specifically, it appears beneficial to increase the ratio of omega-3 to omega 6 fats in the diet. So why not categorize meats according to their omega-3/omega-6 ratios?

Some meats with a higher ratio of omega 3 to omega 6
Beef liver
Grouper
Braised shortribs

Some meats with a low ratio of omega 3 to omega 6
Ground turkey
Tuna salad
Chicken livers

Cooking meat over high or direct heat is known to promote the formation of carcinogens. So why not put hamburgers, grilled pork chops, and barbecued chicken into one group and pot roast, baked chicken, and poached fish in the other?

I could go on, but I'm sure you get my point.  None of these designations is perfect but ALL of them seem more valid than "red" and "white." At least there are actual criteria involved.

Mostly, I'm disappointed in this study because it reinforces our tendency to look at foods or nutrients (like fats, carbs, and now, so-called red meat) as "good or "bad," without enough consideration of the context of the entire diet or the substantial differences within these groups.  Despite the headlines being generated by this study, I'm not convinced that eating red meat (as opposed to white) categorically increases your risk of heart disease or cancer. 

Other (better?) reasons to reduce your meat intake

Aside from the impact of red meat consumption on disease risk--which I think this week's study does little to illuminate, there are other good reasons to consider cutting back on meat of all kinds. Many are outlined in an editorial by Barry Popkin, which appears in the same issue of the Archives:

• Over-consumption of animal protein increase the global food prices (including non-meat foods)
• Animal crops consume up to 5 times more of our dwindling water supplies than do plant crops
• Livestock production accounts for 55% of land erosion, 37% of pesiticide use, and 50% of antiobiotics consumed in the U.S.
• Livestock production consumes a large amount of fossil fuel and contributes to greenhouse gases

Personally, while I don't worry that red meat per se is increasing my risk of disease, I find these very compelling reasons to eat less meat of all colors. That's why I'm a new and enthusiastic supporter of the Meatless Monday campaign, a public (and planetary) health initiative that encourages consumers to enjoy one meatless day each week. Care to join me?