Why Meat And Protein Are Not The Same

(Photo credit: Wikipedia)

In the last week alone, there’s been enough conflicting research on meat to turn a person veggie (and that might not be a bad way to go). Among the most recent study results, animal protein will give you heart disease and breast cancer, and possibly kill you. On the upside it may save you from a stroke, and it helps build muscle. There are obviously some caveats at play. One issue is that even within a given category (e.g., animal protein), the health effects can vary greatly. The other question is whether we can have too much protein overall, even of the “purest” kind. While eating more protein isn’t necessary for most Americans – we take in an awful lot already – where we get our protein is the question.

This post appeared on Forbes.

So what do we do? The answer actually hasn’t changed very much over the years, despite the apparent uptick of conflicting evidence: Eat adequate but not excessive amounts of protein, certainly from plants, and possibly from fish, eggs, and poultry. And if you’re going to indulge in red meat (and there is evidence that some people perhaps should), just about everyone advises to do it sparingly.

Here’s a recap of the research in the last week. One study found that red meat was linked to an increase in the risk of breast cancer, in a study of over 88,000 nurses in the Nurses’ Health Study II. Nuts, beans, fish, and poultry, didn’t seem to pose the same risk, however, and poultry alone was linked to a lower risk of breast cancer.

Another study found, not surprisingly, the meat consumption was linked to heart disease in a study of 37,000 middle-aged men – but there was difference when the researchers broke it down and looked at processed vs. unprocessed meat. Men who ate mostly unprocessed red meat didn’t have any greater risk of heart disease, but men who ate mostly processed meats – hotdogs, sausages, and such – had a greatly increased risk of heart disease and cardiac-related death.

Finally, one study appeared at first glance to provide a ray of hope for the meat lover, finding that high-protein diets might lower the risk of stroke, likely for blood-pressure lowering reasons. Animal protein was associated with a significantly reduced risk of stroke in a meta-analysis of over 250,000 people. But again, a caveat: The authors say the findings do not extend to red meat, since it’s known to increase the risk of stroke. Therefore, headlines touting the fact that “protein lowers stroke risk!” along with a picture of steak are misleading, and readers should realize that the source really does matter.

There are a few reasons why protein may both healthy and unhealthy, depending on the type, amount, and stage of life you’re in. Proteins are made up of amino acids, which are critical in just about every element of our cells’ structure and function. Some amino acids can be made by the body, but others can’t, so we have to consume them. The presence or absence of these essential amino acids, of which there are nine, are what make a protein “complete” or “incomplete.” Animal sources of protein are typically complete – eggs, dairy products, and meat/poultry/fish. Vegetables generally offer only incomplete proteins, which is why it’s important for vegetarians to pair different plant sources. (Quinoa may be the exception.)

So protein is essential, but in high doses, some have suggested it may also be detrimental. One reason is that it appears to trigger the production of a growth factor, IGF-I, which is linked to cancer cell proliferation. Some studies, like this recent one, have found that any type of protein, but animal protein in particular, is linked to an increased cancer risk. Valter Longo, who headed the study, says that “[a]lmost everyone is going to have a cancer cell or pre-cancer cell in them at some point,” says Longo. “The question is: Does it progress? Turns out one of the major factors in determining if it does is protein intake.”

The other issue is that we don’t eat protein alone: It comes with fats, carcinogens, and hormones. Red meat in particular seems to be in a class of its own. It has been shown in a number of studies to increase the risk for colon cancer; there is less evidence that other forms of cancer are connected to red meat. Although the mechanism isn’t totally clear, some researchers have suggested it’s the form of iron in red meat that may trigger the formation of cancer-causing N-Nitroso compounds. Others have suggested that it’s the heterocyclic amines (HCAs) — carcinogens are released when meat is cooked under higher temperatures. And red meat has been linked to heart disease many times over, but likely for reasons related to fat content, rather than protein.

Photo: diagnosisdiet.com

So one issue is that meat and protein are not exactly interchangeable, since any kind of protein carries along with it lots of other compounds. Steak and turkey breast may have very different effects on the body. And again, the harder question is whether high doses of protein from any source pose health risks. Longo stresses that from his study, at least, all forms of protein were linked with cancer, even that from plants. “Keep in mind that for cancer, plant proteins at high levels are still associated with a 3-fold higher mortality. But this is not as bad as that for animal protein (4-fold). For overall mortality instead, the animal-to-plant switch makes a big difference.”

The protein-health connection will need a lot more research before we understand it completely. The effects of a single molecule in foods made of many, many molecules are very hard to isolate. In the meantime, keep protein intake moderate: Most organizations recommend swapping out red meat for other sources, and taking in about 46 grams per day for women, and 56 grams per day for men.

So have a little protein, but avoid the fats, hormones, and carcinogens, where you can. Plants, fish, and eggs are probably best, if you crave it, a burger every now and then probably won’t kill you. Of course, eating plant-based proteins also gives you the peace of mind that you’re not contracting Mad Cow Disease along with it. While the recent scare seems to be largely a technical glitch, and not any real biological cause for concern, the vegetarians out there will breathe a sign of relief that the issue doesn’t pertain to them.