More Confusion about Red Meat

This past week, two opposing research studies were published. The first got major press and might sound familiar. It suggested eating red meat could cause heart disease because it contains the nutrient l-carnitine, which the researchers believed would cause a change in gut bacteria, which in turn would produce something called TMAO. TMAO is associated with higher levels of heart disease. Notice, nothing about that chain of sentences said red meat causes heart disease, although that’s what news headlines suggested based on this particular study, which was published on April 7, in the journal Nature Medicine. Five days later, the second study came out and received little to no press. On April 12, Mayo Clinic Proceedings released the results of a meta-analysis (a study of all quality studies) on l-carnitine, finding l-carnitine “significantly improves patient outcomes following heart attack.” Confused yet? Let’s break it down.

Is it possible that consuming l-carnitine prior to developing heart problems can cause heart problems; however, once you develop heart problems, consuming l-carnitine can lessen the risk of further heart problems? Anything is possible, I suppose, but it’s not likely. Why can there be such strongly opposing points of view on this nutrient? And how does this nutrient tie in so strongly with meat consumption? Finally, why can’t the media seem to tell the full story on this subject rather than worrying people with inflammatory, misleading headlines?

Each year, there seems to be at least one or two studies published, pointing the finger at red meat as a cause of heart disease. Actually, it was last April that headlines suggested red meat consumption caused cancer, a topic I covered in Will Red Meat Really Kill You?  Sure, the media hype grabs people’s attention, but these headlines are inevitably based on single, observational studies that use some type of food frequency questionnaire. It’s always important to take these media dishes with a serious grain of salt.

An observational study is used to show consistent patterns. In the case of meat consumption, people are usually asked questions about what they eat and the current status of their health. Questions about meat consumption are often phrased like this: “In the past week, how often did you eat a meal containing meat (hamburgers, steak, pizza, cold cuts, bacon, etc.?”

Hopefully, you can already see the flaws with such a question. You’re trying to isolate red meat as the culprit in health problems, but then you lump in processed meats with unprocessed meats and even include starchy foods like pizza and hamburgers. Suddenly, you’re dramatically changing the dietary patterns you’re looking at. Even The China Study, which is often touted as proof that a vegetarian diet is healthier, is based on such research. Those who eat meat regularly often eat other foods that likely contribute to heart disease, which has nothing to do with the meat itself. The bottom line: meat is often unfairly blamed for health issues that could be caused by other foods meat-eaters tend to include in their diets.

For many years, the prevailing message warned that red meat caused health problems because it contained so much fat. Thankfully, the tide is turning on that assumption. Even the authors of the first l-carnitine study admit that saturated fat has been wrongfully accused of causing heart disease. Although red meat, when studied correctly, has never been shown to cause heart disease, the study’s authors still seemed to be hung up on the observational research associating red meat with heart disease. They simply chose a different angle on the connection,  focusing on l-carnitine, an amino acid.

The relentless pursuit to find a problem with red meat reminds me of a story I’ve read a few times in various books. The story goes like this (author unknown):

A police officer sees a drunk man searching for something under a streetlight and asks what the drunk has lost. He says he lost his keys and they both look under the streetlight together. After a few minutes the policeman asks if he is sure he lost them here, and the drunk replies, no, that he lost them in the park. The policeman asks why he is searching here, and the drunk replies, "this is where the light is." 

In the case of red meat, observational research seems to have created such momentum in the case against red meat that researchers seem bound and determined to keep looking for problems with red meat, rather than focusing on the other foods people who eat red meat tend to eat along with it. That could be the case for l-carnitine.

To summarize the flawed first study, red meat contains l-carnitine. In a very limited number of subjects, a by-product of gut bacteria metabolism called TMAO was higher from supplementing with l-carnitine and from eating meat. TMAO has been associated with higher rates of heart disease. Nonetheless, there are too many flaws to the study and insufficient information to genuinely support the researchers’ conclusion, which is itself rather circuitous: red meat causes heart disease because it contains l-carnitine, which may raise TMAO, which has been associated with higher rates of heart disease.

I’ve read three very well-written reviews of the study, which I encourage you to read if you want more detail on the research.

Finally, what I find most amusing about the hype around this study, is this: red meat is not the greatest source of l-carnitine; seafood is! If l-carnitine really was the issue, why didn’t the media headlines proclaim seafood as the cause of heart disease? It would be more accurate if l-carnitine were really the problem, but I don’t hear anyone arguing that seafood causes of heart disease….

On that subject, let’s look at the aforementioned second study.

On the opposite end of the health spectrum, the Mayo Clinic had the following to say about l-carnitine in their study published just a few days after the first study made headlines:

This systematic review of the 13 controlled trials in 3,629 patients, involving 250 deaths, 220 cases of new heart failure, and 38 recurrent heart attacks, found that L-carnitine was associated with:

Significant 27% reduction in all-cause mortality (number needed to treat 38)Highly significant 65% reduction in ventricular arrhythmias (number needed to treat 4)Significant 40% reduction in the development of angina (number needed to treat 3)Reduction in infarct size

First author James J. DiNicolantonio, PharmD, Wegmans Pharmacy, Ithaca, NY, observes, “Although therapies for acute coronary syndrome (ACS), including percutaneous coronary intervention, dual antiplatelet therapy, b-blockers (BBs), statins, angiotensin-converting enzyme inhibitors (ACEIs), omega-3 fatty acids, and cardiac rehabilitation, have markedly improved clinical outcomes, adverse cardiovascular (CV) events still occur too frequently after ACS. One promising therapy for improving cardiac health involves using L-carnitine to improve free fatty acid levels and glucose oxidation.”

Yes, do the double take. Does this prove that l-carnitine improves heart health? No, but the volume of research suggesting its health benefits is pretty significant. As the researchers point out, l-carnitine plays an important role in fat and glucose metabolism, which is important for reducing the likelihood of developing metabolic syndrome, a known contributor to heart disease.

Any time we talk about eating meat (and most other foods), it’s important to reiterate that the source and quality are important. You should always buy the best quality you can afford. A beef patty from a fast food chain and  grass-fed t-bone steak are dramatically different in quality and nutrition.

That said, animal-based protein sources in general remain great sources of high-quality protein, which is important for maintaining low body fat levels, recovering from exercise, supporting the immune system and increasing or maintaining bone density.

If your goal is to maintain a healthy cardiovascular system, there are bigger, more impactful choices you can make rather than worrying about whether or not to eat red meat. In fact, simply stressing out about the question is a more sure-fire risk in itself, since worry can cause inflammation, a known risk for heart disease. Sugar and other excessive starch, low vegetable intake, a sedentary lifestyle, and insufficient sleep have all have been shown to lead to heart disease and a number of other health problems. You’re better served focusing your time and efforts on these choices.

That said, if you’ve bought into the results of the first study, suggesting red meat causes heart disease, be sure to avoid seafood as well, since that’s the greater source of l-carnitine. For me, I’ll continue eating red meat in some of my meals, along with plenty of non-starchy vegetables, but not with a bun, French fries or as part of a pizza.

Thanks for reading. Share your thoughts, comments and questions below.