I am sure that you have seen the recent publicity about carnitine, red meat and cardiovascular disease. What you probably haven’t seen though is the new report from the EPIC project looking at the relationship between food and disease. And what about the finding that carnitine actually improves cardiac health after a heart attack.
I see that you are confused by now so let me take you through the facts.
Bugs transform carnitine to TMAO
Let’s cover the negative findings first. In a multi-centre study, researchers found that carnitine in red meat was metabolised into TMAO (trimethylamine-N-oxide) by certain bacteria in the large intestine. They found that such bacteria were more prevalent in meat eaters compared to vegans and vegetarians and thus more TMAO was produced when meat eaters consumed a carnitine supplement. So far not a problem. Carnitine is present at the highest levels in beef at around 95 mg per 100 g. This is followed by pork at around 25 mg per 100 g, while most other foods contain less than 5 mg per 100 g, except specific carnitine supplements of course. Carnitine itself is actually supposed to be good for you. We need carnitine for our fat metabolism, but we can usually form enough ourselves through bio-synthesis involving lysine and methionine without consuming carnitine directly.
But TMAO might be a problem for certain mice. The researchers used a rather peculiar genetically modified mouse strain prone to develop atherosclerosis to test the impact of TMAO on the cardiovascular system. And of course they found that it induced atherosclerosis. But the relevance of this finding to humans is unclear. TMAO is not a problem for aquatic organisms. Saltwater fish, sharks and rays, molluscs, and crustaceans actually need TMAO to act as an osmolyte to stabilise proteins and counteract the effects of urea. It is also higher in deep-sea fishes and crustaceans, where it may counteract the protein-destabilising effects of pressure. And here comes the really interesting finding. Consumption of fish, and halibut in particular, can produce 107 times more TMAO than consumption of red meat. So what are we really talking about here? No correlations have been found between fish consumption and cardiovascular disease. To be fair to the researchers they didn’t draw the inferences to red meat that the popular press did.
But carnitine could be heart protective
So let’s look at the beneficial effects of carnitine itself. In critically reviewing a number of published key controlled trials, researchers found a clear association between carnitine intake and a significant reduction in deaths after a heart attack. This meta-analysis found that research results supported the potential use of carnitine in acute myocardial infarction and possibly in secondary coronary prevention and treatment, including angina. Carnitine’s potential role in treating heart disease was actually reported already in the late 1970s. During a heart attack blood flow to the affected part of the heart is reduced and natural carnitine is depleted. By supplying extra carnitine it is believed that free fatty acid levels and glucose oxidation can be restored. So carnitine can actually improve cardiovascular health.
Something is wrong here, these seem to be contradictory findings? It cannot be good and bad at the same time.
So let’s look at real life results. Recently researchers announced the results of a big new nutritional study in Europe. Known as the European Prospective Investigation in Cancer and Nutrition (EPIC), it included more than half a million people from 10 European countries who were queried on a host of different factors, from how much and what they ate to their levels of education, their age, their weight, and whether they’d ever smoked. The researchers examined the association of meat consumption with all-cause and cause-specific mortality in about 26,000 participants that died during the 15 year study.
Public health advocates have long warned that overconsumption of red and processed meat can lead to heart disease and other ailments. Yet the scientific evidence supporting this hypothesis has never been wholly convincing. After correcting for some measurement errors, the EPIC study concluded that red meat intake was not associated with increased mortality. As a matter of fact all-cause mortality was higher among participants with very low or no red meat consumption. This confirmed previous results from a large Japanese study that also found no increase in heart disease deaths from moderate meat consumption.
However, the EPIC results showed a moderately positive association between processed meat consumption and mortality, in particular due to cardiovascular diseases, but also to cancer. But the researchers also noted that people who eat a lot of processed meats are also more likely to smoke, eat few fruits and vegetables, and have lower levels of education. They’re much fatter and exercise less than the rest of the sample. They tried to adjust for all this but that is not an easy task.
Not individual food items but the overall diet
People are usually unhealthy in myriad ways that make it nearly impossible to zero in on a single food item as the source of health problems. And it is surely too simplistic to focus on a single food with all the interactions between items in the total diet.
I just told my 89 year-old Dad about the benefits of eating broccoli highlighted in a previous post. And his immediate reaction was that maybe the benefits of the broccoli in his favourite sausage and broccoli dish might even out the negative aspects of the sausage.
- Does Red Meat Clog Your Arteries After All? (marksdailyapple.com)
- Compound In Red Meat, Energy Drinks, Raises Heart Risk Via Gut Bacteria (medicalnewstoday.com)
- Cleveland Clinic researchers discover new link between heart disease and red meat (esciencenews.com)
- Compound in Red Meat, Energy Drinks May Have Heart Disease Link (nlm.nih.gov)