Meat, especially red meat, is often the target of criticism in some nutrition circles. Not always for the same reasons–most seem to appreciate its protein but lambast its fat as “artery clogging”. However, there also exists a number of noted nutritionists, particularly those recommending a “plant based diet”, who claim meat protein itself is unhealthy for a various reasons. One of their claims is that animal protein is acidic and causes bone loss as a result. I already this claim in a previous posts, concluding that it was completely untrue. But what about some of the other claims leveed against meat protein, do they have merit?
One claim I sometimes hear relates to homocysteine. Homocysteine is a compound found in the blood that appears to be a risk factor for cardiovascular disease (1,2). Homocysteine is derived primarily from the amino acid methionine, which meat protein is particularly rich in. This generally serves as the bases for the argument that meat should increase homocysteine levels. This makes some sense in theory, but do studies actually support it? Let’s find out.
One study looked at the effect of two diets during and after weight loss in 79 women (3). One was higher in carbs and the other was higher in protein, the difference in protein primarily coming from meat. Ultimately, no difference in homocysteine levels was noted, although this study may have been unable to detect an effect due to weak adherence.
A weight loss trial on 100 women tested two different weight loss diets on various markers of health (4). One diet was higher in protein, the other higher in carbs. Protein was increased using red meat, chicken in fish. There was no difference in homocysteine levels.
Many of these studies pitted meat protein against (often refined) grain carbs. One study instead fed one group meat and used soy protein in the other group to keep protein levels constant while reducing methionine intake in the soy group (5). This study involved only 13 women, but it found no difference in homocysteine levels between the two protein sources.
Finally, the last study we’ll look at assigned 65 overweight subjects to either a low or high protein diet for 6 months (6). Protein sources were primarily meat and dairy products. There was no difference in homocysteine between the two groups, with the high protein group experiencing a non-significant decrease from the beginning of the trial.
What this evidence shows us is that meat intake does not appear to increase homocysteine levels. This is further supported by several epidemiological studies (7,8,9). Ultimately, the idea that meat increases homocysteine is just another silly myth that just got smashed by the hammer of health!