The links between heart disease and stroke with red meat, dairy products and certain dietary supplements has been strengthened by a new study published recently in the journal Nature Medicine.1
Research into the amino acid L-carnitine, which is found in all these foods groups, has uncovered evidence that bacteria which naturally occurs in the gut breaks L-carnitine down into a product called trimethylamine-N-oxide (TMAO). Scientists know that TMAO contributes towards atherosclerosis (hardening of the arteries) - the deteriorating process that leads to heart attack and stroke.
The study examined the effect of high levels of L-carnitine consumption, either from foods or supplements, over a 12-year period and identified a clear association with increased risk of subsequent death from heart disease and stroke, as well as other causes including cancer. The pattern was strongest for processed meat consumption, with the high-consumers being 30% more likely to die of a heart attack or stroke than those who consumed the lowest levels of processed meat. The risk of 'all-cause' deaths was 44%.
There was no increased risk associated with the consumption of white meat.
Significantly, this study reinforces the warning that dietary supplements are not always healthy, safe or effective. The level of proof required for marketing drugs is much more onerous than that required for making efficacy and safety claims about dietary supplements. In an accompanying press release, one of the authors of the study, Dr Stanley Hazen, recommends that unless you are advised to do so by your doctor, you should not use L-carnitine supplements.
1. Koeth RA, Wang Z, Levison BS, et al. Intestinal microbiota metabolism of l-carnitine, a nutrient in red meat, promotes atherosclerosis. Nature Medicine. Published online April 7 2013