Two studies provide seemingly conflicting information on heart disease
L-carnitine, or carnitine, has been around for a while. The people most familiar with it may be athletes, because for years it has been touted as possibly providing more energy, though the research has not borne out on this topic.
What is L-carnitine and why is it of interest? It is derived from amino acids and most healthy individuals can get sufficient amounts regardless of their type of diet. Carnitine helps in the production of energy in the cell. It is involved in bringing long-chain fatty acids to the mitochondria — “the powerhouse” of the cell — which are then utilized for energy through oxidation. It also keeps potential waste from accumulating in the mitochondria so it performs more efficiently. Thus, it may have antioxidant properties (ods.od.nih.gov/factsheets).
So why is all of this important? L-carnitine may play a role in several chronic diseases, such as heart disease, type 2 diabetes, high blood pressure and even fatty liver disease.
Let’s look at the evidence.
There are two studies with conflicting results on heart disease. In one study, the results are negative, while the other study shows beneficial results. How could that be the case?
In the first study, L-carnitine appears to increase the risk of heart disease through the development of atherosclerosis, or plaque deposits, in the arteries (Nat Med Online. 2013 April 7). L-carnitine is found in foods such as red meat. In this study, mice and healthy human volunteers who regularly ate red meat were observed. Interestingly, the bacteria in the gastrointestinal tract, or gut, in those who consumed red meat were such that L-carnitine was broken down into a metabolite called trimethylamine-N-oxide (TMAO).
This metabolite was then found to increase cholesterol deposits in the arterial walls of mice. In other words, TMAO may promote the development of atherosclerosis. In humans, there was a predicted elevated risk of developing cardiovascular disease and cardiac events, such as heart attacks, strokes and death after three years, but like the mice, only in those that had elevated TMAO levels.
Also of interest, the researchers demonstrated that vegetarians and vegans, when given carnitine supplements, did not produce TMAO. Thus, TMAO production may have to do with microbes that populate the gut of those who consume red meat. This is a preliminary study, mind you, but it makes you wonder if it is the carnitine or the red meat that may be promoting the development of TMAO and the potential for increased atherosclerosis. Carnitine by itself did not cause increased risk of heart disease, but rather the metabolite TMAO did.
In the second study, a meta-analysis (a group of studies) showed those patients given L-carnitine supplements after a heart attack had a statistically significant reduced risk of death from all-causes by 22 percent in 11 trials, ventricular arrhythmias by 65 percent in five trials and chest pain (angina) by 40 percent in two trials (Mayo Clin Proc Online. 2013 April 15).
These were randomized controlled trials (RCTs), the gold standard of studies. The benefits may have been derived from containing the amount of infarct, or dead tissue, in the heart, as well as by increasing the amount of energy in cardiomyocytes (the muscle cells of the heart). In some of the studies, L-carnitine supplements were given for as long as six to 12 months.
Thus, the authors concluded that L-carnitine may be important for those suffering a heart attack, but also in the secondary prevention of a recurrent heart attack. The authors postulated that the mechanism by which L-carnitine derived its beneficial effects was through the improvement in glucose (sugar) utilization in the mitochondria. However, even though it was a meta-analysis, the population size was not large. According to the authors, the patients who might be candidates for carnitine supplementation are those who have had a heart attack and can’t take beta blockers or ACE inhibitors.
Type 2 diabetes
In a meta-analysis (a group of four studies), those given L-carnitine saw an improvement in parameters associated with type 2 diabetes (Exp Clin Endocrinol Diabetes Online. 2013 Feb. 2). There was a significant decrease in fasting glucose (sugar) levels of 14.3 mg/dL and in LDL “bad” cholesterol levels of 8.8 mg/dL. The patients who received L-carnitine were those who were deficient. These studies were RCTs, though they were not large in size.
Role in high blood pressure
In a study involving rats, the results ultimately showed that L-carnitine reduced oxidative stress on the kidneys and helped reverse hypertension-induced kidney damage (Eur J Nutr Online. 2012 Dec. 6). The impact is most likely from the downregulation, or decrease, in inflammatory factors, such as NF-kB, and the upregulation of anti-inflammatory factors, such as NRF2 and PPAR alpha. Thus, L-carnitine may have antioxidant properties that help protect the kidney against damage produced by high blood pressure. These results are exciting, but they are preclinical, or animal-based, and need studies in humans to confirm the results.
Fatty liver disease
As I discussed in last week’s article, fatty liver is a pervasive disease that is benign most of the time, but not always. In a RCT, L-carnitine reduced the liver enzymes significantly (Am J Gastroenterol. 2010;105:1338-1345). These patients had the complication of hepatitis, which was induced by non-alcoholic fatty liver disease. So these were patients on a potentially dangerous road to cirrhosis and, ultimately, to hepatocellular carcinoma (cancer of the liver). In 24 weeks, L-carnitine supplementation not only decreased the liver enzymes, but also cholesterol, glucose and insulin levels. Thus, as the authors concluded, L-carnitine supplementation seemed to improve the overall liver functioning in patients with complications of fatty liver disease.
Though these studies are early or small and more study is warranted, this may be a valuable substance. Thus, it may be worth having your L-carnitine blood levels checked if you have a chronic disease where there might be a deficiency, such as in type 2 diabetes. Check with your physician first, but patients could take L-carnitine supplements if their levels were low or for a protective effect. In cases of heart attacks, high blood pressure and fatty liver disease, carnitine supplementation may decrease organ damage, regardless of your levels.
Dr. Dunaief is a speaker, author and local lifestyle medicine physician focusing on the integration of medicine, nutrition, fitness and stress management. For further information, go to the website www.medicalcompassmd.com and/or consult your personal physician.