Study under review: The effect of (L-) carnitine on weight loss in adults: a systematic review and metaanalysis of randomized controlled trials
Most adults in the U.S. are overweight or obese. While there are a variety of dietary strategies that can lead an individual to weight loss, pharmacotherapy always sounds alluring. After all, taking a pill that promotes weight loss requires almost no work on the part of the user. This is why there are so dietary supplements claiming to promote weight loss. The vast majority of these are ineffective, and the rest seem to only have marginal effects. One supplement in particular that has been touted for weight loss is L-carnitine.
L-Carnitine is synthesized in the liver from the amino acids methionine and lysine, but (as shown in Figure 1) can also be consumed through a variety of food sources, mostly animal products. About 98% of the carnitine in the human body is found in skeletal and heart muscle, and it plays a role in both glucose and fat metabolism. It influences glucose metabolism by stimulating glycolysis, the breakdown of glucose. But carnitine is generally more well-known for its role in fat metabolism, where it shuttles fatty acids across the mitochondrial membrane for oxidation.
While this role in metabolism has led to claims of weight loss, studies have shown that ingesting up to six grams of carnitine per day for 14 days did not change muscle carnitine concentrations and did not cause weight loss. In contrast, other studies have shown carnitine to be effective for weight loss. To evaluate the existing state of the research on L-carnitine and weight loss, researchers conducted a systematic review and meta-analysis of randomized controlled trials.
Carnitine is purported to aid in weight loss, but research on the topic has shown mixed results. To evaluate the existing state of the research on L-carnitine and weight loss, a systematic review and meta-analysis of randomized clinical trials was performed.
References: Rebouche CJ. Ann N Y Acad Sci. 2004 | Rebouche CJ. Carnitine. In: Modern Nutrition in Health and Disease, 9th Edition (edited by Shils ME, Olson JA, Shike M, Ross, AC). | Lippincott Williams and Wilkins, New York, 1999, pp. 505-12.
Other Articles in Issue #23 (September 2016)
Gut bugs and arthritis
Hippocrates said “all disease begins in the gut”, which might be close to the truth. This research looked at a type of gut bacteria that may help protect against rheumatoid arthritis
HMB + ATP = huge muscles?
HMB (short for β-Hydroxy β-Methylbutyrate) has shown promise in limited trials looking at its free acid form. Could combining this form with ATP be a recipe for accelerated muscle gain?
Rematch: EPA vs. DHA for cardiovascular risk factors
NERD #21 already examined the effect of EPA vs. DHA in very high doses. This randomized trial answers whether normal doses of either fatty acid could help inflammation and blood lipids.
Interview: Pablo Sanchez-Soria, PhD
Toxins: a term that's incredibly overused by people who typically don't understand the concepts very well. Dr. Sanchez-Soria is a toxicologist who deals with toxins and disease on a daily basis. Dr. Pablo Sanchez-Soria is a Toxicologist at the Center for Toxicology and Environmental Health, L.L.C. (CTEH®). Dr. Sanchez-Soria has experience in the fields of human and environmental toxicology, as well as molecular and systems toxicology with an emphasis in cardiovascular and metabolic diseases.
Kids will be kids … even if they skip breakfast?
Kids always get bugged by their parents to eat breakfast, so that they can do well in school. But does breakfast consumption actually impact cognition in this population?
Have the fructose alarm bells rang too soon?
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All the data on resveratrol for cardiovascular health
With 21 existing randomized trials looking at resveratrol’s effect on cardiovascular health markers, this meta-analysis was needed to summarize the data and get a sense of how much, if any, it may help.