Double-Blind, Placebo-Controlled, Randomized Clinical Trial of the Effect of the Dietary Supplement S-Adenosyl-L-Methionine (AdoMet) on Plasma Homocysteine (Hcy) Levels in Healthy Human Subjects.
Authors: Thompson Michael A. , Bauer Brent A. , Loehrer Laura L. , Cha Stephen S. , Mandrekar Jayawant N. , Sood Amit , Wahner-Roedler Dietland L. 
Published: October 2019

BACKGROUND: S-adenosyl-L-methionine (AdoMet or SAM-e®) is a commonly used nutritional supplement available in the United States since 1999. AdoMet is metabolized to homocysteine (Hcy), a potential cardiovascular risk factor. A few open-label, single-arm studies have reported on the effect of exogenous AdoMet on the levels of Hcy in humans; however, this has not been tested in a double-blind, randomized clinical trial. As a nutritional supplement, AdoMet is subject only to limited regulation by the FDA, despite being used to treat clinical diseases such as depression and osteoarthritis. AdoMet is the methyl donor for small molecule, DNA, RNA, and protein methylation reactions; therefore, further understanding the biology of the AdoMet/Hcy system is important. We hypothesized that exogenous AdoMet would increase plasma Hcy levels.

METHODS: In a double-blind, placebo-controlled, randomized clinical trial, 93 healthy human subjects were screened and 52 were treated with placebo (26) or 800 mg per day AdoMet (26) pills for 4 weeks. Pre- and post-treatment Hcy levels were measured. The primary endpoint was change in Hcy level. Secondary endpoints included an interim Hcy level, high sensitivity C-reactive protein (hsCRP) levels, lipid profile, and transaminases. Exclusion criteria included pregnancy and concurrent use of medications associated with changes in Hcy.

RESULTS: Of 52 subjects enrolled, 45 were evaluable at the end of treatment. Subject characteristics and dropout rates were similar between placebo and control groups. Adverse events were minor and were not different between placebo and AdoMet. The primary endpoint, change in Hcy, was not significantly different between the groups (mean (umol/L), baseline: 7.43 (placebo), 8.25 (AdoMet), P=0.358; 4 week: 7.66 (placebo), 8.06 (AdoMet), P = 0.683; Baseline − 4 week: 0.23 (placebo), −0.19 (AdoMet), P = 0.427). No statistically significant difference in change in Hcy or hsCRP at 2 or 4 weeks was noted. This was true for both absolute differences as well as relative percent changes. A small decrease in ALT was observed at 2 weeks in the AdoMet group compared to the placebo group (P = 0.027). AdoMet is used in the treatment of liver diseases. There was a small, but statistically significant (P = 0.028) decrease in total cholesterol in the AdoMet group as compared to the placebo group. Interestingly, a subject with the highest baseline Hcy level had a decline in Hcy on AdoMet. Study limitations include no evaluation of AdoMet serum levels or measurement of the effect of AdoMet on DNA methylation patterns.

CONCLUSIONS: AdoMet seems well tolerated and in a dose of 800 mg/day for 4 weeks does not appear to significantly affect Hcy levels in the blood. Future clinical trials of AdoMet should monitor Hcy levels with extended use of AdoMet to confirm its safety with long term use.

Clinicaltrials.gov ID: NCT00284011.