Dietary Methionine and Total Sulfur Amino Acid Restriction in Healthy Adults.
Level 3 - non-randomized controlled study
Controlled feeding trial; randomization between groups or feeding sequences is not stated in the abstract.
PubMed 36806866 · doi:10.1007/s12603-023-1883-3
What was done
Twenty healthy adults (11 females, 9 males) participated in a controlled feeding study assigned to either methionine restriction alone (MetR) or combined methionine and cysteine restriction (total sulfur amino acid restriction, SAAR). Participants completed three 4-week feeding periods separated by 3-to-4-week washout periods: a control diet, a low-level restriction diet (70% MetR or 50% SAAR), and a high-level restriction diet (90% MetR or 65% SAAR). Biomarkers of cardiometabolic risk and safety were measured.
What was found
No adverse effects were observed, and compliance was high. After 4 weeks, SAAR significantly reduced body weight, total cholesterol, LDL, uric acid, leptin, insulin, BUN, and IGF-1, and significantly increased body temperature and plasma FGF-21 (P < 0.05; exact figures not reported in abstract). In the 65% SAAR group, plasma methionine and cysteine levels decreased by 15% and 13%, respectively (P < 0.05). MetR alone yielded fewer changes, significantly reducing BUN, uric acid, and 8-isoprostane, and increasing FGF-21 (P < 0.05).
Why it matters
This study provides early evidence that short-term sulfur amino acid restriction is feasible in humans and produces metabolic and biomarker shifts consistent with animal models of longevity and metabolic health.
Limits
The study is limited by a very small sample size (n = 20 across two diet arms), short intervention durations (4 weeks per phase), and lack of reported randomization or blinding. Absolute effect sizes and confidence intervals are omitted from the abstract for most outcomes.
Cited by
- supports Dietary proteins and specific amino acids such as methionine and cysteine regulate circulating IGF-1 levels in mammals.