Histidine supplementation improves insulin resistance through suppressed inflammation in obese women with the metabolic syndrome: a randomised controlled trial

Randomized controlled trial in obese adult women with metabolic syndrome from Harbin, China. Participants were ages 33-51 years, had BMI 28 kg/m2, and 50 women were randomized to histidine and 50 to placebo; 47 and 45, respectively, were analyzed/completed.

Histidine was given as oral L-histidine tablets at a total dose of 4 g/day, administered as two 1 g tablets after breakfast and two tablets after dinner for 12 weeks. The active regimen was compared with placebo.

Histidine supplementation improved insulin resistance and several obesity-related, inflammatory, and oxidative stress markers over 12 weeks. In the histidine group, HOMA-IR decreased from 3.7.1 to 3.0.1, BMI from 30.9.4 to 30.0.1 kg/m2, waist circumference from 96.1.2 to 93.4.4 cm, and NEFA from 946.38.8 to 773.403.3 mol/l. Adiponectin increased from 8.0.5 to 10.5.6 ng/ml, while TNF- and IL-6 declined from 12.2.4 to 8.2.2 pg/ml and from 6.2.1 to 4.0.3 pg/ml, respectively; SOD and GSH-Px increased. No adverse events were observed.

The analyzed sample was modest (47 histidine and 45 placebo participants), and follow-up was only 12 weeks. The trial was conducted in a specific population of obese women with metabolic syndrome in one Chinese city, which limits generalizability. Mechanistic conclusions about NF-B signaling are based on adipocyte findings and are therefore indirect relative to the clinical outcomes.