Children who are obese or overweight are at a higher risk of developing heart disease. Damage to the lining of the blood vessels may be an early indicator of potential heart disease. Alpha-lipoic acid (ALA) is a supplement that has anti-oxidant and anti-inflammatory effects, and has been shown to improve blood vessel function in adults with metabolic diseases, and children with type 1 diabetes. It is not yet known whether ALA supplementation can benefit cardiovascular health in overweight/obese youths. The aim of this double-blind placebo-controlled randomised trial was to investigate whether supplementation with ALA improved endothelial function and risk factors for cardiovascular disease in overweight and obese youths. 64 overweight/obese youths aged 8-16 years old were given either 800mg ALA or a placebo for 12 weeks. All participants were instructed to follow a balanced low-calorie diet and advised to engage in a moderate daily exercise program (60 min/day at least five days a week). At the end of the study, blood vessel function, as assessed by flow-mediated dilation (FMD) of the brachial artery, did not change significantly in either of the groups. However, the basal and peak diameter of the brachial artery significantly increased after ALA treatment, compared to placebo. There were no significant changes between groups or over time for blood pressure, weight or body mass index (BMI), nor were there any significant changes in glucose, insulin or fat levels within the blood. The authors concluded that ALA supplementation improves the tone of blood vessels and may have a beneficial effect on heart health in overweight/obese youths.