Is Leucine Supplementation Actually Useful for Building Muscle?

Leucine, an essential amino acid, has been shown to help trigger mTORC1 signaling, which initiates protein synthesis. However, the real question is whether supplementing with leucine, when already consuming a diet relatively high in protein and lifting weights, actually leads to better gains in strength and muscle growth. A new systematic review in young, active adults suggests the answer is usually no. Across randomized trials involving healthy, trained participants following similar programs, adding leucine did not improve muscle growth, strength, or recovery compared to a placebo. The same appears to be true even when looking at meta-analyses on the topic in older adults, including those with sarcopenia. Leucine supplementation did not show any clear benefits for lean mass, hand grip strength, or leg press strength, in either older adults who resistance trained or those who didn’t. There appeared to be some benefit of leucine supplementation when it also included vitamin D for handgrip strength, but terms and conditions apply. Similar to younger adults, resistance training paired with an adequate protein intake appears to be sufficient to increase strength and muscle mass. It’s worth highlighting that when mentioning “adequate” protein intake, we’re not necessarily talking about anything extreme. For example, some of the studies on older adults had participants consume roughly 1.2g of protein per kilogram of body weight, which is likely enough to tick a lot of muscle growth boxes. In summary, it’s unlikely that leucine supplementation is necessary for individuals who are already consuming a balanced diet and engaging in regular resistance training. Additionally, BCAA or EAA supplementation may not be a superior option for spiking muscle protein synthesis compared to a complete source of protein. The key takeaway is that a well-balanced diet and consistent resistance training are sufficient for maintaining muscle mass and strength, making supplements like leucine a potential unnecessary expense.