S-methyl-D-cysteine is primarily known for its presence in certain plants, especially in garlic and other Allium species. It serves as a natural organosulfur compound that contributes to the antioxidant properties of these plants. In dietary supplements, it supports detoxification processes by enhancing glutathione production, a key antioxidant in the body. It may also play a role in reducing oxidative stress and supporting cardiovascular health due to its influence on sulfur metabolism. Additionally, S-methyl-D-cysteine is studied for its potential anti-inflammatory effects and its ability to modulate immune function, making it relevant in nutraceutical and functional food applications.