Dietary supplement with methylsulfonylmethane and vitamin C MSM is the abbreviation for methylsulfonylmethane, which contains organically bound sulfur. Sulfur is essential for the human body, as it is a building block involved in the formation of amino acids, hormones, and enzymes, among other things. Vitamin C supports collagen formation for normal cartilage and bone function in the body and also makes an important contribution to the normal function of the immune system and to the protection of cells from oxidative stress. Note: Not recommended for children, pregnant women, and breastfeeding mothers. Vegan. Lactose-free.