Sulfur (S) is a chemical element and a macronutrient necessary for all living organisms. This element is the third most abundant mineral in the human body, following calcium and phosphorus.
Sulfur is a structural component of two of the twenty protein-building amino acids: methionine, which must be obtained through diet, and cysteine. The presence of sulfur in these amino acids allows for the formation of disulfide bonds, which are instrumental in stabilizing the three-dimensional structure of proteins, a process that determines their function. Sulfur is also involved in various metabolic processes and is part of cofactors like glutathione, which plays a role in the body’s antioxidant defense.
Sulfur Compounds in Food and Nutrition
The primary way the public interacts with sulfur on a daily basis is through the consumption of certain foods, where the element is present either as part of amino acids or as unique organosulfur compounds. Protein sources, including eggs, meat, fish, and legumes, provide the body with the sulfur-containing amino acids methionine and cysteine. Methionine is used by the body to initiate protein synthesis, while cysteine’s ability to form disulfide bonds contributes to the structural integrity of many proteins. These amino acids are essential for maintaining the body’s pool of organic sulfur and supporting overall sulfur homeostasis.
Beyond protein, specific vegetables are well-known for their unique sulfur-rich compounds, which are often responsible for their pungent flavors and aromas. The allium family, which includes garlic, onions, and leeks, contains S-alk(en)yl-L-cysteine sulfoxides like alliin. When garlic is crushed or chopped, the enzyme alliinase converts alliin into allicin, a highly reactive compound that contributes to fresh garlic’s distinctive odor and is associated with various biological activities.
Cruciferous vegetables, such as broccoli, kale, cabbage, and cauliflower, are rich in sulfur-containing compounds called glucosinolates. When the plant tissue is damaged, an enzyme called myrosinase converts glucosinolates into biologically active molecules, including sulforaphane. Broccoli sprouts, in particular, are recognized as a concentrated source of sulforaphane precursors. These vegetable-derived organosulfur compounds are linked to the activation of detoxification enzymes and the reduction of oxidative stress within the body.
Sulfur in Skincare and Topical Treatments
Sulfur is a long-standing ingredient in dermatology, valued for its mild but effective properties when applied externally to the skin. It is commonly used in products formulated to treat conditions such as acne, rosacea, seborrheic dermatitis, and dandruff. Sulfur’s mechanism of action is primarily attributed to its keratolytic and antibacterial effects.
The keratolytic action helps to gently soften and thin the outer layer of the skin, promoting the shedding of dead skin cells and helping to unclog pores. This process occurs as sulfur interacts with skin cells to form hydrogen sulfide, which helps to break down the bonds between keratinocytes. Its antibacterial and antifungal properties work to inhibit the growth of microorganisms, including the bacteria associated with acne breakouts and the fungi that contribute to dandruff.
Topical formulations containing sulfur typically range in concentration from 2% to 10%. It is often found in acne spot treatments, cleansing bars, and shampoos, sometimes combined with other exfoliants like salicylic acid to enhance its effects. The main drawbacks of sulfur in cosmetic products are its characteristic odor and the potential for it to cause skin dryness or irritation in some individuals.
Supplements and Medications Containing Sulfur
Sulfur compounds are manufactured into concentrated supplements and pharmaceuticals for systemic health benefits. Two popular examples in the supplement market are Methylsulfonylmethane (MSM) and Glucosamine Sulfate, which are frequently marketed together for joint health. MSM is an organic sulfur-containing compound that is approximately 34% sulfur by weight, providing a source of the mineral believed to support the structural integrity of connective tissues, including cartilage, tendons, and ligaments.
Glucosamine Sulfate is an amino sugar that is a component of joint cartilage and is thought to stimulate the body’s ability to manufacture collagen and repair connective tissue. Taking MSM supplements may help reduce inflammation and stiffness associated with joint degeneration, a benefit that is sometimes enhanced when combined with Glucosamine Sulfate. These supplements are typically ingested as capsules or powder to provide a higher concentration of sulfur than is easily obtained through diet alone.
In the pharmaceutical industry, the sulfur-containing sulfonamide drugs, often called sulfa drugs, represent a distinct class of synthetic antimicrobial agents. These medications function by acting as competitive inhibitors of an enzyme in bacteria, preventing the microbes from synthesizing folic acid, which is necessary for their growth and multiplication. Due to their unique chemical structure, these drugs carry a risk of allergic reaction in a small percentage of the population, requiring careful prescribing.
Sulfur in Common Commercial Materials
Sulfur plays a role in various industrial processes and is a component in several common commercial materials. One of the most historically significant uses of sulfur is in the vulcanization of rubber, a process that transforms natural rubber into a more durable, elastic, and heat-resistant material. During vulcanization, sulfur atoms form cross-links between the long polymer chains of the rubber, which strengthens the material for applications like vehicle tires, shoe soles, and hoses.
Sulfur is also an important element in agriculture, where it is classified as a secondary macronutrient necessary for optimal crop growth. It is a component of plant proteins and enzymes, and it plays a role in chlorophyll synthesis and nitrogen metabolism. Farmers use sulfur-containing fertilizers, such as ammonium sulfate or gypsum, to ensure adequate soil levels, especially since industrial air quality improvements have reduced the amount of sulfur deposited naturally from the atmosphere.
The largest single commercial use of sulfur worldwide is in the production of sulfuric acid. Sulfuric acid is a foundational compound used in manufacturing everything from detergents and pigments to explosives. Nearly half of its global production is dedicated to the fertilizer industry for making phosphate-based and ammonium sulfate fertilizers. It is also the electrolyte commonly known as “battery acid” in lead-acid batteries found in cars and backup power systems.