Because the role of elemental sulfur in human nutrition has not been studied extensively, it is the purpose of this article to emphasize the importance of this element in humans and discuss the therapeutic applications of sulfur compounds in medicine. Sulfur is the sixth most abundant macromineral in breast milk and the third most abundant mineral based on percentage of total body weight.
The sulfur-containing amino acids (SAAs) are methionine, cysteine, cystine, homocysteine, homocystine, and taurine. Dietary SAA analysis and protein supplementation may be indicated for vegan athletes, children, or patients with HIV, because of an increased risk for SAA deficiency in these groups. Methylsulfonylmethane (MSM) is another source of sulfur found in the human diet. MSM may be effective for the treatment of allergy, pain syndromes, athletic injuries, and bladder disorders. Increases in serum sulfate may explain some of the therapeutic effects of MSM, DMSO, and glucosamine sulfate. Organic sulfur, as SAAs, can be used to increase synthesis of S-adenosylmethionine (SAMe), glutathione (GSH), taurine, and N-acetylcysteine (NAC).
Other sulfur compounds such as SAMe, dimethylsulfoxide (DMSO), taurine, glucosamine or chondroitin sulfate, and reduced glutathione may also have clinical applications in the treatment of a number of conditions such as depression, fibromyalgia, arthritis, interstitial cystitis, athletic injuries, congestive heart failure, diabetes, cancer, and AIDS. Dosages, mechanisms of action, and rationales for use are discussed. The low toxicological profiles of these sulfur compounds, combined with promising therapeutic effects, warrant continued human clinical trails.
Solid sulfur is yellow, brittle, odorless, tasteless, and insoluble in water. The term “thiol” refers to compounds containing sulfur. The structure of sulfur allows for a variety of oxidation states. The biosynthesis of organic sulfur compounds from sulfate takes place mainly in plants and bacteria, whereas the oxidation of these compounds to sulfate is characteristic of animal species. Sulfur is excreted as sulfate, the urinary excretion of sulfate generally reflecting input from either inorganic or amino acid sources. Most of the literature regarding sulfur intake considers the sulfur-containing amino acids (SAAs) as the primary source of this element in the diet. Researchers who have examined the role of sulfur in biological systems have controlled the amount of sulfur intake through regulation of protein intake. For ethical reasons, most of the work has been on animals. The well-known beneficial actions of organosulfur compounds (isothiocyanates, diallyl sulfide, allicin) found in garlic, onions, and other vegetables will not be discussed because excellent reviews already exist.
Compounds containing sulfur are found in all body cells and are indispensable for life. The primary sulfur-containing compounds of interest in humans are methionine, cysteine, homocysteine, cystathione, Methylsulfonylmethane (MSM), S-adenosylmethionine (SAMe), taurine, [alpha]-keto-[gamma]-C[H.sub.3]-thiobutyrate, methanethiol, thiamin, biotin, alpha-lipoic acid (ALA), coenzyme A, glutathione (GSH), chondroitin sulfate, glucosamine sulfate, fibrinogen, heparin, metallothionein, and inorganic sulfate. With the exception of the two sulfur-containing vitamins, thiamin and biotin, all of these sulfur compounds are synthesized from just one parent compound, methionine. In addition, sulfur is needed for a number of chemical reactions involved in the metabolism of drugs, steroids, and xenobiotics. Glutathione, taurine, N-acetyl-methionine, and inorganic sulfate can all have amino acid bioactivity by sparing the need for dietary methionine or cysteine.
The RDA committee recommends a combined SAA intake of at least 13 mg/kg per day. This is equivalent to approximately 910 mg/day for a 70 kg adult. Other authorities believe this figure to be too low and recommend an intake of 25 mg/kg/day of SAA for adults. Animal protein has a higher net protein utilization factor (NPU) and usually contains more protein by weight than most plant foods. Therefore, it is harder to obtain individual amino acids from a given gram of plant protein than from a gram of animal protein. For this reason, human diets entirely animal free (vegan) may lead to sub-optimal sulfur amino acid status. This could occur because the diet may be too low in total protein, composed of proteins of low digestibility, or be low in SAAs. Any of these factors in isolation or occurring together could lead to SAA deficiency. Not all plant foods are low in SAAs. Some commonly eaten plant foods high in methionine are corn, sunflower seeds, oats, chocolate, cashews, walnuts, almonds, and sesame seeds, in that order. Meat, fish, poultry, eggs, dairy products, peas, and beans contain sulfur in varying quantities. Bioavailable, organic sulfur is also available in tablet and powdered forms. Any diet that provides protein is also providing some sulfur.
Sulphur after Exercise
Excessive physical stress, such as is seen in athletic overtraining, inflicts minor trauma on the athlete’s body and can deplete plasma glutathione levels,and increase urinary loss of sulfate. For the athlete in training, muscle catabolism or a decrease in plasma GSH are counterproductive. Suboptimal intakes of sulfur amino acids during training may exert a proinflammatory influence because, at low levels of intake, cysteine is preferentially incorporated into protein rather than GSH. It follows that methionine and cysteine could be used to ameliorate loss of lean tissue and GSH stores. Cysteine and methionine are abundant in whey protein. Methionine can be converted into cysteine (cysteine is the rate-limiting step in glutathione synthesis). Lipoic acid could be used to reduce oxidative stress and to preserve vitamin E and C status.
Heal Infections with Sulfur
Sulfa drugs are used in the treatment of various infections. Precipitated sulfur, aka “Milk of Sulfur” is a topical scabicide, antiparasitic, antibacterial, antifungal, and keratolytic. Sublimed sulfur, aka “Flower of Sulfur” is a topical scabicide and antiparasitic ointment. It is precipitated sulfur powder. Its color is light yellow (lime). It smells like a lemon. It is helps the skin heal, and people usually mix it with a cold cream. It is used to treat just about any skin problems like acne, sores, insect bites, rashes, bacterial infections, bed sores, dermatitis, eczema, fungus/yeast infections, psoriasis type problems, ring worm, wounds that won’t heal and more. Sulfur is one of the oldest medications in use to treat acne. Sulfur and acne treatment have a history that goes back over 5 decades. It used to be applied to wounds to prevent infection. Before the invention of antibiotics there were few affective drugs other than sulfur for infections. Even after the development of the many drugs that were considered to be miracles, there are still uses for sulfur drugs that have withstood competition from synthetic chemical replacements. The time-tested results combined with the safety of sulfur should be a notice for everyone that prefers a less invasive, natural approach to healing.
Purified Sulfur Heals Radiation Damage
Purified sulfur has been used as a therapeutic agent to reduce a reaction to combined radiotherapy called autosensitization, a type of autoimmunity associated with radiation therapy. Thirty-four women with diagnoses of cervical cancer (stages I and II) were given 0.5-1.0 g of purified sulfur mixed with 0.25 g of glucose orally in the morning every 2-3 hours before irradiation. A significant decrease in the reaction to therapeutic irradiation was noted in the sulfur group and no side effects were observed. Because radiation causes damage to DNA through free-radical intermediates, thiols with a net-positive charge may protect against radiation poisoning because they concentrate in the microenvironment of DNA and scavenge free radicals.
Toxicology of Sulfur
With a few exceptions, the sulfur compounds discussed in this article all have very low toxicological profiles. Adverse effects from topically applied sulfur are uncommon and are mainly limited to the skin. There are reports of fatalities in infants after massive external application.
In patients with ulcerative colitis (UC), whey protein or other foods high in SAA should be used with caution. There is evidence linking protein fermentation and subsequent formation of sulfide in the pathogenicity of this disease. Hydrogen sulfide, sulfide, and thioacetic acid are produced and cause irritation to the colonic mucosa, resulting in possible damage to colonic epithelial cells, and leading to inflammation.
SAMe may worsen the symptoms of Parkinson’s disease and should be avoided until it is proven safe for these patients.
A concern arises in the use of NAC in HIV-positive patients because NAC can raise serum glutamine to above normal levels. Too much NAC may cause glutamine production to be favored over urea production eventually to the point that toxic ammonia accumulates. The dosage schedule can be determined by monitoring plasma glutamine levels.
There are a number of medical conditions for which sulfur compounds could be used therapeutically. Methionine and cysteine can be used to increase SAMe, GSH, taurine, and NAC, and to promote detoxification of xenobiotics via the sulfation pathway. Dietary SAA analysis and SAA or protein supplementation may be indicated for vegan athletes, children, or patients with HIV, because of increased risk of SAA deficiency in these groups. A vegan diet, however, is capable of supplying adequate SAA if foods high in methionine are included. Methylsulfonylmethane may be effective for allergy, pain syndromes, athletic injuries, and bladder disorders. Glucosamine and chondroitin sulfate appear effective for maintaining cartilage matrix integrity. Chondroitin, in particular, has a number of pharmacological properties including effects on bone mineralization, production of proteoglycans, increased synovial fluid viscosity, and inhibition of proteases involved in cartilage degradation. New data support the hypothesis that increases in serum sulfate may mediate the therapeutic effects of glucosamine. Other sulfur compounds such as SAMe, DMSO, taurine, and reduced glutathione also have clinical applications in the treatment of a number of conditions, such as depression, fibromyalgia, arthritis, interstitial cystitis, athletic injuries, congestive heart failure, diabetes, cancer, and AIDS.