Chemists make sodium bisulfite by combining sulfuric acid and table salt. Manufacturers use this substance as a food preservative, so you can find it listed on many food labels. Unfortunately, sodium bisulfite and a related compound — sodium metabisulfite — can cause serious side effects.
Many people consider sodium bisulfite harmless, but this food additive can have unexpected effects. The authors of a paper that appeared in the August 2015 issue of the Journal of Food Composition and Analysis found that sodium bisulfite lowers the thiamine content of rice.
Read more: Harmful Effects of Preservatives in Foods
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Benefits of Sodium Bisulfite
As a cleaner, sodium bisulfite can help purify toxic wastewater. For example, the authors of a paper in the February 2017 issue of Estuarine, Coastal and Shelf Science used chlorine to kill harmful bacteria in wastewater. They then neutralized this addition with sodium bisulfite to prevent the chlorine from contaminating the water supply.
As a preservative, manufacturers add sulfites like sodium bisulfite to decrease the growth of bacteria and fungi. This addition prevents browning and limits spoilage, according to an article featured in the October 2017 issue of PLOS One.
Aquaculture workers also use sodium bisulfite. For example, the authors of a review published in the Journal of Food Science in October 2013 showed how sodium bisulfite greatly improved seafood's appearance. The chemical made catfish fillets less yellow and more bright.
Manufacturers often process shrimp in a similar way, according to a paper in the January 2018 issue of the Annual Research and Review in Biology. First, workers catch and kill the shrimp. They then coat the them with sodium bisulfite as a bleaching agent. Finally, they freeze the shrimp to prevent blackening.
Risks of Sodium Bisulfite
The many benefits of sodium bisulfite might come at a price. After a series of allergic reactions, the U.S. Food and Drug Administration banned sulfites like sodium bisulfite from fresh foods. Yet many farmers continue to use these food additives. For example, the writers of a report featured in the February 2012 issue of the journal Meat Science found illegal levels of sulfites in about 5 percent of meat samples.
Sulfites can cause side effects such as abdominal pain, diarrhea, hives, low blood pressure and even life-threatening anaphylaxis, according to a paper published in the winter 2012 issue of Gastroenterology and Hepatology from Bed to Bench. From 3 to 10 percent of people with asthma have a sulfite sensitivity. Such people are even more vulnerable to the many side effects of sulfites.
The authors of an article in the March 2014 issue of the Yonsei Medical Journal studied 26 sulfite-sensitive subjects and put their reactions into two categories: asthma or rash. They noted that the asthma reaction can occur faster and to a smaller amount of sulfite. It was also more likely to cause hospitalization.
The researchers also explored the mechanisms underlying sulfite sensitivity. They suggested that having a genetic predisposition — sulfite oxidase deficiency — could play an important role.
Sodium Metabisulfite in Food
Sodium metabisulfite has proven even more problematic. When manufacturers put metabisulfite in food, they might expose you to great risk. It damages the reproductive organs, at least in animal subjects, according to an article in the International Journal of Reproductive Biomedicine in December 2015. These researchers showed that sodium metabisulfite decreased testosterone production and sperm count of rats.
It also may damage the central nervous system. A study published in the March 2013 issue of Experimental Neurobiology found that sodium metabisulfite caused memory loss in rats. Interestingly, these researchers also showed that the active substance in turmeric — curcumin — blocked the harmful effects of sodium metabisulfite.
Read more: Risks & Benefits of Taking Turmeric
Like some other substances, sodium metabisulfite causes a skin reaction in vulnerable people. The writers of a paper in the November 2012 issue of Contact Dermatitis evaluated several thousand people and found that almost 5 percent of them had a negative skin reaction to sodium metabisulfite.
- Journal of Food Composition and Analysis: "Thiamine Content and Technological Quality Properties of Parboiled Rice Treated With Sodium Bisulfite"
- Journal of Food Science: "Chemical Treatments for Reducing the Yellow Discoloration of Channel Catfish (Ictalurus punctatus) Fillets"
- Meat Science: "Investigation on the Presence of Sulphites in Fresh Meat Preparations"
- Gastroenterology and Hepatology From Bed to Bench: "Adverse Reactions to the Sulphite Additives"
- Yonsei Medical Journal: "Two Major Phenotypes of Sulfite Hypersensitivity"
- Experimental Neurobiology: "Curcumin, the Main Part of Turmeric, Prevents Learning and Memory Changes Induced by Sodium Metabisulfite, a Preservative Agent, in Rats"
- Contact Dermatitis: "Allergic Contact Dermatitis Caused by Sodium Metabisulfite"
- Estuarine, Coastal and Shelf Science: "Death From Below"
- PLOS One: "Sulfites Inhibit the Growth of Four Species of Beneficial Gut Bacteria at Concentrations Regarded as Safe for Food"
- Annual Research and Review in Biology: "Comparative Studies of the Impacts of Freshwater, Cultivated and Preserved Tiger Shrimps on Consumers' Health"
- International Journal of Reproductive Biomedicine: "Sodium Metabisulfite-Induced Changes on Testes, Spermatogenesis and Epididymal Morphometric Values in Adult Rats"