Sulfite Oxidation - How the body processes sulfites

In my quest to understand sulfite sensitivities, I decided to find out what happens when a person ingests sulfites. What does the body do? Surprisingly, this was not a simple task for me so fair warning, this post will be very technical. I have made every attempt to diffuse the science into understandable everyday speak, if you would like to see the literature in its full scientific glory please follow the source links or email me for a copy of the journal article. Now on to the good stuff...

According to Parcell, compounds containing sulfur are found in all body cells and are indispensable for life. Sulfur is the sixth most abundant macromineral in breast milk and the third most abundant mineral determined by percentage of total body weight in adults. The term "thiol" refers to compounds containing sulfur. Sulfur is not normally added to the diet as a supplement because it occurs naturally in the following amino acids:

• Methionine
  
• Cysteine
  
• Cystine
  
• Homocysteine
  
• Homocystine
  
• Taurine

When sulfur is ingested it is converted to sulfate and excreted through urine or reused by the body. In plants and bacteria this process is called biosynthesis and in humans it is called oxidation.

So what's the difference between the the suffixes - ide, ate, ite?

• Ide is the ending used by binary compounds. The metal name goes first, then the nonmetal followed by ide. Sulf+ide = sulfide.


• Ate means with oxygen. Sulf+ate = sulfate.
  
• Ite means means less oxygen. Sulf+ite = sulfite.

Which brings us to sulfite oxidase, how the body processes sulfites.

According to Changjian et al, molybdenum (Mo) is the only second transition metal that has known biological functions in all forms of life; over 50 molybdoenzymes are known to catalyze oxidation-reduction reactions that are essential in the metabolism of carbon, nitrogen and sulfur. For animals there are two molybdoenzymes in sulfite oxidase family: Animal Sulfite Oxidase (a mitochondrial enzyme) and A. thaliana Sulfite Oxidase.

So when a person ingests sulfites, the sulfites are oxidized to sulfates at the molybdenum center and the reduced equilivants (sulfates and the reduced enzyme) are excreted through urine or reused by the body. This explains why a person with a sulfite sensitivity may benefit from taking a molybdenum supplement - having more molybdenum in their system means it is available to help in the oxidase of sulfites.

Additional sources:

Feng, Changjin, Gordon Tollin, John Enemark. Biochim Biophys Acta 2007; 1774(5): 527-539.

Parcell, Stephen. Alternative Medicine Review 2002; 7(1): 22-24.