Vitamin U is a mucin secretagogue

Summary - Vitamin U is a nutrient abundant in vegetables and fruit whose main function is to stimulate the secretion of mucin and enable the formation of the mucous bilayer that protects the stomach from acid and
Helicobacter pylori.

In the human body, Vitamin U heals and protects against peptic ulcers. It does so by stimulating the secretion of mucins onto the walls of the digestive tract, acting as a precursor to the biosynthesis of the master antioxidant glutathione, and supplies methyl groups for gene regulation, polyamine biosynthesis and a range of other molecules. Of these three functions, stimulating mucin secretion is the most direct way in which Vitamin U works.

In the stomach, there is an alkaline mucous bilayer gel that protects the stomach from gastric acid, pepsin digestion and bacterial infection. Mucus consists of two layers - a deep gel-like layer attached to cells and a superficial loosely-attached layer on top. The proteins that make up mucus are called mucins (MUC1, MUC5AC, MUC6), which are heavily-glycosylated proteins that attract water, thereby forming a gel. Mucins are made in foveolar cells lining the stomach and are stored in vesicles awaiting summons to the lumen. At the surface, some mucins stay attached to the cells and act as an anchor for the loosely-bound mucins to attach by disulfide bonds. When this mucous bilayer is disrupted, gastric juice can reach the lining of the stomach causing irritation and inflammation. Left long enough, a peptic ulcer may form.

Your body has a number of different ways to stimulate the secretion of mucin. The molecules that trigger secretion are called mucin secretagogues. The prime mucin secretagogue is prostaglandin E2, a hormone-like molecule that has many functions in the human body. It has a protective role in stomach function, suppressing production of gastric acid and pepsin, while at the same time promoting secretion of mucin and the alkaline molecule bicarbonate (Park et al). NSAIDs reduce prostaglandin E2 synthesis by inhibiting COX-1, leading to less mucin, less protection and a greater risk of ulcers.

Vitamin U (S-methylmethionine) is a nutrient found in all vegetables and fruit, and especially members of the cabbage family. Vitamin U protects the digestive tract by stimulating the secretion of mucin from the foveolar cells. In 1996, Watanabe et al. showed that exposing gastric mucous cells to L-cysteine or methylmethionine sulfonium chloride (MMSC or Vitamin U) prevented the formation of stomach ulcers caused by exposure to 50% ethanol. They demonstrated that Vitamin U and cysteine work in a similar manner via a sulfhydryl group. Interestingly, Vitamin U does not have a sulfhydryl group, but rather a sulfonium group. Consequently, Vitamin U is usually described as a latent sulfhydryl. The fact that Vitamin U and L-cysteine activities were inhibited by the pre-administration of the sulfhydryl inhibitor N-ethylmaleimide suggests that Vitamin U is active as a sulfhydryl. Vitamin U is stable at acid pH, so activation probably takes place in foveolar cells. 

In a follow up study, Watanabe et al. (2000) found that Vitamin U and cysteine induced the transport of vesicles containing mucin from deep within the cytosol to the cell surface for release into the stomach lumen, thereby forming a protective barrier. Interestingly, the movement they observed was independent of Ca2+ and cAMP. When signal transduction occurs via an endogenous molecule like prostaglandin-E2, there is a rise in the concentration of cAMP. When the P2 purinergic receptor is activated by ATP, there is an accompanying rise in Ca2+. Yet sulfhydryl-instigated movement did not induce a change in Ca2+ or cAMP levels. The authors suggested sulfhydryls promote mucus movement by a non-receptor mediated process.

Irrespective of how Vitamin U works, there's good evidence that drinking fresh vegetable juice or taking Vitamin U supplements may help restore your mucous bilayer, ease discomfort and heal your ulcers.

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