(2) Saccharomyces boulardii is a non-pathogenic yeast originally isolated from the surface of lichee nuts. It has been widely used in Europe to treat diarrhea. In France it is popularly called "Yeast against yeast" and is thought to help clear the skin in addition to the gut. Clinical trials have demonstrated the effectiveness for S. boulardii in the treatment or prevention of C. difficile diarrhea, antibiotic diarrhea and traveler's diarrhea[132, 133]. Experimental data suggest that the yeast owes its effect to stimulation of SIgA secretion[134]. SIgA is a key immunological component of gut barrier function.

Passive elevation of gut immunoglobulin levels can be produced by feeding whey protein concentrates that are rich in IgA and IgG. These have been shown to be effective in preventing infantile necrotizing enterocolitis[135].

(3) Lactobacillus caseii var GG is a strain of lactobacillus isolated and purified in Finland. Like S.boulardii, Lactobacillus GG has been shown effective in the prevention of traveller's diarrhea and of antibiotic diarrhea and in the treatment of colitis caused by C. difficile. Lactobacillus GG limits diarrhea caused by rotavirus infection in children and in so doing improves the hyperpermeability associated with rotavirus infection.[136-139] The mechanism of action is unclear. The ability of other Lactobacillus preparations to improve altered permeability has not been directly tested, but is suggested by the ability of live cultures of L. acidophilus to diminish radiation-induced diarrhea, a condition directly produced by the loss of mucosal integrity.

(4) Glutamine is an important substrate for the maintenance of intestinal metabolism, structure and function. Patients and experimental animals that are fasted or fed only by a parenteral route develop intestinal villous atrophy, depletion of SIgA, and translocation of bacteria from the gut lumen to the systemic circulation. Feeding glutamine reverses all these abnormalities. Patients with intestinal mucosal injury secondary to chemotherapy or radiation benefit from glutamine supplementation with less villous atrophy, increased mucosal healing and decreased passage of endotoxin through the gut wall[140-143].

(5) Glutathione (GSH) is an important component of the anti-oxidant defense against free radical-induced tissue damage. Dietary glutathione is not well absorbed, so that considerable quantities may be found throughout the gut lumen following supplementation[144]. Hepatic GSH is a key substrate for reducing toxic oxygen metabolites and oxidized xenobiotics in the liver. Depletion of hepatic glutathione is a common occurence in Leaky Gut Syndromes contributing to liver dysfunction and liver necrosis among alcoholics and immune impairment in patients with AIDS. The most effective way to raise hepatic glutathione is to administer its dietary precursors, cysteine or methionine. Anti-oxidant supplementation for Leaky Gut Syndromes should therefore include both GSH and N-acetyl cysteine. Because protozoa are more sensitive to oxidant stress than are humans and because most anti-parasitic drugs and herbs work by oxidative mechanisms, high dose anti-oxidant supplementation should be witheld during the treatment of protozoan infection, especially during treatment with Artemisia.

(6) Flavonoids are potent, phenolic anti-oxidants and enzyme inhibitors with varied effects depending on the tissues in which they act. Quercetin and related flavonoids inhibit the release of histamine and inflammatory mediators. Taken before eating, they may block allergic reactions which increase permeability. Catechins have been used in Europe to treat gastric ulcerations. The flavonoids in milk thistle (silymarin) and in dandelion root (taraxacum) protect the liver against reactive oxygen species[145].