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Q: Garlic

I read in an AIDS newsletter recently that "garlic is believed by many nutritionists to have natural anti-fungal properties and may help to prevent candidiasis." Do you believe this and if so, why? Do garlic pills work too?

A: Barbara J. Scott, MPH, RD responds:

Garlic has been shown to have antibacterial, antiviral and antifungal properties. Benefits on digestive disturbances and cardiovascular system, and a possible protective effect against the development of stomach cancer have also been shown. Specific research with either treatment or prevention of candidiasis especially in HIV infected individuals is still needed. Current clinical applications (supported by clinical studies) include arteriosclerosis, common cold, cough/bronchitis, fevers, inflammation of the mouth and pharynx (not clear whether this applies to candidiasis). In folk medicine (use supported by practice over time), garlic has been used internally for arteriosclerosis, high blood pressure, colds, coughs, bronchitis, and gastrointestinal ailments. It has been used externally for corns, warts, calluses, muscle pain, arthritis.

Because garlic may have both systemic and local (by direct contact) effects, its potential effectiveness against candidiasis might depend on the mode of administration: "External" - held in the mouth to be effective against oral candidiasis or perhaps as a suppository for vaginal candidiasis has not been documented in the literature to my knowledge. This type of use might be tried, but as these tissues are extremely sensitive, care should be taken to start with small amounts as some allergic reactions (contact dematitis and burn-like skin lesions on skin exposed to garlic) have been documented. The effectiveness of internal (swallowed) garlic against a bacterial that causes ulcers has been shown. Therefore, it is possible that it may also have an effect on candidias of the GI tract.

The chemical properties of garlic have been researched extensively, and many active compounds have been identified in the bulb (fresh or dried) and oil. The primary compounds, allinins, are transformed into the active forms when the bulbs are minced or ground. At present, it appears that the best way to get the most benefit is to consume fresh raw garlic (cut up to release enzymes that in turn activate the beneficial compounds) in relatively large amounts each day to get the best source of the active compounds. However, consumption of enteric coated capsules or tablets of garlic that have been dried at relatively low temperatures and labeled with the amount of allicin may also be effective.

Since many of the active ingredients are at least partially destroyed by the acid in the stomach, the most effective means of getting the greatest effects include:

a. Fresh garlic (cut up first to release enzymes to activiate allicin): Chew or hold in your mouth as long as you can. Inclusion of garlic in cooking may also be effective as the other foods consumed may have some protective effect against the stomach acid and allow the garlic to pass into the small intestine.

b. Buy enteric coated capsules or tablets (the protective coating allows them to pass intact through the acid stomach and into the small intestine where enzymes can act under the alkaline conditions present there.)

Usual dosages recommended are:
Fresh Garlic: 1 to 4 cloves daily Capsules or tablets (dried form): 4 to 12 mg of allicin daily (this information should be included on the label of any quality garlic product).

Intake at these levels should pose no risk for a healthy person. However, some side effects that have been observed include allergic reaction, heartburn, flatulence, and other GI upset. In addition, since consumption of garlic can reduce blood clotting time, persons taking anticoagulant medications or aspirin, should avoid eating large amounts of garlic. Large doses of garlic can affect the menstrual cycle and are not recommended for either pregnant or lactating women. Other foods in the same family include leeks, shallots, and onions. Increasing these in your diet may also be beneficial.

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