According to "Phytochemicals as Bioactive Agents," there is a lot still unknown about how garlic works, including which of its components are the most beneficial, and which is the best delivery system. Without further research, the primary benefit of garlic oil capsules over other forms, such as powdered or fresh garlic, is convenience. However you ingest it, garlic may be beneficial to your health.
Garlic is a member of the lily family and produces a substance called allicin, which is a precursor to sulfur. In addition to a high sulfur content, garlic also contains selenium, the amino acid arginine and flavonoids, which are a type of phytochemical -- compounds produced by plants -- that affect humans in a beneficial way. "Phytochemicals as Bioactive Agents" states allicin breaks down quickly, converting to other, more bioactive compounds that are likely what makes garlic possibly beneficial for health.
Benefits of Garlic
Purported benefits of garlic include lowering high cholesterol, reducing high blood pressure and supporting a healthy immune system. A study in the May 2000 issue of "Applied and Environmental Microbiology" found garlic effective against Helibacter pylori, a type of bacteria that can cause ulcers. Garlic may help prevent a variety of cancers, including gastrointestinal, according to the National Cancer Institute, though the exact amount needed remains undetermined.
Metabolic Syndrome Protection
A study published in the July 2011 "Nutrition & Metabolism" revealed garlic may have a beneficial effect on metabolic syndrome, which is a collection of disorders -- typically high blood sugar, blood pressure and cholesterol levels, along with obesity -- that increase your risk of getting diabetes by five times and doubles your chances of having heart disease. Researchers divided rats into three groups, feeding two groups mainly corn syrup to gain weight and increase cholesterol and glucose levels. One of those groups also received raw garlic, and the control group was fed mainly cornstarch. The group receiving raw garlic and corn syrup had less weight gain, improved insulin sensitivity and lower triglyceride and blood sugar levels than the corn syrup-only and control groups.
Side Effects and Precautions
Using garlic can cause an allergic reaction, bad breath or body odors. High doses might lead to stomach upset, diarrhea or heartburn, especially on an empty stomach. Don't use garlic with the HIV medication saquinavir, because garlic can reduce its potency. Garlic can thin the blood, so avoid using before surgery, during pregnancy or with other blood-thinners. According to Drugs.com, short-term use of garlic supplements during breastfeeding appears safe. Garlic might actually encourage infants to suckle longer and influence future taste preferences.