The most common symptom of peripheral arterial occlusive disease is intermittent claudication, discomfort in the legs that is triggered by exercise and relieved with rest. The underlying cause is atherosclerosis. Risk factors associated with the development of peripheral arterial disease include cigarette smoking, raised blood cholesterol and other fats (lipids), high blood pressure and diabetes. Garlic has been used as a medicinal therapy since ancient times. The main active ingredient is an unstable odorous sulphurous compound called allicin so that active ingredients may be lost in processing, and with different types of preparation. Commercially available preparations of garlic are reported to have beneficial effects on some of the risk factors for vascular disease. With fresh garlic, at least seven cloves of garlic per day are needed. Apart from the odour, garlic has only minor gastrointestinal side effects.

The review authors made a thorough search of the medical literature and found one controlled trial in which 78 participants with peripheral arterial occlusive disease were randomised to receive garlic or a placebo medication. The dose of garlic was two coated tablets of 200 mg oral standardised garlic powder twice daily. Both men and women, aged 40 to 75 years, were included although sixteen did not keep to their treatment.

After twelve weeks of treatment, pain-free walking distance increased similarly whether receiving garlic or placebo. Similarly there was no difference in the changes in blood pressure, heart rate and pressure differences between the ankle and brachial pressures. No severe side effects were observed although more people taking garlic (28%) than placebo (12%) complained of a noticeable garlic smell. Peripheral arterial occlusive disease is a long-term (chronic) condition and any improvements in symptoms would require longer-term treatment and follow up than in this study.