Comparing Effects of 3 Sources of Garlic on Cholesterol Levels

Garlic supplements are the most consumed herbal products in the United States. The most common health claim made for garlic supplements is cholesterol lowering activity. This claim has not been supported by recent clinical trials and meta-analyses. However, data suggest that it is not necessarily the garlic that has been ineffective, but rather the particular garlic preparations being used. To date, the predominant type of garlic preparation used in these clinical trials has been dried garlic powders. A few clinical trials have reported beneficial lipid effects using an aged garlic extract, and only a small number of inconclusive uncontrolled trials have used fresh garlic. A rigorous trial directly comparing different types of garlic preparations for their effects on serum lipids is needed.

Adults with moderately elevated low density lipoprotein cholesterol (LDL-C) will be randomized to one of four groups for 6 months: fresh garlic, dried powdered garlic tablets, aged garlic extract tablets, or placebo control. The fresh garlic will be provided to patients with "study sandwiches"; all other groups will receive the same study sandwiches without the garlic. All patients will take daily study tablets, but the tablet assignment will be double-blind. Patients will pick up study sandwiches twice a week and study tablets once every 2 weeks for 28 weeks. Blood samples will be taken once a month, with additional blood draws at the start and end of the study.

Inclusion criteria

• LDL-C 130-190 mg/dL (fasting single sample)
• BMI (body mass index) 19-30 kg/m2 (42-66 lb/m2)
• Weight stable for last 2 months
• Not actively on a weight loss plan
• Ethnicity representative of local population
• No plans to move from the area over the next 9 months

Exclusion criteria

• Pregnant, lactating, within 6 months postpartum, or planning to become pregnant in the next year
• Diabetes (type I or II) or history of gestational diabetes
• Heart disease
• Active neoplasms
• Renal or liver disease
• Hyperthyroidism or hypothyroidism
• Lipid lowering medications (known to affect lipid metabolism, platelet function, or antioxidant status)
• Blood pressure medications
• Excessive alcohol intake (self reported, more than 3 drinks/day)
• Currently under psychiatric care or severely clinically depressed