Garlic and cardiovascular risk

• there is contradictory evidence relating to the effects on cardiovascular risk:
  • a small study (1) investigated the effects of garlic extract supplementation on blood lipid profile and oxidant/antioxidant status were investigated in volunteer subjects with high blood cholesterol
    • a total of 23 volunteer subjects with high blood cholesterol (>5.98 mmol/L) participated in the study
      • of them, 13 patients were evaluated as a hypertensive group and the others a normotensive group
        • before (first sample) and after (second sample) garlic extract consumption for 4 months, routine blood analyses including lipid parameters and liver and kidney function tests were performed
        • serum total cholesterol, low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL) cholesterols, and triglyceride levels were found to be significantly lowered, but HDL high-density lipoprotein cholesterol level increased after the extract use
          • total:HDL cholesterol ratio was also found to be significantly decreased after the extract use
          • systolic and diastolic blood pressure values were also found to be significantly lowered after extract supplementation in the hypertensive group, but no similar changes were observed in the normotensive group
  • however a larger study investigating the LDL effects of different garlic preparations found (2)
    • that none of the forms of garlic used in this study, including raw garlic, when given at an approximate dose of a 4-g clove per day, 6 d/wk for 6 months, had statistically or clinically significant effects on LDL-C or other plasma lipid concentrations in adults with moderate hypercholesterolemia
• in patients with type 2 diabetes (3)
  • metabolic action of garlic powder tablets was investigated in a 4-week double-blinded placebo-controlled study in 60 type 2 diabetic patients
    • study revealed that garlic powder tablet usage resulted in better metabolic control due to the lowering of fasting blood glucose, serum fructosamine and serum triglyceride levels - note though that triglyceride levels in diabetic patients will generally improve with improved glycaemic control

Reference:

• (1) Durak I et al. Effects of garlic extract consumption on blood lipid and oxidant/antioxidant parameters in humans with high blood cholesterol. J Nutr Biochem. 2004 Jun;15(6):373-7.
• (2) Gardner CD et al. Effect of raw garlic vs commercial garlic supplements on plasma lipid concentrations in adults with moderate hypercholesterolemia: a randomized clinical trial. Arch Intern Med. 2007 Feb 26;167(4):346-53.
• (3) Sobenin IA et al. Metabolic effects of time-released garlic powder tablets in type 2 diabetes mellitus: the results of double-blinded placebo-controlled study. Acta Diabetol. 2007 Sep 6