By: Thomas Pickering, MD, DPhil, FRCP, Director of Integrative and Behavioral Cardiology Program
of the Cardiovascular Institute at Mount Sinai School of Medicine, New York.

There is some evidence that people who eat a lot of garlic may be at lower risk of cardiovascular disease, but the mechanism by which garlic confers protection is unclear. It does not appear to have much effect on blood pressure or blood cholesterol levels.

A study conducted in Germany has now provided a possible answer. Professor Gustav Belz and his colleagues identified 100 healthy men and women aged between 50 and 80 years who had taken garlic regularly in the form of four to five 100 mg garlic pills a day for the past seven years. They were compared with another 100 subjects, who resembled the garlic takers in all major respects except that they did not take garlic.

The two groups had identical blood pressure and cholesterol (including total and HDL cholesterol) levels. They did, however, show a marked difference in the stiffness of their aortas (the aorta is the large artery leaving the heart), which was measured by the velocity of the pulse wave traveling along it during each heart beat (the rationale behind this is that stiffer arteries conduct the pulse wave faster). Garlic users had substantially lower pulse wave velocities, indicating that their aortas were less stiff.

Doctor’s comments

As we grow older, our arteries tend to become stiffer, and this is one reason why the systolic pressure goes up with age, whereas the diastolic doesn’t. The simplest explanation for this is that when the heart pumps blood into a stiff arterial system, the arteries expand less, so the pressure goes up more. Systolic hypertension of the elderly, as it is called, is a risk factor for strokes and heart attacks, and treating it lowers this risk. Stiff arteries may also be more susceptible to damage of the delicate lining. However, stiffening of the arteries does not occur at the same rate in everyone, and it is quite likely that dietary factors could influence the process. The people in this study who took garlic did not have lower systolic blood pressures than the others, but this may be partly because of the way the subjects were chosen: anyone who had systolic hypertension requiring treatment was excluded.

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