The effect of different garlic preparations on blood lipids and blood pressure have recently been subject to meta-analysis. (see previous paper). Although standardised garlic powder preparations appear to be moderately effective (1,2) very little data exist for garlic oils and there are no reported comparative studies. In the last 5 years garlic preparations, in various forms, have become increasingly popular with the general public with claims to 'maintain a healthy heart and circulation' encouraging patients to self medicate. However, without a proper comparison can these claims be justifiable for all types of garlic?
In this randomised investigation, the first comparative study, conducted in a specialist practice in Bromsgrove, 80 patients were recruited with fasting cholesterol in the range 5.3 to 7,8 mmol/l and random-y allocated to receive either 600 mg dried garlic powder standardised to 1.3% alliin equivalent to (1.6% allicin (Kwai, Lichtwer Pharma GmbH) or 0.6 mg garlic oil, containing 0.6% garlic oil (Hofels, Seven Seas). Both medications were dosed three times daily for a period of 4 months treatment and total cholesterol, triglycerides, blood pressure and body mass were measured at entry and then monthly.
Both groups received dietary advice and all measurements were made by a desk top analyser under the quality control scheme, validated by the biochemistry department of The University of Birmingham LDL-cholesterol was calculated using the Friedwald equation. The two groups were comparable at baseline with respect to lipid values, but patients randomised to receive garlic powder had significantly higher starting blood pressures.
Brief results are summarised in Table 2 following statistical analysis. A five point scale to assess the acceptability of each medication was devised and tablet counts were performed to monitor compliance with a t.d.s. dosing schedule.
| POWDER | OIL | |
| Total Cholesterol Start | 6.67 | 6.27 |
| Total Cholesterol Finish | 5.76 | 6.07 |
| LDL Start | 4.48 | 4.08 |
| LDL Finish | 3.75 | 4.06 |
| Systolic BP Start | 151 | 138 |
| Systolic BP Finish | 124 | 138 |
| Diastolic BP Start | 96 | 88 |
| Diastolic BP Finish | 79 | 86 |
Clearly it is unwise to assume that all commercially available garlic supplements are equally
efficacious. Thus we should be careful if recommending such a course of action in patients with
moderately raised cholesterol or blood pressure. The reasons for such significant differences in
effect between these two popular garlic products is probably due to standardisation of starting
materials. Whilst it remains likely that patients will continue to purchase these products on a large
scale for numerous reasons, if a cardiovascular benefit is required only standardised garlic powder
products can be expected to produce significant beneficial results.
References
1. Santos O DeA, Grunwald J (1993) Effect of garlic powder tablets on blood lipids and blood
pressure - a six month placebo controlled double blind study. British Journal of Clinical Research 4:
37-44
2. Silagy CS, Neil HAW, (1994) Garlic: Its Cardio-protective properties. Current Opinion in
Lipidology 5: 6-10