582
Letters to the Editors
et al., 1988), it is tempting to speculate that the proximal tubular response to exogenous dopamine is different from that induced by gludopa. D.F.S. is a Research Assistant of the National Fund for Scientific Research (NFWO), Belgium.
D. F. SCHOORS & A. G. DUPONT Department of Pharmacology, Vrije Universiteit Brussel (VUB), Brussels, Belgium
Received 19 June 1989, accepted 20 December 1989
References Jeffrey, R. F., MacDonald, T. M., Brown, J., Rae, P. W. H. & Lee, M. R. (1988). The effect of lithium on the renal response to the dopamine prodrug gludopa in normal man. Br. J. clin. Pharmac., 25, 725-732.
Thomsen, K. (1984). Lithium clearance: a new method for determining proximal and distal tubular reabsorption of sodium and water. Nephron, 37, 217-223.
Garlic and cardiovascular risk factors This interesting review article (Kleijnen et al., 1989) did not unfortunately relate to the state of the art in clinical research concerning garlic in general and certain garlic preparations in particular. In the last 3 years more than one dozen clinical research studies have been performed with concentrated garlic tablets. Dr Kleijnen & colleagues' review refers to only one of these trials dating from 1985 and studies of other garlic products are similarly excluded. The research program has included studies investigating cholesterol, triglycerides, LDL and HDL, blood pressure, fibrinolysis, blood viscosity, etc. This includes work carried out at different university hospitals, research institutions as well as multicentre studies with general practitioners. Much of this work has been recently presented at the first International Garlic Symposium in Germany, the results of which have now been published in English and made widely available to the British medical profession in a special supplement of Cardiology in Practice (Anon.,
1989). A main conclusion of Dr Kleijnen was that large amounts of garlic are needed to prove clinical effectiveness (up to 28 cloves). This did indeed appear to be the case according to early trials using garlic. Certainly few patients would find such a level of daily consumption practical or socially acceptable. Very high levels of garlic clove have in the past been necessary to provide relatively very small amounts of active oils or other derivatives. This follows partly from garlic's high water content (60%) accounting for much
of its bulk and because its active substance allicin rapidly breaks down once created by cutting or crushing. It is now possible to produce dehydrated garlic powder to a standardised level of the allicin mother substance alliin. Moreover production expertise has also developed enabling these ingredients to be preserved within a protected tablet form. These developments have enabled effective clinical work to be undertaken for the first time with a standardised product available at a relatively low and acceptable dosage level. Our studies have been performed with daily dosages of 300-900 mg garlic powder (equivalent to about 1 clove of garlic). We were able to show a mean reduction of blood cholesterol of approximately 10% and of triglycerides 13%. A second point of criticism was the postulated inherent difficulty of performing double-blind studies with garlic or garlic preparations. This, too, was certainly true in the past but has largely been circumvented by the availability of a tablet product which overcomes the odour and taste problem for most people. We absolutely agree that totally odourless garlic preparations are ineffective, since the medical effects are based on the action of alliin and its sulphur smelling secondary and tertiary products. Control of the odour problem depends on the galenic preparation of garlic powder, so that formation of smelling products occurs in the intestine. At the dosages used in our trials only 5-10% of all patients developed any such garlic 'signs'. These cases can be easily identified and omitted prior to
Letters to the Editors statistical evaluation thus enabling proper doubleblind studies to be conducted. The humble garlic clove is increasingly being shown to have exciting potential as a safe prophylactic for everyday use against cardiovascular risk factors. We do hope that you will be able to incorporate this new information about garlic and garlic preparations in your Journal, and in particular the developments in dosage and double-blind study capability.
583
J. GRUNWALD Lichtwer Pharma GmbH, Drewitzer Strasse 8, 1000 Berlin 28, FRG Received 18 January 1990, accepted 25 January 1990
References Anon. (1989). Symposium on the chemistry, pharmacology and medical application of garlic. Cardiol. Pract., 10, suppl., 1-15. Kleijnen, J., Knipschild, P. & Terriet, G. (1989)
Garlic, onions and cardiovascular risk factors. A review of the evidence from human experiments with emphasis on commercially available preparations. Br. J. clin. Pharmac., 28, 535-544.
Letters to the Editors
et al., 1988), it is tempting to speculate that the proximal tubular response to exogenous dopamine is different from that induced by gludopa. D.F.S. is a Research Assistant of the National Fund for Scientific Research (NFWO), Belgium.
D. F. SCHOORS & A. G. DUPONT Department of Pharmacology, Vrije Universiteit Brussel (VUB), Brussels, Belgium
Received 19 June 1989, accepted 20 December 1989
References Jeffrey, R. F., MacDonald, T. M., Brown, J., Rae, P. W. H. & Lee, M. R. (1988). The effect of lithium on the renal response to the dopamine prodrug gludopa in normal man. Br. J. clin. Pharmac., 25, 725-732.
Thomsen, K. (1984). Lithium clearance: a new method for determining proximal and distal tubular reabsorption of sodium and water. Nephron, 37, 217-223.
Garlic and cardiovascular risk factors This interesting review article (Kleijnen et al., 1989) did not unfortunately relate to the state of the art in clinical research concerning garlic in general and certain garlic preparations in particular. In the last 3 years more than one dozen clinical research studies have been performed with concentrated garlic tablets. Dr Kleijnen & colleagues' review refers to only one of these trials dating from 1985 and studies of other garlic products are similarly excluded. The research program has included studies investigating cholesterol, triglycerides, LDL and HDL, blood pressure, fibrinolysis, blood viscosity, etc. This includes work carried out at different university hospitals, research institutions as well as multicentre studies with general practitioners. Much of this work has been recently presented at the first International Garlic Symposium in Germany, the results of which have now been published in English and made widely available to the British medical profession in a special supplement of Cardiology in Practice (Anon.,
1989). A main conclusion of Dr Kleijnen was that large amounts of garlic are needed to prove clinical effectiveness (up to 28 cloves). This did indeed appear to be the case according to early trials using garlic. Certainly few patients would find such a level of daily consumption practical or socially acceptable. Very high levels of garlic clove have in the past been necessary to provide relatively very small amounts of active oils or other derivatives. This follows partly from garlic's high water content (60%) accounting for much
of its bulk and because its active substance allicin rapidly breaks down once created by cutting or crushing. It is now possible to produce dehydrated garlic powder to a standardised level of the allicin mother substance alliin. Moreover production expertise has also developed enabling these ingredients to be preserved within a protected tablet form. These developments have enabled effective clinical work to be undertaken for the first time with a standardised product available at a relatively low and acceptable dosage level. Our studies have been performed with daily dosages of 300-900 mg garlic powder (equivalent to about 1 clove of garlic). We were able to show a mean reduction of blood cholesterol of approximately 10% and of triglycerides 13%. A second point of criticism was the postulated inherent difficulty of performing double-blind studies with garlic or garlic preparations. This, too, was certainly true in the past but has largely been circumvented by the availability of a tablet product which overcomes the odour and taste problem for most people. We absolutely agree that totally odourless garlic preparations are ineffective, since the medical effects are based on the action of alliin and its sulphur smelling secondary and tertiary products. Control of the odour problem depends on the galenic preparation of garlic powder, so that formation of smelling products occurs in the intestine. At the dosages used in our trials only 5-10% of all patients developed any such garlic 'signs'. These cases can be easily identified and omitted prior to
Letters to the Editors statistical evaluation thus enabling proper doubleblind studies to be conducted. The humble garlic clove is increasingly being shown to have exciting potential as a safe prophylactic for everyday use against cardiovascular risk factors. We do hope that you will be able to incorporate this new information about garlic and garlic preparations in your Journal, and in particular the developments in dosage and double-blind study capability.
583
J. GRUNWALD Lichtwer Pharma GmbH, Drewitzer Strasse 8, 1000 Berlin 28, FRG Received 18 January 1990, accepted 25 January 1990
References Anon. (1989). Symposium on the chemistry, pharmacology and medical application of garlic. Cardiol. Pract., 10, suppl., 1-15. Kleijnen, J., Knipschild, P. & Terriet, G. (1989)
Garlic, onions and cardiovascular risk factors. A review of the evidence from human experiments with emphasis on commercially available preparations. Br. J. clin. Pharmac., 28, 535-544.
