Tomato Extract for Hypertension?

Abstract

In this issue of Cardiovascular Drugs and Therapy, professor Paran and her colleagues report on the beneficial effect of tomato extract on blood pressure in patients who were insufficiently controlled with antihypertensive drugs [1]. In a randomized, placebo-controlled, double-blind cross-over trial they compared the extract to placebo in 50 hypertensive patients who had already been treated with a variety of drugs. While placebo did not have a measurable effect on blood pressure, the extract caused a fall of approximately 13/4 mmHg. The magnitude of this result is comparable to what the same investigators found earlier in a group of untreated subjects with mild hypertension [2]. Taken together, this suggests that the use of antihypertensive agents as in the current study did not modify the hypotensive potential of the extract. This makes the observations even more clinically meaningful and it certainly adds a new tool to the array of life-style interventions which we frequently recommend to our patients. A strong point in the study is that blood pressure was always measured with an automatic device. Nevertheless, it should also be noted that a substantial portion of the study population was over 65 years of age. As ageing is generally thought to be associated with increased oxidative stress, it may be that there is more to be gained with antioxidant therapy in the elderly than in the young. Whether the beneficial effects of tomato extract can be extrapolated to patients with less advanced age, thus remains to be determined. It would also be interesting to know whether a high baseline intake of antioxidant substances from whatever source would enhance or just mitigate the response to the extract. Although Paran and associates have carefully executed their study, there is a point of concern. In fact, the degree of blood pressure changes that they observed is greater than what one would expect. With a baseline blood pressure of, on average, 139/80 mmHg when the two groups were combined one would not anticipate a change in systolic pressure of 10 mmHg or more. Even the most powerful drugs usually do not produce that effect. One wonders, therefore, whether other factors could have contributed to the decline in pressure. Indeed, with other life-style measures such as a high intake of fruit and vegetables gave a fall in blood pressure of ‘only’ 4 mmHg systolic and 1.5 mmHg diastolic was observed [3]. Nevertheless, if at the population level the intake of tomatoes or tomato extract would increase to match that in the Paran study and if the population mean of blood pressure would fall to the same or perhaps a lesser extent, this would have enormous consequences in terms of reduction of cardiovascular risk. Despite the clear-cut effects of the tomato extract, it remains enigmatic why it lowers blood pressure so profoundly. Direct effects on blood pressure of lycopene, beta-carotene, folate, vitamin C and vitamin E have not been described. However, tomatoes are rich in potassium, Cardiovasc Drugs Ther (2009) 23:107–108 DOI 10.1007/s10557-008-6161-4