The trial offers further evidence that tripeptides can benefit the more than 100 million individuals suffering from raised blood pressure throughout the world. Hypertension is a risk factor for stroke and cardiovascular disease, and is a growing problem in developing countries.
Calpis, a fermented milk, is manufactured by the Japanese company of the same name, which is one of the top ten functional food companies in that market with 2003 sales of $1 billion.
The drink contains two tripeptides (valine-proline-proline and isoleucine-proline-proline). Previous research findings have indicated that the bioactive peptides in fermented dairy foods significantly lower blood pressure and animal data suggests that this may be through inhibiting ACE. ACE (angiotensin converting enzyme) inhibitors made by drug companies have been found to be beneficial in treating hypertension but they also have side effects.
Dr Shunsaku Mizushima and colleagues at the University of Tokyo randomly assigned 46 hypertensive men, aged 23 to 59, to drink a bottle of the milk drink or a placebo milk, everyday for four weeks.
They found that systolic blood pressure fell significantly by 4.3 points in the Calpis group after two weeks and by 5.2 at the end of the study. In the placebo group, changes were not statistically significant.
Writing in this month's issue of the American Journal of Hypertension (17(8):701-6), the researchers say the trial "demonstrated the beneficial effect of sour milk on blood pressure in borderline hypertensive men who were not taking anti-hypertensive medication".
European companies are also marketing fermented milk for its effect on blood pressure. Finland's Valio has developed the Evolus brand milk, which carries a health claim for its blood pressure-lowering effect. The drink has also been licensed to an Icelandic company Mjolkursamsalan, the first product using Valio's technology to be launched outside Finland.
Calpis also markets Ameal S, a dietary supplement that helps to maintain a healthy blood pressure, that has been approved as a FOSHU (Foods for Specified Health Use) food.