Thursday, January 10, 2008

Vitamin-mineral supplement fails to reduce BP

Vitamin-mineral supplement fails to reduce BP

By Caroline Price

09 January 2008

J Hum Hypertens 2008; 121: 43-49

MedWire News: Study findings have failed to find any effect of consuming milk supplemented with additional potassium, calcium, magnesium, selenium, and vitamins C and E on blood pressure (BP).

The results "confirm the discrepancy between dietary intervention studies showing reasonable BP lowering effects and intervention studies with a combination of minerals or vitamins showing no effect," say the authors.

This highlights the need to explore potential BP lowering effects of vitamins and minerals consumed in "natural matrices" in the diet rather than as supplements, they add.

In a research letter to the Journal of Human Hypertension, P de Leeuw (University Hospital Maastricht, The Netherlands) and colleagues explain that dietary intervention studies have shown impressive reductions in BP, probably due in part to the mineral and vitamin components of such diets. Yet interventions with combinations of either minerals or vitamins have provided mixed results.

In the current study, the researchers tested the BP lowering effect of a combination of minerals and vitamins. They randomly assigned 124 adults with untreated mild hypertension to take a supplemented skimmed milk drink or a placebo drink daily for 8 weeks.

The milk was supplemented with 446 mg calcium, 100 mg magnesium, 40 µg selenium, 180 mg vitamin C, 30 mg vitamin E and tocopherol equivalents, and either 1500 mg (high-K) or 750 mg (low-K) potassium per serving.

At the end of the study, office systolic BP had decreased by 4.6, 4.5, and 5.1 mmHg from baseline in the low-K supplement, high-K supplement, and placebo groups, respectively. The differences in BP reduction among groups were nonsignificant.

Reductions in office diastolic BP, pulse pressure, 24-hour systolic BP, 24-hour diastolic BP, and heart rate over the 8 weeks did not differ among the three groups either.

The results "are in contrast with many studies addressing interventions with the individual components," the authors write. They note that the doses of the individual minerals and vitamins may have been too low, and that combinations of vitamins and minerals may counter the effects of the individual components.

Meanwhile, the contrast with findings of dietary interventions may reflect the reduction of components with negative effects by diet replacement, the increased presence of as-yet unidentified components in dietary interventions, or altered bioavailability of nutrients when provided in a dairy matrix.

"Future studies should focus on assessing the effect of subsets of combinations of minerals and vitamins in natural matrices to get a better understanding of the possible antagonistic action between some of these ingredients," de Leeuw and co-authors conclude.


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