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Dark Chocolate: A Good Treat-ment for Hypertension; Soy Staves Off Bone Loss

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Good news for chocoholics! Data from a very well designed clinical study show that a daily dose of dark chocolate can reduce both systolic and diastolic blood pressure in untreated individuals with early stage hypertension.

Dirk Taubert and colleagues at the University Hospital of Cologne, Germany, studied a cohort of 44 adults (24 women; 20 men) aged 56 to 73 with untreated prehypertension (130/85 mmHg–139/89 mmHg), or stage 1 hypertension (140/90 mmHg–160/100 mmHg).

They randomized the participants to either daily treatment with 6.3 g of dark chocolate, containing 30 mg of polyphenols, or 5.6 g of white chocolate with no polyphenols.

The authors note that the participants were not regular chocolate-eaters prior to the study. Addition of the chocolate added less than 2% total caloric intake to their average daily diets, and it did not require any other dietary adjustments. They followed the patients for 18 weeks.

The primary outcome measure was change in blood pressure (BP). Those eating dark chocolate daily had a mean systolic BP reduction of 2.9 mmHg and diastolic reduction of 1.9 mmHg, without any changes in body weight, lipid profile, or glucose metabolism. The pressure drops were greater in those with higher baseline pressures, and the results were similar in men and women. White chocolate, however, caused no changes in blood pressure (Taubert D, Roesen R, Lehmann C, et al. JAMA. 2007; 298: 49–60).

The investigators measured SW-nitrosoglutathione, a marker for vasodilative endothelial nitric oxide, and found that it inversely correlated with changes in systolic and diastolic BP in the dark chocolate group, but remained unchanged in the while chocolate group.

The great news here is that we can get a small but meaningful lowering of blood pressure, without any weight gain, from a substance that most of us really enjoy. Previous short term studies have shown that high doses of cocoa, 100 g per day, for as little as two weeks can improve endothelial function and reduce blood systolic pressure by 12 points, and diastolic by 8 points. This effect is thought to be due to the cocoa polyphenols and their ability to increase production of nitric oxide in the vascular endothelium.

In the current study, although the blood pressure reductions are small, they are still clinically significant: a 3 mmHg drop in systolic pressure is estimated to reduce relative risk for stroke by 8%, cardiovascular disease by 5% and all-cause mortality by 4%. The pressure decreases obtained with daily dark chocolate are similar to what one typically sees with the Dietary Approaches to Stop Hypertension (DASH) diet, but you can guess which approach your patients will prefer! We do need other chocolate studies with more patients, higher baseline blood pressures, and non-White participants, but the Taubert study makes a pretty strong case for taking a daily chunk of polyphenol-rich dark chocolate.

Soy Phytoestrogen Prevents Bone Loss

The soy saga continues. Italian investigators recently published compelling evidence that daily intake of genistein, a key phytoestrogen from soy, along with calcium and vitamin D can actually increase femoral and lumbar bone mineral density in women at risk for osteoporosis.

The study involved 389 postmenopausal women aged 49 to 67 with a femoral neck bone mineral density (BMD) of less than 0.795 g/cm2 (indicative of osteopenia), who were randomized to treatment with either 54 mg per day of pure soy-derived genistein or placebo. The women in both groups also took daily calcium and vitamin D.

Researchers at three medical centers measured femoral neck and lumbar spine BMD at baseline and again after 24 months. They also measured serum levels of bone-specific alkaline phosphatase, markers of bone turnover (urinary excretion of pyridinoline and deoxypyridinoline), insulin-like growth factor 1 (IFG-1) and endometrial thickness.

After 2 years, femoral neck BMD was increased by a mean of 0.035 g/cm2 in the group taking genistein, while it declined by a mean of 0.037 g/cm2 in the women who received placebo. A smaller positive change was also seen at the lumbar spine for genistein, with a correspondingly smaller loss of lumbar BMD in the placebo group (Marini H, Minutoli L, Polito F, et al. Ann Intern Med. 2007; 146: 839–847).

Bone turnover decreased significantly in the women on genistein, and bone-specific alkaline phosphatase and IGF-1 also significantly increased. None of these markers changed in the placebo group. Genistein did not significantly change endometrial thickness but did reduce the mean number of hot flashes.

Genistein was not without side effects, particularly gastrointestinal symptoms. The withdrawl rate from the study due to these side effects was 19% in the genistein group versus 8% in the placebo group.

Previous studies show that women with high soy intake had a lower risk for osteoporosis. The current report provides further strong evidence that daily isoflavone intake (54 mg genistein), along with 500 mg of calcium and 400 IU of vitamin D can not only stave off bone loss, but actually increases lumbar and femoral BMD. The BMD changes are corroborated by observed decreases in urinary markers for bone resorption and the increase in circulating leveles of the bone formation markers.

It is true that twice as many women had side effects in the genistein group and discontinued treatment. But these side effects are considerably less problematic than those reported by many women taking bisphosphonate drugs to prevent osteoporosis. Although I do not consider genistein alone to be an adequate treatment for women with osteoporosis, I definitely recommend it for women with osteopenia, especially up to the age of 65, before they reach the point where they're at very high risk for fractures.

 

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