Into the Heart

Chocolate: A Cardio-Vascular Effect

High oxidative stress, and reduced antioxidant defenses play a significant role in the pathogenesis of coronary artery disease (atherosclerosis). Brussels Sprouts, red peppers and other intense colored vegetables & berries have abundant antioxidant nutrients and afford cardio-vascular protection. Studies now suggest dark chocolate has potent antioxidant properties.

A 2007 study assessed the effect of flavonoid-rich dark chocolate compared with cocoa-free (placebo) chocolate on coronary vascular and platelet function in twenty-two heart transplant recipients. Even though the major of individuals will not have a heart transplant, the results of this study are relevant to cardio-vascular function in general.

Coronary vasomotion was assessed before and two hours after ingestion of 40 g of dark (70% cocoa) chocolate or placebo chocolate. Two hours after ingestion of flavonoid-rich dark chocolate, coronary artery diameter increased significantly. However, coronary artery diameter was unchanged for the placebo group.

Impaired endothelial function and increased platelet activation also contribute to coronary artery disease: atherosclerosis. The endothelium is a thin layer of protective cells that line the lumen of the artery. Platelets are tiny cells that cluster at sites of injury. Platelets are components of plaque build-up in the artery.

This study also found endothelium-dependent coronary vasomotion improved significantly after dark chocolate when compared to the placebo group. Platelet adhesion decreased in the dark chocolate group but remained unchanged in the placebo group.

Flavonoid-rich dark chocolate appears to have potential cardio-vascular benefit.  Enjoy in moderation.

Source:
Dark Chocolate Improves Coronary Vasomotion and Reduces Platelet Reactivity
Andreas J. Flammer, MD; Frank Hermann, MD
Circulation. 2007;116:2376-2382.

Prunes: Abundantly Antioxidant

Antioxidants are compounds that help protect cells from damage caused by free radicals. When healthy cells are damaged, they are more susceptible to aging, cardiovascular disease and certain types of cancers. Antioxidants up-regulate enzymes involved in the repair of cellular damage.

Oxygen Radical Absorbance Capacity is a test tube analysis that measures the total antioxidant power of foods per 100 grams. Prunes, which are dried plums, had the highest antioxidant score of 5570 per 3.5 ounces, raisins scored 2,830 and blueberries scored third at 2,400.

Of additional cardiovascular benefit, dried plums provide approximately 5 to 7 grams of dietary fiber per 100 grams, about 60 percent of which is pectin. Pectin as a type of soluble dietary fiber has been shown to lower serum cholesterol in those with high cholesterol. The dietary fiber in dried plums increases fecal bile acid excretion which results in a cholesterol-lowering effect.

The glycemic index of prunes is low, as such prunes do not cause a spike in blood sugar. A rapid rise in blood sugar causes LDL cholesterol to oxidize (become rancid) and contributes to stored body fat.

Enjoying the natural sweetness of prunes four times a week is heart healthy.

Sources:
U.S. Dept of Agriculture: lists oxygen radical capacity of fruits/vegetables
http://www.ars.usda.gov/is/pr/1999/990208.htm

Consumption of Prunes as a Source of Dietary Fiber in Men with Mild Hypercholesterolemia
Tinker, L.F., Schneeman, B.O., Davis, P.A., Journal of Clinical Nutrition 1991: 1259–65

Red Wine Improves Insulin Sensitivity

Extensive studies have shown that red wine consumption is associated with less cardiovascular mortality in the general population and diabetic individuals.  The ability of red wine to improve insulin sensitivity is a key cardioprotective mechanism.

The phrase "insulin sensitivity" refers to the ability of cells to accept glucose. Insulin is a transporter and regulator of glucose. After glucose is taken up by cells, insulin has completed its task. Circulating insulin levels are then lowered. The glucose is used by the cell for energy.

If cells are not receptive (sensitive) to insulin . . . cells will lack (glucose)energy/fuel. Circulating insulin levels will remain high and too much glucose will say in the bloodstream, which contributes to high cholesterol and triglycerides. Increased insulin also causes stored body fat.

A 2004 study conducted in Italy explored the relationship between insulin sensitivity and red wine consumption. The study analyzed two groups of individuals with type 2 diabetes. One group consumed red wine for two weeks. The other group did not consume red wine.  The study group with type 2 diabetes, that consumed red wine, improved insulin mediated whole body glucose disposal by 43%.  Insulin mediated whole body glucose disposal did not change in the non wine drinking group.

Two weeks of red wine consumption markedly attenuated (lessened) insulin resistance in type 2 diabetics.

Source:
Red wine consumption improves insulin resistance but not endothelial function in type 2 diabetic patients
NAPOLI Raffaele; COZZOLINO Domenico ; GUARDASOLE Vincenzo MDs
Metabolism, Clinical and Experimental   
2005, vol. 54, no3, pp. 306-313

Estrogen Replacement and Blood Pressure

Postmenopausal women tend to have higher blood pressure than premenopausal women; suggesting a protective role of the hormone estrogen on blood pressure regulation. This protective effect is in part due to the inhibition or regulatory effect of estrogen on the sympathetic nervous system. Heightened sympathetic nervous system stimulation constricts blood vessels by stimulating A-1 receptors located on the surface of vascular smooth muscles.

The route of estrogen administration is a major determinant of the effect of estrogen replacement therapy (ERT) on sympathetic discharge. The study noted below found that sympathetic nervous system discharge (stimulation) decreased significantly from baseline during transdermal ERT but not during oral ERT or placebo.

The decrease in sympathetic nerve discharge achieved only with transdermal administration is not thought to be a dose related because serum estradiol concentrations achieved with oral ERT were comparable to those with transdermal ERT. However, with oral administration the liver is exposed to a supraphysiological concentration of estrogen resulting in decreased hepatic synthesis of insulin-like growth factor-1 (IGF-1).

Administration of IGF-1 has been shown to decrease sympathetic nerve activity and blood pressure in rats. Deficiency of this growth factor is associated with sympathetic overactivity and elevated blood pressure in humans.

Of additional interest, reduction in IGF-1 induced by oral estrogen preparations is accompanied by reduced lean body mass and increased fat mass (adiposity), which is a powerful predictor of elevated sympathetic discharge and blood pressure.

Therefore, it seems plausible that during oral estrogen replacement, sympathetic overactivity related to IGF-1 deficiency and/or increased (fatty tissue) opposes the direct effect of estrogen to decrease sympathetic discharge.

Avoidance of first-pass hepatic (liver) metabolism with transdermal estrogen replacement allows the estrogen-induced sympathetic inhibition to be unopposed.

As such, the route of administration is an important consideration in optimizing the beneficial effects of estrogen replacement on blood presure and cardiovascular health.

Estrogen is also thought to act on the central nervous system by decreasing sympathetic nerve discharge, the neural stimulus for norepinephrine release from peripheral sympathetic nerve terminals. Estrogen replacement has been shown to both activate vasodilator mechanisms mediated by nitric oxide or prostacyclin and inhibit vasoconstrictor response to norepinephrine.

Sources:
Transdermal Estrogen Replacement Therapy Decreases Sympathetic Activity in Postmenopausal Women
Wanpen Vongpatanasin, MD; Meryem Tuncel, MD
Circulation. 2001;103:2903.

Estrogen Replacement, Vascular distensibility, and Blood Pressures in Postmenopausal women.
DeMeersman R, Zion AS, Giardina EGV, et al.
Am J Physiol. 1998;274:H1539–H1544.