Flavonoid-rich cocoa consumption affects multiple cardiovascular risk factors in a meta-analysis of short-term studies

Dietary flavonoids and the development of type 2 diabetes and cardiovascular diseases: review of recent findings

PURPOSE OF REVIEW

This review summarizes the results on flavonoid intakes and the development of type 2 diabetes and cardiovascular diseases.

RECENT FINDINGS

Recent advances in food composition databases have allowed the evaluation of a more comprehensive range of flavonoids in epidemiological studies. In addition, the number of randomized trials of flavonoid-rich foods has increased rapidly. Results from both cohort studies and randomized trials suggest that anthocyanidins from berries and flavan-3-ols from green tea and cocoa may lower the risk of type 2 diabetes and cardiovascular diseases. Meta-analyses of randomized trials indicate that the strongest evidence exists for a beneficial effect of green tea on LDL-cholesterol and a beneficial effect of flavan-3-ol-rich cocoa on endothelial function and insulin sensitivity. Few randomized trials had a long duration or evaluated pure flavonoid compounds.

SUMMARY

Evidence from cohort studies and randomized trials suggest beneficial effects of food sources of anthocyanidins (berries) and flavan-3-ols (green tea and cocoa) on cardiovascular health. These findings need to be confirmed in long-term randomized trials, and evaluation of pure compounds will be important to establish what specific flavonoids and doses are effective.

Blood pressure-lowering effect of dietary (-)-epicatechin administration in L-NAME-treated rats is associated with restored nitric oxide levels

Epidemiological and intervention studies have shown that the intake of certain chocolates or cocoa products decreases blood pressure (BP) in humans. (-)-Epicatechin is the most abundant flavanol present in cocoa seeds and its derived foods. This work investigates the effects of dietary (-)-epicatechin on BP in rats that received N(ω)-nitro-l-arginine methyl ester (L-NAME) for 4 days. (-)-Epicatechin administration prevented the 42mm Hg increase in BP associated with the inhibition of NO production in a dose-dependent manner (0.2-4.0g/kg diet). This BP effect was associated with a reduction in L-NAME-mediated increase in the indexes of oxidative stress (plasma TBARS and GSSG/GSH(2) ratio) and with a restoration of the NO concentration. At the vascular level, none of the treatments modified NOS expression, but (-)-epicatechin administration avoided the L-NAME-mediated decrease in eNOS activity and increase in both superoxide anion production and NOX subunit p47(phox) expression. In summary, (-)-epicatechin was able to prevent the increase in BP and in oxidative stress and restored NO bioavailability. The fact that (-)-epicatechin is present in several plants usually consumed by humans gives the possibility of developing diets rich in those plants or pharmacological strategies using that flavonoid to diminish BP in hypertensive subjects.

Cocoa polyphenols and their potential benefits for human health

This paper compiles the beneficial effects of cocoa polyphenols on human health, especially with regard to cardiovascular and inflammatory diseases, metabolic disorders, and cancer prevention. Their antioxidant properties may be responsible for many of their pharmacological effects, including the inhibition of lipid peroxidation and the protection of LDL-cholesterol against oxidation, and increase resistance to oxidative stress. The phenolics from cocoa also modify the glycemic response and the lipid profile, decreasing platelet function and inflammation along with diastolic and systolic arterial pressures, which, taken together, may reduce the risk of cardiovascular mortality. Cocoa polyphenols can also modulate intestinal inflammation through the reduction of neutrophil infiltration and expression of different transcription factors, which leads to decreases in the production of proinflammatory enzymes and cytokines. The phenolics from cocoa may thus protect against diseases in which oxidative stress is implicated as a causal or contributing factor, such as cancer. They also have antiproliferative, antimutagenic, and chemoprotective effects, in addition to their anticariogenic effects.

Blueberry intervention improves vascular reactivity and lowers blood pressure in high-fat-, high-cholesterol-fed rats

Growing evidence suggests that intake of flavonoid-containing foods may exert cardiovascular benefits in human subjects. We have investigated the effects of a 10-week blueberry (BB) supplementation on blood pressure (BP) and vascular reactivity in rats fed a high-fat/high-cholesterol diet, known to induce endothelial dysfunction. Rats were randomly assigned to follow a control chow diet, a chow diet supplemented with 2 % (w/w) BB, a high-fat diet (10 % lard; 0·5 % cholesterol) or the high fat plus BB for 10 weeks. Rats supplemented with BB showed significant reductions in systolic BP (SBP) of 11 and 14 %, at weeks 8 and 10, respectively, relative to rats fed the control chow diet (week 8 SBP: 107·5 (SEM 4·7) v. 122·2 (SEM 2·1) mmHg, P= 0·018; week 10 SBP: 115·0 (SEM 3·1) v. 132·7 (SEM 1·5) mmHg, P< 0·0001). Furthermore, SBP was reduced by 14 % in rats fed with the high fat plus 2 % BB diet at week 10, compared to those on the high-fat diet only (SBP: 118·2 (SEM 3·6) v. 139·5 (SEM 4·5) mmHg, P< 0·0001). Aortas harvested from BB-fed animals exhibited significantly reduced contractile responses (to L-phenylephrine) compared to those fed the control chow or high-fat diets. Furthermore, in rats fed with high fat supplemented with BB, aorta relaxation was significantly greater in response to acetylcholine compared to animals fed with the fat diet. These data suggest that BB consumption can lower BP and improve endothelial dysfunction induced by a high fat, high cholesterol containing diet.

Higher anthocyanin intake is associated with lower arterial stiffness and central blood pressure in women

BACKGROUND

Although a high intake of some flavonoid subclasses may reduce cardiovascular disease mortality, data regarding the in vivo mechanisms of action are limited.

OBJECTIVE

We examined associations between habitual flavonoid intakes and direct measures of arterial stiffness, central blood pressure, and atherosclerosis.

DESIGN

In a cross-sectional study of 1898 women aged 18-75 y from the TwinsUK registry, intakes of total flavonoids and their subclasses (flavanones, anthocyanins, flavan-3-ols, polymers, flavonols, and flavones) were calculated from validated food-frequency questionnaires by using an updated and extended USDA database. Direct measures of arterial stiffness and atherosclerosis included central systolic blood pressure (cSBP), central diastolic blood pressure, mean arterial pressure (MAP), augmentation index, pulse wave velocity (PWV), and intima-media thickness.

RESULTS

In multivariate analyses, a higher anthocyanin intake was associated with significantly lower cSBP (mean ± SE: -3.0 ± 1.4 mm Hg for quintile 5 compared with quintile 1; P-trend = 0.02), MAP (-2.3 ± 1.2 mm Hg for quintile 5 compared with quintile 1; P-trend = 0.04), and PWV (-0.4 ± 0.2 m/s for quintile 5 compared with quintile 1; P-trend = 0.04), whereas a higher flavone intake was associated with a lower PWV (-0.4 ± 0.2 m/s for quintile 5 compared with quintile 1; P-trend = 0.04). Although a higher wine and berry intake was associated with a lower PWV, no associations were observed for total and other flavonoid subclasses.

CONCLUSIONS

These data, which include direct measures of arterial stiffness and thickness, suggest that higher intake of anthocyanins and flavones are inversely associated with lower arterial stiffness. The intakes of anthocyanins associated with these findings could be incorporated into the diet by the consumption of 1-2 portions of berries daily and are, therefore, relevant for public health strategies to reduce cardiovascular disease risk.

Flavonoids and metabolic syndrome

Increasing evidence indicates that several mechanisms, associated or not with antioxidant actions, are involved in the effects of flavonoids on health. Flavonoid-rich beverages, foods, and extracts, as well as pure flavonoids are studied for the prevention and/or amelioration of metabolic syndrome (MS) and MS-associated diseases. We summarize evidence linking flavonoid consumption with the risk factors defining MS: obesity, hypertriglyceridemia, hypercholesterolemia, hypertension, and insulin resistance. Nevertheless, a number of molecular mechanisms have been identified; the effects of flavonoids modifying major endpoints of MS are still inconclusive. These difficulties are explained by the complex relationships among the risk factors defining MS, the multiple biological targets controlling these risk factors, and the high number of flavonoids (including their metabolites) present in the diet and potentially responsible for the in vivo effects. Consequently, extensive basic and clinical research is warranted to assess the final relevance of flavonoids for MS.

Elucidation of (-)-epicatechin metabolites after ingestion of chocolate by healthy humans

After absorption in the gastrointestinal tract, (-)-epicatechin is extensively transformed into various conjugated metabolites. These metabolites, chemically different from the aglycone forms found in foods, are the compounds that reach the circulatory system and the target organs. Therefore, it is imperative to identify and quantify these circulating metabolites to investigate their roles in the biological effects associated with (-)-epicatechin intake. Using authentic synthetic standards of (-)-epicatechin sulfates, glucuronides, and O-methyl sulfates, a novel LC-MS/MS-MRM analytical methodology to quantify (-)-epicatechin metabolites in biological matrices was developed and validated. The optimized method was subsequently applied to the analysis of plasma and urine metabolites after consumption of dark chocolate, an (-)-epicatechin-rich food, by humans. (-)-Epicatechin-3'-β-d-glucuronide (C(max) 290 ± 49 nM), (-)-epicatechin 3'-sulfate (C(max) 233 ± 60 nM), and 3'-O-methyl epicatechin sulfates substituted in the 4', 5, and 7 positions were the most relevant (-)-epicatechin metabolites in plasma. When plasmatic metabolites were divided into their substituent groups, it was revealed that (-)-epicatechin glucuronides, sulfates, and O-methyl sulfates represented 33 ± 4, 28 ± 5, and 33 ± 4% of total metabolites (AUC(0-24)(h)), respectively, after dark chocolate consumption. Similar metabolites were found in urine samples collected over 24h. The total urine excretion of (-)-epicatechin was 20 ± 2% of the amount ingested. In conclusion, we describe the entire metabolite profile and its degree of elimination after administration of (-)-epicatechin-containing food. These results will help us understand more precisely the mechanisms and the main metabolites involved in the beneficial physiological effects of flavanols.