Page 17 - Nutrinsight-3

NutrInsight • Do we need dietary polyphenols for health?
• Orange flavanones and CVD
In a randomised, double-blind placebo-controlled crossover trial lasting 4 weeks, Morand et al showed that the flavanone, hesperidin, contributes to the vascular protective effects of orange juice [Morand et al., 2011]. In this study, 24 healthy, overweight men (age 50-65 y) were given either 500 mL orange juice (OJ) naturally containing 341.9 mg of flavonoids in which 292 mg was hesperidin, 500 mL control drink plus 2 capsules containing each 146 mg of hesperidin (CDH), and 500 mL control drink plus 2 capsules of placebo (CDP) each day. In the fasted state, OJ and CDH reduced diastolic blood pressure compared to CDP (p < 0.02). Microvascular endothelial activity, measured by combined laser Doppler flowmetry and iontophoresis, was not affected after chronic intake of OJ and CDH during 4 weeks. On the other hand, acute intake of OJ and CDH improved postprandial microvascular endothelial activity. It is interesting to note that hesperidin supplementation didn’t differ in term of effects compared to orange juice with naturally-occurring hesperidin.
• Black tea and FMD and blood pressure
There are numerous studies that have investigated the effects of consuming tea on FMD and blood pressure (BP). A dose response relationship was demonstrated between black tea and FMD [Grassi et al., 2009]. Black tea intake decreased systolic (-2.6 mmHg, P = 0.0007) and diastolic (-2.2 mmHg, P = 0.006) BP as well as stiffness index (P = 0.0159). But in fact, it has also been shown that green tea is as effective at improving FMD responses as black tea [Jochmann et al., 2008]. This is somewhat surprising because the nature of the polyphenols in black tea are completely different to those in green tea; green tea largely contains monomeric catechins such as epigallocatechin gallate (EGCG) whereas black tea contains only minor quantities of monomers and instead is rich in higher molecular weight products of catechin oxidation including theaflavins, thearubigens and theatannins. This should be allowed thanks to the metabolisation of these phenolic compounds by the gut microbiota [Lee et al., 2006].
Conclusion on polyphenols and CVD
Epidemiological data tends to show a positive association between polyphenols especially flavonoids and CVD and CHD (flavonols, flavanols and flavanones reduce the risk of CHD mortality by around 20%).
Data from intervention trials are less consistent. However, they provide information related to the way polyphenols may have positive effects on CVD and CHD, including improvements in endothelial function and lipoprotein profiles. The positive effect on endothelial function could also be linked to the improvement observed in blood pressure and reduced risk of hypertension.
A precise characterization of food composition in term of polyphenol profile, along with a better understanding of interactions with the food matrix, should help identify the bioactive compounds and allow determining the required dose for expected effect.
There is also a need for well-controlled intervention studies taking into account the inter-individual variability related to polyphenol bioavailability and metabolism.
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