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Title: Effect of polyphenol-rich dark chocolate on anthropometric, nutritional, biochemical and physiological markers in normal weight and overweight adults
Author: Farhat, Grace
ISNI:       0000 0004 5346 4714
Awarding Body: Queen Margaret University
Current Institution: Queen Margaret University
Date of Award: 2014
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Polyphenols are phytochemicals widely available in plants. Dark chocolate (DC) is a high source of polyphenols, particularly flavanols. Studies previously reported a beneficial effect of polyphenol-rich dark chocolate (PRDC) on insulin sensitivity and oxidative stress, while its effects on blood pressure, serum lipid levels and inflammation remain unclear. In addition, a research area regarding the effect of PRDC on body weight control emerged recently. Two investigations were carried out. Study I (61 participants) looked at the effect of PRDC on insulin sensitivity in normal weight and overweight adults, while Study II (14 participants) investigated the effect of PRDC on body weight in overweight individuals. Volunteers received 20g of either PRDC (500mg of polyphenols) or placebo DC (low in polyphenols) daily for 4 weeks (Study I) or 12 weeks (Study II). Anthropometric measures and blood, saliva and urine samples were taken. Results showed that 4 weeks of PRDC supplementation decreased insulin levels (p<0.001) and HOMA-IR (p=0.003), and increased QUICKI (p<0.001), but had no significant impact on glucose levels (p=0.16). However, participants administered placebo DC showed an increase in insulin (p=0.014), HOMA-IR (p=0.003), TG (p= 0.008), glucose (p=0.041) and BMI (p=0.007) levels and a decrease in QUICKI (p=0.013). No significant changes in blood pressure, other serum lipid levels or glucocorticoid hormones were noted in both groups. In study II, there was an increase in BMI in the whole study population (p=0.046) with no significant difference between groups. Results indicate a potential implication of PRDC in the prevention of risk factors for cardiovascular diseases. Findings also highlight the detrimental effects of placebo DC, and propose the analysis of polyphenol content of different DC brands in the market. The increase in BMI and other markers only in the placebo group after four weeks, suggests that PRDC may counteract the adverse effects of fat and energy in the diet. However, the increase in BMI in both groups after 12 weeks implies further investigations to test the counteracting effect of PRDC over the long term.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Dietetics, Nutrition and Biological Sciences