The research on flavonols, in particular those found in green tea and chocolate, is clearly becoming an exciting field. The weight-loss market seems to be a big focus for these flavonols, as well as cardiovascular function and, more recently, cognitive function. Mark J Tallon, PhD, presents the latest research and applications
Ingredient suppliers telling customers 1,2 or 1,3-diphenylpropane (flavonol)-based compounds can boost health can say goodbye to their sales potential. However, tell them that in real-world language — chocolate enhances cognitive performance, prostate health and circulation — and business will be booming. Flavonols are indeed chemicals but how you market them is key. More importantly to the future success of the sector is science, which ultimately drives marketing claims.
Perhaps one of the most fortuitous discoveries is the link between health and once forbidden foods such as chocolate, wine, green tea and whole host of exotic and familiar fruits. The food-science industry owes this consumer boost in awareness to flavonols and the emerging science role related to weight loss and cardiovascular health.
Green tea has been a big winner in the wellness market and, recently, the weight-loss category. Although green tea may have some functional benefits, providing a standardised dose per serving is difficult, which has directed the research focus on its active flavonols, namely epigallocatechin gallate (EGCG). Recent data from human studies indicate that the consumption of green tea and green-tea extracts may help reduce body weight, mainly body fat, by increasing thermogenesis (calories lost as heat) and fat oxidation. However, few human studies have investigated the metabolic effects of the most predominant tea catechin EGCG. In an attempt to overcome this data void, researchers have been trying to assess the potential mechanism behind the ability of green tea to influence weight loss.1
In a randomised double blind, placebo-controlled, crossover trial, six overweight men were given 300mg EGCG/day for two days. Fasting and postprandial changes in energy expenditure (EE) and substrate oxidation (use of carbohydrates, protein and fat for energy) were assessed. Resting EE did not differ between EGCG and placebo, although respiratory quotient (a measure of fuel source) was significantly lower with EGCG compared to the placebo. This suggests an increased reliance on fat as a source of energy. These findings also suggest that EGCG alone has the potential to increase fat oxidation in men, and may therefore contribute to the anti-obesity effects of green tea. However, more studies with a greater sample size and a broader range of age and BMI are needed to define the optimum dose.
In a similar study from the School of Health Sciences, University of South Australia researchers evaluated the metabolic effects of EGCG supplementation, but also when combined with a programme of regular aerobic exercise in overweight/obese post-menopausal women.2
Thirty-eight women exercised at moderate intensity, walking three times per week for 45 minutes at 75 per cent maximum heart rate, and took 150mg EGCG (Teavigo) or placebo twice daily for 12 weeks. Blood parameters (lipids, glucose and insulin), blood pressure, heart rate and arterial function were assessed at 0, 6 and 12 weeks. Body composition including abdominal fat was assessed at weeks 0 and 12.
Waist circumference, total body fat, abdominal fat and intra-abdominal adipose tissue were reduced in both groups, with no difference between placebo and EGCG. EGCG did, however, significantly decrease resting heart rate and reduced plasma glucose in subjects with impaired glucose tolerance. These results suggest that moderate consumption of EGCG can improve the health status of overweight individuals undergoing regular exercise by reducing heart rate and plasma glucose concentrations. Loss of body fat, however, may require a higher intake, prolonged use of EGCG, other catechins or addition of metabolic stimulants.
An apple a day
Recent evidence suggests that there is a modicum of truth in those words, at least for the obese. In a well controlled trial conducted in Japan on 71 moderately obese male and female subjects with a body mass index ranging from 23 to 30, researchers evaluated the efficacy of 12-week intake of polyphenols extracted from apples and hop bract (600mg/day).3
Over a 12-week period, the supplementation of polyphenol-containing capsules significantly decreased total cholesterol and LDL-cholesterol levels. The effects of the apple polyphenol-containing capsules were more marked than those of the hop bract polyphenol-containing capsules. However, what was very interesting is that the visceral fat and the level of adiponectin (which regulates glucose and fatty acid storage) in the group administered apple polyphenols improved compared to controls. These results demonstrate that apple polyphenols can regulate fat metabolism in healthy subjects with a relatively high body mass index. Further work in nonobese and overweight subjects are warranted, especially when integrated with a calorie-controlled diet.
The dark side of health
Dark chocolate has been big news on the health platform front due to its flavonol content in the form of cocoa. Recent promotion from Nestlé in Australia may be a sign of where the industry is moving in relation to suggested use and functionality of chocolate.
In a study from Chiba University in Japan, researchers assessed the effects of flavonoid-rich dark chocolate in healthy subjects on coronary circulation, which may have applications in cardiovascular disease states.4 The randomised, single-blind design of the study was conducted over two weeks in 39 healthy men. Subjects were randomly assigned a daily intake of either flavonoid-rich dark chocolate (45g including cacao polyphenol 550 mg/day, 200 kcal) or nonflavonoid white chocolate (35g, including cacao polyphenol 0 mg/day, 140 kcal) as a control. Assessment of coronary circulation and oxidative stress was made before and after two weeks of intake.
Flavonoid-rich dark chocolate consumption significantly improved coronary circulation compared to nonflavonoid white chocolate consumption. Intake of dark (but not white) chocolate, MDA-LDL, triglyceride (TG) and heart rate (HR) significantly influenced the change of coronary circulation after two weeks of intake.
The study authors concluded that flavonoid-rich dark chocolate could significantly improve coronary circulation in healthy adults, independent of changes in oxidative stress parameters, blood pressure and lipid profile, whereas nonflavonoid white chocolate had no such effects.
Chocolate a no-go for bone health?
A research group from Western Australia studied the relation between chocolate consumption and measurements of whole-body and regional bone density as well as strength in 1,001 women aged 70-85 years.5 Bone density and strength were measured, as was the frequency of chocolate by questionnaire and condensed into three categories: or = 1 time/day.
The results of the investigation suggest that the higher frequency of chocolate consumption was related to lower bone density and strength. Daily chocolate consumption, compared to those eating it less than once a week, was associated with a 3.1 per cent lower whole-body bone density, with similarly lower bone density of the total hip, femoral neck, tibia, and heel; and with lower bone strength in the tibia and the heel. Adjustment for covariates did not influence interpretation of the results. Older women who consume chocolate daily had lower bone density and strength. Suggesting confirmation of these findings could have important implications for prevention of osteoporotic fracture.
However, this study did not account for the type or flavonol and calcium content, which is known to significantly influence health and specifically bone function. Furthermore, the measurement of dietary intakes from recall and questionnaire is notoriously inaccurate; as such these results should be approached with caution.
The research on flavonols is clearly becoming an exciting field and the studies above confirm just a small portion of the potential impact. Extracts from a variety of plant and botanical sources have been show to significantly affect lipolysis and weight control, including Sauropus androgenus,6Nelumbo nucifera,7Cissus quadrangularis,8Rosa canina,9 as well as other polyphenolics and isoflavones.10,11 The weight-loss market seems to be a big focus for these flavonols, as well as cardiovascular function and, more recently, cognitive function.12
Flavonols will need to be looked upon in the context of EU and nutrient profiling. Nutrient profiling will set the stage for what level of fat and sugar will be defined as 'healthy' and, as such, a company wanting to maintain a health claim based on active content (ie, flavonols) must deliver them in a healthy food matrix (product/formulation). Coca via and other premium functional foods delivered in a potentially nonhealthy format (high in sugar) may struggle to retain their health claims based on flavonol research. Therefore, the use of innovative food technology to reformulate many European products toward lowering 'nonhealthy' components (fats/sugar), yet retaining indulgent taste, will be a significant challenge. The flavonol market, as delivered in supplement format, will remain strong but the challenge of a mass market related to health claims for the functional-foods and beverage markets will be a significant factor in the years to follow.
Mark J Tallon, PhD, is chief science officer of NutriSciences, a London-based consultancy firm specialising in health-claim substantiation, product development and technical writing. www.NutriSciences.net. Respond: email@example.com
1. Boschmann M, Thielecke F. The effects of epigallocatechin-3-gallate on thermogenesis and fat oxidation in obese men: a pilot study. J Am Coll Nutr. 2007; 26(4): 389S-395S.
2. Hill AM, et al. Can EGCG reduce abdominal fat in obese subjects?J Am Coll Nutr. 2007; 26(4):396S-402S.
3. Nagasako-Akazome Y, et al. Apple polyphenols influence cholesterol metabolism in healthy subjects with relatively high body mass index. J Oleo Sci. 2007; 56(8): 417-28.
4. Shiina Y, et al. Acute effect of oral flavonoid-rich dark chocolate intake on coronary circulation, as compared with non-flavonoid white chocolate, by transthoracic Doppler echocardiography in healthy adults. Int J Cardiol. 2007 Nov 26 [Epub ahead of print]
5. Hodgson JM, et al. Chocolate consumption and bone density in older women. Am J Clin Nutr. 2008; 87(1):175-80.
6. Yu SF, et al. 3-O-beta-D-glucosyl-(1-->6)-beta-D-glucosyl-kaempferol isolated from Sauropus androgenus reduces body weight gain in Wistar rats. Biol Pharm Bull. 2006; 29(12): 2510-3.
7. Ohkoshi E, et al.Constituents from the leaves of Nelumbo nucifera stimulate lipolysis in the white adipose tissue of mice. Planta Med. 2007; 73(12):1255-9.
8. Oben JE, et al. The effect of Cissus quadrangularis (CQR-300) and a Cissus formulation (CORE) on obesity and obesity-induced oxidative stress. Lipids Health Dis. 2007 4;6:4.
9. Ninomiya K, et al. Potent anti-obese principle from Rosa canina: structural requirements and mode of action of trans-tiliroside. Bioorg Med Chem Lett. 2007 1;17(11):3059-64.
10. da-Silva WS, et al. The small polyphenolic molecule kaempferol increases cellular energy expenditure and thyroid
hormone activation. Diabetes. 2007; 56(3):767-76. 11. Aubertin-Leheudre M, et al. Six months of isoflavone supplement increases fat-free mass in obese-sarcopenic postmenopausal women: a randomized double-blind controlled trial. Eur J Clin Nutr. 2007; 61(12):1442-4.
12. Bisson JF, et al. Effects of long-term administration of a cocoa polyphenolic extract (Acticoa powder) on cognitive performances in aged rats. Br J Nutr. 2008; 8:1-8 [Epub ahead of print]