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Superfoods Catherine Collins RD FBDA Principal Dietitian St Georges Hospital NHS Trust To be covered: Superfoods vs whole diet approach | Definition of a ‘superfood’ | Potential benefits of superfood constituents | Limitations of research vs food-based diet | Food classification | By nutrient content: z z | By ability to prevent disease: z z | Protein Type of fat Iron rich foods to correct anaemia Vitamin D to prevent rickets By non-nutritive functional content: z z Prebiotic fibres for gut bacteria Plant phytochemicals as anti-oxidants Food classification | ‘Cultural’ superfoods: z | ‘Prestige’ foods: z z | z z Tridosha Yin-yang Galenic humoral ‘Sympathetic magic’ foods: z z z | Difficult to obtain Often protein based ‘Body image’ foods: z | Dominant staple / source of calories / essential Pomegranate Walnut Eggs ‘Physiological’ food groups Derrick Jelliffe; AJCN 1967 The ‘Mediterranean Diet’ | Dr Ancel Keys 1904 - 2004 | Physiologist at the University of Minnesota | Director of the ‘Seven Countries Collaborative Study’ | Dietary principles ratified in subsequent research of over 450 clinical papers….. | | | | | | | 12 studies addressing ‘Mediterranean Diet’ 1,574,299 subjects followed for 3-18 years … of which eight cohorts (514,816 subjects, 33,576 g) 9% reduction in overall mortality 9% reduction in death from cardiovascular disease 6% reduction in risk of cancer, or dying from cancer 13% reduction in risk of Parkinson’s disease and Alzheimer’s disease Sofi et al: BMJ 2008 Risk of developing, or dying from cancer: Risk of dying from heart disease: Benefits of diet and lifestyle change: middle age | | 15,792 men and women aged 45 to 64, part of the Atherosclerosis Risk in Communities (ARIC) Study 970 (8.4%) newly adopted a healthy lifestyle: z z z z at least 5 fruits and vegetables daily at least 2.5 hours per week of exercise maintain BMI between 18.5 – 30 stopped smoking OR 95% CI Heart attack or stroke 0.65 0.39-0.92 All cause mortality 0.60 0.39-0.92 King et al; American Journal of Medicine 2007 Nutrition and health: quality of evidence Mediterranean diet ‘Superfoods’ Early nutrition research: the ‘ positive reductionist’ approach James Lind | Performed randomised controlled dietary trial | Citrus fruits prevented scorbutic lesions (1753) | 1794 – lime juice regularly given to sailors | 1912 – chemical structure of Vitamin C identified Takaki Kanehiro | Identified poor diet as a cause of beri-beri (1884) | View against prevailing opinion that beri-beri was an infectious disease | 1910 - Umetaro Suzuki identifies chemical structure | Eijkman identifies B1 and wins 1929 Nobel prize Recent nutrition research: the ‘negative reductionist’ approach | | | | | | 22 randomized controlled trials, 161,045 subjects 88,610 in antioxidant supplement groups vs 72,435 in placebo or no-intervention groups no preventive effect on cancer RR 0.99 (CI 0.96–1.03) no preventive effect on cancer according to type of antioxidant, or type of cancer significant increased risk of bladder cancer RR 1.52 (CI 1.06–2.17) in a subgroup of four trials Myung et al; Ann Oncol 2010 | | | 67 randomized controlled trials, 232,550 subjects No effect on primary or secondary prevention of disease, Vitamin A, selenium and Vitamin E supplements may increase mortality Bjelakovic et al: Cochrane Rev 2008 Superfood: a definition “a food considered especially nutritious or otherwise beneficial to health and well-being” OED THE TIMES: Top 100 foods to boost productivity Superfoods list, 2007 | | | | | | | | | almonds aronia berry banana cauliflower cherry juice chocolate fig guava kiwi • • • • • • • • • mushrooms oregano quinoa rabbit stew seaweed and algae shake tea tofu (-) tomato walnuts Anti-oxidant potential | Remove or reduce free radicals or other reactive oxygen species (ROS) that can cause cell damage | facilitate anti-oxidant enzyme reactions | Moderate the production of toxic metabolites Phase I detoxification Phase I enzymes involved are 'activators'. Common enzyme group are the CYP groups eg CYP450 They alter the chemical your body needs to remove, by adding single nitrogen or oxygen molecules. This small change makes it simpler for Phase II enzymes to effectively remove the substance | | | | Oxidation Reduction Hydrolysis Hydration Phase II detoxification Phase II enzymes called 'excretors' bind to the byproduct of Phase I enzymes They conjugate with the altered chemical such as glutathione. This makes the substance water soluble, for easier transport and elimination | | | | | Sulphation Glucuronidation Acetylation Methylation Amino acid conjugation Hussain et al. Nature Reviews Cancer 3, 276 2003 Polyphenols: Flavonoids Flavonols: tea, onions Flavones: parsley, celery Flavanones: citrus fruits, tomato, mint Isoflavones: soya, red clover Anthocyanidins: red wine, black or red fruits Flavanols: tea, wine, chocolate Phenolic acids Hydroxybenzoic acid: tea, blackberries, raspberries Hydroxycinnamic acids: coffee, blueberries, wheat Phenolic alcohols Tyrosol: extra-virgin olive oil, wine, beer Stilbenes Resveratrol: grapes, berries, peanuts Lignans Secoisolariciresinol: flaxseed D’Archivio et al; 2007 Problems with food assays: unstable phytochemicals In vitro (‘test-tube’) degradation over time | | | | Oxidation of this anti-oxidant forms hydrogen peroxide+ quinones Shift oxidative damage from lipid peroxidation (cell membranes) to thiol arylation (less potent damage) Free radical toxicity is blocked BUT exchanged for a lesser type of toxicity Disadvantage in test tube monitoring – different in the body Curcumin Thangapazham et al; AAPS Journal 2006 | anti-inflammatory, antioxidant, and antitumour properties | The effects of polyphenols - such as curcumin - are more pronounced in vitro, using high concentrations which are not physiologically achievable from food, in vivo | A clinical dose of 3.6g curcumin is sufficient to achieve in vivo biochemical influence Curcumin (diferuloylmethane) | Turmeric powder contains 3.1% curcumin by weight, so ‘research-to-recipe’ equivalence would require consumption of 110g of turmeric powder daily | ‘Curry prevents cancer’ is clearly an exaggeration of the knowledge currently available | poor curcumin bio-availability can be exploited to afford bowel prophylaxis for familial adenomatous polyposis – topical influence reduces size and amount of pre-cancerous polyps forming in the large bowel Phytochemical bioavailability: influenced by cooking | Lycopene bio-availability increased 55% Increased naringenin | Increased carotene availability | Glucosinolates: z Boiling 30 mins È 70% z Steaming, microwaving, stir-frying Æ no change in bioavailability | Quercetin: z 75% loss from boiling for 15 minutes z 65% after microwave cooking z 30% after frying | Physiological duration: pomegranate juice vs tea Ellagitannins half life of 2-3 hours Seeram et al; J Nutr 2006 EGCG and other tea catechins half life of 2-4 hours Yan et al; J Nutr 2004 It’s inevitable that … “Food, not specific nutrients, is the fundamental unit to health in human nutrition” Professor Linda Tapsell Director of the Smart Foods Centre University of Woolongong, W Australia “We are confusing ourselves and the public by talking so much about nutrients when we should be talking about foods…” “consumers get the idea that diet and health can be understood in terms of specific nutrients” “It’s not the best approach and may be wrong” Professor David Jacobs University of Minnesota Mediterranean diet: examples of dietary synergy | Vitamin D (oily fish) helps absorption of dietary calcium (dairy foods, green leafy veg) | Prebiotic fibres in vegetables and grain-based foods provide fuel source for bowel or probiotic bacteria and increase mineral bioavailability | Olive oil aids absorption of phytochemicals (such as lycopene, lutein) and fat soluble nutrients – vitamins including beta-carotene | Mono-unsaturated fats reduce inflammation, as do fish oils | Vitamin C helps to absorb non-meat sources of iron | citrus flavonoids eg quercetin + Vitamin C work synergistically FA synthesis Urea cycle Summary | ‘Superfood’ is a marketing concept, exploiting the biological functionality of food compounds | Cancer chemoprevention with dietary phytochemicals continue to be evaluated | A ‘whole diet’ approach is the optimal approach to health: a ‘Superdiet’ rather than ‘Superfood’ approach