Eg. vitamin D. Plausible biological mechanism, consistent studies.Essentially inductionist principles. Critique: Rely heavily on the subjective judgement of the reviewer. Temporality particularly important (prospective studies stronger). Expanding scientific literature makes almost all plausible hypotheses supported.
Important, because in a prominent publication summarising findings, not one mention of the health effects of fructose was mentioned.
How much sugar do you think Nzers eat on average?
Why the about face????
'Low carb downunder' conference
Has nutrition research helped us with our food choices? Simon Thornley (Epidemiologist) University of Auckland
Summary What is science/epidemiology? A brief history of human nutrition I get involved… diversion into tobacco Food addiction? What next?
My view Yes, but many nutrition scientists are not listening to the data Fructose, sugar, carbohydrates are often overlooked
What is science or research? “In God we trust, all others bring data” William Edward Deming “First establish the facts, then seek to explain them” Aristotle
Science Anarchistic; consensus not useful Hypothesis and argument Disproof over proof Uncertainty over absolutes Integration
A basic epidemiological study… Disease Subjects What we eat Focus on statistical over biological evidence…
Error… Many contradictory studiesNot included in CI or p-value Accounted for by 95%[Quantitative bias analysis] Error confidence interval and p-value Selection bias recruitment %Information Systematic Random biasAccuracy of measures? Unmeasured False +ve False –ve ~5% ~10 to 20% confoundingRCT? From literature?
Bradford-Hill Criteria Strong RCT better than association? observational study Consistent? Makes sense Does cause come before effect? More exposuremore disease?
Salt restriction Salt restriction ↓ blood pressure Observational studies show both ↑ and ↓ survival (unmeasured confounding) Only randomised study shows benefit in group that didn’t restrict salt. Taylor, R. S., Ashton K. E., T. Moxham, L Hooper, and S. Ebrahim. "Reduced Dietary Salt for the Prevention of Cardiovascular Disease." Cochrane Database of Systematic Reviews, no. 7 (2011). http://www.mrw.interscience.wiley.com/cochrane/clsysrev/articles/CD009217/frame.html .
Is the idea falsifiable?HOW DOES SCIENCE GOWRONG?
How it works in theory… Idea Experiment Interpret New Idea Generate Test Inferences from Refinehypothesis hypothesis experiment hypothesis
In reality…? Experiment Interpret New Idea Generate Test Inferences from Ideahypothesis hypothesis experiment Refine hypothesis
Some history…NUTRITION IDEAS OVER THELAST 100 YEARS…
What happened in the 1960s? Diet-heart hypothesis Heart disease caused by saturated fat Response: reduce fat (↑sugar or carb.) Cheap sugar (HFCS in USA) American Heart Assoc other English speaking countriesTaubes G. The Diet Delusion. New York: Vermilion; 2007.
My thoughts on obesity…Medical training Public Health Research ResearchTraditional Tobacco Similarities Critique ofNutritional theory addiction between energy density- Energy density obesity and Focus on sugar smoking1994 2005 2007 2011
The medical gurus say sugar isOK? “Excess sucrose has largely been exonerated as an important dietary factor in the aetiology of type-2 diabetes...”J. I. Mann and A. S. TruswellDiseases of overnourished societies and the need for dietary change: in theOxford Textbook of Medicine, 4th Edition. Postprandial glycemia (GI) used to exonnerate sugar…
Sugar: traditional views 30% increase over last 30 yearsPopkin BM, Nielsen SJ. The sweetening of the worlds diet. Obesity Research 2003;11(11):1325-32. “Empty calorie”Nestle M. Soft drink "pouring rights": marketing empty calories to children. Public Health Reports 2000;115(4):308-19. Fructose not mentioned Something is missing?
Update... AHA turns around. “Fructose... has been indirectly implicated in the epidemics of obesity and type 2 diabetes”Circulation 2009;120;1011-1020
Fructose: what has changed? GI ignores fructose Sweeter than glucose Linked to: Gout, diabetes, weight gain, metabolic syndrome Hypertension, rotten teeth High triglycerides, dyslipidaemia, CVD Tends to ↑ hungerJohnson, R.J., et al., Hypothesis: Could Excessive Fructose Intake and Uric Acid Cause Type 2 Diabetes? Endocr Rev, 2009. 30(1): p. 96- 116.Segal, M.S., E. Gollub, and R.J. Johnson, Is the fructose index more relevant with regards to cardiovascular disease than the glycemic index? European Journal of Nutrition, 2007. 46(7): p. 406-17.
What about saturated fat? Recent summaries no association with heart disease.Skeaff CM, Miller J. Dietary Fat and Coronary Heart Disease: Summary of Evidence from Prospective Cohort and Randomised Controlled Trials. Ann Nutr Metab 2009;55:173–201Mente A, de Koning L, Shannon HS, Anand SS (April 2009). A systematic review of the evidence supporting a causal link between dietary factors and coronary heart disease. Arch. Intern. Med. 169 (7): 659–69.
Food addiction: evidence Addiction pathways Eating is automatic Rats sugar induces withdrawal; not fat.
My inbox... “For three weeks I cut all sugar and flour… then… mood swings…, depression…, stomach pain…, joint and muscle pain…, the shakes….”
“People who knew me started thinking I washiding a drug problem.”
Overeater’s Anonymous “When you are addicted to drugs you put the tiger in the cage to recover; When you are addicted to food, you put the tiger in the cage, but take it out three times for a walk” Kerri-Lynn Murphy Kriz
Critique: Academia “Any addictive … hypothesis cant explain the rise that weve seen over the last … 30 years of obesity.”Prof. Boyd Swinburn, Professor of Population Health, Deakin University 13 Jan 2009
Synopsis Nutrition focuses on energy not hunger Low fat idea predates obesity epidemic Sugar intake continues to ↑ Likely subtle addiction Likely cause of major risk factors for heart disease Many nutrition researchers stuck in energy paradigm (cf. some pop science)