'Low carb downunder' conference
-
Upload
simon-thornley -
Category
Health & Medicine
-
view
321 -
download
1
description
Transcript of '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
What we eat
Subjects
Focus on statistical over biological evidence…
Error… Many contradictory studies
Error
RandomSystematic
False +ve~5%
False –ve~10 to 20%
Selection biasrecruitment %
Information bias
Accuracy of measures?
Unmeasured confoundingRCT? From literature?
Accounted for by 95% confidence interval and p-value
Not included in CI or p-value [Quantitative bias analysis]
Confounding…
Dental cariesCoronary Heart
Disease
Sugar consumption
Bradford-Hill Criteria
Strong association? Consistent? Does cause come
before effect? More
exposuremore disease?
RCT better than observational study
Makes sense
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.
HOW DOES SCIENCE GO WRONG?
Is the idea falsifiable?
How it works in theory…
IdeaGenerate
hypothesis
ExperimentTest
hypothesis
InterpretInferences from
experiment
New IdeaRefine
hypothesis
In reality…?
IdeaGenerate
hypothesis
ExperimentTest
hypothesis
InterpretInferences from
experiment
New IdeaRefine
hypothesis
NUTRITION IDEAS OVER THE LAST 100 YEARS…
Some history…
Museum photo…
Dairy photo
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.
THE ACCEPTED STORYBrain washing?
Nutrition to the rescue…
A – B = CA = Energy in (food)B = Energy out (burned, metabolism)C = Energy stored (as fat)
Cause↑A/↓B→↑C – obesigenic environment (↑energy in/ reduced energy out)
THE GOOD!What’s ok...
THE BADIt’s not OK... Ever!
http://longwhitekid.files.wordpress.com/2011/08/anchor-best-new-zealand-butter-380h-x-270w-heavy-card-21.jpg
Salt
WE ALL LIVED HAPPILY EVER AFTER?
Year
Ob
esi
ty p
reva
len
ce (
% >
= b
od
y m
ass
ind
ex
30
kg
/ m
2 )
10
20
30
1980 1990 2000
Australia Austria
1980 1990 2000
Belgium Canada
1980 1990 2000
Czech Republic Denmark
Finland France Germany Hungary Iceland
10
20
30
Ireland
10
20
30
Italy Japan Korea Luxembourg Mexico Netherlands
New Zealand Norway Poland Portugal Slovak Republic
10
20
30
Spain
10
20
30
Sweden
1980 1990 2000
Switzerland United Kingdom
1980 1990 2000
United States
AN ALTERNATIVE VIEW EMERGES…
My thoughts on obesity…
Medical trainingTraditional Nutritional theory - Energy density
Public HealthTobacco addiction
ResearchSimilarities between obesity and smoking
ResearchCritique of energy densityFocus on sugar
1994 2005 2007 2011
Why does a smoker smoke?
WithdrawalSymptoms Duration (weeks)
Irritability < 4
Depression < 4
Restlessness < 4
Poor concentration <2
Increased appetite >10
Craving to smoke >2
Automatic behaviour
Rational behaviour
Addiction Automatic,
withdrawal, harm
Automatic breathing
CortexMid brain/brain stem
Subconscious learning…
Withdrawaldiscomfort
Puffcigarette
WithdrawalreliefMore
puffs
Nicotine metabolised
How do cigarettes work...?
Nicotine delivery
Royal College of Physicians, Nicotine in Britain, 2000
FOOD ADDICTION?
Carbohydrate?
Eating and addiction? Atkins Diet An executive who had tried obesity surgery,
laxatives, diets, everything…
“Often I would shake until I could put some sugar in my mouth”
“I had an hour’s drive from my office to my home, and I knew every restaurant, candy machine and soft drink dispenser”
What about glucose? Is refined starch the same as nicotine? Are low GI foods the obese person’s
equivalent to a smoker’s nicotine patch or gum?
Bread: white v. wholegrain
Glucose: glycemic index?
What about sugar? Sugar is actually low/moderate GI
I TAKE A LOOK AT SUGAR?
The medical gurus say sugar is OK? “Excess sucrose has largely been
exonerated as an important dietary factor in the aetiology of type-2 diabetes...”
J. I. Mann and A. S. Truswell
Diseases of overnourished societies and the need for dietary change: in the Oxford 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 world's 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;55:173–201
Mente 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.
In the headlines…
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 was hiding 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 can't explain
the rise that we've seen over the last … 30 years of obesity.”
Prof. Boyd Swinburn, Professor of Population Health, Deakin University 13 Jan 2009
SO WHAT?
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)
More details
Thank you!
Slides and my articles are available at: www.slideshare.net/sithor