How the way food is processed and cook can alters its health affects on us.

1. Food Processing and Health
“It’s not just what you eat, but how you
cook it too”
Associate Professor Tim Crowe
School of Exercise and Nutrition Sciences
Deakin University
tim.crowe@deakin.edu.au
@CroweTim
www.thinkingnutrition.com.au
Nutrition @ DEAKIN
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2. Topics to be Covered
1. Inflammation: what is it and when can it be
bad for us?
2. Update on trans fats
3. Effect of heating on cooking oil
4. Advanced glycation end-products (AGEs)
5. Acrylamide production in baking
6. Charring of food producing HCAs and PAHs
7. Practice implications
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3. What is Inflammation?
• Body's normal response to protect against infection,
injury, or disease
• Involves activation of monocytes, neutrophils, and
lymphocytes and the release of inflammatory mediators
• Without inflammation, wounds and infections would never heal
• Acute inflammation: Initial response to harmful stimuli and involves
↑movement of leukocytes to the injured tissues
• Chronic inflammation: Leads to a progressive shift in the type of
leukocyte cells present at site of inflammation, particularly the
presence of macrophages
• Macrophages: secrete coagulation factors, reactive O2 species,
cytokines, growth factors, nitric oxide and also induce
continued recruitment of monocytes from circulation
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4. The Inflammatory Process
Source: http://iahealth.net/inflammation/
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5. Chronic Inflammation and Disease
• Impairs endothelial function
and vascular lining
• Increases platelet activation
and clotting
• Depletes intrinsic antioxidants
• Generates free radicals and amplifies oxidative stress
• Delays wound healing and tissue regeneration
• Promotes cell aging and premature cell death
• Suppresses or amplifies immune responses
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6. Causes of Chronic Inflammation
Unlike acute inflammation showing redness, swelling and pain,
chronic inflammation can be invisible
Causes
• Autoimmune diseases e.g. such as rheumatoid arthritis, lupus
• Infectious agents e.g. H. pylori, viruses
• Atherosclerosis
• Environmental e.g. smoking
• Allergens
• Central adiposity: more macrophages localised in fat will
thus produce more inflammatory mediators
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7. Treating Inflammation
•Exercise: Negative association between PA and
CRP
•Weight loss: ↓ body fat means reducing the
‘inflammatory factories’ being the fat cells
•↑fruit, vegetables, fish, olive oil
•↑fibre (inversely associated with CRP)
•↓ trans and saturated fats
•Moderate alcohol
•Quitting smoking
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8. Trans Fats
• Unsaturated fat that behaves like a saturated fat
because of its chemical structure
• Occurs in nature (e.g. CLA in dairy), but in small
amounts. Most come from hydrogenation
• Intermediate melting temp and shelf stability makes
them desirable (texture and mouthfeel) for use in food
industry
• Recommended to be <1% of EI
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9. Trans Fats
Hydrogen + Vegetable Oil
=
Partially Hydrogenated
Vegetable Oil (“PHVO”)
Up to 6 different trans fats produced in this process
•
•
Straight molecules (trans fat)
can pack more closely
against one another (like
saturated fat), making the
substance more solid and
stable
Adding hydrogen also
prevents the oil from
becoming rancid as quickly
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10. Trans Fats and CVD
• ↑ LDL, VLDL, TG and ↓HDL and LDL particle size
• ↑ inflammation via CRP, TNF-α and IL-6
• Inhibition of FA incorporation into cell membranes
(affecting fluidity and signalling)
• Interfere with elongation and saturation of FAs
• Linked with IR, visceral adiposity and development of
T2DM
• 2%↑ in EI from trans fats = 23%↑ in CVD risk
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11. Trans Fats and CVD
Mozaffarian D et al. Trans fatty acids and cardiovascular disease
N Engl J Med 2006;354:1610-1613
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12. Regulation of Trans Fats: International
• Denmark (2003) and Switzerland (2008) banned the
sale of foods in which trans fat is more than 2% of
total fat content
• US (2008) requires listing of trans fats on label (<0.5 g
can be labelled as ‘trans free’)
• New York and Philadelphia banned restaurant/fastfood sales of foods with >0.5 g trans fat per serve
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13. Regulation of Trans Fats: Australia
• FSANZ not in favour of requiring trans fats to be labelled as believes will
•
•
•
•
have a small effect on consumption
FSANZ dietary modelling estimates intake at 0.5% of EI with 90% of
Australians having trans fat intake <1% EI/day* (WHO recommends trans fats
contribute < 1% of daily EI)
Around 60% to 75% of TFA intake is derived from ruminant foods
FSANZ (2009) reviewed the outcome of non-regulatory measures to reduce
TFAs in the food supply and found intakes of TFAs from manufactured
sources ↓ by around 25 to 45 percent since 2007*
For Australians with total TFA intake >1% of EI: pastry products, sausages
and luncheon meats, and creamy style pasta dishes contributed
disproportionally to high TFA intakes
* Intakes
of Trans Fatty Acids in New Zealand and Australia. Review Report – 2009
www.foodstandards.gov.au/_srcfiles/TFAs_intakes_2009.pdf
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14. Trans Fat Intake: Aus vs US
• Australia: 0.5% of EI as TFA (majority from ruminant sources)
• US: 2.6% of EI as TFA (80% from PHVO and 20% from ruminant
sources)
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15. Reducing Trans Fats in the Diet
• Read labels: the amount of trans fat in a food must be
declared if a nutrition claim is made about cholesterol,
saturated or unsaturated fat, or trans fatty acids
• Choose margarines that have
<1% trans fatty acids
• Reducing intake of the ‘usual
culprits’
• HF tick foods (<0.2% TFA of fat for all products
except margarines and vegetable oils which
must limit trans fat to <1% of total fat)
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16. Behaviour of Oil during Cooking
• Prolonged oil use causes polymerisation reactions, which
cause foaming and ↑ viscosity, ↓quality of foods, and
↑susceptibility of oil to oxidation
• Various compounds produced from oil during frying:
• Aldehydes and ketones
• Hydrocarbons
• Lactones and alcohols
• Oxidised sterols
• Peroxidised fatty acids
• Free radicals
• Health effects unlikely except for when using near-rancid
oil and/or high consumption
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17. Smoke Point
• Temperature at which a cooking fat or oil begins to
break down and give off smoke
• At this point, deterioration of flavour and nutritional
quality begins and the oil is more prone to bursting
into flame (i.e. its flash point)
• Not only is the smoke dangerous, but the materials
that remain in the liquid start to affect the flavour of
the food being cooked
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18. Smoke Point
•Smoke point determines what the oil can be
used for, dictating the maximum useable
temperature of the oil
•A high smoke point is ideal for deep-fat frying
•Oil which has oxidised because of exposure to
air, heat and light will have a lower smoke point
•Using oil repeatedly will also make it smoke
sooner from ↓ smoke point
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19. Smoke Point of Oils
Olive Oil (Extra Virgin)
191°C
Olive Oil (Virgin)
199°C
Canola
204°C
Olive Oil, high quality (Extra Virgin)
207°C
Almond Oil
216°C
Grapeseed Oil
216°C
Coconut Oil
232°C
Peanut Oil
232°C
Sunflower Oil
232°C
Palm Oil
235°C
Soybean Oil
238°C
Olive Oil (Extra Light)
242°C
Canola Oil (high oleic acid)
246°C
Safflower Oil
266°C
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20. Antioxidants and Oil Stability
• PUFA content a major determinant of oxidation susceptibility
Canola as an Example
• Canola oil ± vitamins C and E used for deep-fat frying potatoes
once per day for 10 days or once per week for 10 weeks*
• Smoke point ↓ over 10 fryings (17% in control and 9% in
antioxidant supplemented)
• Canola oil without antioxidants found to safe to use 8 times on
a daily basis, or 7 times on a once-weekly basis
• Canola oil with antioxidants, smoke point did not decrease
below 170°C in both daily and weekly fryings and safe to
use at least 10 times for both frying intervals
* Önal
B and Ergin G. Antioxidative effects of a-tocopherol and ascorbyl palmitate
on thermal oxidation of canola oil. Nahrung 2002;46:420-426
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21. Choice Recommends
Choosing the right cooking oil - August 2010
www.choice.com.au/reviews-and-tests/food-and-health/food-and-drink/groceries/cooking-oils.aspx
All-purpose oils
• Grapeseed
• Sunflower
Oils for stir-fry cooking
• Peanut
• Macadamia
Oils for low heat cooking and salad dressings
• Olive
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22. Advanced Glycation End-Products (AGEs)
• Arise exogenously by heating food, or endogenously through
normal metabolism and aging
• Formed from non-enzymatic reaction of reducing sugars with
free amino groups of proteins, lipids, and nucleic acids (Maillard
reaction – leads to browning)
• Oxidative stress due to hyperglycaemia can ↑ AGE formation
• Pathological effects of AGEs related to ability to promote
oxidative stress and inflammation
• ↑ vascular permeability, inhibition of vascular dilation, and
oxidised LDL linked to causative role in the vascular
complications of diabetes
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23. NFκB: Nuclear factor kappa B – regulates inflammatory genes
RAGE: Receptor for advanced glycation end products
ROS: Reactive oxygen species
Source: http://www.bmb.leeds.ac.uk/teaching/icu3/lecture/26/
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24. Diet and AGEs
• Heating (grilling, frying, roasting) has a significant
accelerating effect in generation of AGEs in food
processing
• ∼10% of ingested AGEs is absorbed with food
• Animals studies show relationship between high dietary
AGE intake and oxidative stress, IR, T2DM and
development of complications (vascular and renal)
• Restriction of dietary AGEs in animals associated with a
significant ↓ in circulating levels of vascular disease
markers (e.g., adhesion molecules) as well as of
inflammatory mediators
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25. AGE Content of Foods
• Beef, poultry, fish and eggs high in AGEs
when cooked in a similar way
• High-fat cheese can be a significant source
(from pasteurisation and long holding times at room temp) as
too snack foods (chips, biscuits)
• Short heating time, low temperature, high moisture, and preexposure to acidified environment can limit AGE formation
• Grains, legumes, breads, F&V, and milk lowest sources unless
prepared with added fat
Detailed listed of AGE content of foods
Uribarri J et al. J Am Diet Assoc 2010;110:911-916
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26. AGEs and Cooking Methods
Marinated in Vinegar
Marinated in Lemon Juice
1 = Raw beef
2 = Roasted beef with no
vinegar/lemon
3 = Roasted beef after
marinating with
vinegar/lemon for 1 hour
Beef (25 g) roasted for 15 minutes at 150°C with or without pre-marinating
in 10 mL vinegar (A) or lemon juice (B) for 1 hour
*Significant changes compared to the raw state (P<0.05)
#Significant changes compared to cooked without marinating samples.
Uribarri J et al. J Am Diet Assoc 2010;110:911-916
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27. Low AGE Diet
• 36 subjects (18 healthy and 18 T2DM) randomised to ‘normal’
diet or isocaloric low-AGE diet (↓50%; boil, stew, steam food
instead of frying, baking, grilling) for 4 months*
• No significant changes in metabolic markers on ‘normal’ diet
for healthy controls or T2DM (apart from effects normal for an
ongoing high AGE diet)
On low AGE diet for T2DM patients:
– Insulin, HOMA, leptin, TNF-α, NF-κB, and serum AGEs all ↓
– ↑ AGER1 (AGE receptor; negative regulator of AGE action), SIRT1
(modulator of insulin action) and adiponectin (↑ insulin sensitivity)
On low AGE diet for healthy controls:
– ↓ seen only in serum AGEs and isoprostanes (inflammatory
eicosanoid-like substances)
*Uribarri
J et al. Diabetes Care 2011;34:1610-1616
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28. Acrylamide
• Found in plant-based baked starchy foods (potato chips,
biscuits, breakfast cereals, toasted bread, coffee)
• Not typically found in meat, dairy or seafood
• Arises from reaction b/w reducing sugars and AAs at high temp
(Maillard reaction) - not found in food prepared below 120°C
• Debate over current exposure levels being of significance c.f.
cancer effects seen in animals (typically 300 to 1000-times
greater exposure dose) though concern expressed for highintake consumers*
• Few observational studies link it to ↑ cancer risk, with most
showing a negative finding
*www.who.int/foodsafety/chem/jecfa/summaries/summary_report_64_final.pdf
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29. Acrylamide
• International Agency for Research
on Cancer (IARC) classifies
acrylamide as "probably
carcinogenic to humans" on basis
of evidence from animal studies
• Food exposure levels higher than
that expected to occur as a result
of contact between food and food
packaging or use of cosmetics
Spivey A. Environ Health Perspect 2010;118:A160–A167
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30. Ways to Decrease Acrylamide
• ↓cooking time, blanching potatoes before frying, and postdrying (drying in a hot air oven after frying) can ↓acrylamide
content of some foods
• Soaking raw potato slices in water for 15-30 minutes before
frying or roasting helps ↓ acrylamide formation during cooking
• Cooking potato chips to a light golden colour and using
maximum temperatures of 175°C when deep-frying and 230°C
when baking
• Toast to lightest acceptable colour
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31. Red Meat and Colorectal Cancer
• ↑ risk estimates in the range of 20 to 50% for highest vs
lowest intakes of red meat in prospective studies
• World Cancer Research Fund 2007 report* rates the evidence
as ‘Convincing’
• Not clear whether it’s the intake of red meat (?excess haem
Fe), form of meat (esp. processed), high fat diets, formation of
nitrosamines, or the way meat is cooked
• Cooking (charring) of meat produces two types of carcinogens
– Polycyclic aromatic hydrocarbons (PAHs)
– Heterocyclic amines (HCAs)
*The
Second Expert Report, Food, Nutrition, Physical Activity, and the Prevention of Cancer: a
Global Perspective www.dietandcancerreport.org
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32. HCAs and PAHs
• Heterocyclic amines (HCAs): formed at high temps (and long
cooking times) from reaction of creatine or creatinine, AAs, and
sugar
• Found in fried, grilled and BBQ meat, poultry and fish
• Potent mammary, lung, colon, stomach and prostate mutagens
in animal models (at very high doses of HCAs though)
• Polycyclic aromatic hydrocarbons (PAHs): produced from
incomplete combustion of organic compounds
• Formed in cooking and smoking of meat
• Flames from grilling over fire contain PAHs that can adhere
to the surface of meat
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33. Recent Evidence for Charring
1. Case control: 50% ↑prostate cancer risk with ≥1
serve/wk of grilled or well-done meat John EM et al. Nutr Cancer
2011;63:525-537
2. Case control: >3 serves/wk charred meat doubled risk of
3.
4.
hyperplastic polyps Burnett-Hartman AN et al. Nutr Cancer 2011;63:583-592
EPIC study: HCA intake associated with 1.47 RR (1.131.93; P=0.002) for colorectal adenoma for highest vs
lowest quartiles of intake Rohrmann S et al. Am J Clin Nutr 2009;89:1418-1424
EPIC study also showed ↑ adenoma risk with
consumption of extremely browned meat
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34. Reducing HCA and PAH Exposure
• Avoid direct exposure of meat to an open flame or a hot metal
surface and avoid prolonged cooking times (especially at high
temperatures)
• Marinating can reduce HCA formation by 90%
• Remove any blackened areas before eating
• Clean grill well between uses (scrub off
blackened parts)
• Continuously turning meat over on a high
heat source can substantially ↓ HCA formation
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35. Putting it into Practice
•Diet high in F&V, grains, and quality healthy oils
•Low in processed foods especially deep-fried
take-away, and baked CHO foods
•Combined with choosing lower-temperature
cooking methods will decrease trans fats, AGEs,
HCAs, PAH, and acrylamide intake
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