Nutrition @ DEAKIN

“It’s not just what you eat, but how you cook it too”

Food Processing and Health

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Associate Professor Tim CroweSchool of Exercise and Nutrition Sciences

Deakin University

tim.crowe@deakin.edu.au@CroweTimwww.thinkingnutrition.com.au

Nutrition @ DEAKIN

Topics to be Covered

1. Inflammation: what is it and when can it be bad for us?

2. Update on trans fats3. Effect of heating on cooking oil4. Advanced glycation end-products (AGEs)5. Acrylamide production in baking6. Charring of food producing HCAs and PAHs7. Practice implications

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Nutrition @ DEAKIN

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 inducecontinued recruitment of monocytes from circulation

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The Inflammatory Process

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Source: http://iahealth.net/inflammation/

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Chronic Inflammation and Disease

• Impairs endothelial functionand vascular lining

• Increases platelet activationand 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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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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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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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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Trans Fats Partially Hydrogenated

Vegetable Oil (“PHVO”)=Hydrogen Vegetable Oil+

• 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

Up to 6 different trans fats produced in this process

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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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Trans Fats and CVD

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Mozaffarian D et al. Trans fatty acids and cardiovascular diseaseN Engl J Med 2006;354:1610-1613

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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/fast-food sales of foods with >0.5 g trans fat per serve

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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

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* 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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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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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 ‘usualculprits’

• HF tick foods (<0.2% TFA of fat for all productsexcept margarines and vegetable oils whichmust limit trans fat to <1% of total fat)

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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-rancidoil and/or high consumption

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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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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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Smoke Point of Oils

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Olive Oil (Extra Virgin) 191°COlive Oil (Virgin) 199°CCanola 204°COlive Oil, high quality (Extra Virgin) 207°CAlmond Oil 216°CGrapeseed Oil 216°CCoconut Oil 232°CPeanut Oil 232°CSunflower Oil 232°CPalm Oil 235°CSoybean Oil 238°COlive Oil (Extra Light) 242°CCanola Oil (high oleic acid) 246°CSafflower Oil 266°C

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Antioxidants and Oil Stability• PUFA content a major determinant of oxidation susceptibilityCanola 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 touse at least 10 times for both frying intervals

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* Önal B and Ergin G. Antioxidative effects of a-tocopherol and ascorbyl palmitateon thermal oxidation of canola oil. Nahrung 2002;46:420-426

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Choice Recommends

All-purpose oils• Grapeseed• SunflowerOils for stir-fry cooking• Peanut• MacadamiaOils for low heat cooking and salad dressings• Olive

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Choosing the right cooking oil - August 2010www.choice.com.au/reviews-and-tests/food-and-health/food-and-drink/groceries/cooking-oils.aspx

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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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NFκB: Nuclear factor kappa B – regulates inflammatory genesRAGE: Receptor for advanced glycation end productsROS: Reactive oxygen species

Source: http://www.bmb.leeds.ac.uk/teaching/icu3/lecture/26/

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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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Nutrition @ DEAKIN

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 pre-exposure 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 foodsUribarri J et al. J Am Diet Assoc 2010;110:911-916

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AGEs and Cooking Methods

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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

Marinated in Vinegar Marinated in Lemon Juice

1 = Raw beef2 = Roasted beef with no vinegar/lemon3 = Roasted beef after marinating with vinegar/lemon for 1 hour

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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)

27*Uribarri J et al. Diabetes Care 2011;34:1610-1616

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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 high-intake consumers*

• Few observational studies link it to ↑ cancer risk, with most showing a negative finding

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*www.who.int/foodsafety/chem/jecfa/summaries/summary_report_64_final.pdf

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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

29Spivey A. Environ Health Perspect 2010;118:A160–A167

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Ways to Decrease Acrylamide• ↓cooking time, blanching potatoes before frying, and post-

drying (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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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)

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*The Second Expert Report, Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective www.dietandcancerreport.org

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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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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 hyperplastic polyps Burnett-Hartman AN et al. Nutr Cancer 2011;63:583-592

3. EPIC study: HCA intake associated with 1.47 RR (1.13-1.93; 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

4. EPIC study also showed ↑ adenoma risk withconsumption of extremely browned meat

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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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Nutrition @ DEAKIN

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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