Author: Nina Evans, Researcher & Trainer in Public Health/28 June 2018
As it’s that time of year again for al fresco dining, dodgy t-shirt tans, and ice-cream vans, it’s only right that this blog discusses some of the concerns with one of our British summer time traditions!
Our beloved barbecue; once a summer staple, now a cautioned cooking method. Barbecues have previously been tainted as they often involve cooking too much red and processed meat at high temperatures which causes the production of potentially harmful chemicals. Before we get too bogged down, there may still be some redeeming qualities; a barbecue does promote a few aspects of a Mediterranean dietary approach such as eating at the home, often outside, whilst socialising with family and friends. So what’s our standpoint?
NB This blog will not be covering the ethical/environmental impacts of consuming meat.
Red Meat Consumption
First off, let’s talk about the main food contender when it comes to barbecues – red meat. Several observational studies have shown that red and processed meat is associated with a greater risk of total, cardiovascular and cancer mortality . Many observational studies have associated a high intake of processed meat with an increased risk of a number of common cancers (with strong epidemiological evidence for colorectal), type 2 diabetes and coronary heart disease (CHD) [2-3]. It is worth bearing in mind that observational studies cannot provide a definitive answer as association cannot cause causation. Even so, does the problem just lie with the processed meats?
There is certainly more evidence suggesting processed meats are strongly associated with adverse effects on health. This is likely to be due to the processing means in production such as the addition of vegetable oils (which increase inflammation) and refined carbohydrates (which in isolation have an adverse effect on health). The evidence accumulating has us believing that less meat is probably better for our health (which is consistent with the Mediterranean dietary approach, which is widely considered to be healthy). Current guidelines do not advise to omit red meat as overall it is very nutritious and a good source of protein, vitamin B, iron, and zinc. Grass-fed beef is even more nutritious and contains plenty of omega-3 and higher amounts of vitamin A and E . Our government and the World Cancer Research Fund advises that people should eat no more than 500g of red meat a week (approximately 70g/day) . So, it’s important to distinguish between processed and unprocessed meat as well as grain or grass-fed, as there are vastly different effects between them.
Cooking at High Temperatures
Grilling is an extremely popular due to imparting (let’s face it) delicious flavour to basically anything; meat, fish, veggies, tofu! However, this method of cooking often leads to the production of potentially harmful chemicals. Heterocyclic amines (HCAs), polycyclic aromatic hydrocarbons (PAHs) and advanced glycation end-products (AGEs) are formed when muscle meat (beef, pork, fish, or poultry) is cooked at high temperatures, such as barbecuing. PAHs are formed when the fat from meat, when grilled, melts and drips onto the cooking surface and then rises up and is reabsorbed into the meat. At similarly high temperatures, HCAs are formed when amino acids, sugars, and creatine or creatinine react and new AGEs are created when a chemical reaction occurs between sugars and proteins or fats (diet is the biggest contributor of AGEs however, they can also be formed naturally in the body and are also present in uncooked animal-derived food) [6-7].
Animal models have shown that the restriction of dietary AGEs prevented vascular and kidney dysfunction, diabetes and improves insulin. Animal studies have also shown that exposure to HCAs and PAHs can cause various cancers (including breast, colon, lung, and leukaemia). However, HCA and PAH exposure from cooked meat in population studies have not established a definitive link between these chemicals and cancer in humans. The main limitation for this is the difficulty in determining the level of chemical exposure. Some epidemiological studies have found that high consumption of well-done barbecue meat was associated with colorectal, pancreatic and prostate cancer, whereas some have not. As for AGEs, high levels have been are associated with the majority of chronic diseases and conditions such as heart and liver disease, diabetes and Alzheimer’s. When AGEs have been restricted in diets in healthy participants and patients with diabetes and kidney disease, research has shown reduced markers of oxidative stress and inflammation [6-7]. Overall, cooking meat at high temperatures, especially when using methods which have direct contact with a flame, are thought to be contributing to potentially harmful chemicals like HCAs, PAHs, and AGEs. However, there doesn’t yet seem to be enough data to reach a conclusion as to if they’re carcinogenic. Even so, as well as considering the type of meat we’re eating, maybe we also need to consider the cooking method we use.
In comparison to their high-temperature counterparts (barbecuing, grilling and broiling), gentler cooking methods such as stewing, baking, steaming and boiling are an effective strategy to reduce HCA, PAH and AGE formation in foods.
Top Barbecuing Tips
But let’s say we are going to continue barbecuing through this long, hot (fingers crossed!) summer; here are some top tips to reduce the potentially harmful effects which may be associated with them:
* Keep cooking times short and remove meat from high heat before it becomes charred
* Eliminate/reduce processed red meats, such as sausages and opt for grass-fed unprocessed products
* Marinating meat products in olive oil, lemon juice, red wine or garlic can help reduce HCAs significantly
* Increase non-meat options on the grill (as vegetables do not create the same amount of these potentially harmful chemicals when burned) and accompany with a range of healthy salads
* Avoid drinking alcohol in excess & of course, keep topped up with sunscreen!
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- Wang, X., Lin, X., Ouyang, Y.Y., Liu, J., Zhao, G., Pan, A. and Hu, F.B. 2016. Red and processed meat consumption and mortality: dose-response meta-analysis of prospective cohort studies. Red and processed meat consumption and mortality: dose-response meta-analysis of prospective cohort studies. Public Health Nutrition. [Online]. 19(5), pp. 893-905. [Accessed 6 June 2018]. Available from: https://www.ncbi.nlm.nih.gov/pubmed/26143683
- Bouvard, V., Loomis, D., Guyton, K.Z., Grosse, Y., Ghissassi, F.E., Benbrahim-Tallaa, Guha, N., Mattock, H. and Straif, K. 2015. Carcinogenicity of consumption of red and processed meat. Lancet Oncology. [Online]. 16(16), pp. 1599-1600. [Accessed 6 June 2018]. Available from: https://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(15)00444-1/abstract
- Micha, R., Wallace, S.K and Mozaffarian, D. 2010. Red and processed meat consumption and risk of incident coronary heart disease, stroke, and diabetes: A systematic review and meta-analysis. Circulation. [Online]. 121(21), pp.2271-2283. [Accessed 6 June 2018]. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2885952/
- Daley, C.A., Abbott, A., Doyle, P.S., Nader, G.A. and Larson, S. 2010. A review of fatty acid profiles and antioxidant content in grass-fed and grain-fed beef. Nutrition Journal. [Online]. 9(10). [Accessed 6 June 2018]. Available from: https://www.ncbi.nlm.nih.gov/pubmed/20219103
- World Cancer Research Fund. [No date]. Limit consumption of red and processed meat. [Online]. [Accessed 7 June 2018]. Available from: https://www.wcrf-uk.org/uk/preventing-cancer/cancer-prevention-recommendations/limit-red-meat-and-avoid-processed-meat
- National Cancer Institute. 2017. Chemicals in meat cooked at high temperatures and cancer risk. [Online]. [Accessed 6 June 2018]. Available from: https://www.cancer.gov/about-cancer/causes-prevention/risk/diet/cooked-meats-fact-sheet
- Uribarri, J., Woodruff, S., Goodman, S., Cai, W., Chen, X., Pyzik, R., Yong, A., Striker, G. and Vlassara, H. 2013. Advanced glycation end products in food and a practical guide to their reduction in the diet. Journal of the American Dietetic Association. [Online]. 110(6). [Accessed 6 June]. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3704564/