When meat is cooked at a high temperature or exposed to flame, it can produce chemicals that over time are dangerous to our health. These chemicals are Heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs).
What are HCAs and PAHs?
When amino acids, creatine and sugars come in contact with high temperatures, heterocyclic amines are formed [1,2].
Polycyclic aromatic hydrocarbons are produced when the fat from meat drips on to an open flame that then causes smoke. The smoke exposes the surface of the meat to PAHs, increasing its content . They are therefore also produced from smoking processes which is one reason why we are advised to keep smoked meats as sometimes food only.
What determines the production of HCAs and PAHs?
There are a number of factors that will influence the production of these chemicals. The below points all play a role in the formation of HCAs and PAHs:
- The duration of the cooking time and whether the meat is cooked to rare, medium or well done.
- Cooking temperature.
- Type of meat.
- Cooking method.
Those foods that are cooked at high temperatures or for a long time will produce more HCAs and PAHs e.g. well done meat and barbequed/ grilled meat have high amounts of HCAs . Any method that results in charring or that exposes meat to smoke will lead to the formation of PAHs.
Meat roasted or baked in the oven should contain significantly less HCAs than grilled, broiled or fried meat .
Do these chemicals really increase my risk of cancer? How?
Once these two chemicals are ingested, the body metabolises them using a process known as bioactivation that is driven by enzymes in our body . Experiments have shown HCAs and PAHs to be mutagenic, meaning they can cause changes to our DNA that can increase cancer risk . Only after undergoing this bioactivation process can the HCAs and PAHs cause damage to our DNA.
Studies have determined that the level of enzyme activity that is responsible for the bioactivation process differs between individuals. Meaning some people will have a higher enzyme activity than others and will therefore be more susceptible to DNA damage from HCAs and PAHs . This therefore determines the risk of cancer imposed by these chemicals .
The research behind the potential increase in cancer risk
Studies have been conducted using rodents and have shown a link between HCA and PAH ingestion and cancer development . A review of the research indicates that rats provided with a diet supplemented with HCAs went on to develop cancer in the breast, colon, prostate, liver, skin and other areas . The rodents who were supplemented with PAHs went on to develop tumours in their gastrointestinal tract, lungs and leukaemia .
It is, however, important to note that the rodents were fed intakes of HCAs and PAHs much higher than a human would consume . Unfortunately it is difficult to study the effects of these chemicals on humans. It is very hard to determine the level of HCAs and PAHs consumed by a person and also the activity of the enzymes that will metabolise them . Additionally, people can be exposed to PAHs from environmental sources such a tobacco smoke and pollution – this may also impact the results .
However, there have been a number of epidemiologic studies that have performed detailed dietary questionnaires to determine the participants meat intake and cooking process . This then provides an estimate of the level of HCA and PAH exposure. From these studies, there has been a link drawn between exposure to the two chemicals and an increased risk of prostate, breast, pancreatic, lung, oesophageal, stomach and colorectal cancer in humans [1, 3].
How to decrease the formation of HCA and PAH in your meat
There are steps you can take to help reduce the amount of HCAs and PAHs your meat will produce.
- Avoid exposing meat directly to a flame or a very hot cooking surface (as in pan frying).
- Avoid cooking meat for lengthy periods of time – particularly at a high temperature.
- Flip meat often when cooking at higher temperatures. This can actually reduce the production of HCAs substantially compared with letting it sit on one side for a prolonged amount of time before turning.
- Remove any areas of meat that have been charred.
- Do not make gravy and sauces using the meat drippings.
Contact us for results focused nutritional advice
This article was written by our dietitian Belinda Elwin who is a Dietitians Association of Australia member and Accredited Practising Dietitian and Nutritionist. If you have questions about healthy eating, make an appointment. We‘ll provide you with a simple and effective routine targeted to your concerns. Contact us today.