Burnt offerings
LIKE millions of others across America, your correspondent spent July 4th in the back garden burning meat—or, more precisely, trying hard not to do so. Ever since warnings were first raised back in the 1970s about certain forms of cancer being caused by heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs)—chemicals created when muscle meats such as beef, pork, fowl and fish are cooked at high temperature—he has remained leery about searing things on the grill.
In such circumstances, high temperature means anything above 300ºF (ie, 150ºC). That is barely warm in terms of modern outdoor grills, which can easily reach 700ºF or more if left unattended for a few minutes. At such temperatures, everything can quickly turn into a burnt offering. While the burnt parts of the meat are often the tastiest, they are not exactly the healthiest. With a growing brood of young bodies to feed, your correspondent decided this year to err on the side of caution, seeking to keep the burnt bits to a minimum. In short, to take the potential carcinogens off the menu.
No question that, in laboratory tests, numerous HCAs and PAHs have shown themselves to be mutagenic—ie, capable of altering the DNA in body cells in a way that increases the risk of cancer. Rodents fed diets containing supplements of both types of chemical developed tumours in various organs. However, on a weight-for-weight basis, the doses involved were thousands of times greater than the amount people could normally expect to digest.
That said, various epidemiological studies using questionnaires have shown associations between those who consume lots of fried or barbecued meat and incidences of cancer of the colon, pancreas, prostate and other organs. People who ate medium to well-done beef, for instance, were three times more likely to suffer from stomach cancer than others who ate rare or medium-rare meat. In another study, men who consumed a third of an ounce (ten grams) a day of well-done meat—whether crispy bacon, sausage, steak, pork or hamburger—had a 40% higher risk of prostate cancer.
Such epidemiological data provide evidence of a possible connection between HCAs and PAHs in food and cancer. But this evidence is not irrefutable. It could be that other carcinogens, such as the nitrites found in processed meats, play a significant role. Also, the free iron (ie, heme) in meat can produce dangerous free radicals capable of damaging cells. These, too, can lead to cancer. The fact is that researchers still cannot say for sure whether HCA and PAH compounds do, indeed, cause tumours in humans. In short, no smoking gun has yet been found.
Dietary recommendations issued jointly by the World Cancer Research Fund and the American Institute for Cancer Research in 2007 urged people to reduce their consumption of red meat and smoked foods generally, but said nothing about acceptable levels of HCAs and PAHs. There was nowhere near enough evidence, the report concluded, to link either chemical categorically to increased risk of cancer. To this day, there are no federal guidelines covering the consumption of food containing HCAs or PAHs.
In such circumstances, high temperature means anything above 300ºF (ie, 150ºC). That is barely warm in terms of modern outdoor grills, which can easily reach 700ºF or more if left unattended for a few minutes. At such temperatures, everything can quickly turn into a burnt offering. While the burnt parts of the meat are often the tastiest, they are not exactly the healthiest. With a growing brood of young bodies to feed, your correspondent decided this year to err on the side of caution, seeking to keep the burnt bits to a minimum. In short, to take the potential carcinogens off the menu.
No question that, in laboratory tests, numerous HCAs and PAHs have shown themselves to be mutagenic—ie, capable of altering the DNA in body cells in a way that increases the risk of cancer. Rodents fed diets containing supplements of both types of chemical developed tumours in various organs. However, on a weight-for-weight basis, the doses involved were thousands of times greater than the amount people could normally expect to digest.
That said, various epidemiological studies using questionnaires have shown associations between those who consume lots of fried or barbecued meat and incidences of cancer of the colon, pancreas, prostate and other organs. People who ate medium to well-done beef, for instance, were three times more likely to suffer from stomach cancer than others who ate rare or medium-rare meat. In another study, men who consumed a third of an ounce (ten grams) a day of well-done meat—whether crispy bacon, sausage, steak, pork or hamburger—had a 40% higher risk of prostate cancer.
Such epidemiological data provide evidence of a possible connection between HCAs and PAHs in food and cancer. But this evidence is not irrefutable. It could be that other carcinogens, such as the nitrites found in processed meats, play a significant role. Also, the free iron (ie, heme) in meat can produce dangerous free radicals capable of damaging cells. These, too, can lead to cancer. The fact is that researchers still cannot say for sure whether HCA and PAH compounds do, indeed, cause tumours in humans. In short, no smoking gun has yet been found.
Dietary recommendations issued jointly by the World Cancer Research Fund and the American Institute for Cancer Research in 2007 urged people to reduce their consumption of red meat and smoked foods generally, but said nothing about acceptable levels of HCAs and PAHs. There was nowhere near enough evidence, the report concluded, to link either chemical categorically to increased risk of cancer. To this day, there are no federal guidelines covering the consumption of food containing HCAs or PAHs.
But everything known about both sets of compounds suggests they are carcinogenic. HCAs are formed when amino acids (the building blocks of proteins) and sugars react at high temperature with an energy-boosting acid called creatine that is found in muscles. So far, some 17 different HCAs that have the potential to cause cancer in humans have been identified in cooked meat. One of them, harmane, is also a potent neurotoxin associated with “essential tremor”—a neurological disorder that is 20 times more prevalent than Parkinson’s disease. Essential tremor causes shaking of the arms, head, jaw and voice, generally in people over 65 years of age, though it strikes a significant number of others in their 40s.
By contrast, PAHs are widespread organic pollutants, produced when fuels such as oil, coal, tar or wood are burned. Carmakers go to great pains to remove them from vehicle exhausts. On the barbecue, PAHs are formed when fat and juices from the meat drip onto the red-hot coals or splash-plates, causing flames and smoke to engulf the meat. On contact, PAH compounds in the flames adhere to the surface of the meat. Using a smoker instead of a grill is no better. Smoked foods contain their share of PAHs as well.
The Environmental Protection Agency in the United States has classified seven PAH compounds as probable human carcinogens. One of them (benzo[a]pyrene) was the first chemical carcinogen ever discovered—in the smoke of cigarettes. Over the past four decades, its role in causing lung cancer has been all too graphically demonstrated.
Such a state of affairs is almost enough to put a person off his food. But not quite. There are plenty of sources of protein that do not naturally contain HCAs, nor produce them when cooked. Tofu is a good example; liver is another. But those hungering for red meat need not despair. Marinating beef in beer or red wine for six hours reduces the levels of two of the more worrisome HCAs by up to 90%. Want some burnt chicken? Soak the bird’s bits overnight in a marinade containing olive oil, lemon juice and garlic. Why this should reduce the HCA level in chicken is not entirely clear. By all accounts, though, it works a treat.
Your correspondent’s solution is first to tenderise and zap any bugs in the meat using a microwave oven, and then to steep it overnight in a marinade (this traditional Memphisrecipe is a good start). A couple of hours before eating, the marinated meat should be transferred to a roasting pan, covered with foil and placed at the cool end of a grill where the temperature is no higher than 220ºF. Basting with leftover marinade should be done every 20 minutes or so. Take the meat out of the pan when tender, place it on the hot end of the grill with the heat cranked up, and turn it every few minutes until brown.
Does such a rigmarole reduce the carcinogens in meat? Probably, but by how much is impossible to say. Does it affect the flavour? Indubitably. Though he missed sinking his teeth into the usual blackened bits during this year’s July 4th celebrations, your correspondent thought the procedure produced quite the juiciest chunk of meat he has tasted in many a month. As masters of outdoor grilling will always attest, low and slow is the way to go. It certainly adds to the flavour and may even make the food safer all round to eat. Even if it doesn't, it's worth the extra effort anyway.
By contrast, PAHs are widespread organic pollutants, produced when fuels such as oil, coal, tar or wood are burned. Carmakers go to great pains to remove them from vehicle exhausts. On the barbecue, PAHs are formed when fat and juices from the meat drip onto the red-hot coals or splash-plates, causing flames and smoke to engulf the meat. On contact, PAH compounds in the flames adhere to the surface of the meat. Using a smoker instead of a grill is no better. Smoked foods contain their share of PAHs as well.
The Environmental Protection Agency in the United States has classified seven PAH compounds as probable human carcinogens. One of them (benzo[a]pyrene) was the first chemical carcinogen ever discovered—in the smoke of cigarettes. Over the past four decades, its role in causing lung cancer has been all too graphically demonstrated.
Such a state of affairs is almost enough to put a person off his food. But not quite. There are plenty of sources of protein that do not naturally contain HCAs, nor produce them when cooked. Tofu is a good example; liver is another. But those hungering for red meat need not despair. Marinating beef in beer or red wine for six hours reduces the levels of two of the more worrisome HCAs by up to 90%. Want some burnt chicken? Soak the bird’s bits overnight in a marinade containing olive oil, lemon juice and garlic. Why this should reduce the HCA level in chicken is not entirely clear. By all accounts, though, it works a treat.
Your correspondent’s solution is first to tenderise and zap any bugs in the meat using a microwave oven, and then to steep it overnight in a marinade (this traditional Memphisrecipe is a good start). A couple of hours before eating, the marinated meat should be transferred to a roasting pan, covered with foil and placed at the cool end of a grill where the temperature is no higher than 220ºF. Basting with leftover marinade should be done every 20 minutes or so. Take the meat out of the pan when tender, place it on the hot end of the grill with the heat cranked up, and turn it every few minutes until brown.
Does such a rigmarole reduce the carcinogens in meat? Probably, but by how much is impossible to say. Does it affect the flavour? Indubitably. Though he missed sinking his teeth into the usual blackened bits during this year’s July 4th celebrations, your correspondent thought the procedure produced quite the juiciest chunk of meat he has tasted in many a month. As masters of outdoor grilling will always attest, low and slow is the way to go. It certainly adds to the flavour and may even make the food safer all round to eat. Even if it doesn't, it's worth the extra effort anyway.
No comments:
Post a Comment