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Although there’s growing evidence linking red meat consumption with increased risk of death from cancer and cardiovascular disease, the research results aren’t entirely consistent and differ across populations. “The association between unprocessed red meat and mortality risk is more pronounced in studies conducted in the United States compared with studies conducted in Europe or Asia,” says Frank Hu, MD, PhD, MPH, an epidemiologist at Harvard T.H. Chan School of Public Health in Boston. Hu suggests this might be because Europeans don’t grill as often as Americans, and Asians eat less red meat. Other experts also have suggested that this discrepancy might be due to differences in Western dietary and lifestyle patterns. One of the most recent strikes against red meat, especially processed red meat, came in an October news report from the International Agency for Research on Cancer (IARC), an independent agency of the World Health Organization (WHO). The report said that processed red meat was “carcinogenic to humans” and fresh red meat was “probably carcinogenic.” The statements were based on an expert review of the science that was summarized in Lancet Oncology.
A few days later, after a whirlwind of confusing media reports, the WHO released a statement clarifying that the IARC’s recent review confirmed the WHO’s older 2002 recommendation to moderate consumption of processed meat to reduce the risk of cancer. It went on to say that the IARC review “does not ask people to stop eating processed meats but indicates that reducing consumption of these products can reduce the risk of colorectal cancer.” No mention was made of fresh red meat. Not surprisingly, dietitians are left to help put the news into perspective.
The Healthy Eating Plate from Harvard T.H. Chan School of Public Health recommends that people “limit red meat, and avoid processed meats such as bacon and sausage.” Advice from the American Institute for Cancer Research is similar and goes a bit further, suggesting that to reduce cancer risk, people should “eat no more than 18 oz (cooked weight) per week of red meat,” while completely avoiding processed meat.
Understanding Observational Studies
The majority of the research on red meat and chronic disease risk is epidemiologic or observational in nature. Observational data have limitations, says Wayne Campbell, PhD, a member of the 2015 Dietary Guidelines Advisory Committee; a professor in the department of nutrition science at Purdue University in West Lafayette, Indiana; and a recipient of research funding from the National Pork Board and the Beef Checkoff, a marketing and research program designed to increase domestic and international demand for beef. “One limitation is that they do not provide cause and effect relationships.” A causal relationship generally is more likely when the association is strong, especially with a relative risk (RR) above 2, and when it’s clear that risk increases as the dose increases, and results are consistent across studies.4
Thus, dose-response evaluations can add clarity. For example, in a July 2015 meta-analysis of red and processed meat consumption and mortality that was published in Public Health Nutrition, Hu and colleagues found that compared with those who consumed no or very little processed meat, RR was 1.11 for one serving per day of processed meat; 1.19 for two servings; 1.27 for three servings; and 1.35 for four servings per day for all-cause mortality.
Another limitation of some epidemiologic research, including some studies evaluated by the IARC, is the practice of transforming servings of red meat into grams, says Dominik Alexander, PhD, MSPH, principal epidemiologist at EpidStat Institute in Ann Arbor, Michigan, and a recipient of research funding from the Beef Checkoff. “Doing that makes an assumption that if someone reports a serving of red meat that it equates to a certain gram amount, but we know there’s variability in portion sizes of meat that people report eating,” he says. Hu and his colleagues acknowledged that a limitation of their recent meta-analysis was the fact that serving sizes of red and processed meat weren’t specified in four of the nine studies included in their analysis, therefore requiring them to assume all servings were 100 g in size for total and unprocessed red meat and 50 g for processed meat.
Red Meat and the Heart
Red meat frequently is flagged as a concern for heart health, but not all studies agree. A 2015 systematic literature review of 11 epidemiologic studies, published in Meat Science, found that a larger intake of red meat was a significant risk factor for coronary artery disease (CAD) in four studies, but no significant association was found in five other studies. Processed red meat generally was associated with an even greater risk of CAD than unprocessed red meat. Similarly, a recent epidemiologic study of red meat consumption and heart failure published in the International Journal of Cardiology found that processed, but not unprocessed, red meat consumption was associated with an increased risk of heart failure.
An aspect of red meat consumption that likely impacts such study results is the difference between lean and fatty cuts. “Our research shows that reasonable amounts of lean beef can be included in a heart-healthy diet, and it can elicit favorable effects on key endpoints that define metabolic syndrome and coronary heart disease,” says Penny Kris-Etherton, PhD, RD, a professor of nutrition at the Pennsylvania State University in University Park, and a recipient of research funding from the Beef Checkoff.
Specifically, Kris-Etherton and her colleagues found that adults with elevated cholesterol who ate lean beef daily (up to 5.4 oz) but restricted saturated fat intake to less than 7% of total calories as part of a heart-healthy diet, had significant decreases in total cholesterol and LDL cholesterol compared with those who ate a diet that contained minimal red meat but 12% of total calories from saturated fat.
Red Meat and Cancer
Research evidence linking red meat, especially processed red meat, with cancer risk generally has been more consistent. Hu’s 2015 meta-analysis published in Public Health Nutrition (described earlier), found that each daily increase in processed red meat servings was associated with a 1.08 increased summary RR of cancer mortality.
Similarly, just months before the IARC report made headlines, Alexander and colleagues published a meta-analysis on red meat intake and colorectal cancer, which reviewed 27 independent studies, and found a slightly increased summary RR of 1.10 for those consuming higher amounts of red meat vs lower amounts. However, when they omitted studies that included processed meat items, the RR dropped to 1.05, which was not statistically significant. “We found no increased colorectal cancer risk with up to 100 g [about 3.5 oz] per day of red meat intake when it’s primarily unprocessed red meat,” Alexander says. And like Hu’s study, Alexander’s team found stronger associations between red meat and cancer risk in studies conducted in North America compared with studies published in other countries.
Hu says one challenge in evaluating red meat research is that the number of studies on unprocessed red meat is relatively small. Research tends to focus more on total meat intake and processed meat. “The evidence is pretty strong and consistent that higher consumption of processed red meat, such as bacon, sausage, and hot dogs, is associated with increased total and cardiovascular and cancer mortality,” Hu says.
As both Hu’s and Alexander’s studies also showed, meta-analysis study results can be skewed by unmeasured factors. “It is difficult to disentangle red meat from other factors that we know contribute to risk of disease, such as cancer, and these include BMI, level of physical activity, fiber intake, and other dietary factors,” Alexander says. Although papers on observational studies, such as those used to assess the link between red meat and cancer risk, may say they control for such factors, Alexander explains that you can only control for what you have information on. “For example, if there isn’t a question that asks study participants about calcium intake, and we think that calcium may be important in preventing colorectal cancer, then we’re not controlling or adjusting for that factor.”
In evaluating cancer risk of red meat intake, what cannot be overlooked is how the meat is prepared. In a 2015 study of meat intake, preparation methods, and colorectal cancer risk published in Cancer Medicine, scientists found no evidence of an association between total unprocessed red meat or total processed meat and colorectal cancer risk. However, what they did find was a positive association with colorectal cancer risk when beefsteak was pan-fried.
“When meat is cooked at high temperatures—such as [in] grilling, oven broiling, pan frying, or deep-fat frying—it leads to a Maillard reaction between different compounds in meat, namely amino acids, sugars, and creatine (a substance in muscle tissue), forming carcinogens called heterocyclic amines (HCAs),” says Mariana Stern, PhD, a coauthor of the Cancer Medicine study and a cancer epidemiologist and associate professor at the University of Southern California in Los Angeles, who also served on the IARC working group that reviewed carcinogenicity of red and processed meat. “Pan-frying leads to the highest accumulation of HCAs,” she says, based on her 2015 study in Cancer Medicine.
The other type of carcinogen that can form during meat preparation is polycyclic aromatic hydrocarbons (PAHs). These are formed when fat and juices from meat drip onto the fire of a grill, causing flames. The PAHs in the flames then stick to the surface of the meat. PAHs also can form during smoking of meats. Thus, PAHs can contribute to the carcinogenicity of some processed meats, too.
This doesn’t necessarily mean a person can’t ever eat grilled steak. Avoiding charring is an important health-protective step, as is eating meat as part of an antioxidant-rich, plant-based diet. Results from the 2009 European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford) suggest that if moderate meat eaters (those whose consumption averages 3 oz per day) consume enough fruits and vegetables, their death rates may be similar to vegetarians, says David Klurfeld, PhD, national program leader for human nutrition at the USDA Agricultural Research Service in Beltsville, Maryland.
Factors associated with meat processing also are key considerations. “Processed meats typically are mixtures of fat tissue and protein (muscle tissue) manufactured by human hands,” says Loren Cordain, PhD, professor emeritus in the department of health and exercise science at Colorado State University in Fort Collins and renowned for his research and books on the Paleo Diet.
“These processed meats contain arbitrarily high concentrations of adipose (fat) tissue and low concentrations of muscle tissue,” Cordain says. “Accordingly, because adipose tissue retains much lower concentrations of vitamins and minerals than muscle tissue, these manmade meat concoctions contain significantly lower concentrations of essential vitamins and minerals than either nonprocessed fresh meat or their wild counterparts. More importantly, almost all processed meats are manufactured with added salt in large concentrations that never could be achieved in fresh meats. High dietary salt concentrations in almost all foods are associated with increased risk of gastrointestinal cancers (mouth, throat, esophagus, stomach, and colon), along with increased risk of cardiovascular disease.”
The WHO includes hot dogs, ham, sausages, corned beef, beef jerky, and canned meat among its examples of processed meats. When meat is processed by curing and/or smoking, carcinogenic compounds called N-nitroso compounds (NOCs) are formed, Stern says. “NOCs are present whether you buy nitrate-cured meat or natural meat cured with celery extract, which also contributes nitrates involved in the formation of NOCs.”
Because NOCs are carcinogenic, meat producers haven’t ignored the concern surrounding processed meat. “In the 1980s, after it was discovered that there were high levels of nitrites in bacon and processed meats, manufacturers reduced the amounts of nitrites and added antioxidants, such as ascorbate (vitamin C) and erythorbate, to help protect against the formation of NOCs,” Klurfeld says.17 “So, from a health perspective, the processed meats we eat today are much less of a cancer concern than they were 40 years ago.”
According to the USDA Food Patterns depicted in MyPlate, adult men and women are advised to consume 5- to 6.5-oz equivalents of protein foods daily, with specific amounts varying based on a person’s age, gender, and level of physical activity. MyPlate guidelines further clarify that a 1-oz equivalent of protein includes 1 oz of cooked lean beef, pork, poultry, or seafood; 1 egg; 1/2 oz of nuts or seeds, or one tablespoon of nut butter; or 1/4 cup of cooked beans or roasted soybeans. In comparing this with actual protein intake, the Scientific Report of the 2015 Dietary Guidelines Advisory Committee stated that across all age groups (including males and females), nearly 60% of Americans meet intake recommendations for protein foods, which includes all of the protein sources just listed. However, protein also comes from dairy and grains, in addition to foods in the USDA MyPlate protein group, in which case protein intake in terms of grams per day is considered adequate in Americans.
However, getting enough protein can be challenging for certain groups. “As people age into their 50s, 60s, 70s, and beyond, they progressively need less energy in order to meet their needs and avoid weight gain,” Campbell says. “So if you just cut back on the amount of food you usually consume, you’re going to be eating less protein.” Campbell participated in a recent scientific protein summit convened in Washington, D.C., which concluded that consuming adequate protein (up to twice the Recommended Dietary Allowance [RDA]) may help slow the progressive loss of muscle mass that occurs in aging. “Another age group that may fall short on protein is people on highly restrictive diets, such as teenage girls and young women attempting to avoid weight gain,” Campbell says.
The RDA for protein set by the Institute of Medicine is 0.8 g of protein per kilogram of body weight. “That is the low threshold of what people are recommended to consume,” Campbell says. “Consuming protein in the range of 1 to 1.4 g of protein per kilogram of [body] weight will increase the rate at which your body forms protein in muscles, if you’re physically active. There also may be some benefit to consuming those higher amounts of protein if you’re on an energy-controlled or weight loss diet, in which case it can help you retain lean body mass.”
Another aspect of protein intake that’s receiving increased attention is when to consume protein. “There’s a lot of compelling research about spreading protein intake throughout the day, so you get about 25 to 30 g of protein per meal, rather than eating the majority in the evening at dinnertime,” says Melissa Joy Dobbins, MS, RDN, CDE, owner of Sound Bites, Inc, in Chicago, and a member of the Beef Expert Bureau for the National Cattlemen’s Beef Association. “Protein is the most satiating macronutrient, and research suggests it’s helpful for weight control,” Dobbins says. This protein should come from a balanced variety of lean or low-fat animal foods (if desired) and minimally processed plant foods. Certain plant foods can make a substantial contribution to protein intake. Notably, 3 oz of cooked tempeh has 16 g of protein, and 1 cup of cooked quinoa has 8 g of protein.
While many worry about the health impact of eating red meat, some people choose to reduce consumption based on concern for the planet. According to the Environmental Working Group, beef has the highest carbon footprint compared with poultry, fish, and plant foods. “The top environmental concerns with red meat production are greenhouse gas emissions, water and land use, fertilizers, and antibiotic use,” says Roni Neff, PhD, MS, an assistant professor of environmental health sciences at Johns Hopkins Bloomberg School of Public Health in Baltimore, and a program director at the Johns Hopkins Center for a Livable Future. Neff explains how the following concerns pertain to red meat production:
- Greenhouse gas emissions: “Greenhouse gases are particularly of concern with ruminants, such as beef and lamb, which belch methane—that’s a powerful greenhouse gas, many times more powerful than carbon dioxide,” Neff says. “Ruminant belching is actually the top source of livestock greenhouse gas emissions.”
- Water use: “We’re using water at unsustainable levels,” Neff says. “The biggest use is to irrigate crops used for animal feed.”
- Fertilizers and land use: “These are required to produce animal feed in today’s industrial system,” Neff says. “To produce the fertilizer, we’re using nitrogen and phosphorus at unsustainable levels.”
- Antibiotic use: Neff says up to 80% of the antibiotics used in the United States are going into animal feed. “Pork producers, for example, have found that by administering small, subtherapeutic doses of antibiotics to hogs in their feed, the animals are able to grow larger, faster,” Neff says. “One of the problems with this practice is that it leaves behind the resistant bacteria, which can breed and spread antibiotic-resistant infections. These infections can then spread from the animals, to the farm workers, to the communities nearby, and then into the broader population.”
“There’s so much prejudice now against red meat,” Kris-Etherton says. “Are we prepared to tell people to totally give up red meat? I’m a little nervous about that because, first of all, I believe you can have a healthful diet that includes small amounts of lean beef as part of a healthful dietary pattern that’s high in protective, antioxidant-rich foods, such as vegetables, fruits, whole grains, and nuts. Secondly, I’m really afraid of the unintended consequences of suddenly eliminating all red meat from the diet. Try to be really wise in translating the latest research. If it’s decided to eliminate beef or red meat, make sure the diet is implemented healthfully so that it meets all nutrient recommendations.”
Hu clarifies that recommendations to cut back on red meat doesn’t mean everyone needs to become vegetarian or vegan. “Just move meat from the center of the plate to the side of the plate so meat isn’t the primary source of calories or macronutrients,” he says. “We can still have a moderate amount of meat as part of an overall healthful dietary pattern. But, we should minimize the consumption of processed meat, such as hot dogs, bacon, and sausage.”
From an environmental perspective, Neff says the rate at which we’re eating meat can’t continue. “We need to dramatically reduce the amount of beef that we’re eating, and dietitians can play a really important role in shifting these norms to help people eat a diet that’s both healthier for them and more sustainable for the planet,” Neff says. “Dietitians can position this as a real positive in terms of the variety and great taste of other foods that people can include more often in place of meat.” RDs can tell clients and patients that while red meat contains protein and other nutrients and can be part of a healthful diet, they should reduce consumption in favor of protein-rich plant foods to promote overall health and preserve the health of the planet.
Tips on Eating Red Meat
- The more common red meats include beef, veal, bison, pork, lamb, mutton, horse, and goat.
- Moderation. “According to eating patterns recommended by the USDA, people can healthfully include 1.8 oz, so about 2 oz, of red meat a day,” says Penny Kris-Etherton, PhD, RD, a professor of nutrition at the Pennsylvania State University in University Park, and a recipient of research funding from the Beef Checkoff. The American Institute for Cancer Research recommends no more than 18 oz (cooked weight) per week of red meats.
- Choose lean cuts. “Loin” and “round” are key words to remember when shopping for lean cuts of meat. “Ask the butcher to recommend a lean cut, and then ask about the best way to prepare it so it will stay moist and juicy,” says Melissa Joy Dobbins, MS, RDN, CDE, owner of Sound Bites, Inc, in Chicago, and a member of the Beef Expert Bureau for the National Cattlemen’s Beef Association.
- Emphasize variety. “Get a variety of protein sources, including lean red meat, poultry, seafood, low-fat dairy products, beans, peas, nuts, and nut butters, mainly because they provide different nutrients,” Kris-Etherton says.
- Swap higher fat for lean. “People can use lean red meat instead of the fatty red meat they might normally use in burgers, meatloaf, meatballs, pizza, tacos, burritos, chili, lasagna, and other mixed dishes,” Kris-Etherton says.2
- Opt for lean when eating out. “Sirloin steak not only is lean but is also one of the most popular cuts you’ll find in restaurants that serve steak,” Dobbins says. “A typical pork chop is actually lean, too, as is pork tenderloin.”
- Marinate lean meats. “Leaner meats can be a little tougher, so marinate them for at least 30 minutes before cooking to help tenderize the meat and keep it moist,” Dobbins says. She suggests a simple marinade made of oil and an acid (such as vinegar), to which you can add herbs and other flavorings. “Nonsugary marinades can significantly reduce the formation of carcinogens during cooking,” adds Mariana Stern, PhD, a cancer epidemiologist and an associate professor at the University of Southern California in Los Angeles.
- Lower the cooking temperature. Cook meat at a slightly lower temperature for a longer time. “The hotter the temperature, the more carcinogens that accumulate when meat is cooked,” Stern says. “If you flip the meat often, such as when you’re pan frying, it seems to reduce the formation of carcinogens.”
- Add antioxidants. One study found that adding an antioxidant-rich spice mix (about 2 tsp spice mix per 4 oz raw meat)—including ground cloves, cinnamon, oregano, rosemary, ginger, black pepper, paprika, and garlic powder—to beef patties before grilling reduced formation of a carcinogen (malondialdehyde) in the cooked burger by 71%.3
- Go meatless on Mondays. Cut back on how much meat you eat by mixing it into a dish that mostly contains other ingredients, says Roni Neff, PhD, MS, an assistant professor of environmental health sciences at Johns Hopkins Bloomberg School of Public Health in Baltimore, and a program director at the Johns Hopkins Center for a Livable Future.
- Spread out meat portions throughout the day. “Use some of that leftover steak from dinner to make a breakfast burrito in the morning,” Dobbins says.
- Limit processed meat. “These meats are often high in sodium and fat, and we recommend people limit them across the board for blood pressure control, weight control, heart health, and to reduce cancer risk,” Dobbins says.
Source: Today’s Dietitian
Recommendations of Red Meat Consumption for Cancer Prevention by the American Institute for Cancer Research
Limit consumption of red meats (such as beef, pork and lamb) and avoid processed meats.
To reduce your cancer risk, eat no more than 18 oz (cooked weight) per week of red meats, like beef, pork and lamb, and avoid processed meat such as ham, bacon, salami, hot dogs and sausages.
Red meat refers to beef, pork and lamb–foods like hamburgers, steak, pork chops and roast lamb. The term processed meat refers to meats preserved by smoking, curing or salting, or by the addition of preservatives. Examples include ham, bacon, pastrami and salami, as well as hot dogs and sausages.
The evidence from the expert report that red meat is a cause of colorectal cancer is convincing. This evidence is much stronger now than it was in the mid-1990s. Red meat contains substances that are linked to colon cancer. For example, heme iron, the compound that gives red meat its color, has been shown to damage the lining of the colon.
Studies also show that people who eat a lot of red meat tend to eat less plant-based foods, so they benefit less from their cancer-protective properties.
There is also convincing evidence that choosing processed meat increases the chances of colorectal cancer. The expert panel advises limiting red meat and avoiding processed meat. Studies show we can eat up to 18 ounces a week of red meat without raising cancer risk. Research on processed meat shows cancer risk starts to increase with any portion.
When meat is preserved by smoking, curing or salting, or by the addition of preservatives, cancer-causing substances (carcinogens) can be formed. These substances can damage cells in the body, leading to the development of cancer.
Source: American Institute for Cancer Research
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