Red and Processed Meats May Be Unhealthy

A recent study supports growing evidence that eating too much meat may be unhealthy. Researchers from the U.S. National Cancer Institute found that a diet rich in red and processed meats increased the risk of death, particularly from cancer and heart disease.

In the study, published in the Archives of Internal Medicine, researchers analyzed data from more than half a million people (aged 50-71) who were enrolled in the National Institutes of Health-AARP Diet and Health Study. Meat intake was estimated through a food questionnaire.

People in the high-intake group for red meat ate an average of 4.5 ounces daily, while those in the lowest-intake group ate a little more than half an ounce daily. For processed meat, people in the high-intake group ate an average of 1.5 ounces daily compared to 0.11 ounces in the low-intake group.

During the 10-year follow-up period, the researchers recorded the number of deaths and their causes. They adjusted for other risk factors, such as age, smoking, obesity and alcohol consumption.

By the end of the study, 47,976 men and 23,276 women died from various causes. In those who ate the most red meat, the overall risk of death increased by 31 percent in men and 36 percent in women, compared to those who ate the least. The risk of fatal cancer increased by 22 percent in men and 20 percent in women, and the risk of fatal heart disease increased by 27 percent in men and 50 percent in women.

In those who ate the most processed meat, the overall risk of death increased by 16 percent in men and 25 percent in women, compared to those who ate the least. The risk of fatal cancer increased by 12 percent in men and 11 percent in women, while the risk of fatal heart disease increased by nine percent in men and 38 percent in women.

In contrast, people who ate higher proportions of white meat, such as turkey, chicken or fish, were less likely to die during the study period than those who ate the lowest proportions.

These results are somewhat limited by the study design because the data relied on the participants' memories of what they ate.

It has been suggested that cancer risk may be increased by compounds called heterocyclic amines (HCAs), which are formed when red meat is cooked at high temperatures. HCAs have been linked to various cancers, including stomach, colorectal, pancreatic and breast cancers in humans.

Red meat also contains high amounts of saturated fats, which have been shown to increase the risk of heart disease.

In a related study, published in the American Journal of Epidemiology, diets rich in red meat were linked to age-related macular degeneration (AMD), the leading cause of blindness in aging Americans. In the study, 6,734 people (aged 58-69) completed food frequency questionnaires in 1990-1994. During the follow-up period (2003-2006), the participants were monitored for the development of AMD.

The researchers found that people who ate red meat 10 or more times per week were 47 percent more likely to develop AMD than those who ate it less then 4.5 times per week. The authors suggest that these effects may be attributed to compounds in the meat that cause oxidative damage.

Additional research is needed to determine exactly how red meat might increase the risk of AMD.

For more information about different types of diets, please visit Natural Standard's Health & Wellness database.

Comments

[Michael Edson, MS, L.Ac.]

As people continue to live longer, the incidence of eye diseases, such as macular degeneration, is on the rise. These types of debilitating eye diseases rob people of vision and can result in individuals losing their independence.

It is believed that the visual system requires up to 25% of the nutrients we take into our bodies in order to stay healthy. Impaired circulation and/or poor absorption of nutrients can significantly contribute to eye disease. Regular exercise and management of emotional stress are also critical for maintaining health.

Eye conditions/diseases such as macular degeneration, glaucoma, diabetic retinopathy, cataracts and many others can be responsive to specific nutritional supplementation

For example, there is a great deal of peer-reviewed research now showing that vision can be preserved through a proper diet and specific nutritional supplementation and that macular degeneration is a nutritionally responsive eye disease, along with a recent study demonstrating that red meat should be curtailed or eliminated from the diet.

The recent B-vitamin study showing that those that supplement with B6, B12 and folic acid have a significant lower risk of getting macular degeneration is one of many studies proving macular degeneration to be a nutritionally responsive eye disease.

The Archives of Ophthalmology recently published a meta-analysis on omega-3 fatty acid and fish intake and its effect on the prevention of age-related macular degeneration (AMD). This study identified 274 abstracts, 3 prospective cohort, 3 case-control, and 3 cross-sectional studies.

Using quantitative methods, a high dietary intake of omega-3 fatty acids was associated with a 38% reduction in the risk of late AMD. Fish intake (2x per week) was associated with reduced risk of early and late AMD.

More omega-3 and AMD specific studies need to be conducted to further investigate omega-3s effect on AMD. Ref: Arch Ophthalmol. 2008;126(6):826-833.

Essential nutrients include lutein, zeaxanthin, omega-3 fatty acids, taurine, Ginkgo biloba, lycopene, vitamin A, vitamin E, zinc, copper, selenium for example, that can help both prevent the onset of eye disease such as macular degeneration as well as help preserve vision for those with macular degeneration.

Daily eye exercises also help maintain healthy vision. For a demo of 3 great eye exercises by Dr. Grossman, one of the Country's leading behavioral optometrists, go to http://www.youtube.com/watch?v=W10j2fL0hy0

For more information on nutrition and macular degeneration and related research studies, go to Natural Eye Care for Macular Degeneration.

[B. O.]

This article from the National Cancer Institute, http://www.cancer.gov/cancertopics/factsheet/Risk/heterocyclic-amines, gives a good break down on the production of HCA’s in muscle meat. Its says that HCAs are formed when amino acids, the building blocks of the proteins that make up the muscle meat, combine with creatine, another chemical found in the cells. Higher temperatures ( > 400-450ºF) produced more HCA; cooking methods such as frying, broiling, and barbecuing are done at high temperatures and produce high HCAs. Oven roasting and baking are usually done at lower temperatures (350ºF) and boiling water is about 212ºF . These lower temperature cooking methods produce fewer HCAs. Meat cooked longer (well-done) will form slightly more HCAs than meat cooked less (medium or medium-rare). So I’m glad that my prime rib, medium-rare, is still best way to go, when I want red meat. And red wine had antioxidants, which can help counter the oxidative damage of red meats, so that’s important, too. Glad I have scientific justification for my tastes.

[Jeremy]

I noticed that the study indicates that the risk of developing fatal heart disease and the overall risk of death increased more in women than in men. This is an interesting fact because it has always been my understanding that men are at a higher risk for developing heart disease. Has anyone read any other studies with similar results? Has anyone read any studies discussing the possible reasons why women may have a higher increase in risk of death than men (both eating a diet high in processed meats).

[Susan]

After reading this article, I became curious about the amount of red meat that is recommended and healthy to eat per day for an average person. I did some research, and discovered that experts at the American Institute for Cancer Research (AICR) recommend no more than 18 ounces of red meat (cooked) per week. They also recommend avoiding processed meats. The AICR reports that every 3.5 ounces of red meat eaten per day increases the risk for colorectal cancer by 30 percent.

[Mary B.]

With people becoming more and more aware of the dangers of consuming too much red meat, I wonder if there are statistics showing a shift away from red meat and towards white meat. I looked into this and found that the annual consumption of beef by an average person decreased by 14 percent since 1970, according to the USDA’s Economic Research Service reports. I wasn’t able to find any other information. Does anyone know if this is correct?

[Jill]

I read an interesting study in Diabetes Care, which stated that the women who consume too much of heme iron, found in large amounts in red meat, have as high as a 28 percent increased risk of developing type 2 diabetes. The mechanism of this process is not well understood; however, the study suggests that too much heme iron is involved in the creation of excess reactive oxygen (oxidative stress), which affects the body’s ability to respond to insulin. Iron effects glucose metabolism, and glucose interrupts several metabolic pathways of iron. Heme iron is much more readily absorbed than other forms of iron. The study followed 85,000 middle-aged women for 20 years.

[Hannah D]

About the women being at increased risk for heart disease in this study...

I'm not a dietitian, epidemiologist or a statistician, so when the study says it corrected all these other risk factors, I'm not exactly sure what that means. My guess is that women tend to eat less red meat than men do and therefore tend to have lower incidences of heart disease over all. However, in this study, meat intake was absolute (high > 4.5 oz/day), not relative. Men and women who ate > 4.5 oz/day probably had more male-like risk factors and that's why the numbers for these women jumped up so much compared to most women while the men in the “high red meat” category may not have been that much different than most men so their number jumped relatively less.

And I could be way off here, but if you picture who these women are who are in the "high red meat" category, it may not be a surprise that their risk for heart disease went up, no matter what the statisticians do with their “corrections."

[Ryan P.]

In 2009, a study was published in Cancer Research indicating that red meat, processed meat and meat mutagens are independently associated with increased risk of lung cancer (results were statistically significant). This was a population-based case-control study of 2,101 lung cancer cases and 2,120 controls. The study estimated the intake of heterocyclic amines (HCA) and benzo(a)pyrene (BaP) in both the cases and the controls. HCA’s and BaP were significantly associated with an increased risk of lung cancer (adenocarcinoma and squamous cell carcinoma).

[DJ Bernie]

I'm surprised by the lung cancer connection. I can see the colorectal connection (undigested red meat can stay in the GI tract for extended periods of time) and the oxidative damage to the eye is not intuitive, but the explanation is logical. However, it is hard to see how the lungs could be damaged by ingesting meats. However, the only organ besides the heart to get 100% of the body's blood flow is the lungs. Perhaps because the lungs get so much blood flow any carcinogens in the blood will affect the lungs. The lungs cells may not have the enzymes to protect themselves from oxidative damage the way the liver cells do, making them very susceptible to cancer. I have also heard that when barbecuing, the smoke from the grill is more carcinogenic than even cigarette smoke. Maybe the lung cancer patients were big barbecuers.

[Matt S]

I would be interested to know whether these results would be the same if replicated in other countries that have different farming techniques than the United States. Corn-fed cows, such as most of those in the United States, require antibiotics. U.S. farmers also commonly give cows synthetic growth hormones; the European Union bans this practice because many believe hormone-treated cows are unsafe for human consumption. Perhaps some of the negative health effects from eating larger quantities of red meat are due, at least partially, to farming practices in the United States.

[Adele]

I'd like to know if there's a difference in cancer risk between eating red meats that are baked or pan-fried, vs. eating red meats that have been charcoal grilled. If more HCAs are formed when meat is cooked at high temperatures, it stands to reason that barbecuing could be especially hazardous.

[Cindy S]

According to the article, “These results are somewhat limited by the study design because the data relied on the participants' memories of what they ate.” I agreed with this assessment, until I started looking up studies about the accuracy of dietary recall. I was stunned by this 2003 study at http://jn.nutrition.org/cgi/content/full/133/8/2663 (The reliability of 10-year dietary recall: Implications for cancer research). According to the results, subjects were able to accurately recall their diets from 10 years earlier, corroborated by food diary entries from that time period!

[Amy]

As a die-hard vegan, I think it is important for humans to stay away from all meats. High cholesterol is one of the leading contributors of heart disease. While the genes that you inherit do play a significant role, diet can counter most genetic risk. Vegans tend to have low blood cholesterol because they eat less total fat, less saturated fat and no dietary cholesterol because plants and fruits do not contain cholesterol.

Studies have shown that red meat has the strongest association with breast cancer. The more vegetables that women eat, the less likely they are to get breast cancer. Vegetables and fruits also have disease-preventative mechanisms, such as antioxidants, detoxification enzymes, blood pressure reduction mechanisms, antibacterial and antiviral activities, and immunostimulants.

Heating any food to cooking temperatures causes some carcinogens to form. So the next time your're in the kitchen frying up a steak or burger that produces HCAs, consider making yourself a tofu burger, which does not produce any HCAs.

[JP]

Mary, I'm not sure if anyone is going be able to refute statistics from the USDA’s Economic Research Service report. Unless you want me to go ask Victor at the Stop and Shop deli? He might know... Yeah, he said it's down 12% since 1970 at his place, but in this economy it's hard to know if its public education or Bush's fault.

[Amy]

The production of red meat from factory farms is not just killing the humans that consume it on a daily basis, but it also has a major effect on our environment. Over the years, huge factory farms have taken over the business, shutting down the smaller, local farms. These large-scale farms are major contributors to global warming. The EPA estimated that animal waste from factory farms has polluted more than 35,000 miles of river in 22 states and contaminated groundwater in 17 states. Livestock produce millions of tons of manure each year, which is sprayed onto croplands of left to sit in lagoons. The livestock pollution kills fish and contaminates drinking water.

Methane is excreted by animals from the type of feed they consume. Cattle are among the major emitters of methane because of the digestive process. Carbon dioxide is also emitted during livestock feed production. The EPA has stated that animal agriculture is the single largest source of methane emissions in the U.S. Wow!!
So when you’re thinking about how eating red meat affects your health, don’t forget how it affects the environment.

[Carrie]

To Adele’s question:

There are four factors that influence HCA development: the type of food, cooking method, temperature and time. The most important factor for the formation of HCAs is temperature. Frying, broiling and barbecuing produce the largest amount of HCAs because the meats are cooked at such a high temperature. Oven roasting and baking are done at lower temperatures, so lower levels of HCAs are formed. Obviously, the best options would be to stew, boil or poach your food.

[Justine P.]

I had no idea that diets consisting of mostly red meat could lead to macular degeneration! Dr. Edson, thank you for talking about the dependence of eye health on diet. My mother would always tell me to eat carrots while growing up, but even as an adult, I never seriously considered the link between diet and vision. My vision has been getting worse recently, but now I know that this isn't totally out of my control and that there are preventative measures out there.

[martha magnus]

This study really alarmed me at first because my family eats red meat about once a week, some of us twice. But when I heard these findings about the hazards of red meat covered on NPR, the reporter finished by comparing these risks to the risks of tobacco and smoking. I don't have the exact numbers off the top of my head, but it made concern over red meat seem like rather small potatoes in terms of overall health risk when you look at how deadly tobacco use is. Still, we’ll be eating turkey burgers more than beef burgers, and I won’t be so quick to say yes to my daughter’s favorite: breakfast sausage.

[Kara]

Amy, I agree that a diet high in vegetables and fruits, whole grains and legumes, and low in saturated fats is a much better diet for humans for so many reasons. I think it may take some time to convince folks that this is the healthiest way to go after literally centuries of being carnivores. As a dedicated vegetarian for more than 20 years, I do believe in the adage "everything in moderation" and try not to be too much of a preacher. Evolution takes time.

[Kendra]

I’m with Amy on assessing the environmental impact of raising meat for human consumption. As well as contributing to greenhouse gases, the amount of water used for livestock production is massive, at about 8% of the world water use (www.fao.org/ag/magazine/0612sp1.htm).

While I am a vegetarian, and have been for more than two decades, I do feed my children chicken a couple of times a week, and they have sandwich meat in their lunches. However I am careful to buy meat that doesn’t contain nitrates. I wonder how nitrates in processed meats correlate to cancer and heart disease risk.

[Angie]

Sodium nitrates are used for preserving processed meats because it preserves the bright pink color, it prevents growth of bacteria and it is cheap!

The answer to your question Kendra: When nitrates are added to meat and cooked, they are combined with amines, a cousin of ammonia that occurs naturally with meat. When amines and nitrates combine they form N-nitroso compounds, which are believed to be cancerous. Ingesting this into your body increases the risk of colorectal cancer and pancreatic cancer.
It’s quite simple, the less meat and processed meat you eat, the less risk you have of getting cancer!

[Tandy G.]

The negative statistics for those indulging in a high intake of red meat and processed meat may not be surprising given all we have been hearing over the past number of years in terms of saturated fats, nitrates and salt. What surprised me was that women are more vulnerable than men statistically. I am wondering what might be contributing to that difference. Was the amount of time devoted to exercise the same?

The other surprise was that those with a high intake of the white meat (turkey, chicken and fish) were healthier than those who had a low intake of the same. Is that because those with the low intake had a higher intake of red meat products, or that they were semi-vegetarian in their habits?

With the exception of the white meat of fowl and fish, it appears that moderation is still the guiding principle in all things. Proportionately small amounts of red meat to the other foods that we consume is the safer way to go.

[Ava C.]

I have off and on over the years followed the blood-type diet. Given the statistics of how high and low intake of red meats affected longevity in the subjects of this research, I am curious to know if there was any consideration of blood type as described in the book, Eat Right for Your Blood Type. For example, if all the subjects had been O type, where red meats are considered highly beneficial, then according to the author of the book, the men should not have suffered adverse effects.Type O women however, while also encouraged to eat red meat, are recommended half the size allotted to men. So, if they stick to the 2.5oz amount, they would be in keeping with the study’s findings of low-intake women.

On the other hand, if the men or women were type A, as I am, then any red meat compromises their health. I am not an advocate for the blood type diet, but it would be interesting to note if that plays any part in the findings of these research.

[BD]

The question that raises the most concern to me is how much of this unhealthiness is directly related to different hormones and androgens that are given to cattle and livestock these days. So much artificial manipulation of the natural maturing process in these animals has been commonplace for the past decade or more. Red meat is always laced with fat, and the processed meats I personally don’t want to even know how they are processed. So, that being said, red meats are high in fat, sodium and synthetic hormones. Go figure that eating too much of them would be unhealthy.

Also, when buying chop meat, for example, the consumer is asked to pay extra for leaner cuts and packages. The difference between fat contents can be extreme from the lowest grade to the highest grade. Unfortunately, the market conundrum of consumers having to be wealthy to be healthy continues to exist.

[Eugene]

The National Cancer Institute (NCI) stated that heterocyclic amines (HCAs) can be found in more than just red meat; it is also found in the “white meats” like fish, pork and poultry. The data given stated that cooking at higher temperatures actually increases the amount of HCAs...as if I needed another reason to avoid fast-food.

The good news is if you are worried about HCAs, the NCI stated that microwaving meats for two minutes prior to cooking, HCA content decreases by 90%, and if you drain off the liquid that comes out of the meat, it further reduces the amount of HCA.

It would be interesting if they conducted a study that compared cancer rates in people who cook everything in a slow cooker to people who use the George Foreman cooker. In society's “faster-is-better” mentality, could this be one of the reasons for the increase in incidence of cancer-related diagnoses?