Friday :: Jul 3, 2009

The Beef With Beef: Global Warming and Cancer

by Turkana

What you eat impacts not only your own health but the health of the entire planet. It's important to keep that in mind. It's important to keep the science in mind. Then, it's about personal choice.

From a January article in Scientific American:

Most of us are aware that our cars, our coal-generated electric power and even our cement factories adversely affect the environment. Until recently, however, the foods we eat had gotten a pass in the discussion. Yet according to a 2006 report by the United Nations Food and Agriculture Organization (FAO), our diets and, specifically, the meat in them cause more greenhouse gases carbon dioxide (CO2), methane, nitrous oxide, and the like to spew into the atmosphere than either transportation or industry.

More specifically:

In 1999 Susan Subak, an ecological economist then at the University of East Anglia in England, found that, depending on the production method, cows emit between 2.5 and 4.7 ounces of methane for each pound of beef they produce. Because methane has roughly 23 times the global-warming potential of CO2, those emissions are the equivalent of releasing between 3.6 and 6.8 pounds of CO2 into the atmosphere for each pound of beef produced.

Raising animals also requires a large amount of feed per unit of body weight. In 2003 Lucas Reijnders of the University of Amsterdam and Sam Soret of Loma Linda University estimated that producing a pound of beef protein for the table requires more than 10 pounds of plant protein with all the emissions of greenhouse gases that grain farming entails. Finally, farms for raising animals produce numerous wastes that give rise to greenhouse gases.

In February, Science News added this:

For the good of the planet, we’re all being asked to reduce our carbon footprints — the quantities of greenhouse gases, aka GHGs, associated with our actions. Since some 30 percent of the global warming potential attributable to society’s GHG emissions stems from the production of foods and beverages, menu choices are critical, noted Ulf Sonesson of the Swedish Institute for Food and Biotechnology in Goteborg, today. From this climate perspective, meat eaters are the big hogs.

How big?

For instance, roughly half of the GHG emissions due to human diets come from meat even though beef, pork and chicken together account for only about 14 percent of what people eat.

From a climate perspective, beef is in a class by itself. It takes a lot of energy and other natural resources to produce cattle feed, manage the animals’ manure (a major emitter of methane, a potent GHG), get the livestock to market, slaughter the animals, process and package the meat, dispose of the greater part of the carcass that won’t be human food, market the retail cuts, transport them home from the store, refrigerate them until dinner time, and then cook the beef.

Tally the GHG emissions associated with all of those activities, Sonesson says, and you’ll find it’s the global-warming equivalent to spewing 19 kilograms of carbon dioxide for every kg of beef served. Swine are more environmentally friendly. It only takes about 4.25 kg of CO2 to produce and fry each kg of pork. At the other end of the spectrum are veggies. The climate costs associated with growing, marketing, peeling and boiling up a kg of potatoes, by contrast, is just 280 grams, Sonesson reported.

The article explains that the process of producing grass-fed beef cattle is actually worse than that of producing corn-fed beef cattle. There's no good answer other than reducing consumption of beef. Replacing all beef production with chicken production would reduce the carbon footprint by seventy percent. Reducing the developed world's beef consumption by less than half, to a level the U.S. Department of Agriculture says still is healthy, would reduce the associated emissions by about forty-four percent.

Simply put, if you're a meat-eater, and you want to make a personal contribution to the effort to ameliorate climate stress, reducing or eliminating your consumption of beef would be a great step. But there's another reason to reduce your beef intake, and it's also a very personal one. Your health.

The BBC is reporting on a new study published in the British Journal of Cancer, which found that vegetarians and pescetarians are less likely than meat eaters to get certain types of cancer. The study followed 61,566 people.

The researchers said they found marked differences between meat-eaters and vegetarians in the propensity to cancers of the lymph and the blood, with vegetarians just over half as likely to develop these forms of the disease.

In the case of multiple myeloma, a relatively rare cancer of the bone marrow, vegetarians were 75% less likely to develop the disease than meat-eaters.

The reduction was less notable for fish-eaters with these cancers. The reasons, researchers said, were unclear, but potential mechanisms could include viruses and mutation-causing compounds in meat - or alternatively that vegetables confer special protection.

There were also striking differences in rates of stomach cancer. Although the numbers of cases were small, fish-eaters and vegetarians were about a third as likely to develop the disease as meat-eaters.

The study is free, online, and opens with this explanation:

Vegetarians do not eat meat or fish. Meat has been suspected of influencing the risk for several types of cancer. For example, in the systematic review by the WCRF/AICR (World Cancer Research Fund/American Institute for Cancer Research), an expert panel concluded that both red meat and processed meat are convincing causes of colorectal cancer, and that there was some evidence suggesting that high intakes of red or processed meat increased the risk for cancers of the oesophagus, stomach, pancreas, lung, endometrium and prostate (WCRF/AICR, 2007).

A few prospective studies have been established with the aim of studying the long-term health of vegetarians, and have used recruitment methods designed to ensure that a substantial number of the participants were vegetarians. Some findings on cancer incidence rates in vegetarians have been reported from the Adventist Health Study in California (Fraser, 1999), the Oxford Vegetarian Study (Sanjoaquin et al, 2004), the UK Women's Cohort Study (Taylor et al, 2007) and EPIC-Oxford (Key et al, 2009). These reports included data for only a few cancer sites. To provide more information on cancer incidence in vegetarians, in this study, we report on the incidence of malignant cancer at 20 sites or groups of sites, plus all incident malignant cancers combined, in a pooled analysis of data from two prospective studies in the United Kingdom, namely the Oxford Vegetarian Study (Appleby et al, 1999) and the EPIC-Oxford cohort (Davey et al, 2003).

And the Guardian adds:

Co-author Naomi Allen, from the Cancer Research UK epidemiology unit at Oxford University, said: "Previous research has found that processed meat may increase the risk of stomach cancer, so our findings that vegetarians and fish eaters are at lower risk is plausible. But we do not know why cancer of the blood is lower in vegetarians."

She said the differences in cancer risks were independent of other lifestyle factors including smoking, alcohol intake and obesity.

However, Allen urged caution over the interpretation of the findings. "It is a significant difference, but we should be a bit cautious since it is the first study showing that the risk of cancer of the blood is lower in vegetarians. We need to know what aspect of a fish and vegetarian diet is protecting against cancer. Is it the higher fibre intake, higher intake of fruit and vegetables, is it just meat per se?"

The study also reported that the total cancer incidence was significantly lower among both the fish eaters and the vegetarians compared with meat eaters.

The article says that in 2007, the World Cancer Research Fund found a link between red and processed meat and cancer of the bowel, and that a 2005 study funded by the Medical Research Council, Cancer Research UK and the International Agency for Research on Cancer found that eating two portions of red meat a day raised the risk of bowel cancer by 35%.

In the BBC report, the study's lead author, Tim Key, says it's too early to be able to ask for dramatic changes in people's eating habits, as it's only one study; but it certainly calls for more research. The numbers are striking, but exact causality has yet to be determined. As the study itself concludes:

Total cancer incidence was significantly lower among both fish eaters and vegetarians than among meat eaters. This difference in total cancer incidence between meat eaters and non-meat eaters could not be ascribed to any one of the major cancer sites examined. We are unaware of other data comparing total cancer incidence in meat eaters and non-meat eaters, and the reason for this small difference is not known. More data are needed to further our understanding of this observation, which if confirmed is likely to be due to differences for specific cancer sites.

The results presented in this study are simply descriptive of the incidence of cancer in fish eaters and vegetarians relative to meat eaters. More detailed analyses of individual cancer sites are needed to explore, for example, whether the differences observed might be linked to particular types of meat or to other dietary or lifestyle characteristics of non-meat eaters that were not adjusted for in the current analysis.

A potential weakness of this type of study is the accuracy of the assessment of vegetarian status. The diet group was assigned on the basis of the answer to four questions, asking specifically about whether participants ever ate meat, fish, dairy products and eggs. When the diet group in EPIC-Oxford was assigned on the basis of answers to the same four questions in a follow-up questionnaire 5 years later, 85% of the vegetarians were allocated to the same diet group as at the time of recruitment (Key et al, 2009), suggesting that the assessment of vegetarian status is accurate and stable over at least several years, and may be a substantially more stable dietary characteristic than epidemiological estimates of nutrient intakes.

In conclusion, this study suggests that the incidence of all malignant neoplasms combined may be lower among both fish eaters and vegetarians than among meat eaters. The most striking finding was the relatively low risk for cancers of the lymphatic and haematopoietic tissues among vegetarians.

In conclusion, what to eat is about as personal a choice as any of us can make. None of us are pure. None of us are perfect. But it is always important that our choices be informed.

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Turkana :: 8:48 AM :: Comments (3) :: Digg It!