Meat - Facing the Dilemmas

Meat: the challengeConsumersContraction and convergence is good for our healthTony McMichaelThe world is eating more and more meat, andmeat production is contributing increasingly toglobal greenhouse gas emissions. Both excessmeat consumption and a change in the globalclimate pose risks to human health.In 2006 the Food and Agricultural Organization(FAO) issued an important report, Livestock’slong shadow, drawing attention to the impact ofthe livestock production sector on the world’sclimate. The major contributor is entericmethane from ruminant (digastric) grazers –cattle, sheep and goats.Modern humans come from a long line ofmeat-eaters, starting from around two millionyears ago. The widely-accepted ‘expensivetissue hypothesis’ argues that the introductionof meat into the ancestral human diet lessenedthe need for a large and heavy-duty intestinefor digestion and fermentation of plant foods.The gut is a metabolically expensive organ torun. Hence, this dietary shift released preciousenergy that could, via the ‘experiments’ ofnatural selection, be reapplied to another veryenergy-intensive organ, the brain. The earlyhuman gut thus contracted and the brainexpanded.That brain subsequently powered the evolutionof human culture, including the capacity toreshape and exploit diverse environmentsaround the world. Eventually farming emerged,livestock were domesticated, food suppliesexpanded and human populations grew. Thosetrends continued over ensuing centuries, andhave accelerated dramatically in recent times.Globally, both total population size and totalextrasomatic energy use, mostly from fossilfuels, have increased about fourfold since1900.As wealth has accrued and food productionhas become increasingly mechanised, so unitcosts have declined and consumer preferenceshave ‘risen’. Today’s uptrend is for a one-thirdincrease in total meat consumption in theworld by mid-century. FAO argues that this isnot a sustainable trajectory. Either our meatproduction methods must change radically orconsumption levels must decline. Or both.So, the wheel has come full circle. The ancientdietary shift that boosted our cerebral capacityhas led to a crowded and wealthier modernworld in which there are too many of us wantingto eat too much meat, mostly from ruminants.Hence the now-substantial contribution of thelivestock sector to global total greenhouse gasemissions. Estimates by both the UK SternReport and the FAO indicate that this sectorcontributes around one-fifth of total globalemissions. Methane from the ruminant gut isa problem because, molecule for molecule, itcauses much more warming than the betterknowngreenhouse gas, carbon dioxide.Nutrition scientists recommend an individualintake of around 50-100 grams of meat per day,to enhance the diet and to provide sufficientiron and vitamin B12. The high-income worldis, on average, now way above that level, beingwithin the range of 200-300 grams per day. TheUS has the highest per-person daily intake. Incontrast, the average intake in Sub-SaharanAfrica is around one eighth of that Americanlevel.As a world community, we must now considerthe various facets of this environmental andpublic health dilemma:Meat consumption is now rising rapidly inmany parts of the world.There are great differences, at the moment,in per-person levels of meat consumption –some of this reflects cultural preference, somereflects access and affordability. The latterrepresents a moral challenge in inequity.The livestock sector is contributing asubstantial (though under-recognised)proportion of global greenhouse gasemissions.There is moderately persuasiveepidemiological evidence that the risk of largebowel cancer increases at higher levels of redmeat consumption. The risks of breast cancerand of obesity and heart disease may also beincreased, especially in relation to the high fatcontent of meat from intensively producedlivestock. The World Cancer Research Fund’scomprehensive report on Food, nutrition,physical activity and the prevention of cancerexamines this evidence thoroughly.1In a recent paper in The Lancet we proposethat the world should commit to reducing theglobal average daily intake of meat, especiallyred meat from ruminants.2 This would be partof the evolving portfolio strategy – acrossvarious sectors of commerce, energy use andhuman behaviour – to mitigate climate change.The fairest approach is ‘contraction andconvergence’, where the world’s nations agree toreduce average per-person meat consumption(currently just over 100 grams per day) and todo so equitably. High-consuming populationswould reduce their intake and low-consumingpopulations could increase their intake up tothe agreed average level.To avoid an increasing contribution to globalwarming from the livestock sector, werecommend a global average target figure of 90grams of meat per day – with not more than 50grams from ruminant animals. Indeed, manypopulations have potential access to other,often healthier, sources of meat; in Australiait would be good for the environment andfor the nation’s health to eat more kangaroomeat, which is lean and contains omega-3 fattyacids.This would be a win-win strategy. Globalwarming would be slowed. Health risks wouldbe reduced in high-consuming populations,and there would be gains in nutritional statusin lower-income countries where deficienciesof iron, protein and energy in the diet wouldbe reduced, conferring particular benefits onchild health and development. Any increasesin cancer, heart disease or obesity-relateddiabetes in those lower-income countrieswould be limited by the ceiling intake figure of90 grams/day.Phased in over several decades, this would begood for the planet, for global equity and forpopulation health.Professor Tony McMichael is anepidemiologist at the AustralianNational University, Canberra.His particular interest is studyingenvironmental influences onpopulation health, especially today’slarger-scale influences from climatechange, food systems and theurban environment.1 WCRF/AICR (2007) Food, nutrition, physical activity, andthe prevention of cancer. www.dietandcancerreport.org2 McMichael AJ, Powles JW, Butler CD, Uauy R. (2007)Food, livestock production, energy, climate change, andhealth.The Lancet, September 13.www.foodethicscouncil.org | Volume 2 Issue 4 | Winter 2007 05