Agriculture and nutrition农业与营养Hidden hunger隐性饥饿
How much can farming really improve people’s health? 农业到底能为促进人类健康贡献多少？
IN A market in southern Uganda two traders squat behind little piles of sweet potatoes and a sign that says “with extra vitamin A”. A passing shopper complains about the price: 10% more than ordinary sweet potatoes. Yes, say the traders, but they’re better, bred with extra vitamin A. The bargaining goes back and forth, but the struggle to improve the crop has already been won. Since 2007, when an outfit called HarvestPlus began distributing the “biofortified” rootcrop in Uganda and Mozambique, 50,000 farmers have started to plant it or crops like it. Vitamin A intake has soared and the produce commands a premium. The shopper eventually buys some.
Nutrition has long been the Cinderella of development. Lack of calories—hunger—is a headline-grabber, particularly as rising food prices push more people towards starvation. But the hidden hunger of micronutrient deficiencies harms even more people and inflicts lasting damage on them and their societies. It, too, worsens as food prices rise: families switch from costly, nutrient-rich, fruit, vegetables and meat to cheaper, nutrient-poor staples.
In 2008 the Copenhagen Business School asked eight eminent economists to imagine they had $75 billion to spend on causes that would most help the world. Five of their top ten involved nutrition: vitamin supplements for children, adding zinc and iodine to salt and breeding extra micronutrients into crops (like those sweet potatoes). Others included girls’ schools and trade liberalisation.
Of the 40 nutrients people need, four are in chronically short supply: iron, zinc, iodine and vitamin A. Vitamin A is essential for the mucous membranes that protect the body’s organs, such as the eyes. Lack of it causes half a million children to go blind every year; half of them die within a year as their other organs fail. Vitamin A supplements were the Copenhagen experts’ top choice. Zinc deficiency impairs brain and motor functions and causes roughly 400,000 deaths a year. Shortage of iron (anaemia) weakens the immune system and affects, in some poor countries, half of all women of child-bearing age.
Too hungry to think properly饿得无法集中精神
The missing nutrients bite wide and deep. Education levels drop (malnourished children concentrate poorly); earning-power weakens. Even marriage chances wane: malnourished boys marry women of lower educational levels when they grow up.
Common responses include handing out vitamin pills and fortifying common foods with micronutrients (such as putting iodine in salt). But policymakers are now asking whether farming could do more to improve nutrition. That was the subject of a recent conference in Delhi organised by the International Food Policy Research Institute and attended by 1,000-odd politicians, scientists and activists.
Farming ought to be especially good for nutrition. If farmers provide a varied diet to local markets, people seem more likely to eat well. Agricultural growth is one of the best ways to generate income for the poorest, who need the most help buying nutritious food. And in many countries women do most of the farm work. They also have most influence on children’s health. Profitable farming, women’s income and child nutrition should therefore go together. In theory a rise in farm output should boost nutrition by more than a comparable rise in general economic well-being, measured by GDP.
In practice it is another story. A paper* written for the Delhi meeting shows that an increase in agricultural value-added per worker from $200 to $500 a year is associated with a fall in the share of the undernourished population from about 35% to just over 20%. That is not bad. But it is no better than what happens when GDP per head grows by the same amount. So agriculture seems no better at cutting malnutrition than growth in general.
Another paper?? confirms this. Agricultural growth reduces the proportion of underweight children, whereas non-agricultural growth does not. But when it comes to stunting (children who do not grow as tall as they should), it is the other way round: GDP growth produces the benefit; agriculture does not. As a way to cut malnutrition, farming seems nothing special.
Why not? Partly because many people in poor countries buy, not grow, their food—especially the higher-value, more nutritious kinds, such as meat and vegetables. So extra income is what counts. Agriculture helps, but not, it seems, by enough.
In addition, when poor people do have a bit more cash, they do not spend it all on food, as nutritionists hope (see also Economics focus). A study from Maharashtra, in western India, back in 1983, found that poor people spent two-thirds of their extra income on food; and the very poorest did not spend much more of their extra money than the least poor, even though they had just one-sixth of the income. People spent almost 40% of their additional rupees on wheat, rice or sugar: costly and (in the case of sugar) not very nutritious. So even when the poor do spend more on food, they do not buy the stuff that is most nutritious or the best value. In a forthcoming book** Abhijit Banerjee and Esther Duflo of the Massachusetts Institute of Technology conclude that “the poor seem to have many choices, and they don’t elect to spend as much as they can on food.”
此外，当穷人手里多一点钱时，他们并不会像营养学家所期望的那样，将这些多出来的钱花在食物上（参考阅读Economics focus）。一份1983年印度西部Maharashtra邦的研究报告发现，穷人将额外所得的2/3用于购买食物。而最贫穷的人与次贫穷的人相比，就算前者额外收入仅占后者的1/6，也不会花费更多来购买食物。人们额外收入中的几乎40%都用于购买小麦、大米和糖：花费颇多（尤其是糖）且营养价值不高。因此，就算穷人购买更多食物，也不等于他们能买最有营养或价值最优的食物。MIT的Abhijit Banerjee和Esther Duflo即将发行的新书如此总结道：“穷人们似乎有很多选择，但是却不愿花太多钱在食物上。”
Agriculture, then, is no magic solution. But farming could do more to improve nutrition—as is clear from countries’ widely varying records. Malawi, Bangladesh and Vietnam all increased agricultural value-added by roughly $100 a head from 1990 to 2007, and cut malnutrition by 15-20 percentage points. Egypt, Guatemala and India pushed up agricultural value-added more—yet their malnutrition rates rose.
The success stories are instructive. In 1990 a charitable organisation called Helen Keller International started to encourage market gardens in Bangladesh, providing women (mostly) with seeds and advice. By 2003 (the year of the latest available research), four-fifths of families in the target area had gardens, against 15% in the whole country. Almost all women and children were eating green vegetables three times a week, compared with only a third beforehand. And vitamin A intake had soared. Projects like this work because they improve what people like to eat anyway.
Changing the mix of crops works, too. Many countries’ food policies are essentially about providing cheap grain, which is just a start. When people do not have enough calories, staples such as rice and wheat are vital: they provide the most calories per dollar. But when people have enough calories they need to diversify towards vegetables, pulses and meat. In many places, irrigation and fertiliser subsidies, government marketing and other schemes implicitly or explicitly favour cereal farmers. So poor countries go on encouraging cereals longer than they need to. And plant breeders tend to raise cereals which maximise calories, not nutrients.
Policymakers can also try to increase women’s control over farming decisions (in some countries, only men may own land or get agricultural credit, for instance). They could boost research into more nutritious non-staple crops; and provide clean water and better transport, which especially benefits kitchen gardeners, because their produce goes off.
But there are limits. Malnutrition does the most damage in the first 1,000 days of life. In those months maternal health, breastfeeding and infant care, not agriculture, matter most. Better farming can mean more calories and higher incomes. But with nutrition, it offers only a few steel bullets, not a silver one.