5.2 When farming changed the plate

Key points

Finland’s programme was a before-and-after with no comparison country, but every link was measured, year after year.
Biofortification grows more of a nutrient into the crop itself, by breeding or by fertilising.
A food that fills a deficiency is not a high-dose pill given to people who already have enough.
Growing more doesn’t guarantee eating better.

Chapters

Key terms

Biofortification: Growing more of a nutrient into a crop itself, by breeding or by fertilising. Finland’s selenium fertiliser and orange-fleshed sweet potato, rich in beta-carotene, are examples. The convincing cases measure more than one link in the chain from crop to diet, and use a design that fits the question.
Mediator: A variable on the path from treatment to outcome: how the effect gets there, like leaf zinc between a spray and the grain, or diet between farm support and child growth. Adjusting for a mediator blocks the route the treatment works through, so the rule is never to adjust for anything the treatment causes.
Before-and-after comparison: Comparing an outcome before and after a change, such as Takaki’s navy voyages on different diets. It is the simplest evidence and, on its own, the weakest, because prices, weather, fashions and other policies change at the same time. Adding a comparison group, or measuring every link of a chain, makes it much stronger.

Transcript

Last time's quick check: food tables from different decades differ in variety, place, laboratory and method all at once, so a fall in the numbers can't be pinned on any one of them. Finland's soils are naturally low in selenium, a trace element people need in small amounts.

In the 1980s the Finnish government decided to add selenium to the multi-nutrient fertilisers used on farms across the country, starting in the middle of the decade. Through the crops, the grass, the animals and the milk, selenium reached people's plates. Within a few years, selenium intakes and the levels in people's blood rose substantially, and the dose in the fertiliser was adjusted over the years as the monitoring came in.

It's a before-and-after with no comparison country, the design Module 3 warned about. Why trust it? Because every link in the chain was measured: selenium in the fertiliser, the crops, the foods, the diet and the blood, year after year. When each link moves, in the right order, the chain holds.

Biofortification means growing more of a nutrient into the crop itself, by breeding or by fertilising. Finland's selenium was one kind. Another is orange-fleshed sweet potato, rich in beta-carotene, which the body turns into vitamin A. It was bred and promoted in parts of Africa where vitamin A deficiency is common.

In studies in Mozambique and Uganda, families given the vines and nutrition advice ate more vitamin A, including their young children. Remember the beta-carotene pills from Module 3 that did harm? Different people, a different dose, a different form. A food that fills a deficiency is not a high-dose pill given to people who already have enough.

Lind's question again: what exactly is "it"? And remember the Kenya trial: farm support plus food, nutrition and hygiene support improved children's growth more than farm support alone. Growing more doesn't guarantee eating better. And from Module 1, a crop is only as nourishing as the way it's processed and cooked.

The cases that convince share three things. A clear mechanism at every link. Measurements at more than one link, not just the start and the end. And a design that fits the question: a national programme followed for years, or trials where families could be randomised. That's the standard any claim about farming and nutrition should meet. Next: back to the wheat farm, from a pattern to a plan.

Questions

Why is Finland’s selenium programme convincing without a comparison country?

Because every link in the chain was measured: selenium in the fertiliser, the crops, the foods, the diet and the blood, year after year. When each link moves, in the right order, the chain holds. The dose in the fertiliser was also adjusted over the years as the monitoring came in.

What is biofortification?

Growing more of a nutrient into the crop itself, by breeding or by fertilising. Finland’s selenium fertiliser was one kind. Orange-fleshed sweet potato, rich in beta-carotene, which the body turns into vitamin A, was bred and promoted in parts of Africa where vitamin A deficiency is common.

Sources

Alfthan, G., Eurola, M., Ekholm, P. et al. (2015). Effects of nationwide addition of selenium to fertilizers on foods, and animal and human health in Finland: from deficiency to optimal selenium status of the population. Journal of Trace Elements in Medicine and Biology, 31, 142–147. doi:10.1016/j.jtemb.2014.04.009
Low, J.W., Arimond, M., Osman, N. et al. (2007). A food-based approach introducing orange-fleshed sweet potatoes increased vitamin A intake and serum retinol concentrations in young children in rural Mozambique. The Journal of Nutrition, 137(5), 1320–1327. doi:10.1093/jn/137.5.1320
Hotz, C., Loechl, C., de Brauw, A. et al. (2012). A large-scale intervention to introduce orange sweet potato in rural Mozambique increases vitamin A intakes among children and women. British Journal of Nutrition, 108(1), 163–176. doi:10.1017/S0007114511005174
Hotz, C., Loechl, C., Lubowa, A. et al. (2012). Introduction of β-carotene–rich orange sweet potato in rural Uganda resulted in increased vitamin A intakes among children and women and improved vitamin A status among children. The Journal of Nutrition, 142(10), 1871–1880. doi:10.3945/jn.111.151829
Wegmüller, R., Musau, K., Vergari, L. et al. (2022). Effectiveness of an integrated agriculture, nutrition-specific, and nutrition-sensitive program on child growth in Western Kenya: a cluster-randomized controlled trial. The American Journal of Clinical Nutrition, 116(2), 446–459. doi:10.1093/ajcn/nqac098

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