Wetenschap - 8 november 2001

Vegetables not enough to supply the world with vitamin A

Vegetables not enough to supply the world with vitamin A

Development organisations overestimate the usefulness of vegetables in providing vitamin A to the Third World. "Children would have to eat about half a kilo of spinach every day to meet their requirements," explains Machteld van Lieshout of the sub-department of Human Nutrition and Epidemiology. Despite the unrest she examined the uptake of vitamin A in children in Indonesia, using isotopes to help her.

Van Lieshout went twice to Bogor in Indonesia to do research. The first time she left earlier than she had planned: "We watched the riots which led to Suharto's fall on TV," says Van Lieshout. "It was quiet where we were, but we left anyway, just to be safe." The second time she went, Van Lieshout was aware that there could be troubles. She planned her research to finish before the elections started.

Van Lieshout examined how much betacarotene children need to be able to make enough vitamin A. "A diet of dairy and meat products contains enough vitamin A," she explains. "But if your diet consists mainly of vegetables, for instance spinach, squash and palm oil, you will take in more betacarotene. Your body can convert this into vitamin A." But the human body does not absorb all the betacarotene in vegetables, nor does it convert all of what it absorbs into vitamin A.

The PhD researcher discovered that millions of people who cannot afford dairy or meat, receive about three times less vitamin A than scientists have previously assumed. This is partly because there are other substances in food that hamper the body's ability to absorb betacarotene and convert it to vitamin A.

Isotopes

Van Lieshout worked with a special form of betacarotene. A laboratory in the Dutch town of Leiden replaced carbon atoms with a heavier sort of carbon in the betacarotene molecules, specially for her research. "These are stable isotopes," explains Van Lieshout. "They aren't dangerous, they don't emit radiation." Van Lieshout added the 'heavy' betacarotene to the food that the children ate. Using special instruments developed in Chicago she was able to track down the heavy betacarotene in the blood of the children, as well as the vitamin A made from it.

Researchers intend to use the technique developed by Van Lieshout to examine the controversial golden rice, a genetically modified crop that contains betacarotene, aimed at reducing vitamin A shortages in developing countries.

Machteld van Lieshout will receive her PhD on 9 November. Her promotors are Professors Jo Hautvast and Clive West of Wageningen University.

Willem Koert

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