Good nutrition starts with bioavailability science

In 2018 the world produced enough calories to feed everyone on Earth. However, distribution was sadly inequitable – about 700 million people still went hungry. And over 30 per cent of food was wasted.

Although there was theoretically enough to eat, there were two major shortfalls in important nutrients – calcium and vitamin E. Globally, they were short by about a third, on average. Vitamin E is found in many plant oils, and as New Zealanders are well aware, milk and its derivatives are a rich source of calcium.

Generalisations are just that. In each country, there are subgroups getting too much and not enough, of calories, protein, vitamins and trace elements. Many young women in New Zealand are iron-deficient and don’t consume enough calcium, putting them at risk of osteoporosis later in life. Some of our elderly people don’t eat enough protein. Selenium is deficient in our soils.

We simplistically assume that if we could only stop or reduce food waste, all would be well. The saving would feed the extra 2.5 billion people yet to be born between now and 2050.

Many New Zealanders are making tremendous efforts to rescue food that would otherwise end up in the tip and distribute it to those in need. But even if we could prevent all food waste in the world it would not solve the shortage of vitamin E and calcium. The foods that are wasted do not generally contain much of them – people don’t usually tip out oils or milk.

A mathematician at the Riddet Institute, Dr Nick Smith, is refining a model that number-crunches all the interrelated factors in what it takes to feed the world properly. Meaning, not just enough to fill stomachs, but all the different vitamins and minerals you need for good health and development.

It takes account of crop production, feed sources for animal production, population age distribution (children have different requirements to adults), waste, and non-food uses of food crops, such as biofuels.

The model, called Delta (the mathematical symbol for difference), was initiated by a broad NZ science consortium and is led by the institute.

Nutrition scientists were concerned that environmental and economic factors were starting to override considerations of human health when it comes to food. Delta starts with how to feed people first, and then tries to fit the scenarios within environmental and economic sustainability constraints.

A very important factor in the model is a feature of food called bioavailability – that is how many of a food’s nutrients will actually be absorbed by the body. An oft-used example of variable bioavailability is iron. We have to eat more than 10 times the weight of spinach than beef to get the same amount of iron, even though spinach has a higher concentration of iron.

The trade-offs with any food – animal or plant – when it comes to the environment (water use, greenhouse gas emissions, soil degradation, and food miles) are many and subject to great debate. They are a tricky challenge for modellers.

Smith’s aspiration as a PhD student was to apply mathematics to real world problems that matter. It’s hard to think of a more important equation.

The Riddet Institute is hosting a dialogue, “Feed our Future”, at Te Papa, Wellington, June 9, about the key global issues and local decisions we need to make.


This article originally appeared on Stuff on 5th April 2021 and is reproduced here  –  

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