Food is medicine

May 2010

Food provides energy to power our bodies and is the source of many essential vitamins, nutrients and minerals that cannot be obtained any other way.

Part of the food security challenge is to deliver not just as much food as possible, but food of sufficient nutritional quality – food that nourishes and sustains life and wards off disease.

Scientists are only just beginning to understand the complex ways that food delivers nutrients to the body. Ever since the ‘vital amines’ were identified around the turn of the 19th century as compounds needed in tiny amounts to prevent diseases such as scurvy, rickets and beriberi, researchers have raced to identify, classify and manufacture the chemical elixirs later rechristened ‘vitamins’.

And yet more than 100 years after the first compounds were identified, studies often produce conflicting results. For instance, multi-vitamin supplements were once heralded as a ‘no harm’ addition to a healthy diet. Now, a consensus is emerging that the average healthy individual does not need them. Consequently, messages to the public and policy-forming politicians are mixed.

Raising the bar

Funded by the Medical Research Council in 1998, the MRC Human Nutrition Research Unit (HNR) was established as a national centre of excellence to advance knowledge of the relationships between human nutrition and health.

HNR’s work includes a large-scale dietary survey programme, which includes collating a vast food composition database to track exactly what nutrients are in food in the UK. Recent additions to the database include phytate, vitamin K1, silicon, and haem and non-haem iron content of foods.

As well as tracking what manufacturers put into food, HNR records what consumers put in their bodies. Along with partners including the National Centre for Social Research (NatCen) and the Food Standards Agency, HNR regularly quizzes 1,000 people across the UK on their eating habits as part of the National Diet and Nutrition Survey rolling programme.

Results show that the ‘5-a-day’ message is getting through and that adults are on average eating 4.4 portions of fruit and vegetables a day, and that over a third of men and women are now meeting the guideline. The nation is eating less saturated fat, less trans fat, and less non-milk extrinsic sugar (NMES) than it was 10 years ago.

However, intakes of saturated fat and NMES are still above recommended levels. People are also still not eating enough fibre and oily fish consumption remains low.

International dimension

HNR undertakes similar survey work abroad, and MRC-funded nutrition units in Cambridge have been working in the Gambia for over 30 years collecting dietary records (the MRC is the UK’s single largest investment in medical research in a developing country). The large data set and cooked food samples analysed play a valuable part of the assessment of health and disease in Africa, and can be compared to data collected elsewhere.

Worldwide data can be used to improve peoples’ health where it is most needed. In developing countries, 200 million people suffer from vitamin A (retinol and carotenoids) deficiency worldwide, which can cause nightblindness, poor outcomes in pregnancy, and diminishes the body’s ability to fight infections.

Hard science

By labelling plants themselves (intrinsic labelling) with chemical isotopes (in this case deuterium, or heavy water) HNR researchers can safely observe nutrients being absorbed in the gut from the food matrix itself – not just the compound in isolation – which might not behave the same way. By using the data in combination with labelled carotenoid compounds (extrinsic labelling), a novel method is being developed to assess the how different forms of processing and cooking affect carotenoid bioavailability in humans.

The research means that people could avoid missing out on the plants’ natural benefits, whether in large scale manufacture or small scale preparation, and similar studies are underway to look at vitamin C metabolism and bioavailability, and the relationship between the blood plasma concentration of vitamin K and dietary intake.

Studies such as these are also important in light of efforts to breed or engineer plants to manufacture high nutrient levels. Both approaches to improve plants’ traits require significant investment, and it’s important that breeders are shooting for the right goals. It’s another reason why studying nutrient absorption from the whole food matrix is preferable to looking at a compound in isolation – it’s a more realistic model of how food is consumed and reflects how the other food and the food matrix can affect nutrients’ bioavailability.

Related links

• Diet - what are people eating big survey