Tomatoes are particularly suited to biofortification techniques ranging from conventional plant breeding to modern biotechnology such as gene editing, putting them at the top of the shopping list for researchers looking to improve the nutritional value of everyday foods.

Biofortification, increasing the micronutrient content in food, is a great tool to address ‘hidden hunger’, where diets contain enough calories but lack vital nutrients for health.

A contemporary example of tomato biofortification comes from Professor Cathie Martin FRS’ group, where researchers have used gene editing to make precise changes in the genome of tomato plants so that they accumulate high levels of pro-vitamin D3 in the fruit and leaves.

Experiments over the summer of 2023, some of the first trials of gene-edited crops in the UK, showed that exposure to sunlight, or shining UVB light on the plants, further converts provitamin D3 into vitamin D3, which is the more stable form that is useful for human health.

Brenda Mionki, a PhD rotation student on the EDESIA programme at Norwich Research Park has used gene editing techniques to almost double the amount of vitamin D accumulating in the fruit and leaves of tomatoes. The leaves could  be used to make vitamin D supplements suitable for vegetarians and vegans.

The plants are now being cross-bred with sweeter tasting and striped varieties of tomatoes that can be marketed as the ‘Sunshine’ tomato, a nod towards its increased vitamin D content.

“These consumer traits, appearance and taste, are vital,” says Brenda. “We have a scientific discovery which could make a health impact across society in products like soups and sauces, but in terms of the fruit itself look and taste are very important to consumer choice. Because of the ‘sunshine’ appearance, people will know that they are vitamin D tomatoes instantly. Most cultures in the world use tomatoes. They are inexpensive and tasty, and we are making them even healthier.”

While infectious diseases are decreasing globally, non-communicable diseases are on the rise, at a cost to us all. Food with high nutritional content, and technology such as gene editing, are just some of the ways that vitamin deficiencies can be addressed.

“Projects such as this can support public health interventions on a wide scale, working towards a future in which food is our real health care”, concludes Brenda.

This combination has led to a significant problem; an estimated one in five people in the UK are vitamin D deficient during winter and spring, and worldwide almost one billion people lack enough vitamin D.

People with darker skin, the elderly, those who are pregnant and breastfeeding, and people who are confined indoors are more likely to be deficient. Vitamin D supplementation in winter is now advised for everyone, especially those in high risk groups.

Sufficient levels of vitamin Dare essential for optimum health. It helps the body absorb calcium and phosphorus to keep our bones, teeth, and muscles strong. It also boosts the immune system to fight infections. Low vitamin  D levels have been linked to depression, dementia and a higher risk of cancers.

Vitamin D is produced in our skin when it is exposed to sunlight, hence its nickname as the ‘sunshine’ vitamin. In autumn and winter when daylight is restricted and people’s skin is more covered up, vitamin D is sourced from the diet.

However, vitamin D-rich foods are limited; oily fish, red meat and egg yolks are sources of vitamin D, but plants often lack this essential vitamin. Many supplements are not vegan friendly.

The Quadram Institute has launched one of the first human trials of gene edited food in the UK, to test the bioavailability of the vitamin D tomatoes.

The aim of the ViTaL-D study is to understand whether biofortifying tomatoes usinggene editing leads to higher levels of vitamin D in the blood after people have eaten them. One metric ton of these provitamin D enriched tomatoes were grown in polytunnels at the John Innes Centre and 200 participants with low vitamin D levels were enrolled to eat a regular portion of soup made from them over a three-month trial.

If successful, this trial would be a major step towards using biofortified gene edited tomatoes to support people’s health, and serve as an important scientific precedent for other nutritional interventions to address micronutrient deficiencies.

Tomatoes have been a key crop in the history of the John Innes Centre, from its early days as a horticultural institute.

In the 1930s there were no outdoor tomato varieties available in the UK – they had to be grown in glasshouses or inside homes. At the John Innes Horticultural Institution in Merton, Surrey, the forerunner of today’s centre at Norwich Research Park, breeders used advances in understanding genetics to develop hardy varieties that could for outdoors.

Forward to 2008, and Professor Cathie Martin FRS’ group used Genetic Modification (GM) technology to transfer genes from a garden snapdragon to biofortify tomatoes with purple pigment high in anthocyanins which are powerful antioxidants and anti-inflammatories.

Spin out company Norfolk Plant Sciences, jointly set up by Professor Martin and Professor Jonathan Jones FRS, successfully obtained approval for the tomatoes to go on sale in the United States.

Sixteen years after the purple tomato was first produced, the seeds were in strong demand, with more than 1,200 packets selling within 48 hours of launch, and 9,600 sold in the first week in February 2024. The product, marketed towards home gardeners, has remained popular, adding a dash of colour and extra nutrients to salads.

However, GM crops where DNA is introduced from another species, are not covered by the UK’s precision breeding act but by older, more complex legislation, which means a more challenging commercial route to market.