Tomatoes could become an important source of vitamin D

Vitamin D deficiency is linked to a number of health concerns across the world, and it is often recommended to increase intake by eating more fruits and vegetables. In a new study John Innes Centre, researchers have found a way to maximize vitamin D in tomatoes through gene editing. 

Our bodies produce vitamin D after exposure to UVB light, but food is the biggest source. The new biofortified crop could help millions of people with vitamin D deficiency, which is linked to higher risk of cancer, dementia, and many leading causes of mortality. Recent studies have also identified a link between vitamin D deficiency and increased severity of Covid-19 infection. 

During the winter months, and also at higher latitudes, people need vitamin D from their diet or supplements because the sun is not strong enough for the body to produce it naturally. 

Tomato leaves contain provitamin D3, one of the building blocks of vitamin D at very low levels. Provitamin D3 does not normally accumulate in ripe tomato fruits. The researchers used CRISPR-Cas9 gene editing to revise the genetic code of tomato plants so that provitamin D3 accumulates in the tomato fruit. 

The leaves of the edited plants contained up to 600 ug of provitamin D3 per gram of dry weight. The recommended daily intake of vitamin D is 10 ug for adults.  This may not sound beneficial as tomato leaves are usually discarded. However, the leaves of the edited plants can be used to manufacture vitamin D3 supplements. 

“We’ve shown that you can biofortify tomatoes with provitamin D3 using gene editing, which means tomatoes could be developed as a plant-based, sustainable source of vitamin D3,” said study co-author Professor Cathie Martin.

“Forty percent of Europeans have vitamin D insufficiency and so do one billion people world-wide. We are not only addressing a huge health problem, but are helping producers, because tomato leaves which currently go to waste, could be used to make supplements from the gene-edited lines.”  

The gene-editing had no effect on growth, development or yield of the tomato plants. One tomato contained levels of vitamin D that were equivalent to two medium sized eggs or 28 grams of tuna. Vitamin D in ripe fruit could be further increased by extended exposure to UVB, for example during sun-drying. 

“The Covid-19 pandemic has helped to highlight the issue of vitamin D insufficiency and its impact on our immune function and general health,” said study first author Dr. Jie Li.

“The provitamin D enriched tomatoes we have produced offer a much-needed plant-based source of the sunshine vitamin. That is great news for people adopting a plant-rich, vegetarian or vegan diet, and for the growing number of people worldwide suffering from the problem of vitamin D insufficiency.” 

The research is published in the journal Nature Plants. 

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By Katherine Bucko, Earth.com Staff Writer