Vitamin D plays a vital role in maintaining our health. It is manufactured by the body after the skin's exposure to sunlight, and another major source is food. Fish and dairy products provide the best dietary sources of Vitamin D, which means that it is often hard for people following a plant-based diet to get enough.
The leaves of tomatoes contain one of the building blocks of Vitamin D3, called provitamin D3 or 7-dehydrocholesterol (7-DHC), although only normally at very low levels. Furthermore, provitamin D3 does not occur in the tomato fruits themselves at all.
Coding tomatoes to contain vitamin D
Now, researchers at the John Innes Centre in Norwich have used CRISPR-Cas9 gene editing to make revisions to 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.)
Forty percent of Europeans have vitamin D insufficiency
The researchers used gene editing to turn off a specific molecule in the plant’s genome which increased provitamin D3 in both the fruit and leaves of tomato plants. It was then converted to vitamin D3 through exposure to UVB light.
“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 Professor Cathie Martin, corresponding author of the study which appears in Nature Plants.
“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.”
Vitamin D insufficiency, is linked to higher risk of cancer, dementia, and many leading causes of mortality. Studies have also shown that vitamin D insufficiency is linked to increased severity of infection caused by SARS-CoV-2 / COVID-19.
great news for people adopting a plant-rich diet
First author of the study Dr Jie Li said: “The COVID-19 pandemic has helped to highlight the issue of vitamin D insufficiency and its impact on our immune function and general health. 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.”
As Chief Scientist, John Cristofides explains, "About 90% of circulating vitamin D is derived from the action of the UVB component of sunlight on the skin. The remaining 10% of circulating Vitamin D is derived from dietary sources, which include margarine, some breakfast cereals and liver but oily fish are particularly rich (mackerel, herring, sardines, salmon and fresh, not tinned tuna), whilst eggs, butter, beef and vegetable oils are a relatively poor source."