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Vitamin D is essential for bone development, with a deficiency in childhood leading to skeletal deformations known as rickets.
Also, in adults the deficiency is thought to predispose to many disorders including cancer, depression, neurodegenerative diseases and severe Covid-19.
Our source of vitamin D is mostly dietary, from fish and dairy products, but it is also synthesized in our skin from a precursor called 7-dehydrocholesterol (7-DHC) after exposure to ultraviolet B (UVB) light.
Globally, around a billion people are vitamin D deficient, mainly those with a poor diet in Northern climes where UVB is in short supply.
And now, with many people adopting a plant-rich or vegan diet, this deficiency will likely become more common.
With this in mind, scientists at the John Innes Center in Norwick, UK, have produced ‘biofortified’ tomatoes with increased vitamin D content 1.
This was achieved by using gene-editing to inactivate an enzyme that converts 7-DHC into cholesterol.
In the resulting plants 7-DHC accumulates in the leaves and fruit where it is converted to vitamin D by exposure to UVB.
This produced ripe red tomatoes each containing around 20% of the UK recommended daily dose of vitamin D.
The scientists suggest that sun-drying these tomatoes would increase the vitamin D content, and also that, as the leaves of gene-edited plants contain appreciably more vitamin D than the ripe fruit, these could be used to manufacture plant-based vitamin D suitable. for vegans.
They also propose that other members of the Solanaceae plant family, such as aubergines, potatoes and peppers, could be biofortified in the same way as tomato plants.
But will these gene-edited products ever reach our supermarket shelves?
Although the gene-edited tomato plants grow well in experimental glasshouses, they have yet to be tested in field trials.
But perhaps a more serious problem is that until May 2022 the UK, like the EU, banned the sale of any genetically-modified food products.
But a recent bill introduced by the government proposed to treat gene-edited
food differently from gene-modified products.
Perhaps these vitamin-rich, gene-edited tomatoes will be the first.
test cases. 1) J.LI et al. Nature Plants, 8, 611-616. 2022.