Gene editing has brought beneficial changes to many foods. Now, researchers have engineered a plant that produced tomatoes and leaves that contain vitamin D. Vitamin D is known as the sunshine vitamin, because our bodies can make it when the UVB rays in sunlight hit skin. But many adults are thought to be deficient in vitamin D, which isn't found in many foods and can be difficult to obtain if you can't get a lot of sun. This work, which was reported in Nature Plants, could help restore more people's vitamin D levels to normal.
Insufficient vitamin D has been linked to a variety of health problems including an increased risk of dementia, cancer, and even more severe COVID-19 infections.
Tomatoes naturally produce low levels of a vitamin D3 building block known as provitamin D3, also known as 7-dehydrocholesterol (7-DHC). Provitamin D3 doesn't build up in tomatoes because it gets used for other things; an enzyme called Sl7-DR2 will convert it into other molecules. With CRISPR-Cas 9, the researchers stopped the tomatoes from producing the Sl7-DR2. They found that provitamin D3 began to accumulate significantly in the fruit flesh, fruit peel, and leaves of the engineered tomato plants.
Next, the scientists exposed the provitamin D3 to UVB light, by shining it on tomato leaves or slices of fruit for one hour, which successfully created vitamin D3 from the provitamin.
The recommended daily intake of vitamin D is about 10 micrograms.
The researchers found that after this process, one tomato contained the same amount of vitamin D as 28 grams of tuna fish or two medium-sized eggs. These are some of the only foods that naturally contain vitamin D. There are few options for vegans.
Leaves of the engineered plants carried as much as 600 micrograms of provitamin D3 per gram of dried leaves, so they may even be useful for producing supplements.
"Forty percent of Europeans have vitamin D insufficiency and so do one billion people world-wide," noted corresponding study author Professor Cathie Martin. "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."
Blocking the release of Sl7-DR2 appeared to have no impact on the development, growth, or production of the tomatoes. This same biochemical pathway is found in other crops including potatoes and peppers, so this technique may be applicable to those foods as well.