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Vitamin D, or “sunshine vitamin”, this essential element for many metabolic pathways in our body, plays a crucial role in our health. If we tend to think that it would be enough to expose ourselves to the Sun to obtain it, it happens that this is not enough depending on the country (sunshine). It is then necessary to turn to nutritional resources, especially in winter when sunlight is weakest. However, most foods contain very little vitamin D, and plants (especially fruits and vegetables) contain even less. Scientists then created genetically modified tomatoes to make veritable vitamin D “bio-factories”. which would perhaps make it possible to limit the waste of the leaves – in particular by the manufacture of natural food supplements rich in vitamin D.
Vitamin D is involved in many vital physiological processes in our body, such as the binding of calcium to the bones, and contributes to its good overall development (or to its post-traumatic repair). It also plays a fundamental role in the strengthening and proper functioning of the immune system, including inflammatory processes. Vitamin D deficiency may thus be involved in the risk of cancer for example, and may even be involved in the severity of SARS-CoV-2 (COVID-19) infections, according to certain studies. Deficiency can also be a risk factor for the development of neurological pathologies such as Parkinson’s disease and dementia, including Alzheimer’s. This involvement is explained by the role of vitamin D in the signaling pathways of important neurotransmitters.
Exposed to ultraviolet light, our skin naturally synthesizes vitamin D3, the form of vitamin D most available in nature. However, this ability can vary considerably from one individual to another. In addition, high latitude regions are very little exposed to the Sun in winter. The gaps must therefore be filled by nutritional inputs. However, most of the foods we eat contain little vitamin D, and we must ingest a wide variety of foods to be able to meet the needs for this vitamin. We must also sometimes use food supplements, such as cod liver oil.
In addition, there is today a certain tendency to adopt vegetarian or vegan diets. However, for those concerned, vitamin D resources are even lower, because plants contain much less than fish or meat. The researchers of the new study, published in the journal Nature Plantsthen propose a new vitamin D resource, apparently simple to produce and easily accessible in the long term.
” The provitamin D enriched tomatoes we have produced offer an indispensable vegetable source of the ‘sunshine vitamin’ said Dr. Jie Li, lead author of the study and postdoctoral researcher at the John Innes Institute, UK, in a statement. ” This is great news for people who follow a plant-rich diet — vegetarian or vegan — and for the growing number of people around the world suffering from the problem of vitamin D deficiency. “, she adds. 40% of Europeans and a billion people in the world are indeed deficient in vitamin D.
Vitamin D in leaves and fruits
To give birth to their new tomato plants, the British researchers used the CRISPR-Cas9 gene editing technique. In particular, they deactivated a specific gene of the original plant (the wild tomato) in order to increase the level of provitamin D3 in the leaves and fruits. Exposed to the ultraviolet rays of the sun, these molecules are transformed into vitamin D3.
What you need to know is that the leaves of tomatoes naturally contain molecules called 7-dehydrocholesterol (7-DHC) which can act as provitamin D3. However, they are only present at trace levels and fail to accumulate in mature fruit. The original plant notably secretes a specific enzyme, called Sl7-DR2, which degrades 7-DHC into other molecules.
The scientists then modified the genome of the tomato so that this enzyme is inactive, so that the 7-DHC reaches the ripe fruits. Subsequently, the genetically modified plants saw their levels of 7-DHC increase up to 600 micrograms per gram of dried leaves (the recommended daily intake for an adult is around 10 micrograms). The leaves of these tomatoes can thus be consumed or transformed into by-products instead of being rejected, unlike those of the original tomatoes.
Additionally, 7-DHC has also been observed in fruits. Exposed to ultraviolet radiation for one hour, the leaves and sliced fruit contained a significant amount of vitamin D3. A single tomato contained the vitamin D3 equivalent of two medium-sized eggs or 28 grams of tuna. According to the authors of the study, this quantity can be further increased by prolonging exposure to the Sun by drying, for example.
Furthermore, blocking the enzyme would not affect the growth or yield of tomato plants. Moreover, the technique could also be applied to other Solanaceae (potatoes, eggplants, peppers, peppers, …) whose 7-DHC biochemical pathways are similar to those of tomato.