Scientists have created genetically engineered tomatoes, each containing the same amount of provitamin D3, the precursor to vitamin D, as two eggs or a tablespoon of tuna.

Open field trials of the tomatoes are expected to begin in the UK next month and, if successful, could provide a source of vitamin D compliant with important new dietary guidelines.

Vitamin D

Vitamin D is an essential vitamin in our body to keep our bones, teeth and muscles healthy. Vitamin D is produced and stored in our body on a limited basis; Ultraviolet B rays from the sun are the strongest source of vitamin D and convert provitamin D3 into the form of vitamin D that the body needs. Not getting enough ultraviolet light and preventing its contact with the skin cause insufficient vitamin D synthesis. Here, for geographical reasons, around 13-19% of Britons have low vitamin D levels.

The UK only has enough sunlight between April and September to achieve this and it is insufficient. This means we have to rely on dietary sources or supplements like fatty fish, red meat, egg yolks and mushrooms. This is especially difficult for vegans, as many supplements contain lanolin derived from sheep's wool.

What is Lanolin?

Lanolin is a wax secreted by the sebaceous glands of wool-bearing animals. It is also called wool wax or wool oil. The lanolin used by humans comes from domesticated sheep breeds that are specially bred for their wool.

Guy Poppy, professor of ecology at the University of Southampton, "Gene-edited tomatoes may do better for many of us to accumulate levels of Provitamin D3 needed for healthy eating, since tomatoes are a widely available and easily eaten food." said.

Genetically rearranged tomato plants were created by using an editing technique called Crispr-Cas9 and making minor changes to an existing tomato gene. Jie Li, who led the research at the John Innes Center in Norwich, said: "This is much more like the precision-taking of a gene with a pair of molecular tweezers to add a desired trait to a plant, without adding any foreign DNA from other species and can be implemented much more quickly than the traditional seed breeding process.”

In this case, the focus was on an enzyme found in the tomato plant that normally converts provitamin D3 to cholesterol. By modifying this enzyme, the researchers were able to block this metabolic pathway, the pathway from provitamin D3, which accumulates in the fruits and leaves of tomatoes, to cholesterol.

They calculated that the amount of provitamin D3 in a tomato fruit – if converted to vitamin D3 – would equal the levels found in two medium eggs or 28 grams of tuna. To convert this to active vitamin D3, the fruit will still need to be exposed to UVB light, or potentially grown outdoors. This is something the researchers plan to test in future field trials. The research in question was published in Nature Plants.

"It's a good example of the use of gene editing technologies to make a very specific change in a crop," said Prof Gideon Henderson, chief scientific adviser in the Department of Environment, Food and Rural Affairs.

Such "fine-edited" crops are the subject of a bill outlined in the Queen's speech that would make engineered plants different from genetically modified organisms (GMOs). Its cultivation is subject to the strict European rules that England wishes to leave.

"This is an example of a type of product that may pass traditional GMO legislation but very slowly in the current regulatory environment and may take decades to find its place in the system," Henderson said.

Unlike GMOs, tomato plants do not contain genes from other organisms and could theoretically have been created through selective breeding – albeit much more slowly. Such crops will be allowed under the genetic technology (precision crop development) bill that the environment secretary envisions to pass this year, potentially making the first gene-edited foods available by 2023.

Prof Cathie Martin of the John Innes Center, who oversaw the study, said the study demonstrated the potential for gene editing to improve the nutritional properties of foods, and that the same technique could produce similar changes in any elite tomato variety. “It means that companies can introduce this feature to their patent-protected cultivars or be included in Gardener's Delight as a non-patent-protected tomato variety,” he said.

"The technique could probably works with solanaceous food crops like peppers, chillis, paprika, potatoes, and eggplant."

A probable further benefit of this tomato species for its growers is that they can potentially sell the leaves or unripe fruit to manufacturers for processing into vitamin D tablets,  Martin said.

Reported from The Guardian website.