Ultraviolet B light boosts vitamin D content in plants

Friday 30 Mar 12
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Jette Jakobsen
Senior scientist
National Food Institute
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Plants treated with ultraviolet B (UVB) light have a higher vitamin D content and therefore have the potential to become a new source of vitamin D throughout the year. These are the provisional findings of a PhD thesis at the National Food Institute, Technical University of Denmark.

UVB-illuminated leaves from the solanaceae or nightshade family of plants, which includes the potato and the tomato, have a vitamin D content which is 18-64 times higher than plants which have not been treated with UVB light. These are the findings of a PhD thesis at the National Food Institute where Rie Bak Jäpelt has studied the occurrence and formation of vitamin D in plants.

The purpose of Rie Bak Jäpelt’s work has been to test whether sources of vitamin D can be expanded to include plants in order to better meet people’s vitamin D requirements in the winter months.

Fruit with vitamin D
“When the results show that solanaceae leaves illuminated with UVB light produce such large amounts of vitamin D, it is obvious to assume that the plants’ fruit will also contain vitamin D. Moreover, perhaps in such large quantities that even tomatoes and potatoes may potentially become useful sources of vitamin D,” says Assistant Professor Rie Bak Jäpelt from the National Food Institute.

“During the winter, many people are deficient in vitamin D. However, if it is shown that UVB light also boosts the amount of vitamin D in solanaceae fruit crops, we have created a new source of vitamin D which can boost vitamin D intake, also during the winter,” explains Rie Bak Jäpelt.

The UVB-illuminated solanaceae plants have been cultivated in a mini greenhouse, a so-called growth chamber, which is a closed system where it is possible to regulate light and temperature, for example.

UVB light is the wavelength of sunlight which is required for the skin to produce vitamin D. In Denmark, UVB light does not penetrate the ozone layer from October to March, and we therefore do not produce vitamin D in the winter months.

Two birds with one stone
The Danish Veterinary and Food Administration recommends 600 g of fruit and vegetables a day, and the Nordic Nutrition Recommendations (NNR) recommend a daily intake of 7.5 micrograms of vitamin D for everyone aged 2-60 years. If you replace the 600 g of fruit and vegetables with 600 g of UVB-illuminated leaves from this study, it corresponds to a daily vitamin D intake of 0.2-12 micrograms.

“It shows the potential of using UVB illumination as a method of increasing the amount of vitamin D in plants, especially during the winter when it can be hard to get enough vitamin D,” says Rie Bak Jäpelt.

“But it’s not going to happen tomorrow. First we need to find out how plants produce vitamin D and study how the plants’ vitamin D production can be used to process new and healthier foods,” says Rie Bak Jäpelt.

Read more
Read Rie Bak Jäpelt’s full PhD thesis: Vitamin D in plants – occurrence, analysis and biosynthesis (PDF).

The PhD thesis is a collaboration project with the Department of Plant Biology and Biotechnology, Faculty of Life Sciences, University of Copenhagen. The project is subsidised by the Ministry of Food, Agriculture and Fisheries under the Food Research Programme 2007.

See also the National Food Institute’s press release from 2011: Berigelse af fødevarer med D-vitamin virker  (in Danish) and a press release from 2010: Begrænset viden om D-vitamin og sygdomme (in Danish).