VEGANALYZEVitamin D In Plant-based Foods And Vegan Products
The majority of the vitamin D requirements can be met during the summer months through sunlight. The body produces vitamin D itself through the effect of ultraviolet rays (part of sunlight) on the skin. However, during the winter months in our latitudes, it is difficult to meet the requirements through the skin due to the low angle at which the sun's rays reach us. Once the stored vitamin D reserves from the summer months are depleted, initial symptoms of vitamin D deficiency may occur.
When it comes to vitamin D in foods, the discussion often revolves around:
- Vitamin D2 (ergocalciferol): produced by mushrooms
- Vitamin D3 (cholecalciferol): mainly found in animal-based products; it can also be derived from lichens 1
Cooking has only a minor influence (<10%) on the vitamin D content of the respective food 2.
But what about the presence of vitamin D in plant-based foods? In advance, very few contain vitamin D, so meeting the requirement through diet is generally difficult. vitamin D is found in some plant-based foods or added to processed foods.
Mushrooms with vitamin D
The most notable plant-based sources of vitamin D are mushrooms. Particularly noteworthy are chanterelles (212 µg), morels (206 µg), oyster mushrooms (29 µg), maitake (28 µg), shiitake (18 µg) and button mushrooms (7 µg) - see vitamin D in mushrooms (list). Studies suggest that mushrooms containing vitamin D2 can effectively contribute to improving vitamin D status 3. The ergocalciferol from wild-grown mushrooms, for example, can be well absorbed by humans 4.
Particularly dried shiitake mushrooms contain high amounts of vitamin D (54 µg per 100 g). Even after years of storage, dried mushrooms retain much of their original vitamin D content 5.
Meanwhile, there are so-called vitamin D mushrooms available. These are champignons whose vitamin D content has been artificially increased through UV irradiation. A portion of champignons covers the daily requirement of vitamin D as they contain 30 times more vitamin D than regular mushrooms.
Vitamin D occurrence in processed products
Most vitamin D is found in processed products as an added form. This includes cereal, soy yogurt, plant-based drinks, and margarine. However, the latter often contains vitamin D3 of animal origin. Therefore, special attention should be paid to avoid purchasing it. Information about this can be found in the printed nutritional table and ingredients list. Nevertheless, food and products with enhanced vitamin D concentrations are an effective way to increase plasma vitamin D concentrations [25(OH)D] without having adverse health effects 6.
Recently, selected orange juices have also been fortified with vitamin D, which is an effective method to maintain and safely increase vitamin D levels in the body 7 8. Be sure to check that the juices contain plant-based vitamin D2 (ergocalciferol) or synthetic D3 and no gelatin.
Click here for the table of plant-based foods and products containing vitamin D.
Will there be wheat flour with vitamin D soon?
A study from the United Kingdom provides new evidence that fortifying wheat flour with vitamin D could also be a feasible option for improving vitamin D status 9. Simulating an enrichment of 10 μg vitamin D per 100 g of wheat flour would reduce the risk of vitamin D deficiency in the United Kingdom among at-risk groups (children aged 18 to 36 months, women aged 15 to 49 years, and adults aged ≥65 years) from 93% to 50%.
New possibilities to increase plasma levels of vitamin D and thus prevent deficiency may also come from bread fortified with vitamin D 10. The availability of such bread in the market is not yet known.
Food irradiation to increase vitamin D content
Partially, mushrooms are irradiated with ultraviolet light to increase the Vitamin D2 content 11 12. Study results from 2011 already demonstrate that the additional Vitamin D2 from UVB-treated mushrooms is bioavailable, making them a promising alternative to increase plasma vitamin D concentration 13. During the study, participants received a weekly dosage of 700 µg (28,000 IU) of vitamin D in the form of mushroom soup during the winter. Plasma concentrations increased by 3.9 nmol/L over a period of 2 weeks.
Currently, research is being conducted on UVB irradiation of fruits and vegetables. Promising results have been achieved with the production of vitamin D3 in nightshade plants such as tomatoes, potatoes, and bell peppers 14. Vitamin D3 has also been detected in alfalfa after artificial irradiation in multiple tests 15 16.
In addition, work is being done on the UV irradiation of bread. The European Food Safety Authority (EFSA) examined UV bread as a novel food in terms of its safety 17. The risk of allergic reactions is similar to conventional bread. Under the examined conditions, UV bread is considered safe. According to EFSA, after baking, the bread is exposed to UV rays, which convert ergosterol present in the bread due to yeast fermentation into vitamin D2. The vitamin D2 content ranged from 0.75 to 3 μg per 100 g (with 1 to 5 g of yeast per 100 g of dough) in UV-treated bread.
Do avocados contain vitamin D?
There are conflicting statements regarding the vitamin D content of avocados. Some institutes claim that vitamin D is present, while others have not been able to detect vitamin D (see avocado nutritional values).
Presence of vitamin D in dark green vegetables?
Some websites also mention vitamin D in dark green leafy vegetables such as alfalfa, dandelion, nettle, or watercress. We could not find any scientific studies to support these claims.