Ergocalciferol in fortified bread and vitamin D blood levels in women
What it found
Bread made with ergocalciferol from UV-treated yeast barely raised vitamin D2 blood levels in young women over 8 weeks.
A daily ergocalciferol pill worked much better but lowered vitamin D3 levels.
What they found
Studies in people
Ergocalciferol bread and total vitamin D
Eating bread made with UV-treated yeast did not change total vitamin D levels in the blood compared with the placebo group. The average starting level across all women was 65·1 nmol/l.
Ergocalciferol pills versus bread
Taking a 25 µg ergocalciferol pill each day raised vitamin D2 blood levels far more than eating the same amount from the yeast bread. The pill also raised total vitamin D levels compared with the placebo.
Vitamin D3 raised levels most
A daily 25 µg vitamin D3 pill increased total vitamin D blood levels more than either the ergocalciferol pill or the ergocalciferol bread. It also raised vitamin D3 levels more than any other group.
Ergocalciferol pills lowered vitamin D3
Women taking the ergocalciferol pill saw their vitamin D3 blood levels fall over the 8 weeks. The bread group and the placebo group kept similar vitamin D3 levels throughout.
Parathyroid hormone changes
The vitamin D3 pill lowered parathyroid hormone levels compared with the ergocalciferol pill and the ergocalciferol bread. The ergocalciferol pill and bread groups stayed near their starting levels.
What the authors conclude
- They conclude that ergocalciferol from UV-treated yeast in bread was poorly absorbed by the women in this trial.
- They suggest the baking process or the form of the yeast may have stopped the body from using it well.
- They note their results add to evidence that ergocalciferol is less effective than vitamin D3 at raising total vitamin D levels and that it can lower vitamin D3 in the blood.
How it was done
In northern Europe, winter sunlight is too weak for the body to make enough vitamin D. The authors wanted to see if bread baked with UV-treated yeast could be a cheaper plant-based way to boost vitamin D levels.
Thirty-three healthy women aged 20 to 37 took part in an 8-week trial in Finland during winter. They were split into four groups eating regular bread with a placebo pill, regular bread with a 25 µg ergocalciferol pill, regular bread with a 25 µg vitamin D3 pill, or bread made with UV-treated yeast providing 25 µg of ergocalciferol plus a placebo pill. Blood samples were taken at the start, after 4 weeks and after 8 weeks.
What it can’t tell you
- This trial only included young healthy women in Finland, so the results may not apply to men, older adults or people with low starting vitamin D levels.
- The study lasted 8 weeks, so it cannot show what happens to vitamin D levels over a longer period.
Who paid
- Authors work at
- University of Helsinki, Finland; Technical University of Denmark, Denmark; University College Cork, Republic of Ireland
The paper
- Title
- Effects of vitamin D2-fortified bread v. supplementation with vitamin D2 or D3 on serum 25-hydroxyvitamin D metabolites: an 8-week randomised-controlled trial in young adult Finnish women
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Itkonen ST, Skaffari E, Saaristo P, et al (2016). Effects of vitamin D2-fortified bread v. supplementation with vitamin D2 or D3 on serum 25-hydroxyvitamin D metabolites: an 8-week randomised-controlled trial in young adult Finnish women. The British journal of nutrition. doi:10.1017/S0007114516000192Free full textPubMed 26864127DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error