Low levels of vitamin D are linked to increased risk of soft bones, bowel cancer and diabetes.
We can get vitamin D from oily fish, eggs, bread and breakfast cereals but we depend on the action of sunlight on our skins for most vitamin D.
In Britain for most of the year the sun is not powerful enough and supplements are recommended.
Current UK advice recommends supplements of 0.01mg for pregnant and breast feeding women.
Babies and children from the age of 6 months until 5 years are advised to take a supplement.
Everyone over 65 should take supplements in winter and early spring.
Rickets is on the rise again in Britain.
M&S is the first UK retailer to add Vitamin D to its bread. Yeast that naturally produces vitamin D is used in the bread production.
A deficiency of Vitamin D can lead to rickets in children and osteomalacia in adults.
About 10 million people in UK are not getting enough Vit D and children under 4 may be given the supplement.
NHS recommends that anyone over 65 or those that cover up their skin for cultural reasons should take a 10mg supplement.
Claire Hughes, head of nutrition at M&S said ‘We want to make it easy for our customers to increase their intake of vitamin D.’