Although estimates vary, most experts agree that a large percentage of people living in the US and Europe are not getting enough vitamin D. Low D levels are associated with an increased risk of osteoporosis, rickets, muscle weakness, some cancers (including breast, colon, and prostate cancer), heart disease, type 1 diabetes, and several autoimmune diseases such as multiple sclerosis (MS), rheumatoid arthritis, and Crohn's disease.
Maintaining healthy levels
The majority of circulating vitamin D in the body comes from exposing the skin to ultraviolet light--that is, spending time in the sun. The problem is that some geographic areas just don't get enough year-round sunlight for the body to produce sufficient vitamin D. If you live anywhere north of Flagstaff, Arizona, chances are you won't get enough vitamin D during the sun-shiny months to last you through the winter. Sunscreen use is another factor: while it may help prevent skin cancer, it also blocks those rays of light your body uses to manufacture vitamin D.
Naturally occurring food sources of vitamin D are scarce, but include oily fish (like salmon, trout, and herring), egg yolks, sun-dried mushrooms, and cod liver oil. Other than that, fortified foods are the only non-sun source of vitamin D.
Supplements & liquid sunshine
The new study compared the vitamin D-raising effects of orange juice fortified with vitamin D2 or D3 with that of supplement capsules containing D2 or D3, and placebo. For 11 weeks, 86 people between the ages of 18 and 84 were given one of these combinations each day:
- placebo plus plain orange juice,
- placebo plus orange juice with 1,000 IU vitamin D2 or D3,
- or plain orange juice and a capsule containing 1,000 IU vitamin D2 or D3.
- Blood samples were collected each week to track changes in the people's vitamin D status.
Vitamin D levels increased in all of the people who were given vitamin D, regardless of the source. No changes in vitamin D status were seen in the placebo group, suggesting that the increase in vitamin D levels in the supplemented groups was not due to sun exposure. The authors concluded, "Fortification of orange juice with vitamin D2 or vitamin D3 is a resourceful way of enhancing vitamin D status in adults and children."