Ask the Nutritionist
Q: I am a cancer survivor and it was recommended by one of the Dana-Farber nutritionists to take a vitamin D supplement. What blood level of vitamin D is beneficial to cancer survivors?
Chris Mulcahy, Hartford, Connecticut
A: Recent research suggests that having adequate vitamin D levels may both reduce the risk of developing cancer and provide benefits for cancer survivorship.
Our skin can make vitamin D from the sun, but the amount produced is affected by a number of factors including skin color and sunscreen, as well as geographical like the amount of sunlight, cloud cover, and smog there are where you live. There are also limited dietary sources of vitamin D, including salmon, tuna, cod liver oil, and fortified dairy. For most people living in New England, especially during the sun-deprived winter, supplementation is usually recommended.
The 25(OH)vitamin D test is the best indicator of vitamin D status. The level of 25(OH)vitamin D in the blood is a reflection of the vitamin D produced by your skin, as well as the amount consumed from food or supplements.
Our understanding of vitamin D is still evolving, but studies suggest that the optimal level of 25 (OH) vitamin D for cancer survivors is between 40-60 ng/mL. The general amount of supplementation currently recommended is a total of 1000 International Units per day. If your blood level is less than 30 ng/mL, it is recommended that you start at a total supplemental dose of 2000 IU per day. Check the amounts of vitamin D in other supplements you may already be taking, such as multivitamin or calcium, to see how much additional vitamin D you may need to reach the total daily recommended intake based on your blood level.
Levels of 25(OH) vitamin D should be rechecked 8-12 weeks after beginning supplementation. If necessary, your dose should be adjusted accordingly to reach the serum level goal of approximately 50 ng/mL.
Speak to your physician or a registered dietitian before starting any supplements.