In a recent review article published in Nutrition Reviews, a group of Australian researchers analyzed the vitamin D levels of cancer patients to determine how many were deficient in the vitamin and how this was affecting their health.
Vitamin D deficiency and insufficiency is a global health problem, and it is even more common for cancer patients in the US to have lower vitamin D levels than adults in the general population.
In the studies this particular review looked at, 31% of the cancer patients were vitamin D deficient while 67% were insufficient. Previous research suggests that cancer patients with low vitamin D levels have poorer health and survival rates, but it is uncertain if taking vitamin D can help in these areas.
The authors looked at the results of 36 studies of cancer patients that reported vitamin D levels at or after diagnosis. Most of the studies were conducted in the United States and looked at women with breast cancer, but other types of cancer were included too.
The main results in their review were:
- Vitamin D deficiency was most common in patients with cancer of the blood, bones, and lymph nodes.
- The more overweight the patients were, the more likely they were to be low in vitamin D.
- At least 2,000 IU of vitamin D per day was required to raise blood levels. Lower amounts did not improve vitamin D status.
- The evidence for vitamin D reducing fractures, pain, and risk of death was mixed.
There are many reasons that could explain why some of the studies showed benefit of vitamin D for fractures, pain and risk of death while others did not. Many studies gave less than 2,000 IU of vitamin D per day and most only lasted for between two and four months. This is probably not long enough to know if vitamin D is doing anything or not. Another problem was that some of the studies did not test vitamin D levels until up to 270 days after diagnosis, so in these cases it is impossible to know what the blood levels of the patients were when they were diagnosed with cancer.
Because many of the positive results came from studies that gave people enough vitamin D to have blood levels higher than what the government recommends, we won’t know for sure just how much vitamin D can help people with cancer until more well-designed studies giving people higher amounts of vitamin D are conducted. In the mean time, if you have cancer, work with your doctor or nutritionist to take enough vitamin D to maintain sufficient vitamin D levels.