Vitamin D-cancer link inconclusive
Q. I’m totally confused by the conflicting things I’m hearing about whether Vitamin D can reduce cancer risk. What’s the current advice about vitamin D?
A. The current national recommendations for vitamin D from the Institute of Medicine (IOM) are 600 IU/day for adults up to age 70 and 800 IU for older adults, but these are based primarily on evidence for bone health. The IOM report concluded that research on whether vitamin D reduces cancer risk is inconsistent.
In cell studies, researchers have identified ways that vitamin D can keep cancer in check, and in other studies they’ve shown that animals deficient in vitamin D show early signs of prostate cancer and develop faster growing colon cancer.
Some large human studies do link lower blood levels of vitamin D with greater risk of certain cancers, but overall these studies show mixed results. In fact, there are also studies that link very high blood levels of vitamin D (achievable only with supplements) with greater risk of pancreatic and prostate cancer.
A new analysis involving more than 2,400 women followed for 10 years shows no link between blood levels of vitamin D and cancer-related or overall deaths. Individuals taking the same amount of vitamin D can end up with different blood levels of the nutrient, so researchers are working to identify what blood levels seem to bring most protection without raising health risks. According to Dr. JoAnn Manson, professor at Harvard Medical School, “Before we assume there’s any cancer protection from higher amounts, we need rigorous controlled testing.”
She is directing the VITamin D and OmegA-3 Trial (VITAL), the first large-scale randomized trial of vitamin D (2000 IU daily) in the prevention of cancer and cardiovascular disease (vitalstudy.org), and other trials are underway as well.
Meeting the current RDA for your age is smart for overall health. If you choose to go slightly higher (4000 IU is the highest dose considered safe) – which most likely requires either a supplement or highly fortified food – it should be safe, but don’t assume there’s added cancer protection.
Q. You’ve talked about tuning in to hunger signals to guide my portion sizes. But what can I do when I feel like eating even though I’m not hungry? I think that’s the root of my excess weight.
A. Great job at tuning in to hunger signals! People can feel like eating – despite lack of hunger – for a variety of reasons.
The next step, when you realize that you are not hungry, but feel an urge to eat anyway, is to tune in again. Can you figure out what’s behind the urge? Maybe you are actually thirsty and simply need to drink more water. Or is more sleep what you really need? You might be trying to address feelings such as stress, anger, loneliness or boredom with food.
Set aside time when you are not in the midst of one of these urges to make a list of things other than food that might meet the need. For example, you could take a crossword puzzle break from challenging work, do deep breathing or phone a good friend when feeling stressed.
Here’s a little trick: behavioral therapists often note that this desire to eat when not hungry tends to come in a wave. If you aren’t truly hungry, the urge will usually pass if you can distract yourself with something else for a little while. So when the urge comes to eat and you are not hungry, check your pre-planned distraction ideas list and try one of the possibilities there before you head for food.
Ÿ Provided by the American Institute for Cancer Research.