How much sunshine do you get on any given day? I ask because the amount of vitamin D that you get might determine whether you survive colorectal cancer. A Scottish study recently showed how crucial having enough vitamin D is—a matter of life or death.

The study analyzed 1,598 people who had had surgery for life-threatening colorectal cancer. The goal—to see whether there was a connection between how long a person survived and how much vitamin D was in his or her blood at the time of surgery.

A healthy vitamin D level is from 21 nanograms per milliliter (ng/mL) to 50 ng/mL. Between 12 ng/mL and 20 ng/mL is inadequate…and less than 12 ng/mL is considered vitamin D deficient. Fifty percent of patients in the Scottish study were vitamin D deficient and 27% had inadequate levels at the time of their surgeries—not surprising since Scottish people in general don’t absorb a lot of vitamin D from sunshine because of Scotland’s northern latitude (and frequent cloudy weather). But what the researchers found is that patients with higher vitamin D levels had a lower risk of death from colorectal cancer. While 20% of the patients with the lowest levels of vitamin D died within five years, it took 10 years before the death rate hit 20% among patients with the highest levels of vitamin D. What’s more, the patients with the highest levels of vitamin D had a one-third lower risk of dying from any cause (not just colorectal cancer) compared with patients with the lowest levels.

This research about vitamin D is great news for scientists who develop cancer treatments because it means they may be able to save more lives with vitamin D supplementation—but it comes with a challenge. People with colorectal cancer, as well as people with noncancerous intestinal problems, such as inflammatory bowel disease (IBD, which includes Crohn’s disease and ulcerative colitis), irritable bowel syndrome (IBS) and celiac disease (gluten intolerance) can have trouble absorbing enough vitamin D from food and even supplements.


You need between 10 and 15 minutes of full, sunscreen-free sunshine at least three times a week to get enough vitamin D, according to the National Institutes of Health. Your skin absorbs ultraviolet B rays from the sun and uses them to create the vitamin. Your body also stores and accumulates vitamin D. And yet vitamin D deficiency is a major problem in America and in northern latitudes in general. Sure, we can also get it from foods. Eggs, fatty fish (salmon, tuna, trout and mackerel) and fortified milk and cereal are vitamin D–rich and there’s always the fail-safe of a vitamin D supplement, but what if you do have problems absorbing dietary vitamin D?

If you are older than age 50, especially if you have a family member who has or had colorectal cancer or if you have IBD (Crohn’s disease or ulcerative colitis) or a similar inflammatory or erosive intestinal disease, you may be at increased risk for colorectal cancer. And if you do have an intestinal disease, there is a good chance that you are not getting enough vitamin D despite eating the right foods and taking a supplement. So, besides keeping up with colorectal cancer screening, make sure to have your vitamin D level checked during doctor visits. This is usually part of the routine blood test done during a physical exam—make sure it isn’t skipped. If the test shows that you are not getting enough vitamin D, work with a nutritionist or gastroenterologist to get back on track. You may need to take a higher dose of a vitamin D supplement than you have been taking and you may need to have your vitamin D blood levels checked every few months. Especially, don’t scrimp on sunshine! If you do have problems absorbing dietary vitamin D, getting enough may be as simple as talking a nice long walk on the sunny days of the week.