The Sunshine Vitamin
Vitamin D is for More Than Just Your Bones
In the midst of our Northern summers, when many of us take holidays, spend time at the beach, and soak up the sun’s rays, the sun helps us produce vitamin D, also known as the Sunshine Vitamin. But our Northern sun exposure is probably not enough.
There is a lot of talk about the benefits of vitamin D these days, including studies suggesting that vitamin D may help in reducing the risk of developing a host of chronic conditions, including some types of cancer. The important role vitamin D plays in bone health is well known. It is necessary for calcium absorption and helps keep up blood phosphorous levels, another important ingredient in healthy bones. Without this important vitamin, we are at increased risk of developing osteoporosis and bone fractures. Recent research has uncovered compelling evidence that the Sunshine Vitamin may be linked to a decreased risk of death from cardiovascular causes, more positive prognoses for breast cancer patients, reduced risk of multiple sclerosis, and even lessening mental health conditions such as schizophrenia and depression. While the majority of this new data is from observational studies, indications are promising enough to warrant attention.1
Vitamin D and GI Disease
D is a fat-soluble vitamin and this is of particular interest within the gastrointestinal tract. If you have a bowel disease, you may have difficulty absorbing dietary fat, and are therefore at greater risk for vitamin D deficiency. This vulnerability includes persons with Crohn’s disease, untreated celiac disease, pancreatic enzyme insufficiency, and those who have had certain sections of their bowel removed.14 Another gastrointestinal area where vitamin D levels come into play is in reducing risk of colon cancer and in extending the life of colon cancer patients. Colon cancer is the third most common cancer and the second most common cause of death from cancer for both men and women.2
Diet is probably the most important factor when it comes to colon cancer. Diets high in fat and red meat are associated with an increased risk of colon cancer, whereas diets high in fibre, calcium, fruits, and vegetables help prevent colon cancer.3 For more than 20 years, studies have demonstrated that vitamin D offers some protection against colon cancer. For example, in 1996, Harvard researchers showed that higher levels of vitamin D in the bloodstream reduced the risk of colon cancer. In fact, the men with the highest total vitamin D intake were about 50% as likely to develop colon cancer compared to men who had the lowest total intake.4 Other studies since then have supported these findings.
What about patients who already have colon cancer? Does vitamin D provide them with any benefit? Yes. A recent study by the Dana-Farber Cancer Institute and the Harvard School of Public Health has demonstrated that colon cancer patients who have high levels of vitamin D have a reduced risk of death compared to patients who are vitamin D deficient.5 This evidence suggests that vitamin D might protect against colon cancer and might help extend the life of those with colon cancer.6
Getting Enough Vitamin D
Vitamin D should be an important part of your daily diet. However, as you will see from the accompanying chart, it could be challenging to ensure sufficient quantities of vitamin D from limited dietary sources, such as fortified milk, Shiitake mushrooms, and some types of fish.
While human beings can synthesize vitamin D from direct exposure to sunlight, research to date is inadequate to produce clear guidelines, as time of year, geographic latitude, time of day, cloud cover, smog, skin type, and use of sunscreen are among the multitude of factors that affect vitamin D synthesis.7
Those living in Canada produce little to no vitamin D from October to March because the sun’s UV rays are insufficient for vitamin D synthesis.8 This should not be a problem during the Summer months, right? Well, while it is true that the sun is strong enough during summertime to help us produce vitamin D, there are other considerations to keep in mind. The Canadian Cancer Society and the Canadian Dermatology Association both recommend the use of sunscreen and staying out of the sun during mid-day hours, when the sun’s rays are strongest, in order to reduce the risk of skin cancer.9,10 These recommendations reduce the potential for producing vitamin D. Sunscreen SPF 15 reduces vitamin D production by 99%.11 The Canadian Cancer Society and the Canadian Dermatology Association recognize the importance of vitamin D. Both organizations recommend a vitamin D supplement containing 1,000 IU.12,13
Vitamin D has demonstrated health benefits relating to colon cancer, and some persons with gastrointestinal disease could be at risk for further depletion of this vitamin. Discuss the use of vitamin D supplements with your healthcare professionals. Vitamin D is not the only protecting factor against disease, so any supplementation should be part of a healthy diet, overseen by your healthcare provider.
Common Sources of Vitamin D14,15
Approx. Vitamin D2 and D3† Content
|Natural common dietary sources|
|Salmon, fresh wild, 3.5oz (~100g)||600-1000 IU of vitamin D3|
|Salmon, fresh farmed, 3.5oz (~100g)||100-250 IU of vitamin D2 or D3|
|Salmon, canned, 3.5oz (~100g)||300-600 IU of vitamin D3|
|Sardines, canned, 3.5oz (~100g)||300 IU of vitamin D3|
|Tuna, canned, 3.6oz (~100g)||230 IU of vitamin D3|
|Shiitake mushrooms, fresh, 3.5oz (~100g)||100 IU of vitamin D2|
|Shiitake mushrooms, sun-dried, 3.5oz (~100g)||1600 IU of vitamin D2|
|Egg yolk, one||20 IU of vitamin D2 or D3|
|Fortified dietary sources|
|All cow’s milk (fortified),* 250mL||88 IU of vitamin D3|
|Infant formula (fortified), 250mL||100 IU of vitamin D3|
|Margarine (fortified), 1 tsp||25 IU of vitamin D3|
|Yogurt (fortified), 8oz (~230mL)||100 IU of vitamin D3|
|Cheeses (fortified), 3.5oz (~100g)||100 IU of vitamin D3|
|Breakfast cereals (fortified), average serving size||100 IU of vitamin D3|
|Fortified plant-based beverage,** 250mL||80 IU of vitamin D3|
|Over-the-counter tablets, various, ranging||400 IU – 1000 IU vitamin D3|
|Ddrops™ liquid Vitamin D3, 1 drop||1000 IU of vitamin D3|
Table adapted from Health Canada 2004 and Holick, MF 2007.
† 1 ųg (mcg) = 40 IU of vitamin D, when the terms calciferol or ergocalciferol are used, the product usually contains vitamin D2; when the term cholecalciferol is used, the product usually contains vitamin D3
*Cow’s milk is not recommended for children 9 to 12 months of age
**Vegetarian beverages are inappropriate alternatives to breast milk, infant formula, or cow’s milk in the first 2 years of life
In an information update issued in 2007, Health Canada cautioned Canadians of the health risks associated with taking too much vitamin D. The Tolerable Upper Intake level of vitamin D for adults set by Health Canada is 2000 IU/day from all sources of vitamin D, including milk and over the counter supplements.14 Consult your health care professional for more information about vitamin D. You should be aware of the following reported interactions with vitamin D, as they relate to digestive disorders:
- taking stimulant laxatives may impair absorption of dietary vitamin D,
- taking magnesium-containing antacids with vitamin D may increase the risk of high blood magnesium levels, which could lead to muscle weakness and confusion,
- taking cholestyramine (Questran®), a bile salt binder, may decrease intestinal absorption of vitamin D, and
- if you’re on corticosteroid medication, you may need additional vitamin D supplementation to contend with calcium depletion.15
Vitamin D and Crohn’s Disease
The sunshine vitamin may prevent more than bone deterioration.
Approximately one billion people worldwide are not getting enough of the highly beneficial vitamin D. We can synthesize vitamin D through our skin from exposure to sunlight, and there are small amounts of it in some foods. However, many people are still finding it difficult to obtain adequate amounts, which is why healthcare professionals recommend we take supplements to meet our nutritional needs.
In Issue 171 of The Inside Tract® newsletter, we discussed the benefits of vitamin D and how they relate to individuals with gastrointestinal diseases and disorders. We explained that individuals who have difficulty absorbing dietary fat, such as those with Crohn’s disease or celiac disease, may have difficulty obtaining enough vitamin D because it is fat soluble. In addition, we talked about the reduced risk of colon cancer in individuals with adequate vitamin D intake.
Now, new research shows that vitamin D may play a much larger role in the development of Crohn’s disease, as well as many other medical conditions. Canada has the highest incidence and prevalence of Crohn’s disease worldwide. Crohn’s disease is a chronic inflammatory bowel disease characterized by inflammation that can occur anywhere along the digestive tract, and can penetrate the full thickness of the bowel wall. Its symptoms include diarrhea, rectal bleeding, pain, and weight loss. The causes of Crohn’s disease are currently unknown, although immune dysregulation may play a part in the development of this disease.
Medical professionals have long known of vitamin D’s usefulness when it comes to increasing calcium absorption, and therefore aiding bone health; however, researchers have been continuing to release studies that show its efficacy in reducing the risk of many diseases, including colon cancer, multiple sclerosis, rheumatoid arthritis, and type 1 diabetes. The newest study1, published in the journal, Genome Research, shows just how important this humble vitamin really is. Using new technology that recognises the protein that is activated by vitamin D (the vitamin D receptor), the researchers found 2776 vitamin D binding sites, which are places along the human genome where the vitamin bonds to the DNA, affecting the way it works. They also found that 229 specific genes worked significantly differently in response to vitamin D. The researchers found clusters of these vitamin D receptors in areas of the genome responsible for various autoimmune disorders and cancers. This explains exactly why vitamin D helps prevent diseases like multiple sclerosis, rheumatoid arthritis, type 1 diabetes, and colon cancer. Like many other diseases that may be linked to immune regulation, this research shows that Crohn’s disease contains many sites for vitamin D bonding. What this suggests is that an adequate intake of vitamin D may play a part in impeding the development of Crohn’s disease, possibly preventing full development of the disease if supplemented before disease onset.
An important piece of information to take from this research is that if we ensure that pregnant women and young children receive an adequate intake of vitamin D, we could reduce the amount of autoimmune disease and cancer in these individuals when they are older. The researchers believe that with adequate supplementation, we could prevent some cases of Crohn’s disease. However, it is still important for individuals who are older, and those already diagnosed with one of these diseases, to take the vitamin as well, as it is important for general health and preventing other illnesses. The researchers recommend that all people include vitamin D supplements in their diets, or get sufficient time in the sun. But, since sunscreen can interfere with vitamin D synthesis, and obtaining enough sunlight during the winter can be difficult, most healthcare practitioners recommend adults take a daily supplement that includes 1,000IU of vitamin D. Pregnant women and parents of young children should talk to their physicians about how much vitamin D they or their children should be taking.