Vitamin D and Colon Cancer Risk
This week I came across a study published in the Journal of the National Cancer Institute, in June 2018, which reported the results of a study that looked at a person’s circulating levels of vitamin D and their risk of developing colorectal cancer.
Vitamin D is one of my favorite vitamins. It’s a favorite for a couple reasons: when people discover a deficiency it is simple to correct, people actually feel the effects when their levels increase, and it is such an important vitamin that it really promotes improved health in patients. Vitamin D is involved in many aspects of human health including skin health, bone health, hormone production, and mental health issues such as depression and anxiety. It has also been known for a long time that vitamin D, particularly vitamin D3, the active form of vitamin D, can be helpful in the prevention and treatment of chronic illnesses like cancer.
I always include an assessment of vitamin D3 levels in my patients. Over the years I’ve found it extremely rare to find normal levels of vitamin D3 in those who are not supplementing. When I initially bring up the idea of testing, people often ask "don’t I get enough of this just being outside?" My typical reply is "Not likely". The National Institutes of Health suggests that approximately 5–30 minutes of sun exposure between 10 AM and 3 PM at least twice a week to the face, arms, legs, or back without sunscreen usually lead to sufficient vitamin D synthesis. I simply haven’t found this to be true, even in people who spend a great deal more time outside than the NIH suggests is sufficient. The majority of people need to take a vitamin D supplement to achieve a healthy level.
So, back to this latest article about vitamin D3 and colon cancer prevention. I found this latest research interesting because it found that vitamin D3 could indeed help prevent colon cancer, but also because the findings suggest that healthy levels of vitamin D3 may be higher than the current recommendations.
The Office of Dietary Supplements, a branch of the FDA, is responsible for setting the reference ranges, or “normal” values of vitamin and minerals. Vitamin D3 is somewhat unique that in addition to having a normal value, it has also been given a “optimal” value. The table below shows the current vitamin D3 ranges. It’s important to note most laboratories report vitamin D3 levels in nanograms per milliliter (ng/ml), while most researchers seem to use nanomoles per liter (nmol/L). Both of these concentrations are included in the table.
Up until this year the normal range of vitamin D3 reported on laboratory tests was between 30-100 ng/mL (75-250 nmol/L). In early 2018 the normal values for D3 was adjusted to >20 ng/mL (50 nmol/L). This essentially lowered the normal range. I have often counseled patients to try and obtain a vitamin D3 serum level about 40-50 ng/mL.
The vitamin D3 and colon cancer study found that the “normal” range listed for vitamin D3 is too low for colon cancer prevention. This study, which included about 13,000 people, found that vitamin D3 levels varied widely. Importantly, the study made adjustments for body mass index, exercise levels, and other risk factors for colorectal cancer and found that these minimally affected their results. So, when the researchers compared what was considered the current lower range of vitamin D3 sufficiency for bone health to a deficient level, a 31% higher colorectal cancer risk was found for those with the deficient levels. 31% is a pretty big number. The risk reduction was most significant for women. In men there was a risk reduction as well, but it was considered not statistically significant. This doesn’t mean men shouldn’t care about their vitamin D3 levels.
Furthermore, when researchers looked at increasing levels of vitamin D3 they found an inverse relationship to cancer risk; the higher the vitamin D3 levels, the lower the risk of color cancer. This relationship stopped at a vitamin D3 level of greater than 100 nmol/L (40 ng/ml). Serum levels above this did not seem to confer any additional risk reduction.
Based on the findings these researchers concluded that the optimal vitamin D3 concentration for colorectal cancer risk reduction is 75-100 nmol/L (30-40ng/ml). This is a bit higher than the current level considered to be sufficient, and it’s a good idea to consider the “optimal” level of vitamin D3 to start at the old “normal” level of vitamin D of 30ng/ml vs the current recommendations. This could be particularly true for those with high risk for colon cancer, such as those with a strong family history or those trying to prevent a recurrence.
For more information about vitamin D3 as or other health promoting news visit the Longevity Medical Health Center website.