Higher vitamin D levels linked to a 50 percent reduction in colon cancer death rates during a dozen years of follow-up
by Craig Weatherby
The flood of positive health findings on vitamin D—and negative reports concerning people’s general lack of sufficient vitamin D—that began about five years ago continues to flow.
Last week, we covered an epidemiological study that links higher vitamin D levels in men to reduced heart risks (see “Vitamin D May Reduce Heart and Diabetes Risk.”
- Colon cancer patients with relatively high vitamin D blood levels were twice as likely to survive for 12 years, compared to patients with low levels.
- These findings are supported by evidence that vitamin D helps regulate cell growth, and affirm positive results from prior studies.
This week, we’re covering research news about vitamin D’s positive impact on colon health.
Vitamin D may support colon-cancer survivalResearch from Boston’s world-renowned Dana-Farber Cancer Institute reveals that vitamin D may reduce death rates from colon cancer.
[Vitamin D is a hormone-like nutrient that helps shuttle dietary calcium from the stomach to the rest of the body.
And vitamin D also appears to tell cells when to start and to stop dividing. Thus, a shortage can allow uncontrolled, cancerous cell division in the body.
As the authors of a study in nurses reported last year, “Low vitamin D status has long been implicated in colorectal carcinogenesis.… Our data provide additional support for the inverse association between vitamin D and colorectal and, in particular, colon cancer risk” (Wu K et al. 2007).
In the study we’re summarizing today, a Harvard University team led by oncologist Dr. Kimmie Ng, MD, MPH, selected 304 patients diagnosed with colorectal cancer from the large Nurses' Health Study and the Health Professionals Follow-up Study (Ng K et al. 2008).
Fish fit the vitamin D bill; Sockeye salmon stand out
Certain fish rank among the very few substantial food sources of vitamin D, far outranking milk and other D-fortified foods.
Among fish, wild Sockeye Salmon may be the richest source of all, with a single 3.5 ounce serving surpassing the US RDA of 400 IU by about 70 percent:
Vitamin D per 3.5 ounce serving*
Sockeye Salmon—687 IU
Albacore Tuna—544 IU
Silver Salmon—430 IU
King Salmon—236 IU
*For our full test results, click here.
Analysis of the study data reveals that the colon cancer patients with higher levels of vitamin D before their cancer diagnosis were only half as likely to have died over a 12 year period.Like all epidemiological studies this one could not rule out other explanations for the reduced death rates among patients with higher vitamin D levels, which could have simply been markers for other cancer-inhibiting diet, genetic, or lifestyle attributes.
However, given the rapidly increasing weight of positive epidemiological evidence, and new understanding of the role of vitamin D in controlling cell division, the disclaimer included in the authors’ report seems overly cautious: “The data is still too premature to recommend vitamin D for colon cancer patients” (Ng K et al. 2008).
Research disclaimers like this—which essentially ignore the clear implications of all available evidence—constitute little more than butt-covering boilerplate. If that assessment sounds harsh, consider that higher vitamin D levels have consistently been associated with reduced cancer risk… never with increased cancer risk.
And randomized controlled trials to assess vitamin D as a potential therapeutic agent in colorectal cancer have been approved by the FDA: a clear indication that the even this cautious agency believes that vitamin D only discourages growth of colon cancer.
In the meantime, there is no downside—and plenty of upside potential—to ensuring that cancer patients consume adequate amounts of this nutrient, whose anti-cancer physiological effects are very well documented.
- Ng K, Meyerhardt JA, Wu K, Feskanich D, Hollis BW, Giovannucci EL, Fuchs CS. Circulating 25-hydroxyvitamin d levels and survival in patients with colorectal cancer. J Clin Oncol. 2008 Jun 20;26(18):2984-91.
- Wu K, Feskanich D, Fuchs CS, Willett WC, Hollis BW, Giovannucci EL. A nested case control study of plasma 25-hydroxyvitamin D concentrations and risk of colorectal cancer. J Natl Cancer Inst. 2007 Jul 18;99(14):1120-9. Epub 2007 Jul 10.