Two new studies point up the potent anti-cancer power of vitamin D
by Craig Weatherby
As we’ve reported in several articles over the past two years, vitamin D is emerging as the body’s premier anti-cancer agent. (To access them just click here, type “vitamin D" in the search box at upper right, and click “Go”.)
So it’s not surprising that research presented earlier this month suggests that vitamin D—which the body produces in response to sun exposure, and which occurs at high levels only in certain fish—protects strongly against breast cancer.
Higher vitamin D levels reduce breast cancer risk
Brothers Cedric Garland, DPH and Frank Garland, PhD., both from the University of California at San Diego, have been at the forefront of vitamin D and sun exposure research for 25 years.
Their published research began with an influential paper titled “Do sunlight and vitamin D reduce the likelihood of colon cancer?”
The answer to that question was “yes”, and this finding led them to probe this topic more thoroughly than any other group of scientists.
The Garland brothers’ University of California team presented the encouraging results of their latest research at the recent American Association for Cancer Research meeting (Garland CF, 2006).
They conducted a statistical analysis of data collected from 1,760 women who’d participated in prior studies at Harvard University and Saint George’s Hospital Medical School in London, including blood levels of vitamin D and the women’s overall incidence of breast cancer.
And, the results indicate that a woman’s risk of breast cancer falls as her vitamin D levels rise. Specifically, they found a vitamin D blood level of 52 nanograms per milliliter cut women’s breast cancer risk in half.
The researchers noted that a woman would need to consume about 1,000 International Units (IU) of vitamin D per day to attain this protective level, which is more than double the current recommended daily intake of 400 IU.
As Professor Cedric Garland said, “There is a strong inverse dose-response relationship between the serum concentration [blood level] of 25-hydroxyvitamin D [the form used as a measure of vitamin D status] and the risk of breast cancer.”
Consequently, his San Diego team repeated calls by other researchers to increase the daily recommended intake of vitamin D3— from fish, fortified foods, and supplements —from 400 IU to 1,000 IU.
Sadly, the average vitamin D intake in the US is only 320 IU per day, or about one-third of the 1,000 IU per day associated with a 50 percent reduction in breast cancer risk in the San Diego team's study.
And sunshine levels in far northern regions—such as Canada, Scandinavia, and the most northern areas of Russia and the U.S.—are so weak during the winter months that the body makes virtually no vitamin D.
This sobering fact has led to estimates that more than half of the people in northern population centers suffer from insufficient or even deficient levels of this strongly anti-cancer nutrient.
Higher vitamin D intake and sun exposure in young women yields lower breast cancer risk later in life
The second paper on vitamin D and breast cancer risk was presented at the American Association for Cancer Research meeting, this time by Canadian researchers working at Toronto’s Mount Sinai Hospital (Knight JA, 2006).
A team led by Julie Knight, Ph.D. interviewed 576 breast cancer patients and 1,135 healthy women. The found that the women who consumed the most vitamin D between the ages of 10 and 29—the normal age range in which breasts develop fully—reduced their risk of breast cancer by a whopping 40 percent.
The Toronto team also reported that women who met any of three criteria during this age range enjoyed significantly lower risks of getting breast cancer. The three protective factors were these:
- Working or simply being outdoors frequently appeared to cut the average woman’s breast cancer risk by 28 to 45 percent (The body produces vitamin D in response to sunlight hitting the skin).
- Consuming cod liver oil appeared to cut the average woman’s breast cancer risk by 25 percent. This benefit was seen despite the fact that cod liver oil is also high in vitamin A, which reduces absorption of vitamin D.
- Drinking ample amounts of milk appeared to cut the average woman’s breast cancer risk by more than one-third.
As Dr. Knight told the press, “What you are exposed to during breast development may be particularly important in determining future breast cancer risk. Current thinking is that exposures during adolescence or before a full-term pregnancy may have a greater effect, as that is when breast tissue is going through the most rapid development.”
Salmon and other fatty fish make superior sources of vitamin D
Among all of the natural, un-fortified food sources of vitamin D, fatty fish top the list.
An independent lab measured the amounts of vitamin D in single 3.5 ounce servings of our fish, with the results shown in the chart below.
The tests ranked sockeye salmon first (687 IU), followed by albacore tuna (544 IU), silver salmon (430 IU), king salmon (236 IU), sardines (222 IU), halibut and sablefish.
This means that a single 6 oz serving of Vital Choice sockeye salmon, albacore tuna or silver salmon provides 115 percent, 90 percent and 75 percent, respectively, of the higher 1000 IU recommended daily intake, or well above the FDA’s current 400 IU recommendation.
It is interesting that our lab's results differ from official USDA tables, which rank the vitamin D content of sardines just above salmon's. These discrepancies may result from natural variations in the genetics and diet of regionally distinct sardines and salmon. Regardless of the reason, we're happy to report that our salmon and tuna test so high in this vitally important nutrient.
- Garland CF, Mohr SB, Gorham ED, Grant WB, Garland FC. Evidence of need for increased vitamin D fortification of food based on pooled analysis of studies of serum 25-hydroxyvitamin D and breast cancer. Proc Amer Assoc Cancer Res 2006;47:[Abstract 4008]
- Knight JA, Lesosky MR, Barnett H, Raboud JM, Vieth R. Potential reduction in breast cancer risk associated with Vitamin D. Proc Amer Assoc Cancer Res 2006;47:[Abstract 4009].