Vitamin D regulates the flow of calcium into the bloodstream and is essential for normal bone development. Vitamin D also has a role in regulating parathyroid, neuromuscular, immune, and insulin functions. Vitamin D has been found to be associated with lower risks of cardiovascular disease and age-related cognitive impairment, asthma, as well as Hodgkin’s and non-Hodgkin’s lymphoma and esophageal, lung, pancreatic, renal, colorectal, endometrial, prostate, breast, and ovarian cancer.
Many recent studies have explored the relationship between Vitamin D and its protective function with respect to cancer.
(1) An epidemiological study by Cedric Garland PhD focused on the relationship between breast cancer and vitamin D levels as shown in the medical literature. Their conclusion: if women kept their vitamin D blood levels at approximately 52 ng/ml, they could expect a 50% reduction in the risk of breast cancer.
(2) Pamela Goodwin, M.D. and colleagues, retrospectively analyzed more than 500 women over a period of 11 years. Results: women who had been deficient in vitamin D at the time of their breast cancer diagnosis were 73% more likely to die from breast cancer than those with sufficient vitamin D at the time of diagnosis, as well as being almost twice as likely to have recurrence over the 11 year period.
(3) Joan Lappe PhD, RN and her colleagues looked prospectively at more than 400 postmenopausal women over a four-year period of time. Women in the study group were given 1100 IU of vitamin D and 1000 mg of calcium daily. The control group did not receive this. Results: women who took the vitamin D and calcium reduced their rate of cancer by 60%. The authors found that for every 10 ng/ml increase in a woman’s vitamin D blood level, the relative risk of cancer dropped by 35%. These data included all cancers.
For those billion or so of us who may be deficient in vitamin D, taking a multivitamin and drinking milk every day won’t do the job. Because of many variable factors, one size does not fit all. Effective dosing requires measurement through laboratory testing. Clinically, what really counts is not the vitamin D dose but the serum level achieved. For achieving adequate clinical levels, follow-up testing may be required every three months. Once the target level is achieved and the switch is made to maintenance dosing, then the testing frequency can be reduced significantly.
A couple of years ago I was able to converse with a scientist that has been studying Vitamin D for over 30 years. In his opinion many physicians haven’t kept up with studies between the relationship between adequate Vitamin D levels and protection from cancer. Between 2010 and 2012, more than 16,000 new research papers on vitamin D have been archived in the National Library of Medicine’s PubMed. Also, many clinicians are still overly concerned about toxicity based on outdated data, and therefore advise inadequate oral intake levels.
As to toxicity, a useful figure to keep in mind: Full body exposure to direct summer sun for 30 minutes allows the skin to make 10,000 units. The best information I could find is that Vitamin D probably doesn’t become toxic in humans until total dose (oral and sun) surpasses 40,000 units per day for a prolonged period.
For acute poisoning, the LD50 (dose which is lethal to 50 percent of the subjects) in dogs is the equivalent of a 110 lb. human taking 176,000,000 units! And that’s a LOT of 1000 IU capsules! Of course, this is for a single toxic dose, not daily use.
Vitamin D builds up in the fat and chronic use of excessive amounts can indeed be toxic, especially when not taken with cofactors such as magnesium, calcium etc. For example the following data show daily intake amounts over specified time periods that have proven to be toxic:
50,000 IU/day for 8 weeks
200,000 IU/day for 2 weeks
2 million IU/day for 1 week
10,000 IU/day happens to be the “no observed adverse effects level” (NOAEL) of the 2010 Food and Nutrition Board, the amount that has never been shown to cause harm. Do not exceed 10,000 IU/day unless you have a scientific level of understanding of vitamin D metabolism. Everyone taking this fat-soluble vitamin supplement in amounts larger than contained in a daily multivitamin should test their blood levels often. And, duh, don’t go stupid crazy on maxing out your dose!
The researcher I spoke with said that approximately 1 in a 1000 consumers of Vitamin D orally might develop kidney stones at doses above 10,000 units. If you’re a stone former, or have inflammatory bowel disease, cut the dose to below 10K and consult your physician. The largest study that looked at the risk of kidney stones with vitamin D came out of Harvard. They studied 45,616 men over 14 years for a total of 477,000 person-years of follow up. They found no increased risk of kidney stones with vitamin D intake but did not look at sun exposure or 25(OH)D levels. Of interest, they found three things in your diet that protect against kidney stones: high potassium (46% lower relative risk), high magnesium (29% lower relative risk), and high fluid intake (29% lower relative risk). For younger men, higher dietary calcium was associated with a reduced risk of kidney stones (31% lower relative risk). It seems likely that physiological vitamin D intakes will result in a higher relative risk for kidney stones for people on modern American diets (low potassium, low magnesium, high refined carbohydrates, high sodas, and a high acid residue).
The accepted sufficient level for Vitamin D in the general populations is controversial: published guidelines vary between 20 and 60 nanograms/ml.
Generally a good therapeutic range of 25 OH D, suggested by this researcher, is somewhere between 45 and 65 ng/ml for its protection against cancer and its recurrence. If you’re not in the summer sun much, most people will need at least 4000 units daily to get to the lower end of this range. 100 ng/ml is considered the border of toxicity.
There is a WIDE RANGE of response in blood levels to different doses of this supplement. Testing your blood levels to see how the supplement is absorbed is vitally important both to avoid toxicity and to make sure you are receiving the most effective dose.
So what’s a guideline on dosage? Here’s some data from a recent study (5):
- For those severely deficient in vitamin D, each 1,000 IU / day of increased supplementation resulted in an increase of 10 ng / ml in vitamin D blood levels.
- For those with existing blood levels above 30 ng / ml, each 1,000 IU / day of increased supplementation resulted in an increase of 8 ng / ml in vitamin D blood levels.
- For those with existing blood levels above 50 ng / ml, each 1,000 IU / day of increased supplementation resulted in an increase of 5 ng / ml in vitamin D blood levels.
In other words, vitamin D supplementation has a curve of diminishing returns. Those with existing high levels of vitamin D do not experience as much benefit from vitamin D supplements as those with low levels (which is roughly 90% of the population).
For people who want to supplement, it makes sense to take Vitamin D3 (cholecalciferol) with cofactors such as magnesium, calcium etc., and not to take the prescription form of 50,000 units of ergocalciferol (D2) which is not found in vertebrates, and is not nearly so bioactive but does block the receptors for the good stuff, even though it will raise the lab value on a blood test. The vitamin D2 potency is less than one third that of vitamin D3. Vitamin D2 has a shorter half-life in the blood and a lower affinity for the vitamin D binding protein. What this means is that according to a study (4) in the French Internal Medicine Review, “vitamin D2 should not be regarded anymore as suitable for supplementation or fortification.”
For the best utilization of Vitamin D, take it with the evening meal, which should be the largest meal for the day. (6)
No adverse interactions between cannabis and Vitamin D3 are shown in most drug references. (7) However, on one website (8) that says its database includes self-reports from 6 million people since 1977, two interactions have been reported in 2012. These included trouble breathing and fainting. However, no details are given except for the fact that co-used drugs for these two people indicate that they may have been seriously compromised in their respiratory health:
There ARE some medical conditions, such as hyperparathyroidism, that preclude supplementing with Vitamin D without close medical supervision, so consultation with a knowledgeable physician is strongly recommended.
(1) J Steroid Biochem Mol Biol. 2007 Mar;103(3-5):708-11.
Vitamin D and prevention of breast cancer: pooled analysis.
Garland CF, Gorham ED, Mohr SB, Grant WB, Giovannucci EL, Lipkin M, Newmark H, Holick MF, Garland FC.
Source: Department of Family and Preventive Medicine, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA. firstname.lastname@example.org
(2) J Clin Oncol. 2009 Aug 10;27(23):3757-63. Epub 2009 May 18.
Prognostic effects of 25-hydroxyvitamin D levels in early breast cancer.
Goodwin PJ, Ennis M, Pritchard KI, Koo J, Hood N.
Source: Mount Sinai Hospital, 1284-600 University Ave, Toronto, Ontario M5G 1X4, Canada. email@example.com
(3) Am J Clin Nutr. 2007 Jun;85(6):1586-91.
Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial. Lappe JM, Travers-Gustafson D, Davies KM, Recker RR, Heaney RP.
Source: Osteoporosis Research Center, Creighton University, Omaha, NE 68131, USA. firstname.lastname@example.org
(4) Rev Med Interne. 2008 Oct;29(10):815-20. Epub 2008 Apr 11.
[Vitamin D2 or vitamin D3?].
[Article in French] Mistretta VI, Delanaye P, Chapelle JP, Souberbielle JC, Cavalier E.
Source: Service de chimie médicale, CHU de Liège, université de Liège, domaine du Sart-Tilman, Liège, Belgique.
(5) Vitamin D Supplement Doses and Serum 25-Hydroxyvitamin D in the Range Associated with Cancer Prevention
CEDRIC F. GARLAND1, CHRISTINE B. FRENCH2, , LEO L. BAGGERLY3, and ROBERT P. HEANEY4,
“This paper provides a long awaited insight into a dose-response relationship between orally administered vitamin D3 and the resulting levels of serum 25(OH)D in over 3600 citizens. The results will allow new definition of high vitamin D dose safety and reduce concerns about toxicity. This is a landmark contribution in the vitamin D nutrition field!”
Distinguished Professor of Biochemistry & Biomedical Sciences, Emeritus
University of California Riverside\
Viewed 10/13/2012 at http://www.grassrootshealth.net/garland02-11
(6) Mulligan GB, et al. Taking vitamin D with the largest meal improves absorption and results in higher serum levels of 25-hydroxyvitamin D. J Bone Miner Res. 8th February 2010 [epud ahead of print publication]
Other resources on the web:
Contributed by Bill Manewal, RN
Disclaimer: You should never delay seeking medical advice, disregard medical advice, or discontinue medical treatment because of information in this article.