by Dr. Leo Galland
Low Vitamin D and the Vitamin D deficiency symptoms that go with it can generally be avoided by eating Vitamin D enriched foods or taking supplements.
The latest controversy that has spun out of the new Vitamin D RDA announcement has caused some people to turn away from this important vitamin. But that could put them at risk of low Vitamin D and the Vitamin D Deficiency Symptoms that go along with that.
The Vitamin D Controversy
Newspaper headlines exclaim: “Extra Vitamin D and Calcium Aren’t Necessary, Report Says.” Or “Triple That Vitamin D Intake, Panel Prescribes.”
These dueling headlines are both based on the “Dietary Reference Intakes for Calcium and Vitamin D" report just released from the Institute of Medicine (IOM) setting new RDA’s for Vitamin D and calcium. Opposite descriptions of the same story, neither of them is an accurate reflection of the report’s conclusions.
It matters because people have told me they have already stopped taking Vitamin D supplements based upon what they have read in the news, which could mean higher chances of Vitamin D deficiency symptoms.
So I am telling you what I told them—Don’t believe the hype on Vitamin D.
Key Points from the IOM Report on Vitamin D
To begin with, the Vitamin D recommendations that come out of this thousand page report all hinge on one (and only one) number: the blood level of Vitamin D that is considered adequate. The committee set that number at 20 (specifically, 20 nanograms per milliliter). Many Vitamin D researchers have set that number at 32, which makes all the difference.
Vitamin D Deficiency Symptoms
Almost every scientist agrees that blood levels of Vitamin D under 20 are associated with poor health outcomes. Effects and symptoms of Vitamin D deficiency include increased mortality from all causes and increased risk of developing osteoporosis, diabetes, autoimmune diseases, heart disease, depression and several types of cancer. These are the serious drawbacks of having low Vitamin D.
In fact, the lower the Vitamin D levels fall below 20, the greater the risk of having symptoms of Vitamin D deficiency. Almost all scientists agree that when blood levels of Vitamin D are low, it’s easy to correct the deficiency and to raise the level of Vitamin D up to 20 with supplements.
New RDA’s for Vitamin D
The IOM panel concluded that a total intake of 600 IU/day Vitamin D from food and supplements would get most North Americans to a level of 20. They left sunlight out of the Vitamin D RDA equation because it is hard to measure someone’s sun exposure.
So, they increased the Vitamin D RDA for young adults from 200 to 600 IU/day and for older adults from 400 to 600 IU/day. For those over age 71 the Vitamin D RDA was raised to 800 IU/day.
No Epidemic of Vitamin D Deficiency
And because most North Americans presently have blood levels around 20, they stated that there is no epidemic of Vitamin D deficiency and most people don’t need to do anything to raise their blood levels higher. The IOM report is essentially saying that most people are already getting enough Vitamin D. The report triples the Vitamin D RDA, not because people aren’t meeting it, but because that is the amount that should get most people to a blood level of 20.
The IOM panel also expressed concern about much higher blood levels, because some studies have shown increased mortality or cancer rates among those with the highest Vitamin D levels (which could be anywhere from 40 to 100, depending upon the study).
But they also determined that these high levels were unlikely to be reached at intakes under 4000 IU/day, so they raised the tolerable (safe) upper limit for Vitamin D from 2000 IU/day to 4000 IU/day for adults and even stated in the body of the report that an intake of 10,000 IU/day was unlikely to cause harm. This “high” dose is less Vitamin D than most Americans would get from a summer day at the beach without sun block.
So what’s missing from these recommendations? First, almost all the studies show progressive health benefits as blood levels of Vitamin D go from under 10 to about 20. They also show additional health benefits as the levels go from 20 to 32 (and in some studies to 40 or more). The benefits associated with going from 20 to 40 are not as great as the benefits achieved by going from 10 to 20, but they are for the most part statistically significant.
Because it can be harder to get from 20 to 40 than from 0 to 20, much higher doses may be needed to get to the higher level. The IOM panel cautions that the health benefits of taking these higher doses of Vitamin D have not been well established.
The Research on Benefits of Higher Doses of Vitamin D
However, some placebo-controlled clinical trials have demonstrated benefits with high dose supplementation of Vitamin D that have not been seen with lower doses used in other studies:
- A Japanese study found that children taking 1200 IU/day had a decrease in influenza during the winter (1)
- A New Zealand study found that 4000 IU/day reduced insulin resistance (a precursor of diabetes) in Asian women, and the effect only occurred if the blood level rose to 32. (2)
- A Norwegian study found that 20,000 to 40,000 IU/week given for one year reduced depression scores in overweight individuals. (3)
- A clinical trial done at Creighton University in Nebraska found a 75% reduction in the incidence of cancer among post-menopausal women given 1100 IU Vitamin D per day for 4 years. The effect required blood levels greater than 32. (4)
The bottom line: the IOM report does not advise against Vitamin D supplementation and in fact raises both the recommended daily allowance and tolerable upper limits of Vitamin D.
An important observation, buried deep in the report, is that people with lower Vitamin D levels respond faster to supplementation and people with high levels at the end of summer have a steeper drop in their levels during the winter. It is important that you understand why this happens.
Vitamin D induces its own destruction. As Vitamin D levels go up, so does the activity of the enzyme that inactivates it and the activity of this enzyme stays elevated for several weeks after the Vitamin D levels drop. The result is that people taking higher doses of Vitamin D supplements may not have a predictable, stable increase in their Vitamin D levels, and people who get a lot of sun exposure in summer but take no supplements in winter may have a lower Vitamin D level in winter than people who don’t get a lot of summer sun. Winter sun north of the latitude of Atlanta, Georgia is too weak to generate much Vitamin D. People that take high doses of Vitamin D and then stop are also at risk for plummeting Vitamin D levels. (5)
The emerging research indicates that taking high doses of Vitamin D doesn’t guarantee an optimal blood level, but it’s the blood level that correlates with the benefits.
So, when it comes to Vitamin D, one size doesn’t fit all and supplementation should be based on individual needs.
"Dietary Reference Intakes for Calcium and Vitamin D" November 30, 2010, A report by the Institute of Medicine, the health care arm of the National Academy of Sciences.
1) Am J Clin Nutr. 2010 May;91(5):1255-60. “Randomized trial of Vitamin D supplementation to prevent seasonal influenza A in school children.” Urashima M, Segawa T, Okazaki M, Kurihara M,
Wada Y, Ida H.
2) Br J Nutr. 2010 Feb;103(4):549-55 “Vitamin D supplementation reduces insulin resistance in South Asian women living in New Zealand who are insulin resistant and Vitamin D deficient – a randomised, placebo-controlled trial.” von Hurst PR, Stonehouse W, Coad J.
3) Intern Med. 2008 Dec;264(6):599-609.“Effects of Vitamin D supplementation on symptoms of depression in overweight and obese subjects: randomized double blind trial.” Jorde R, Sneve M, Figenschau Y, Svartberg J, Waterloo K.J
4) 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.
5) Anticancer Res. 2009 Sep;29(9):3675-84. How to optimize Vitamin D supplementation to prevent cancer, based on cellular adaptation and hydroxylase enzymology. Vieth R