by Samantha Kimball, PhD, MLT
There seems to be a line drawn in the sand with respect to the debate concerning what the optimal levels of vitamin D are for health, and neither side wants to budge. On one side of the line of the current debate are those who support the recommendations officially set by government agencies. However, most of the researchers who actively study vitamin D consider the latest official advice to be inadequate.
There has been contention about the vitamin D recommendations made by the Institute of Medicine (IOM, which advises both Health Canada and the United States Food and Drug Administration). The IOM released its updated report for vitamin D and calcium in 2010. Yet several groups of vitamin D experts suggest that people should achieve ‘optimal’ levels of vitamin D status, levels that are considerably higher than the ones the IOM recommendations are based on. The IOM’s Recommended Daily Allowance (RDA) of 600 IU/d was calculated to achieve adequate vitamin D status which was determined to be serum 25-hydroxyvitamin D levels [25(OH)D] of 50 nmol/L in 97.5% of the population. On the other hand, the Endocrine Society, Osteoporosis Canada, American Geriatrics society and the European Vitamin D Association all recommend target 25(OH)D levels of at least 75 nmol/L. The Vitamin D Society, Grassroots Health and the Vitamin D Council recommend that 25(OH)D levels be maintained above 100 nmol/L which require intakes well above the RDA and even above the tolerable upper level of intake (UL) in overweight and obese individuals. Why would the subject matter experts disagree with the IOM so openly?
Many critics have asserted the statistical methods used by the IOM committee were not adequate. In 2010, Dr. Walter Willett, from the Harvard School of Public Health, pointed out the statistical error in a debate with Dr. JoAnn Manson, one of the IOM committee members and also of the Harvard School of Public Health, commenting that “the statistical method used by the committee was completely flawed in determining the dose. Because they plotted it all on a figure, fit some fancy curves through it, but those data points were for population means, not for individuals.” Many vitamin D scientists at the time agreed that the RDA and UL were both too low (Vieth, 2004; Dawson-Hughes, 2004; Holick, 2011). The IOM committee cited risk of harm as a reason to be cautious. However, the risk of deficiency seems to be ignored.
The risk of toxicity from vitamin D supplementation is extremely rare. There is a misconception that it is easy to overdose on vitamin D. Vitamin D toxicity only happens if you take extremely high doses for long periods of time, such as 100,000 IU/d for six months or more. Cases in the literature are limited to individual accidents (one family was cooking with concentrated veterinary vitamin D preparation at millions of IU per millilitre of oil) and instances of industrial mishap (one family was ingesting sugar in their tea that contained concentrated vitamin D crystals). The level of risk from vitamin D supplementation is continuously blown out of proportion. The risk of overdosing with vitamin D is extremely small, in fact your risk of death from vitamin D is a million times less than that from overdosing with acetaminophen. This seems to go hand in hand with the myth that an overweight or obese individual will become toxic if they lose weight because vitamin D is fat-soluble. Bariatric surgery studies show conclusively that vitamin D levels do not change with excessive weight loss. Vitamin D is metabolized, it breaks down over time, it does not stay in adipose tissue waiting to exit at the most inconvenient time.
A detailed report of the statistical error was recently published by Drs. Veugelers and Ekwaru from the University of Alberta (Veugelers, 2014)1. Dr. Veugelers used the same data that the IOM utilized to demonstrate precisely where the error occurred. Dr. Heaney and colleagues provided more support with a different approach, they produced a dose-response curve from nearly 4,000 individuals in the Grassroots Health database, to demonstrate that the RDA would not achieve the target 25(OH)D of 50 nmol/L (Heaney, 2015)2.
Health Canada and the IOM have simply stated in the media that there was no error made. They have not responded in a transparent or accountable way to the public, but rather have simply said that they were right. Nor was there a need for Heath Canada to take into account proven statistics to make recommendations for our health. Apparently, Canadians should just take them at their word because only carefully selected government appointed persons are officially regarded as the experts. It is as though the consensus of researchers in the field does not matter.
Quite simply, Canadians are at great risk of being vitamin D deficient. Over 12 million Canadians do not meet the minimum vitamin D guidelines put forth by the IOM committee of 50 nmol/L. If we use the levels experts recommend, above 75-100 nmol/L, the number of people with suboptimal vitamin D status is much higher. This is a problem that has direct public health impact and it is being largely ignored.
Vitamin D is not a “vitamin” as much as it is a hormone. Vitamin D is used by nearly every cell in the body and affects the expression of thousands of genes. The list of diseases that are consistently linked with low vitamin D status is long and includes diabetes, heart disease, autoimmune disorders, mental health and cancer. Getting enough vitamin D is a safe and simple way to reduce risk of chronic disease.
The range of individual response to vitamin D supplementation is broad. A person’s 25(OH)D concentrations that results from a dose is part of the reason the IOM has been so cautious with their recommendations. The expert groups mentioned above recommend a target serum 25(OH)D in the range of 100-250 nmol/L, a range that provides benefit without causing increased risk. By targeting a serum 25(OH)D range, rather than a suggested international unit daily intake, the issue of individual response to dose is a moot point.
Measuring vitamin D blood serum is the final piece of the problem. In several provinces, including British Columbia, Alberta and Ontario, physicians are not allowed to measure 25(OH)D concentrations in their patients unless they have a specific condition on a short list or risk factors for those conditions. Thus, achieving a target 25(OH)D level becomes a problem. If you can’t measure it, you can’t manage it. Add to this the fact that millions of Canadians are deficient and you see the problem. Rather than limiting the number of tests that are performed, perhaps we should be focused on producing a more affordable test.
The issue of the amount of vitamin D we need to take to be healthy, and stay healthy, is a debate that is not likely to go away anytime soon. The IOM and Health Canada need to explain their math if they claim that there was no error made and they need to do so in a transparent fashion. The peer review process is in place for a reason, the IOM and Health Canada should be held accountable just like everyone else, for the sake of Canadian’s health.
In the words of Max Planck, “a new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.” I hope that we do not have to wait that long.
Veugelers PJ and Ekwaru JP. A Statistical Error in the Estimation of the Recommended Dietary Allowance for Vitamin D. Nutrients 2014, 6, 4472-4475; doi:10.3390/nu6104472
Heaney R, Garland C, Baggerly C, French C, and Gorham E. Letter to Veugelers, P.J. and Ekwaru, J.P., A Statistical Error in the Estimation of the Recommended Dietary Allowance for Vitamin D. Nutrients 2014, 6, 4472-4475; doi:10.3390/nu6104472. Nutrients 2015, 7, 1688-1690; doi:10.3390/nu7031688