The Big Vitamin D Mistake: Why the RDA is Dangerously Low

Vitamin D has long been recognized as essential for bone health, immune function, and chronic disease prevention. Yet despite decades of research, official recommendations for daily vitamin D intake remain way too low… so low, in fact, that they leave a large portion of the population deficient.

In a December 7, 2025 video, Dr. John Campbell brought renewed attention to what he describes as a “schoolboy error” in the calculation of the Recommended Dietary Allowance (RDA) for vitamin D, an error that has gone uncorrected for more than a decade.

For the GrassrootsHealth community, however, this is not breaking news. This statistical mistake and its serious public health implications, has been documented, analyzed, and communicated by GrassrootsHealth scientists (such as Dr. Michael Holick, featured in the following video) for years. What is new is that this issue is finally receiving broader public and professional attention.

WATCH DR. CAMPBELL’S VIDEO

The Heart of the Error: “Average vs. Individual”

When the U.S. Institute of Medicine (IOM), now the National Academy of Medicine, established the vitamin D RDA, the goal was to ensure that 97.5% of the population would reach a serum 25(OH)D level of at least 20 ng/ml (50 nmol/L).

The problem lies in how that calculation was made.

Instead of analyzing individual participant data from vitamin D supplementation studies, the IOM averaged results at the study level. This “average of averages” approach smoothed out natural biological variation and led to a false sense of adequacy.

Dr. Campbell explains this with a simple analogy: if the average score in a classroom is a passing grade, that does not mean every student passed. To ensure nearly everyone succeeds, individual performance not averages must be considered.

GrassrootsHealth scientists identified and documented this exact issue years ago, including in the blog written by Dr. Robert Heaney, “IOM Miscalculated the RDA for Vitamin D”, which clearly explains how this statistical oversight led to an RDA that fails most individuals.

How Big Is the Mistake?

When the same data are analyzed correctly at the individual level, the results are startling:

600 IU/day raises serum vitamin D to only 10.7 ng/mL (26.8 nmol/L) for 97.5% of people well below sufficiency.
To ensure nearly everyone reaches 20 ng/ml, intake may need to be as high as 8,895 IU/day.

That means:

The U.S. RDA may be nearly 15 times too low
The UK RDA may be more than 22 times too low

GrassrootsHealth data have long supported this conclusion, showing that much higher intakes are required to reliably achieve and maintain healthy vitamin D levels across diverse populations.

Not New Science, Just Long Ignored

This next video, a recording of our Vitamin D Study Hour with Dr. Michael Holick titled Practical Uses of Vitamin D for Disease Prevention, reviews decades of vitamin D research as well as the history and shortcomings of the RDA and Endocrine Society’s guidelines for vitamin D. Dr. Holick clearly outlines the evidence showing the strong link between vitamin D levels and reduced risk of many chronic diseases, including diabetes, infectious diseases, autoimmune conditions, and cancer. Yet, even with significant decreases in disease risk, these outcomes are not reflected in many current public health guidelines. Dr. Holick explains how this all evolved.

WATCH DR. HOLICK’S VITAMIN D STUDY HOUR

GrassrootsHealth and our panel of scientists have consistently challenged low official recommendations, publishing analyses and population data that demonstrate their inadequacy:

“Current Recommendations Are Too Low” highlights how existing guidelines fail to prevent deficiency.
“GrassrootsHealth Data Supports Much Higher Intake of Vitamin D Than the Current RDA” presents real-world evidence from thousands of participants.
“Big Mistake by the IOM” explains the origin and consequences of the RDA miscalculation in accessible terms.

For over a decade, these findings have been available to policymakers, clinicians, and researchers. Unfortunately, they have been largely overlooked.

Why This Matters for Public Health

Vitamin D deficiency is not limited to bone health concerns. Low vitamin D status has been associated with:

Increased fracture risk and bone disease
Higher incidence of certain cancers, including colorectal and prostate cancer
Elevated risk of type 1 and type 2 diabetes
Impaired immune function
Greater risk of cognitive decline and dementia
Much more…

In countries like Canada, where average dietary intake is only 232 IU/day, and in northern regions where winter sun exposure is minimal, deficiency is widespread. Similar challenges exist across the UK and much of Europe. These realities underscore why relying on outdated RDAs has real consequences for population health.

Growing Attention

In addition to Dr. Campbell’s widely viewed video, this issue has recently gained further attention, including in a detailed Substack article published by Popular Rationalism. Together, these voices reflect a growing recognition that vitamin D guidelines are overdue for correction.

This renewed attention validates what GrassrootsHealth researchers and participants have known for years: the science has been clear yet policy remains in the Dark Ages.

What Should Be Done Now?

Correcting the vitamin D RDA is not merely an academic exercise. It is a public health necessity. GrassrootsHealth continues to advocate for:

Evidence-based vitamin D intake recommendations
Testing serum 25(OH)D levels with a target level of 40-60 ng/ml (100-150 nmol/L) to guide individualized supplementation
Public health policies that reflect biological variability and current evidence

Until official guidelines are updated, individuals, especially those with limited sun exposure, may benefit from testing their vitamin D levels and working with GrassrootsHealth and others in the vitamin D community to determine appropriate intake.

Conclusion

A simple statistical error has contributed to decades of inadequate guidance, leaving millions unknowingly deficient. The time to fix the problem and its resulting health consequences is well overdue.

GrassrootsHealth has been sounding this alarm for over ten years. With growing public and professional awareness, there is renewed hope that health authorities will finally act. Correcting this mistake could improve immune health, reduce chronic disease risk, and enhance quality of life worldwide. The science is clear. The data are strong. The time to update vitamin D recommendations is NOW.

Click here to read more from GrassrootsHealth.

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