---

By Richard Z. Cheng, MD, PhD
Orthomolecular Medicine News Service (OMNS)
October 2026

Editor’s Note: This article is adapted for public education from Dr. Richard Z. Cheng’s recent scientific manuscript, “Overly Conservative Vitamin D Guidelines May Do More Harm Than Good: Beyond Minimum Adequacy—Why Settle for a Passing Grade?”, submitted to MDPI Preprints in October 2026.

The original paper critically examines whether conventional vitamin D recommendations focus too narrowly on preventing deficiency and avoiding toxicity while overlooking opportunities for physiological optimization. Drawing on global epidemiological evidence, research by William B. Grant, Sunil J. Wimalawansa, and colleagues, and a recently published 14-principle framework for micronutrient guidelines, it argues for a more balanced evaluation of vitamin D’s potential benefits and risks.

Are We Confusing “Enough to Survive” with “Enough to Thrive”?
Imagine a school where 60% is a passing grade.

Would we encourage every student to aim for 60% simply because it is enough to pass?

Of course not.

Yet this may be an important limitation of how some nutritional guidelines are developed.

Many guidelines focus on preventing obvious nutritional deficiencies. But preventing deficiency is not necessarily the same as supporting optimal physiological function.

Vitamin D offers a particularly important example.

Some medical guidelines consider a blood vitamin D level of approximately 20–30 ng/mL sufficient. Other researchers, including my colleagues William B. Grant, Sunil J. Wimalawansa, and Paweł Płudowski, have argued that moderately higher levels may provide additional health benefits.

The central question is straightforward:

Are we setting the vitamin D bar too low—and could excessively conservative recommendations leave important health benefits unrealized?

The school analogy illustrates a distinction, not a mathematical rule. Unlike exam scores, higher vitamin D levels are not always better. The challenge is to identify the range that provides the greatest overall health benefit without unnecessary risk.

1. Vitamin D Deficiency Is a Widespread Public-Health Problem

A major 2025 systematic review examined vitamin D status across 102 countries, drawing on research involving approximately 2.37 million people.

Its findings were striking:

Blood vitamin D level / Pooled prevalence
Below 12 ng/mL              18%
Below 20 ng/mL             47%
Below 30 ng/mL             75%

These figures indicate widespread low vitamin D status, although different professional organizations disagree about the threshold for insufficiency. Not everyone below 30 ng/mL has a vitamin D-related illness.

Nevertheless, the scale of the issue warrants serious public-health attention.

Severe vitamin D deficiency can cause rickets, osteomalacia, muscle weakness, and impaired bone mineralization. Vitamin D also plays biological roles beyond the skeleton, including immune signaling and cellular regulation.

Research has linked lower vitamin D levels with several chronic diseases. However, an association does not necessarily mean vitamin D deficiency caused the disease—or that supplementation will prevent it.

The challenge is to identify which health problems can actually be prevented or improved by correcting low vitamin D status.

2. Minimum Adequacy Is Not the Same as Optimal Health

For decades, many nutrient recommendations have focused primarily on preventing deficiency-related diseases.

That is important, but should it be the endpoint?

Consider the school analogy again:

Passing an examination is an achievement. But passing is not the same as excellence.

Likewise, reaching a minimum vitamin D sufficiency threshold does not necessarily mean that every vitamin D-dependent physiological function has been optimized.

In our 2025 peer-reviewed paper published in Nutrients, Grant, Wimalawansa, Pludowski, and I reviewed evidence suggesting that a serum 25-hydroxyvitamin D [25(OH)D] concentration of approximately 40–70 ng/mL deserves consideration as a potential optimization range.

Our analysis explored vitamin D’s possible roles in immune function, metabolism, cardiovascular health, and other biological processes.

Importantly, this proposed range is not an established universal clinical target. Large randomized trials have produced mixed results regarding supplementation’s ability to prevent major diseases.

But we believe those findings should encourage better-designed studies rather than end the investigation into optimal vitamin D status.

A minimum requirement should not automatically be mistaken for an optimum.

3. What About Vitamin D Toxicity?

One reason many guidelines remain cautious about supplementation is concern about toxicity.

Excessive vitamin D intake can cause hypercalcemia (high blood calcium), hypercalciuria (excess urinary calcium), kidney injury, and other potentially serious complications.

These risks must be taken seriously.

However, another important question deserves equal attention:

What are the health consequences of insufficient vitamin D compared with the actual risks of excessive supplementation?

Dr. Sunil Wimalawansa has published a physiological benefit–risk framework illustrating how potential vitamin D benefits may rise, eventually plateau, and be accompanied by greater risks at very high concentrations.

Classical vitamin D intoxication is frequently associated with blood 25(OH)D concentrations above approximately 150 ng/mL.

Yet this does not mean that every concentration below 150 ng/mL is safe. Some studies have raised concerns about adverse outcomes at substantially lower concentrations, and individual susceptibility varies.

A Proposed Five-Zone Vitamin D Framework

To encourage a more differentiated discussion, our recent work proposes the following research-oriented classification:

Serum 25(OH)D w/ Proposed Category & Interpretation
Below 30 ng/mL Low-status region Deficiency or possible insufficiency, depending on clinical context
30–100 ng/mL Proposed safety window Broad potential physiological optimization interval, including the proposed 40–70 ng/mL range
100–150 ng/mL Gray zone — caution Very high concentrations; review supplementation and calcium metabolism
150–200 ng/mL Yellow zone — high concern Concentrations associated with reported clinical intoxication
Above 200 ng/mL Red zone — very high concern Serious toxicity is possible; prompt clinical evaluation is warranted

Important: This classification is a proposed scientific framework, not an established clinical safety standard. The green zone does not mean that 80–100 ng/mL is proven safe or beneficial for everyone. Classical poisoning is only one measure of risk; more subtle or long-term adverse effects also matter.

A proposed target range must ultimately be judged by its impact on actual health outcomes.

4. Could Overly Conservative Guidelines Do More Harm Than Good?

This is the central question of our new scientific manuscript.

Suppose a guideline successfully reduces the risk of excessive supplementation but fails to adequately prevent or address widespread clinically important deficiency.

Can that automatically be called a safer guideline?

We argue that it cannot.

Public-health decisions must account for both sides:

The harm caused by vitamin D deficiency or inadequately treated insufficiency.

The harm caused by excessive or inappropriate supplementation.

The appropriate comparison is not simply the number of people with low vitamin D versus the number reporting toxicity. It is the number and severity of clinical health problems that different supplementation policies can prevent or cause.

A restrictive policy could be harmful if it leaves treatable deficiency unrecognized. Conversely, more aggressive supplementation could be harmful if it exposes people to additional risks without demonstrated benefit.

The objective should be to identify which strategy produces the greatest net improvement in health.

Our recently published 14-principle framework for evidence-based micronutrient guidelines calls for this broader approach, including individualized nutrient needs, functional optimization, dose–response relationships, graded toxicity, and clinically meaningful outcomes.

5. What Should the Public Do?

The evidence supports a more thoughtful approach to vitamin D—not indiscriminate megadosing or automatic acceptance of the lowest recommended intake.

People should consider their risk factors, including age, limited sunlight exposure, malabsorption, osteoporosis, medications, and other relevant medical conditions.

When deficiency is suspected or treatment is indicated, clinicians can use serum 25(OH)D measurements and appropriate follow-up to guide care.

For healthy adults, routine high-dose supplementation or repeated blood testing is not universally recommended. A daily dose that is appropriate for one person may be excessive or insufficient for another.

Anyone considering higher-than-standard supplementation should discuss dosing, calcium balance, kidney health, and monitoring with a qualified clinician.

The proposed optimization range is an important research question—not an instruction for everyone to raise their blood vitamin D level to 70, 80, or 100 ng/mL.

Conclusion: We Should Aim for Better Health, Not Merely Avoid Deficiency

Preventing vitamin D deficiency is essential. But preventing failure should not automatically define the limits of optimal health.

With low vitamin D status affecting substantial portions of the world’s population, we believe nutritional guidelines should critically examine whether their current thresholds and dosing recommendations leave preventable benefits unrealized.

Our position is not that more vitamin D is always better.

Rather, we argue that conservative supplementation should not automatically be equated with safer or more effective medicine.

The goal should be to establish, through rigorous research, which vitamin D levels provide the greatest clinical benefit with acceptable long-term safety.

In education, passing is not the same as excellence.

In medicine, minimum nutritional adequacy should not automatically be treated as optimal physiological health.

Scientific References

Grant WB, Wimalawansa SJ, Pludowski P, Cheng RZ. Vitamin D: Evidence-Based Health Benefits and Recommendations for Population Guidelines. Nutrients. 2025;17(2):277. https://doi.org/10.3390/nu17020277

Cheng RZ. Developing Evidence-Based Micronutrient Guidelines: An Integrative Orthomolecular Systems Medicine Framework. Preprints. 2026;2026102222. https://doi.org/10.20944/preprints202610.2222.v1

Dunlop E, et al. A systematic review and meta-analysis of circulating 25-hydroxyvitamin D concentration and vitamin D status worldwide. Journal of Public Health. 2025. pubmed.ncbi.nlm.nih.gov

Wimalawansa SJ. Infections and Autoimmunity—The Immune System and Vitamin D: A Systematic Review. Nutrients. 2023;15(17):3842. https://doi.org/10.3390/nu15173842

Wimalawansa SJ. Physiological Basis for Using Vitamin D to Improve Health. Biomedicines. 2023;11(6):1542. https://doi.org/10.3390/biomedicines11061542

National Institutes of Health, Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/

About OMNS Global and I-OM.ai
Orthomolecular Medicine News Service (OMNS) provides scientific commentary and public education on nutritional medicine, micronutrients, and their potential roles in disease prevention and health optimization.

OMNS Global and the I-OM Systems Medicine community provide additional educational resources, scientific discussions, and integrative approaches to health.

Explore the community: https://community.i-om.ai/

Editorial note: This article is a public-education adaptation of the author’s vitamin D guideline critique manuscript. Its proposed concentration framework is intended for scientific discussion and does not replace individualized medical advice.

 

 

SmartTan.com news articles regularly report medical and scientific information to keep you abreast of current events related to UV light. This information is not intended to be used by any party to make unwarranted health claims to promote sunbed usage. Indoor tanning businesses are obligated to communicate a fair and balanced message to all clients about your products and services including the potential risks associated with indoor tanning. Contact your Smart Tan representative to find out more about what you can and can’t say in your tanning salon business.

© 2026 International Smart Tan Network. All rights reserved.