It’s time to ACT NOW for the Vitamin D health of the nation

Vitamin D in the UK – what if we could start afresh? Our new paper argues that it’s time to rethink, save lives and improve health resilience.

ACT NOW Vitamin D

CRN UK is proud to have instigated ACT NOW Vitamin D, a new multidisciplinary UK scientific collective committed to improving ‘vitamin D health’ and changing the national landscape and conversation.

Our team brings together experts in molecular and paediatric endocrinology, nutrition science, dietetics, clinical medicine and nutritional epidemiology, and biostatistics: Martin Hewison, Suma Uday, Tom Hill, Jonathan Rhodes, Carrie Ruxton, Chris Sempos and Dr Sam Christie, CRN UK’s Scientific Adviser.

We have now published our first paper in Frontiers in Endocrinology (https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2026.1870408/full). Our proposal challenges the current UK definition of vitamin D deficiency. We argue that the threshold should be aligned with international authorities by increasing it from 25 nmol/L to 50 nmol/L. In practical terms, vitamin D status becomes much simpler: below 50 nmol/L = deficient; 50 nmol/L or above = not deficient.

Why does this matter?
Because nutritional rickets and osteomalacia have still not been eradicated in the UK – despite vitamin D correcting both. Tragically, some babies and infants continue to die from the consequences of vitamin D deficiency. At the same time, evidence linking adequate vitamin D status with wider positive health outcomes continues to grow. Combined with the UK’s northern latitude and increasingly diverse population, it’s time to rethink our approach.

This is only the beginning. Raising the threshold would stimulate important discussions about recommended vitamin D intakes, provide a clearer picture of deficiency across the life course, and simplify both clinical practice and research.

Our next step is to engage with government, professional bodies and other key stakeholders to help catalyse national discussion and, ultimately, improve public health.

More updates to follow.

The Challenge

Vitamin D is essential for bone, muscle, and immune health. Deficiency can lead to serious and sometimes life-threatening illness – because inadequate vitamin D can lead to low calcium, which can adversely affect growing muscle tissue including the heart (known as dilated cardiomyopathy) and the nervous system (low calcium-induced seizures. However, the deficiency diseases – rickets in children and osteomalacia across the life-course – and secondary effects are entirely preventable with adequate vitamin D. New analyses from the UK National Diet and Nutrition Survey (NDNS) and the UK Biobank data show that vitamin D deficiency is becoming more widespread, with growing disparities between population groups.

Key Findings from National Diet and Nutrition Survey Data

Declining Intakes

Declining intakes: Dietary vitamin D intake has fallen sharply, especially among those consuming lower intakes;

Rising Deficiency

Rising deficiency: The percentage of 4–64 year-olds with severe deficiency (serum 25(OH)D <25 nmol/L) has increased;

Heightened Inequalities

Heightened inequalities: Deficiency is most common among people with darker skin, those with raised BMI and individuals unable to expose sufficient skin to UV light.

Why Deficiency Is Rising

Marked declines in vitamin D intake – Declines of up to 50% of vitamin D are evident among those with the poorest diets in terms of micronutrient supply

Significant shifts in diet – Lower consumption of meat and fish (39 and 29% reduction, respectively) – both primary sources of UK dietary vitamin D – compared to two decades ago. Only 10% of adolescents consume fish and seafood

Rising obesity – Vitamin D becomes ‘locked’ inside body fat, reducing its availability in the bloodstream

Demographic change – Larger ethnic minority populations have increased overall numbers of people at higher physiological risk – darker skin requires more sunlight to synthesise vitamin D

Together, these trends have created a “perfect storm” for chronic vitamin D insufficiency across the UK.

Policy Context and the Need for Change

The UK currently defines vitamin D sufficiency as 25 nmol/L serum 25(OH)D, based on advice from the government’s Scientific Advisory Committee on Nutrition (SACN, 2016) This threshold is among the lowest internationally and does not fully reflect evidence linking suboptimal vitamin D levels with adverse health outcomes.

Current UK Position

• Threshold for sufficiency: 25 nmol/L 7
• Supplementation guidance: 10 µg/day for all (winter and spring) 7
• Fortification: limited, voluntary, and inconsistent across food products International Comparisons
• USA (National Academy of Medicine)19, EU (European Food Safety Authority) 20, and US Endocrine Society21: 50 nmol/L is the accepted lower limit of adequacy; WHO and many European nations22: Recognise 50 nmol/L as optimal for bone and muscle health.

Recommendations

ACT NOW Vitamin D proposes that UK public health policy should adopt 50 nmol/L as the minimum threshold for vitamin D sufficiency. This change would:

• Provide a more accurate picture of national vitamin D status and health inequality.
• Align the UK with international best practice, improving research comparability and global collaboration.
• Strengthen prevention of rickets and osteomalacia, reducing avoidable NHS costs.
• Promote equitable health outcomes across ethnic and socioeconomic groups.
• Encourage review of existing policies on supplementation and food fortification.

Looking ahead

Preventing vitamin D deficiency is simple, affordable, and achievable. We urge policymakers, healthcare professionals, and food industry partners to work together to ensure every UK citizen maintains adequate vitamin D levels throughout life.

ACT NOW Vitamin D aims to:
• Support evidence-based policy development.
• Facilitate public awareness and education.
• Promote coordinated research using harmonised definitions and measures.
• Advocate for nationwide fortification and supplementation strategies.

Conclusion

The UK faces a preventable vitamin D health crisis. Adopting a higher sufficiency threshold of 50 nmol/L will modernise policy, improve surveillance and better protect public health – especially among vulnerable groups.