PANDORA-seq – a new way to assess sperm quality

PANDORA-seq reveals sncRNA landscape in human sperm, facilitating sperm quality assessment

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(A) Comparison of the relative ratio of clean reads to raw reads and reads aligned to the genome to clean reads between traditional sncRNA-seq and PANDORA-seq. (B) The scatter plots depicting the correlation of miRNA, tsRNA, and rsRNA expression profiles of paired traditional sncRNA-seq and PANDORA-seq. Spearman correlation coefficients and P-values are shown. (C) Comparison of the relative expression levels of four major sncRNA origins (miRNA, tsRNA, rsRNA, ysRNA, and piRNA) in healthy human sperm determined by the PANDORA-seq protocol. (D) Expression levels of miRNAs, tsRNAs, and rsRNAs in human sperm samples validated by northern blotting. (E) The radar plot showing the different relative expression proportions of each tsRNA subcategory with respect to the two protocols. (F) Northern blotting validation of tsRNALeu(TAG), tsRNALys(TTT), and tsRNAGly(GCC) in human sperm. (G) Visualization of the proportional distribution of cyto-tsRNAs and mt-tsRNAs in healthy human sperm determined by the PANDORA-seq protocol. (H) The radar plots illustrating the relative expression proportions of each tsRNA subcategory in relation to three distinct tsRNA origins (5′, inner′, and 3′). (I) Sequence mapping location (left), expression profile (middle), and reverse transcription PCR validation (right) of tsRNAAla(AGC), tsRNAArg(TCG), and tsRNAGlu(CTC) in human sperm. (J) Distribution of expression proportions for six nucleus-encoded rsRNAs and two mitochondria-encoded rsRNAs. (K) The boxplots showing the relative expression of five nucleus-encoded rsRNAs and two mitochondria-encoded rsRNA categories. (L) Visualization of expression signature and sequence mapping location of rsRNA-18S and rsRNA-28S in human sperm samples. (M) Northern blotting validation of rsRNA-5.8S, selected rsRNA-18S main peaks (peak #1, peak #2), and selected rsRNA-28S main peaks (peak #1, peak #2) in human sperm samples.

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Credit: Ruofan Huang, Yiting Yang, Wenlin Jiang, Zheng Cao, Junchao Shi, Xiao-Ou Zhang, Yunfang Zhang

The global fertility crisis is increasingly attributed to a steady decline in human semen quality, with conditions such as asthenozoospermia (reduced sperm motility) and teratozoospermia (abnormal sperm morphology) accounting for more than half of male subfertility cases.

While small noncoding RNAs (sncRNAs) are known to be abundant in mature sperm and essential for regulating spermatogenesis, traditional sequencing methods have predominantly focused on miRNAs, which represent less than 1% of the total sncRNA population in sperm, whereas transfer RNA-derived small RNAs (tsRNAs) and ribosomal RNA-derived small RNAs (rsRNAs) comprise the majority of the sperm sncRNA profile. These sncRNAs frequently possess chemical modifications and non-canonical terminal structures that hinder adapter ligation and reverse transcription during standard library preparation, thereby making their detection challenging with conventional methods.

In a prospective cohort study published in Genes & Diseases, researchers from Tongji University, Shanghai Institute for Biomedical and Pharmaceutical Technologies (SIBPT), and Chinese Academy of Sciences utilized PANDORA-seq—a panoramic RNA display strategy that employs a two-step enzymatic treatment with T4 polynucleotide kinase (T4PNK) and α-ketoglutarate-dependent dioxygenase (AlkB)—to remove these inhibitory modifications. By applying this method to a cohort of 25 participants categorized into normozoospermia (NZS), asthenozoospermia (AZS), and teratozoospermia (TZS) groups, the researchers generated one of the most comprehensive landscapes of human sperm sncRNAs to date.

The study revealed that tsRNAs and rsRNAs are not only the dominant species, constituting over 97% of the total small RNA population, but are also strongly correlated with clinical indicators of sperm quality, such as motility and morphology. Among rsRNAs, the majority are derived from cytoplasmic 28S and 18S subunits, with 28S-derived sequences alone accounting for over 74% of the rsRNA population. tsRNAs also exhibit distinct patterns, with nuclear-encoded species primarily originating from the 5' end of tRNAs, whereas mitochondrial-encoded tsRNAs are skewed toward internal cleavage sites.

Functional analysis identified robust linear correlations between these specific molecular species and clinical indicators: nuclear-encoded tsRNA-Phe and tsRNA-Lys are positively correlated with progressive motility (PR), whereas rsRNA-28S exhibits a significant negative correlation with motility parameters. Furthermore, rsRNA-5.8S showed a notable negative correlation with both the head shape index (TZI) and the percentage of intact sperm heads, suggesting a potential mechanistic role in regulating sperm morphology.

Conversely, tsRNA species such as tsRNA-iMet, tsRNA-Val, and various 28S-derived rsRNAs were negatively correlated with motility, indicating their association with subfertile states. While correlations between sncRNAs and morphology were generally less pronounced, rsRNA-5.8S remained negatively associated with intact head and head shape indices, and tsRNA-Val showed a positive association with abnormal morphological indices.

To translate these molecular findings into clinical utility, the researchers employed machine learning and LASSO regression based on sperm rsRNA and tsRNA profiles, establishing the male subfertility sncRNA signature (MSsncSig), the AZS-related signature (AZSsncSig), and the TZS-related signature (TZSsncSig). These models demonstrated exceptional diagnostic power, achieving area under the curve (AUC) scores of 0.83 or higher. This predictive capability represents a substantial improvement over traditional WHO semen quality assessments, providing a novel molecular framework for diagnosing male infertility.

In conclusion, PANDORA-seq provides critical insights into the landscape of the human sperm sncRNA repertoire, identifying tsRNAs and rsRNAs as pivotal markers of reproductive health. By establishing correlations between these modified RNAs and sperm fitness, this research offers a robust framework for assessing sperm quality and understanding the molecular mechanisms underlying male subfertility and its potential intergenerational impacts.

Reference

Title of the original paper:  PANDORA-seq reveals human sperm sncRNA signature endowed with sperm quality assessment

Journal: Genes & Diseases

Genes & Diseases is a journal for molecular and translational medicine. The journal primarily focuses on publishing investigations on the molecular bases and experimental therapeutics of human diseases. Publication formats include full length research article, review article, short communication, correspondence, perspectives, commentary, views on news, and research watch.

DOI: https://doi.org/10.1016/j.gendis.2025.101807  

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Journal

Genes & Diseases

DOI

10.1016/j.gendis.2025.101807 

 

(A) The uniform manifold approximation and projection (UMAP) plot visualizing the distribution of human sperm total sncRNAs among healthy controls (NZS, n = 9), AZS samples (n = 9), and TZS samples (n = 7). (B) Dynamic landscapes and length distributions of miRNAs, tsRNAs, and rsRNAs detected. Zoomed panels of miRNA and tsRNA are shown on the plot for clearer visualization. (C) The radar plot showing the expression proportions (normalized by NZS samples) of each tsRNA subcategory in AZS and TZS samples. (D) The heatmap showing Spearman correlation coefficients between tsRNA subcategory abundances. (E) The bar charts showing the expression proportions of six nucleus-encoded rsRNAs and two mitochondria-encoded rsRNAs among NZS, AZS, and TZS. (F) The heatmap showing Spearman correlation coefficients between the rsRNA origin abundances. (G) The heatmap showing expression profile changes in miRNAs based on a log2-transformed scale among NZS, AZS, and TZS. (H) The heatmap showing Spearman correlation coefficients between the top 20 miRNA family abundances.

Credit

Ruofan Huang, Yiting Yang, Wenlin Jiang, Zheng Cao, Junchao Shi, Xiao-Ou Zhang, Yunfang Zhang

 

(A) The discovery cohort of the study. (B) Strategies and workflow of screening sncRNA characteristics for developing the prediction model between subfertile sperm (AZS or TZS) and healthy control (NZS) samples. (C) The ranking results of the random forest classifiers for distinguishing subfertile sperm (AZS and TZS) cases from healthy controls, ordered by feature importance. (D) The receiver operating characteristic (ROC) curve for sncRNA signatures used to distinguish subfertile sperm (AZS and TZS) cases from healthy controls, along with the corresponding area under the ROC curve (AUC) score. (E) Representative linear correlations between selected sncRNA sequences and sperm motility or sperm morphology metrics. (F, I) The ranking results of the random forest classifiers for distinguishing AZS (F) or TZS (I) cases from healthy controls, ordered by feature importance. SncRNA signatures, sperm morphology indicators, sperm motility indicators, and individual sncRNAs were marked as red, orange, purple, and blue points, respectively. (G, J) ROC curve for selected sncRNA signatures used to distinguish AZS (G) or TZS (J) cases from healthy controls, along with the corresponding AUC scores. (H, K) Representative linear correlations between selected sncRNA sequences and sperm motility (H) or sperm morphology metrics (K).

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Ruofan Huang, Yiting Yang, Wenlin Jiang, Zheng Cao, Junchao Shi, Xiao-Ou Zhang, Yunfang Zhang

 

By 2050 Europe’s waste could supply over half of critical material demand

Europe’s vast ‘urban mine’ is mapped – a world first; FutuRaM delivers comprehensive mapping and quantification of critical metals and minerals essential to clean energy, digital technologies, defence and modern industry, and assesses recoverability

WEEE Forum

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EU-funded experts today delivered the most comprehensive assessment ever of Europe’s ‘urban mine’ – materials stocks and waste streams containing a vast, an underutilized reservoir of metals and minerals essential for clean energy, digital technologies, and modern industry. 

At an event to conclude the FutuRaM project, researchers debuted a comprehensive mapping of critical raw materials (CRMs) embedded in discarded products, industrial residues, and demolished infrastructure across the EU27+4 (EU, UK, Switzerland, Iceland, and Norway).view more 

Credit: WEEE Forum

Brussels – EU-funded experts today delivered the most comprehensive assessment ever of Europe’s ‘urban mine’ – materials stocks and waste streams containing a vast, an underutilized reservoir of metals and minerals essential for clean energy, digital technologies, and modern industry. 

FutuRaM (Future Availability of Secondary Raw Materials) project researchers today debuted a comprehensive mapping of critical raw materials (CRMs) embedded in discarded products, industrial residues, and demolished infrastructure across the EU27+4 (EU, UK, Switzerland, Iceland, and Norway).

The unprecedented survey involved analysis of 42 critical elements contained in several waste streams, from electronic waste, vehicles and their batteries to wind turbines, slags and ashes and building construction and demolition debris. 

It revealed that recovery systems could, by 2050, enable Europe to recover between 4.1 and 5.7 million tonnes of CRMs annually, with primary substitution potential ranging from up to 33% under business-as-usual conditions, up to 47% with improved recovery systems and 56% under a circular economy scenario, if the quality of secondary raw materials can substitute for primary. 

This would reduce European reliance on imported materials and strengthen supply security for key technologies such as batteries, electric vehicles, and renewable solar and wind energy.

A key advance of the project is a comprehensive overview for multiple waste streams from items placed on the market to waste generation with a new recovery model that distinguishes between critical raw materials present in waste and those available as secondary raw materials after treatment, addressing a major limitation in previous assessments and allowing more policy-relevant estimates of supply potential.

All the project data are now available through the Urban Mine Platform (urbanmineplatform.eu), a digital tool that helps visualize the availability of CRMs across Europe’s waste streams, analyzed using a common framework that tracks flows from products and components down to individual materials and chemical elements.

The FutuRaM (Future Availability of Secondary Raw Materials) report and the Urban Mine Platform offers a detailed guide for CRMs for the EU27+4 countries which are today largely supplied by China (e.g. rare earth metals, lithium and cobalt), the Democratic Republic of Congo (cobalt), Australia (lithium), South Africa (platinum), and Turkey (boron).

A waste landscape rich in strategic opportunity

The platform and final report brings together harmonized data on seven major waste streams:

• Waste electrical and electronic equipment (WEEE)
• Waste batteries
• End-of-life vehicles
• Construction and demolition waste from buildings
• Slags and ashes from industrial processes
• Mining waste
• Dismantled wind turbines

It confirms that 5.2 million tonnes of CRMs embedded in products were placed on the market in 2022, compared to 2.1 million tonnes embedded in waste and 1.4 million tonnes recovered, highlighting both the scale of material flows and the gap between consumption and recovery.  

By 2050, CRMs in products placed on the market could rise to between 8.4 and 12.2 million tonnes annually as waste generation reaches 5.2 to 6.4 million tonnes, and recovery could reach 4.7 to 5.7 million tonnes underscoring the growing strategic importance of recycling systems.

Many strategically important materials, including lithium, cobalt, and rare earth elements, are largely lost during collection and/or waste processing today. 

Five CRMs – including platinum, and rhodium – have recovery rates of over 80% thanks largely to well-established collection and processing routes. 

Eight others, including aluminium, copper, palladium, and nickel fall in the 40–80% range, where collection and treatment infrastructure is in place but losses remain significant. 

And for 22 CRMs, recovery yields less than one tonne per year across the entire EU27+4 (2022 data) , with most rare earth elements in this category. 

According to the report, with the right legislative and industrial choices made now, within 24 years some 17 CRMs, including cobalt, lithium, and rare earth metals such as dysprosium and neodymium, could achieve recovery rates above 80%.

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A fast-growing waste stream

The volume of products placed on the market that contain CRMs is expected to grow sharply as electrification, renewable energy deployment, and digitalization accelerate. This increase in the mass of CRMs in the urban mine leads to an increase in the amount that could be recovered in the future.

The research found that by 2050, aluminium recovery could grow from about 0.9 million tonnes per year today to as much as 2.7 - 3.5 million tonnes, while copper recovery could rise from 0.3 million tonnes to as much as 0.8 - 1.4 million tonnes annually.

Notably, some of the most valuable materials are the least likely to pass through formal recycling systems as the market value of elements such as gold drives diversion of products into informal and often untracked flows.

Some of the fastest-growing use of CRMs are associated with the transition to electric mobility and renewable energy, leading to greater potential for recovery.

For example:

• Lithium recovery could increase from much less than 1,000 tonnes today to 30,000–52,000 tonnes per year by 2050.
• Cobalt recovery could grow from about 1,000 tonnes to as much as 25, 000 - 40,000 tonnes annually.
• Nickel recovery could increase from about 4,000 tonnes to more than 103,000 - 171,000 tonnes per year.

These increases are driven largely by the expected surge in battery waste as electric vehicles and energy-storage systems reach the end of their life cycles.

Rare earth elements used in wind turbines, WEEE and electric motors are also projected to grow significantly, highlighting the importance of developing recycling technologies for permanent magnets.

Climate dividend: comparable to avoiding the CO2e emissions of Spain

Beyond supply security, recovering critical raw materials from waste also delivers significant environmental benefits.

In recent years, the annual recovery of secondary raw materials from the analyzed European waste streams generated about 38 Mt of direct emissions but avoided 77 Mt through reduced primary extraction, resulting in a net climate benefit of roughly 39 Mt CO₂-equivalent.

By 2050 avoided emissions could reach between 81 Mt and 273 Mt CO₂ equivalent per year, far outweighing direct processing emissions of 71–80 Mt – reinforcing recycling as a major climate mitigation strategy.

Closing the gaps in Europe’s recycling system

Despite the enormous potential, the study highlights major gaps in current collection and recycling systems.

For example, despite Europe being a global leader in WEEE management, nearly half of its electronic waste is handled outside compliant recycling systems, and part of the losses even arise in compliant waste management, leading to the most significant (500 kilotonnes) losses of critical raw materials in 2022.

Similarly, many batteries are improperly discarded or exported , while a large number of end-of-life vehicles remain outside official treatment channels or exported in second hand vehicles outside the EU, leading to losses of over 200 kilotonnes of critical raw materials in 2022.

Improving collection rates, tracking systems, and recycling infrastructure could therefore unlock substantial additional supplies of critical materials.

In the case of batteries, current recycling capacity for lithium-ion technologies is still expanding. Significant quantities of partially processed battery materials known as “black mass” are exported from Europe, meaning valuable resources are not fully recovered within the region.

Key gaps are:

• Making recycling projects more viable in Europe
• Investing in better waste sorting and mechanical treatment/dismantling 
• Investing in innovative recycling techniques
• A new approach

A new approach developed under the FutuRaM project aims to bring order and clarity to one of the most complex challenges in the circular economy: deciding which recycling projects are worth pursuing. Building on the United Nations Framework Classification (UNFC), an internationally-recognized system to assess mining and energy projects, the new tool, known as SARA4UNFC, adapts those principles to waste and recycling. It allows governments, investors, and industry to evaluate not just whether valuable materials exist in waste streams, but whether they can realistically be recovered in a way that is technically feasible, economically viable, and socially and environmentally responsible.

SARA4UNFC is a decision-making tool for turning waste into a reliable source ofCRMs. It helps compare different recycling options, identify the most promising projects, and reduce uncertainty for investment in infrastructure and new technologies. By providing a consistent framework across multiple waste streams and value chains, it also improves communication between stakeholders, from policymakers to private investors, and supports implementation of the EU’s Critical Raw Materials Act. Ultimately, the goal is to accelerate the shift from pilot projects to large-scale recovery systems, making secondary raw materials a dependable part of future supply chains.

Policy recommendations

The report outlines a set of policy actions to unlock Europe’s urban mine potential, including:

• Establish a harmonised EU framework for secondary raw materials reporting and classification.  A common system would ensure consistent, comparable data across Member States, enabling more accurate tracking of critical materials and better-informed policy decisions.
• Institutionalise the Urban Mine Platform as core EU data infrastructure. Embedding the platform within EU systems would provide a permanent, trusted source of data to support monitoring, investment planning, and regulatory implementation.
• Apply the UNFC classification system to secondary resources. Extending this globally recognised framework to recycling projects would improve transparency, comparability, and confidence for investors and policymakers.
• Strengthen enforcement and monitoring of illegal waste flows. Tighter controls and better tracking are needed to prevent valuable materials from being lost through informal channels, exports, or non-compliant treatment.
• Support long-term scenario modelling for strategic planning. Using forward-looking models can help policymakers anticipate future material demand and align infrastructure, investment, and regulation accordingly.
• Invest in skills, awareness, and recycling capacity across value chains. Building technical expertise and expanding recycling infrastructure is essential to scale up recovery and fully integrate secondary materials into supply chains.
• A foundation for Europe’s circular economy

The FutuRaM project marks a major advance in understanding Europe’s urban mine but further work remains.

Improved data collection, stronger alignment between recovery estimates and real-world recycling processes, and better tracking of waste exports will all be necessary to fully unlock the potential of secondary raw materials.

The datasets and analytical tools developed by the project are designed to remain available and reusable, following international FAIR data principles that ensure information is findable, accessible, interoperable, and reusable.

Together, they provide a foundation for long-term monitoring of Europe’s raw-material resources and a practical roadmap for integrating secondary raw materials into Europe’s industrial strategy, strengthening resilience in an increasingly uncertain global supply landscape.

Comments

“Europe’s waste streams already contain vast quantities of critical raw materials.  Harnessing this urban mine will be essential for strengthening supply security, supporting the clean-energy transition, and reducing environmental impacts.”

- Kees Baldé, Senior Scientific Specialist at United Nations Institute for Training and Research - SCYCLE 

“This report allows policymakers, researchers, and industry to assess Europe’s ‘urban mine’ with unprecedented clarity. The data and infrastructure we have built provides a foundation for evidence-based policymaking, long-term monitoring, and strategic investment decisions. Whether Europe realises this potential depends on the choices made now – on legislation, recycling infrastructure, and data collection. Considering these powerful findings, our mindset needs to shift to think of ‘secondary’ sources of CRMs as the new primary source."

- Pascal Leroy, Director General, Waste Electrical and Electronic Equipment (WEEE) Forum

“By applying the UNFC framework to recycling, we are giving policymakers and investors a common language to evaluate secondary raw materials, something that has long been missing in the transition to a circular economy.”

- Soraya Heuss-Aßbichler, Professor of Mineralogy, Ludwig-Maximilians Universität München 

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About FutuRaM

FutuRaM (Future Availability of Secondary Raw Materials) is an EU-funded project that developed datasets, methods, and tools to assess secondary raw material availability across Europe’s key waste streams. Building on the ProSUM initiative, the project analysed 42 critical raw materials in seven waste streams and created the Urban Mine Platform, the most comprehensive digital map of CRMs in the EU27+4. All data is accessible at www.urbanmineplatform.eu and via FutuRaM’s repository on Zenodo.

Working closely with the European Commission and other relevant policy makers, the project ran for four years and was funded under the EU's Horizon Europe research and innovation programme.

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FutuRaM project contributing partners: A short description of each, along with its project role and responsibilities is available here https://bit.ly/47UdohZ 

 

Eureope's FutuRaM project has delivered a comprehensive mapping and quantification of critical metals and minerals essential to clean energy, digital technologies, defense and modern industry – and assessed its recoverability. The report lifts transparency and confidence in Europe’s ‘urban mine’ potential

 

The unprecedented FutuRaM (Future Availability of Secondary Raw Materials) survey involved analysis of 42 critical elements contained in several waste streams, from electronic waste, vehicles and their batteries to wind turbines, slags and ashes and building construction and demolition debris. 

It revealed that recovery systems could, by 2050, enable Europe to meet up to 56% of CRM demand under a circular economy scenario. 

The report and the Urban Mine Platform offers a detailed guide for CRMs for the EU27+4 countries which are today largely supplied by China (e.g. rare earth metals, lithium and cobalt), the Democratic Republic of Congo (cobalt), Australia (lithium), South Africa (platinum), and Turkey (boron).

Credit

WEEE Forum

 

Nutrition’s role in chronic fatigue

Diet and homocysteine may influence fatigue and motivation

Osaka Metropolitan University

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Dietary imbalance, low B12, and folate may correlate with high homocysteine levels and indicate fatigue and low motivation in participants. 

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Credit: Osaka Metropolitan University

With less time and more work, chronic fatigue has become a moniker of modern society. However, this not only reduces the quality of life but also constitutes as a social issue that affects work efficiency and leads to accidents. On the surface, the cause of fatigue is often attributed to not getting enough rest, but there may be another underlying issue—the lack of proper nutrition.

Taking this into account, a research group led by Professor Hiroaki Kanouchi at Osaka Metropolitan University’s Graduate School of Human Life and Ecology focused on nutritional status and water-soluble vitamin deficiencies found in unbalanced diets. The team hypothesized that a lack of folate (B9) and vitamin B12 may be related to fatigue, and centered their research around homocysteine (Hcy), a biomarker known to increase when these deficiencies are present. Blood concentrations of Hcy, folate, and vitamin B12 in approximately 600 healthy Japanese participants were measured. Participants’ fatigue and motivation were assessed using the Chalder Fatigue Scale questionnaire and Visual Analog Scale. The initial results showed that individuals with higher blood Hcy levels had lower levels of vitamin B12 and folate, regardless of sex.

The researchers then examined the relationship between homocysteine levels and fatigue separately for men and women. In their analysis, factors that may influence fatigue, such as age, sleep duration, workload, and dietary habits, were simultaneously accounted for. The results revealed higher Hcy levels were associated with greater physical fatigue in men and higher levels were associated with decreased motivation in women.

“This suggested relationship between vitamin B12, folate, and fatigue in healthy individuals may represent the first report of its kind,” said Professor Kanouchi. “Blood homocysteine levels have traditionally raised concerns in relation to cardiovascular disease, dementia, and fractures. However, our findings suggest that attention should also be paid to fatigue and motivation in the future. To prevent an increase in homocysteine levels, it is important to avoid deficiencies in vitamin B12 and folate. Maintaining a well-balanced diet on a daily basis is essential.”

The findings were published in Nutrients. 

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About OMU  

Established in Osaka as one of the largest public universities in Japan, Osaka Metropolitan University is committed to shaping the future of society through the “Convergence of Knowledge” and the promotion of world-class research. For more research news, visit https://www.omu.ac.jp/en/ and follow us on social media: X, Instagram, LinkedIn.

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Journal

Nutrients

DOI

10.3390/nu18060941 

Method of Research

Observational study

Subject of Research

People

Article Title

Associations of Plasma Homocysteine Reflecting Vitamin B12 and Folate Status with Fatigue-Related Outcomes in Healthy Adults

Article Publication Date

17-Mar-2026

COI Statement

E.N., Y.N. and T.N are employees of Alinamin Pharmaceutical Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

 

Good Vitamin D status among most young children in Sweden

University of Gothenburg

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André Hesselink, Sahlgrenska Academy at the University of Gothenburg.

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Credit: Photo: University of Gothenburg

The majority of young children showed good vitamin D status, no child had indications of deficiency, but among some intake was too low. This is the result of a study encompassing over 1,800 infants in Sweden. Foods providing children with vitamin D also contributed to greenhouse gas emissions.

This study is the first to offer an in-depth analysis of vitamin D intake and status among infants in Sweden following an expansion of mandatory vitamin D fortification in 2018. The initiative focused on certain food groups and the aim was to ensure that more people attain sufficient vitamin D through their diet.

The study included children aged 18 months (1,074 individuals) and four years (746 individuals) whose data were obtained from the survey “Riksmaten småbarn”, covering 2021-2024. The study also evaluated the climate impact of foods providing children with vitamin D.

Low intake but no deficiency

The results show that 16 percent of the 18-month-olds and 61 percent of the four-year-olds were below the average required vitamin D intake (7.5 microgram/day) through diet and vitamin D drops. No children were vitamin D deficient, and most children had sufficient levels, including 93 percent in the younger age group and 96 percent in the older age group.

The most important sources of vitamin D for 18-month-olds were vitamin D drops and fortified dairy products, porridge and cereals; and for the four-year-olds, fortified dairy products and spreads.

At the same time, dairy products contribute to diet-related greenhouse gas emissions. The foods with the highest vitamin D content relative to environmental impact were fortified spreads and fortified plant-based alternatives. This makes plant-based alternatives a climate-friendly source of vitamin D.

Climate impact can be reduced

The study, published in the Nutrition Journal, was conducted by researchers at the University of Gothenburg, Swedish Food Agency and RISE, Research Institutes of Sweden. One of the lead authors is André Hesselink, dietician and doctoral student in clinical nutrition at the University of Gothenburg:

“We have enjoyed an excellent collaboration with the Swedish Food Agency, and our results show the crucial importance of fortified dairy products for vitamin D intake among young children in Sweden, especially after they stop taking vitamin D drops. In addition, the expansion of the mandatory fortification programme provides an opportunity for plant-based alternatives to play a more prominent role in the future for ensuring adequate intake of vitamin D and reducing the climate impact of our dietary habits”, he says.

 

Fact box: Vitamin D

• Required for the formation of strong teeth and bones
• One of few vitamins that we risk ingesting too little of
• Stored in the body over time
• Ingested through diet, mainly from fatty fish and fortified foods
• Formed in the skin by exposure to sunlight (dark skin requires more exposure time)
• Recommended for children in Sweden from 0-2 years of age in the form of supplemental vitamin D drops

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Journal

Nutrition Journal

DOI

10.1186/s12937-026-01318-6 

Method of Research

Observational study

Subject of Research

People

Article Title

High proportion of young children are vitamin D sufficient after expansion of Sweden’s mandatory fortification but dairy products also contribute to a high climate impact