Vitamin D: dietary requirements and food fortification as a means of helping achieve adequate vitamin D status

Vitamin D deficiency is evident in many parts of the globe, even in the sunnier regions, for a variety of reasons. Such deficiency contributes to risk of metabolic bone disease as well as potentially other non-skeletal chronic diseases in both early-life and later-life, and thus strategies for its prevention are of major public health importance. Dietary Reference Intervals (called Dietary Reference Intakes (DRI) and Dietary Reference Values (DRVs) in North America and Europe, respectively) for vitamin D have a key role in protecting against vitamin D deficiency in the population, and these have been re-evaluated in recent years on both sides of the Atlantic. The current DRI and DRVs for vitamin D and their basis will be overviewed in this review as well as some limitations that existed within the evidence-base and which contribute some degree of uncertainty to these new requirement estimates for vitamin D. The review will also compare current population intake estimates for children and adults in North America and Europe against the estimated average requirement (EAR) for vitamin D, as a benchmark of nutritional adequacy. While vitamin D supplementation has been suggested as a method of bridging the gap between current vitamin D intakes and new recommendations, the level of usage of vitamin D supplements in many countries as well as the vitamin D content of available supplements in these countries, appears to be low. The fortification of food with vitamin D has been suggested as a strategy for increasing intake with potentially the widest reach and impact in the population. The present review will highlight the need to re-evaluate current food fortification practices as well as consider new additional food-based approaches, such as biofortification of food with vitamin D, as a means of collectively tackling the low intakes of vitamin D within populations and the consequent high prevalence of low vitamin D status that are observed. This article is part of a Special Issue entitled '17th Vitamin D Workshop'.

Food-based solutions for vitamin D deficiency: putting policy into practice and the key role for research

Recent re-evaluations of dietary reference values (DRV) for vitamin D have established intake requirements between 10 and 20 µg/d. National nutrition surveys indicate that habitual mean intakes of vitamin D in the population are typically in the range 3-7 µg/d. As vitamin D supplementation will not be effective at a population level because the uptake is generally low, creative food-based solutions are needed to bridge the gap between current intakes and these new requirement values. The overarching aim of this review is to highlight how food-based solutions can have an important role in bridging this gap and counteracting vitamin D inadequacy in Europe and elsewhere. The present review initially briefly overviews very recent new European DRV for vitamin D and, while not in agreement on requirement estimates, how they point very clearly to the need for food-based solutions. The review discusses the need for traditional fortification of foods in the dairy and other sectors, and finally overviews recent advances in the area of biofortification of food with vitamin D. In conclusion, increasing vitamin D intakes across the population distribution is important from a public health perspective to reduce the high degree of inadequacy of vitamin D intake in Europe. Fortification, including biofortification, of a wider range of foods, which accommodate diversity, is likely to have the potential to increase vitamin D intakes across the population distribution. Research has had, and will continue to have, a key role in terms of developing food-based solutions and tackling vitamin D deficiency.

The balance between food and dietary supplements in the general population

In the past, vitamins and minerals were used to cure deficiency diseases. Supplements nowadays are used with the aim of reducing the risk of chronic diseases of which the origins are complex. Dietary supplement use has increased in the UK over recent decades, contributing to the nutrient intake in the population, but not necessarily the proportion of the population that is sub-optimally nourished; therefore, not reducing the proportion below the estimated average requirement and potentially increasing the number at risk of an intake above the safety limits. The supplement nutrient intake may be objectively monitored using circulation biomarkers. The influence of the researcher in how the supplements are grouped and how the nutrient intakes are quantified may however result in different conclusions regarding their nutrient contribution, the associations with biomarkers, in general, and dose-response associations specifically. The diet might be sufficient in micronutrients, but lacking in a balanced food intake. Since public-health nutrition guidelines are expressed in terms of foods, there is potentially a discrepancy between the nutrient-orientated supplement and the quality of the dietary pattern. To promote health, current public-health messages only advocate supplements in specific circumstances, but not in optimally nourished populations.

Differences in the dietary requirement for vitamin D among Caucasian and East African women at Northern latitude

CONTEXT

Current vitamin D recommendations have been established based on an assumption that there are no differences between Caucasian and other ethnic/racial groups in terms of vitamin D requirements. This assumption, largely made due to the absence of data, is a key knowledge gap identified by a number of authorities.

OBJECTIVE

To test whether the distribution of dietary requirements for maintaining winter serum 25-hydroxyvitamin D [25(OH)D] concentrations ≥ 30 nmol/L (a priority threshold linked to vitamin D deficiency prevention) differ between Caucasian and Somali women living at northerly latitude.

METHODS

We used data from a 5-month, winter-based, vitamin D₃ dose-related randomized, placebo-controlled trial in Somali (n 47) and Causcian women (n 69), aged 21-64-year old, living in Southern Finland (60°N), to model the vitamin D intake-serum 25(OH)D dose-response relationship. Regression analyses were used to predict the vitamin D intake required to maintain 97.5% (as well as 50, 90, and 95%) of women in both ethnic groups above serum 25(OH)D thresholds of 30, 40 and 50 nmol/L.

RESULTS

Using a model which adjusted for baseline 25(OH)D, age, and BMI, the estimated vitamin D intake that maintained serum 25(OH)D ≥ 30 nmol/L in 97.5% of Caucasian and Somali women was 8 and 18 µg/day, respectively. Ethnic differences were also evident at 40 and 50 nmol/L serum 25(OH)D thresholds.

CONCLUSION

The present study adds further evidence that ethnic differences in the dietary requirement for vitamin D do exist and that dose-response vitamin D intervention studies are required in at-risk target populations specified by ethnicity.

Micronutrient content in enteral nutrition formulas: comparison with the dietary reference values for healthy populations

BACKGROUND

The micronutrient content in standard enteral mixtures should be closer to the dietary reference values for a healthy population since standard enteral diets are formulated for subjects with no special nutritional needs. This study compares the micronutrient content of the most common enteral nutrition (EN) formulas with European dietary reference values (DRVs) for healthy population.

FINDINGS

Sixty-two nutritionally complete enteral formulas were considered. The micronutrient content was calculated by multiplying the value reported on the nutritional information panel of each formula by the daily dose usually prescribed. The comparison between the micronutrient content of all enteral formulas evaluated and the DRVs indicates that daily fluoride and vitamin K requirements were not covered, while an oversupply of many other micronutrients was provided. Moreover, in some enteral formulas, at a dose of 2000 Kcal/day, zinc and vitamin A content exceeded the tolerable upper limits and, for one diabetes-specific enteral formula, the chromium content exceeded the relevant European standards in both 1500 and 2000 Kcal/day diets.

CONCLUSIONS

Most enteral formulas evaluated are generally suitable for patients on long-term total EN and formulas with higher content of a specific micronutrient may be a useful tool for patients affected by specific clinical conditions, at least for a period of time, then switching to standard enteral mixtures. The availability of nutritional enteral formulas, well balanced also for micronutrient intake, will further improve individualized treatments, particularly for patients on long-term total EN.

Iodine nutrition: Disorders, monitoring and policies

Iodine is an essential mineral nutrient and an integral component of thyroid hormones. Iodine deficiency is typically associated with goiter, but can have more serious health implications. Adequate iodine status is important for normal brain development. Iodine deficiency in utero or in early life can cause severe neurological and cognitive impairment. Over the last three decades, global efforts have reduced the prevalence of iodine deficiency disorders (IDD) in many areas of the world with implementation of nutrition policies and programs such as "salt" iodization. However, in a number of areas iodine deficiency is still widespread. Iodine deficiency in remote regions with high poverty will be more difficult to eradicate. Efforts to eliminate IDD in affected areas and sustaining successful iodine programs will be a priority given the substantial public health and economic benefits. A key component will be periodic monitoring of population iodine status to ensure sufficient intakes and the absence of excessive intakes. Median urinary iodine concentration (UIC), a validated biomarker for assessing population iodine status, will facilitate monitoring. Research validating "usual" UIC for use in combination with the Estimated Average Requirement cut-point method will expand its utility and allow accurate determination of the prevalence of inadequate intakes in populations. Further research on the development of biomarkers for assessment of individual iodine status for routine patient care will be important.

Individual participant data (IPD)-level meta-analysis of randomised controlled trials to estimate the vitamin D dietary requirements in dark-skinned individuals resident at high latitude

CONTEXT AND PURPOSE

There is an urgent need to develop vitamin D dietary recommendations for dark-skinned populations resident at high latitude. Using data from randomised controlled trials (RCTs) with vitamin D3-supplements/fortified foods, we undertook an individual participant data-level meta-regression (IPD) analysis of the response of wintertime serum 25-hydroxyvitamin (25(OH)D) to total vitamin D intake among dark-skinned children and adults residing at ≥ 40° N and derived dietary requirement values for vitamin D.

METHODS

IPD analysis using data from 677 dark-skinned participants (of Black or South Asian descent; ages 5-86 years) in 10 RCTs with vitamin D supplements/fortified foods identified via a systematic review and predefined eligibility criteria. Outcome measures were vitamin D intake estimates across a range of 25(OH)D thresholds.

RESULTS

To maintain serum 25(OH)D concentrations ≥ 25 and 30 nmol/L in 97.5% of individuals, 23.9 and 27.3 µg/day of vitamin D, respectively, were required among South Asian and 24.1 and 33.2 µg/day, respectively, among Black participants. Overall, our age-stratified intake estimates did not exceed age-specific Tolerable Upper Intake Levels for vitamin D. The vitamin D intake required by dark-skinned individuals to maintain 97.5% of winter 25(OH)D concentrations ≥ 50 nmol/L was 66.8 µg/day. This intake predicted that the upper 2.5% of individuals could potentially achieve serum 25(OH)D concentrations ≥ 158 nmol/L, which has been linked to potential adverse effects in older adults in supplementation studies.

CONCLUSIONS

Our IPD-derived vitamin D intakes required to maintain 97.5% of winter 25(OH)D concentrations ≥ 25, 30 and 50 nmol/L are substantially higher than the equivalent estimates for White individuals. These requirement estimates are also higher than those currently recommended internationally by several agencies, which are based predominantly on data from Whites and derived from standard meta-regression based on aggregate data. Much more work is needed in dark-skinned populations both in the dose-response relationship and risk characterisation for health outcomes.

TRAIL REGISTRATION

PROSPERO International Prospective Register of Systematic Reviews (Registration Number: CRD42018097260).

Approaches used to estimate bioavailability when deriving dietary reference values for iron and zinc in adults

This review aims to describe approaches used to estimate bioavailability when deriving dietary reference values (DRV) for iron and zinc using the factorial approach. Various values have been applied by different expert bodies to convert absorbed iron or zinc into dietary intakes, and these are summarised in this review. The European Food Safety Authority (EFSA) derived zinc requirements from a trivariate saturation response model describing the relationship between zinc absorption and dietary zinc and phytate. The average requirement for men and women was determined as the intercept of the total absorbed zinc needed to meet physiological requirements, calculated according to body weight, with phytate intake levels of 300, 600, 900 and 1200 mg/d, which are representative of mean/median intakes observed in European populations. For iron, the method employed by EFSA was to use whole body iron losses, determined from radioisotope dilution studies, to calculate the quantity of absorbed iron required to maintain null balance. Absorption from the diet was estimated from a probability model based on measures of iron intake and status and physiological requirements for absorbed iron. Average dietary requirements were derived for men and pre- and post-menopausal women. Taking into consideration the complexity of deriving DRV for iron and zinc, mainly due to the limited knowledge on dietary bioavailability, it appears that EFSA has made maximum use of the most relevant up-to-date data to develop novel and transparent DRV for these nutrients.

Nutritional adequacy in surgical IBD patients

BACKGROUND & AIMS

Despite little evidence available to date, the dietary intake assessment is considered a useful tool to optimize dietary intervention for the improvement of the nutritional status of IBD patients. The primary aim was to compare the dietary intake of IBD patients scheduled for surgery with the dietary reference values (DRVs) for the Italian population (LARN) and the ESPEN guidelines for clinical nutrition in IBD. The secondary aim was to describe the dietary patterns of patients with CD and UC in relation to the disease-specific and nutritional parameters and to compare these results to a control group in order to evaluate if similar nutritional intakes than in oncologic patients are found in IBD.

METHODS

Between January 2019 and March 2020, 62 consecutive IBD patients (46 CD and 16 UC) with age from 18 to 79 years scheduled for surgery were recruited. Patients received a comprehensive nutritional assessment, including food or nutrition-related history, anthropometric and body composition measurements. A group of 61 oncologic patients scheduled for colorectal cancer (CRC) surgery was used as control.

RESULTS

IBD patients showed a higher caloric and nutritional intake than CRC group, despite a higher frequency of underweight, and a lower prevalence of overweight and obesity. IBD patients showed an inadequate intake of proteins, n-3 PUFA, fiber, iron, calcium, potassium, magnesium, zinc, vitamin D and vitamin B12 according to ESPEN guidelines for clinical nutrition in IBD and LARN. Oral intake was not influenced by gender, IBD subtype, longer duration of disease and previous surgery. In CD, fistulizing behaviour negatively influenced oral intake.

CONCLUSIONS

in IBD patients, the evaluation of macronutrients and micronutrients intake before surgery, can contribute to evaluate and to correct the onset of nutritional deficiencies. Specific dietary recommendations seem required, in order to integrate specific nutritional inadequacies. IBD patients referred to surgery have to be considered at high nutritional risk like oncologic patients are.

Development and application of a 2-step methodology to select a reference society providing Dietary Reference Values for national implementation

OBJECTIVE

To describe and discuss a 2-step methodology developed to select a reference society that provides Dietary Reference Values (DRV) for national implementation and to illustrate its application in Switzerland with one macronutrient and one micronutrient.

DESIGN

During Step 1, we searched and compared DRV and methodologies used to define DRV from eight European societies for seven selected nutrients. We repeated this procedure during Step 2 for DRV from two preselected societies for forty-four nutrients.

SETTING

The 2-step methodology applied here for Switzerland may be used in other countries.

PARTICIPANTS

The research team commissioned six external experts from three linguistic regions of Switzerland, who provided their opinions through two online surveys, individual interviews and a focus group.

RESULTS

After Step 1, we excluded five societies because of old publication dates, irrelevant publication languages for Switzerland, difficulty in accessing documents, or because their DRV were mainly based on another society. After Step 2, the two societies were qualified based on the analysis of the values and methodologies used. The need for free and easily accessible scientific background information favoured the European Food Safety Authority (EFSA). We chose alternative societies for nine nutrients for the overall population or subgroups and for the elderly.

CONCLUSIONS

To manage heterogeneous and complex data from several societies, adopting a 2-step methodology including fewer nutrients and more societies during Step 1, and fewer societies but all nutrients in Step 2, was very helpful. With some exceptions, we selected EFSA as the main society to provide DRV for Switzerland.

Sex- and gender-based medicine in pediatric nutrition

Consistent evidence increasingly highlights the significance of integrating sex and gender medicine to ensure a precision approach according to individual patient needs. Gender discrepancies emerge across various areas, even from pediatric age. The importance of recognizing these differences in pediatric nutrition is critical for the development of targeted nutritional strategies and interventions, particularly in cases of associated pathologies, including obesity, metabolic-associated fatty liver disease, eating disorders, and inflammatory bowel disease. The review highlights the biological and sociocultural factors that contribute to different nutritional needs and health outcomes in male and female children. By examining current evidence, we underscore the necessity for precision medicine approaches in pediatric care that consider these sex- and gender-based differences. Moreover, differences in dietary requirements and dietary patterns between males and females are evident, underscoring the need for precise nutrition strategies for a more accurate management of children and adolescents. This approach is essential for improving clinical outcomes and promoting equitable healthcare practices. This review aims to provide an overview of nutrition-related medical conditions exhibiting sex- and gender-specific discrepancies, which might lead to distinct outcomes requiring unique management and prevention strategies. Future research and public health initiatives should address these differences in designing effective lifestyle education programs and nutrition interventions targeting both children and adolescents.