Efficacy of Food Fortification with Vitamin D in Iranian Adults: A Systematic Review and Meta-Analysis

Effectiveness and Potential Toxicity of Bread Fortification With Vitamin D in General Population: A Predictive Modeling Study

BACKGROUND

Vitamin D fortification of bakery's wheat flour, which excludes flours used for confectionaries and bulky breads, can be a suitable strategy to improve vitamin D status of the general population.

OBJECTIVES

This study aimed to generate a predictive model to anticipate the effectiveness and potential risk of vitamin D-fortified bread in different fortification doses in general population.

METHODS

To gather baseline data before implementation of flour fortification, a cross-sectional descriptive study was conducted on a representative sample comprising 1051 subjects aged 7-65 y from 2 cities Birjand and Yazd. Demographic, anthropometric, and laboratory assessments were performed for all subjects. The amount of bread consumption was estimated using a 24-h recall questionnaire. A simulation model was used to examine the impact of various fortification doses of vitamin D in bread on the proportion of both adults and children achieving sufficient circulating 25-hydroxycalciferol [25(OH)D] concentrations (>50 nmol/L) and potential harm thresholds (>375 nmol/L). The baseline serum 25(OH)D concentration data were used as a reference for comparison at each fortification dose. Circulating 25(OH)D between 27.5 and 50 nmol/L and below 27.5 nmol/L was considered as insufficiency and deficiency, respectively.

RESULTS

Substantial proportions of both children and adults fell into the insufficient (37.5% and 37.4%, respectively) and deficient (34.7% and 31.8%, respectively) categories. Our model showed that the fortification dose of 250 IU/100g bread could be an effective strategy for significantly improving vitamin D status in the general population. Higher doses, such as 500 IU/100g, results in >70% of the population achieving sufficient 25(OH)D concentrations. However, starting at 400 IU/100 g bread, a very small percentage (0.1%) of the population could reach potentially harmful concentrations.

CONCLUSIONS

By adding 250-350 IU vitamin D per 100 g bread, over half of the general population can reach to sufficient vitamin D status with no potential risk of toxicity.

Adaptation and validation of a dietary diversity questionnaire to predict nutrient adequacy in children aged 24 to 59 months in Iran: national food and nutrition surveillance

BACKGROUND

Dietary Diversity Score (DDS), as a proxy for nutritional adequacy, can be used as a useful tool to assess diet quality, especially in children, due to its low cost and ease of use in comprehensive studies. This study aimed to develop a questionnaire to estimate dietary diversity and also assess the validity of DDS as an indicator of nutritional status among children aged 24 to 59 months in Iran.

METHODS

In addition to the Dietary Diversity Questionnaire (DDQ), which was designed based on the Food and Agriculture Organization (FAO) protocols, two non-consecutive 24-hour dietary recalls were completed for 471 children aged 24-59 months, recruited using random cluster sampling. Nutrient Adequacy Ratio (NAR) for energy, protein, and micronutrients, and the Mean Nutrient Adequacy Ratio (MAR) were calculated. Serum retinol concentration was assayed using High Performance Liquid Chromatography (HPLC). Children's weights and heights were measured and Height for Age (HAZ), Weight for Age (WAZ), Weight for Height (WHZ), and BMI for Age (BAZ) Z-scores were calculated according to World Health Organization (WHO) criteria in 2006. Pearson correlation analysis was performed to analyze the correlation between DDS and NARs, MAR, anthropometric indicators, and serum retinol.

RESULTS

The mean age of the children was 42.5 ± 0.47 months. The average DDS was 5.19 ± 0.06. DDS showed a positive association with the NAR of energy, protein, and all micronutrients (p < 0.05) except for vitamin K. There was a positive and significant correlation between DDS and MAR (r = 0.271; p < 0.001). In addition, DDS showed a direct, weaker but statistically significant, correlation with serum retinol concentration (r = 0.104; p = 0.026). No significant relationship was found between DDS and children's growth indicators.

CONCLUSIONS

The designed DDQ can be a valuable tool for examining the adequacy of nutritional intake in Iranian children.

Urban and rural residence: their influence on food group consumption in Iran

BACKGROUND

Urbanization is expanding in Iran, leading to the emergence of three distinct socio-geographical areas: urban, rural, and suburban areas. These different areas may exhibit significant variations in dietary patterns. This study investigates the association between people's place of residence and their consumption of different food groups.

METHODS

This study utilized data from Iran's Food and Nutrition Surveillance System (FNS). A total of 1697 participants were randomly recruited from different rural (N = 568), urban (N = 568), and suburban (N = 561) regions across Iran. Their food intake was assessed using a validated dish-based semi-quantitative food frequency questionnaire (DB-FFQ).

RESULTS

Rural males consumed significantly more grains (35.51 g/day, p = 0.03) than urban males, while rural females consumed significantly less dairy (-30.07 g/day, p = 0.03) than urban females. Additionally, rural males and females consumed significantly more fats and oils (3.72 g/day, p = 0.01 for males and 5.2 g/day, p < 0.001 for females) than their urban counterparts. Moreover, both suburban females and males were found to consume significantly less fruit compared to urban individuals, with suburban females consuming - 47.41 g/day (p < 0.001) less fruit and suburban males consuming - 60.42 g/day (p = 0.001) less fruit.

CONCLUSION

Findings showed that rural men's diets are characterized by higher consumption of grains and fats, while urbanization is linked to increased dairy consumption in women. Additionally, the study highlights a worrying lack of fruit consumption in suburban areas. These findings underscore the necessity of implementing specific nutritional policies to promote dietary diversity in various residential areas.

Exploring the determinants of malnutrition in 2-5 year Iranian children using structural equation modeling: national food and nutrition surveillance

BACKGROUND

Childhood malnutrition remains a critical public health challenge in low- and middle-income countries, contributing significantly to morbidity and mortality among children aged 2-5 years. This study was undertaken to assess the nutritional status of 2-5 y children and to explore the main determinants of child malnutrition in eight food insecure provinces of Iran.

METHODS

In each province, participants were invited to attend the health house/center to complete the questionnaire on the pre-appointed day. In this study, an android application comprising electronic questionnaires was employed for data collection. Anthropometric, dietary, food security and socioeconomic status (SES) assessments were performed. Structural equation modeling (SEM) was done to assess the structural relationship of malnutrition indicators (z-score of height to age (HAZ), z-score of weight to age (WAZ) and z-score of weight to height (WHZ)) with other variables.

RESULTS

Overall, 2247 children aged 42.2 ± 0.3 months were enrolled in the study, of whom 1048 (46.6%) were female and 1438 (64%) were urban residents. Based on Z score criteria, 216 (10.1%) of the studied children had less than - 2SD HAZ, 193 (8.4%) had lower than - 2SD WHZ and 188 (8.1%) had lower than - 2SD WAZ. The prevalence rates of stunting, wasting and underweight were not significantly different between boys and girls. Nevertheless, the occurrence of stunting was significantly higher in children residing in rural than in urban areas (p = 0.025). SEM analysis revealed that higher SES had a positive relationship with HAZ (0.089), WAZ (0.163) and WHZ (0.109). The effect of SES was greatest on WAZ, indicated by the highest absolute value of a path coefficient. There were specific indirect effects of father's education on HAZ (0.032, p = 0.001), WHZ (0.045, < 0.001) and WAZ (0.061, < 0.001) through effect on SES and DDS. SES had a direct effect on DDS (0.202).

CONCLUSIONS

Our findings using SEM approach provided more concrete evidence for the effect of the household's SES on child's nutritional status. Nevertheless, we still need to monitor the studied population in the context of our surveillance program to document more conclusive causal associations.

A Mixed Model Approach for Estimating the Optimal Food Fortification of Vitamin D: Experiment Based on Mashhad Cohort Study in Iran

BACKGROUND

Vitamin D deficiency is a prevalent problem in worldwide healthcare related to several system disorders. Food fortification as a solution is associated with several challenges including insufficient coverage of the entire population, required degree of fortification, the vehicles used for fortification and potential toxicity. This study aimed to determine the optimal amount of vitamin D for fortification without surpassing the upper intake level (UL) of intake at the 95th percentile of the Iranian population and compare two methods of food fortification.

METHODS

This study is aimed to develop a model of two different fortifying approaches related to an available dataset called MASHAD cohort study. The dataset comprised demographic and nutritional data of 9704 Iranian individuals living in the Greater Mashhad region. The first approach was a computational method necessary to implement a range of eight foods and calculate the optimal approach. In the second case, we used the European formula method called ILSI.

RESULTS

To find the appropriate value for fortification, we calculated the consumption of 400 IU and 1000 IU supplements of vitamin D. Three micrograms per 100 g in each food was the optimal output. We also used Flynn and Rasmussen's formula on our data. Using these methods, we found that 2.1 micrograms per 100 kcal provides the best result. Hence, using the two different approaches, the results appear to be consistent and promising.

CONCLUSION

One interesting finding was that supplement consumption did not greatly affect the impact of fortification. This observation may support the hypothesis to determine the amount of fortification, and we can ignore the study population's supplement consumption.

Fortification of Staple Foods for Household Use with Vitamin D: An Overview of Systematic Reviews

Vitamin D deficiency is a global public health concern with significant implications for bone health and chronic disease prevention. Our aim was to summarize the evidence from Cochrane and other systematic reviews evaluating the benefits or harms of vitamin D fortification of staple foods for household use. In April 2023, we systematically searched Ovid MEDLINE, Embase, Epistemonikos and the Cochrane Database of Systematic Reviews for systematic reviews investigating the effects of vitamin D fortification of food in general populations of any age. We used Cochrane methodology and assessed the methodological quality of included studies using AMSTAR (A MeaSurement Tool to Assess Systematic Reviews). We assessed the degree of overlap among reviews. All outcomes included in systematic reviews were assessed. The protocol is registered in PROSPERO (registration number: CRD42023420991). We included 27 systematic reviews out of 5028 records for analysis. Overall, 11 out of 12 systematic reviews calculating pooled estimates reported a significant increase in serum 25(OH)D concentrations. The mean change in serum 25(OH)D concentrations per additional 100 units of vitamin D ranged from 0.7 to 10.8 nmol/L. Fortification of food with vitamin D showed a reduction in the prevalence of vitamin D deficiency based on high-certainty evidence. Parathormone (PTH) levels were described to decrease, bone mineral density to increase, while the effects on other bone turnover markers were inconsistent. Fortification did not significantly impact most anthropometric parameters, but it seemed to positively influence lipid profiles. In summary, fortification of food with vitamin D results in a reduction of vitamin D deficiency and might increase serum 25(OH)D concentrations, to varying extents depending on the fortified vehicle and population characteristics. Additionally, fortification may have a positive impact on bone turnover and lipid metabolism but may only have a limited effect on anthropometric parameters.

Vitamin D deficiency prevention policies in Iran: a retrospective policy analysis

Aim

Iran has a higher prevalence of vitamin D deficiency (VDD) than the global level. This study aimed to assess VDD prevention policies in Iran through a policy analysis of agenda setting using the multiple streams framework (MSF).

Methods

Using Kingdon's MSF model, this qualitative analytical study performed a policy analysis on vitamin D-related policies in Iran. The policy documents were reviewed, and in-depth interviews were conducted with stakeholders (n = 27) using the framework analysis method. To categorize data and extract the related themes, MAXQDA version 10 was used.

Results

According to Kingdon's MSF theory, the problem stream included the high prevalence of VDD among Iranian infants (23.3%), adolescents (76%), and adults (59.1%). The policy stream was identified to focus on preventing programs for non-communicable diseases in the health sector. The political stream indicated that national and international support could provide a political climate for this issue.

Conclusion

According to our results, a window of opportunity for policymaking on VDD prevention has opened. However, there are some challenges related to the implementation of these policies. These include the dominance of a treatment-based view rather than a prevention-based approach in the health sector, economic problems, and restricted access to health services due to the outbreak of coronavirus disease 2019 (COVID-19). To strengthen and implement VDD prevention policies, the stakeholders need support from high-level policymakers.

Dietary pattern association with CD4 cells count in patients living with human immunodeficiency virus: A cross-sectional study

Background

Considering contradictory reports about the impact of dietary pattern on CD4 cell count in previous studies and the potential importance of diet on the immune system, this study aimed to assess the association between dietary patterns and CD4 count among HIV-infected patients.

Methods

This cross-sectional study was conducted among HIV-infected patients aged 18-60 who registered in the referral Voluntary Counseling and Testing Center of Shiraz, Iran. The principal component analysis identified nutritional patterns and factors. The association between the score of the dietary patterns and CD4 count was considered in two categories of CD4 more/less than 500 and using backward logistic regression after adjusting for confounders.

Results

A total of 226 participants were included in the analysis. CD4 was significantly lower in males (p < 0.001). Participants with illegal drug use (p < 0.001), HCV (p = 0.001), and HBV (p < 0.001) had lower serum CD4. Four extracted dietary patterns were a Plant-rich diet, Healthy animal-based proteins, a Western diet, and Affordable calorie and protein patterns. There was an association between CD4 and Western diet patterns in the best model in which age, gender, weight, and HBV were included. Each unit increase in Western diet score increased the odds of CD4 less than 500 by 57% (OR = 1.57; CI 95% 1.06-2.34, p = 0.02).

Conclusion

Among the four dietary patterns, the Western diet comprising a high intake of refined sugar and grain, saturated and trans fats, and animal protein sources, especially high-fat red meat, had a statistically significant relationship with a decrease in CD4 cell count.

The association of parathyroid hormone with serum 25-hydroxyvitamin during pregnancy

It is currently debated whether vitamin D requirements during pregnancy differ from those during non-gravid states. In current analyses, we aimed to determine the best model for the association between PTH and serum 25-hydroxyvitamin D (25(OH)D) and the threshold for circulating 25(OH)D at which serum parathyroid hormone (PTH) is suppressed. This multicenter prospective cross-sectional study was conducted on 227 Iranian pregnant women aged 15-45 years in their third trimester of pregnancy. The locally weighted smoothing scatter plot (LOWESS) was used to determine the curvilinear shape of the 25(OH)D/PTH relationship. Linear and non-linear methods were employed to determine the best fit and cut-point for serum 25(OH)D concentration. The median serum 25(OH)D and corresponding serum PTH concentration were 17⋅26 (13⋅44-23⋅08) ng/ml and 19⋅46 (15⋅08-25⋅04) pg/ml in our study population, respectively. The LOWESS curve suggested a non-linear and monotonic with a negative slope relation between PTH (pg/ml) and serum 25(OH)D (ng/ml). The optimal model for the association between PTH and serum 25(OH)D was a one-term fractional polynomial (FP1) (AIC = 1640⋅463). The FP1 analysis identified the 25(OH)D threshold of 12⋅48 ng/ml at which serum PTH rapidly rose. The expected degree of PTH stimulation seems to have a linear trend as 25(OH)D falls below 40 ng/ml. 25(OH)D (ng/ml) and PTH (pg/ml) had a non-linear and monotonic relationship with a negative slope. Our data suggest that a 25(OH)D threshold of 12⋅48 ng/ml is sufficient for parathyroid hormone suppression, which could be used to screen for deficient individuals.

How Much Does Serum 25(OH)D Improve by Vitamin D Supplement and Fortified Food in Children? A Systematic Review and Meta-Analysis

OBJECTIVES

This study was conducted to respond certain important questions regarding the efficacy of vitamin D fortification and supplementation in children using a meta-analytical approach.

METHODS

MEDLINE, PubMed, Embase, Cochrane Library, and Google Scholar were searched, and 2341 studies were found in a preliminary search. After screening of titles and abstracts, 31 studies were selected.

RESULTS

Significant raises in circulating 25-hydroxy vitamin D (25(OH)D) concentrations were observed in both groups that took vitamin D supplement (mean difference [MD] 28.7, 95% confidence interval [CI] 22.5-34.9) and vitamin D-fortified foods (MD 20.29, 95% CI 13.3-27.2). The meta-regression revealed a significant association between age of participants (B -1.4, 95% CI -2.8, -0.02, P = 0.047) and dose of vitamin D (B 0.007, 95% CI 0.003, 0.01, P < 0.001), with the effect on serum 25(OH)D concentrations. The analysis showed that serum 25(OH)D concentration increases by 0.7 nmol/L for every 100 IU of vitamin D intake after adjustment for age, baseline serum 25(OH)D and latitude which is far less than the reported amount in adults.

CONCLUSIONS

Altogether, these findings indicate that in a mass vitamin D fortification program, circulating 25(OH)D concentration response in children may be lower in children than in adults and vitamin D supplementation may still be needed in this subpopulation.

Vitamin D-fortified cooking oil is an effective way to improve vitamin D status: an institutional efficacy trial

PURPOSE

High prevalence of vitamin D deficiency (VDD) justifies a cost-effective and sustainable strategy to combat VDD in the community. This study was undertaken for the first time to evaluate the efficacy of daily consumption of vitamin D fortified sunflower oil with a meal.

METHODS

This single-blind trial was conducted in two separate institutions: one as intervention (D-fortified sunflower oil) group (DO, n₁ = 39) and the other as control (unfortified sunflower oil) group (SO, n₂ = 33). Participants consumed their lunches cooked either with D-fortified or unfortified cooking sunflower oil (500 IU/30 g) for 12 weeks. Dietary, anthropometric and biochemical assessments were done for all participants before and after the intervention.

RESULTS

A total of 65 subjects from both sexes aged 32.5 ± 4 years completed the intervention period. Serum 25(OH)D showed a significant increase in DO and a decrease in SO group (8.8 ± 9.3 vs. - 7.4 ± 6.4 ng/mL, p < 0.001). The rise in serum 25(OH)D in DO group was accompanied by a significant decrease in iPTH (DO: - 10.2 ± 29.4 vs. SO: + 9.2 ± 29.5 pg/mL; p = 0.009). A significant reduction in weight (p = 0.004), BMI (p = 0.029), waist girth (p < 0.001), serum total cholesterol (p = 0.0290) and LDL-C (p = 0.010) was observed in DO, as compared with SO group.

CONCLUSIONS

Cooking oil can be considered as an efficacious vehicle for mass fortification program to combat VDD. The improvement of vitamin D status may bring about betterment of certain cardiometabolic risk factors.

REGISTRATION NUMBER

Clinicaltrials.gov: NCT03826654.