Comparison of the Effect of Daily Vitamin D2 and Vitamin D3 Supplementation on Serum 25-Hydroxyvitamin D Concentration (Total 25(OH)D, 25(OH)D2, and 25(OH)D3) and Importance of Body Mass Index: A Systematic Review and Meta-Analysis

Differential Enhancement of Fat-Soluble Vitamin Absorption and Bioefficacy via Micellization in Combination with Selected Plant Extracts In Vitro

Background/Objectives: Individuals with special metabolic demands are at risk of deficiencies in fat-soluble vitamins, which can be counteracted via supplementation. Here, we tested the ability of micellization alone or in combination with selected natural plant extracts to increase the intestinal absorption and bioefficacy of fat-soluble vitamins. Methods: Micellated and nonmicellated vitamins D3 (cholecalciferol), D2 (ergocalciferol), E (alpha tocopheryl acetate), and K2 (menaquionone-7) were tested in intestinal Caco-2 or buccal TR146 cells in combination with curcuma (Curcuma longa), black pepper (Piper nigrum), or ginger (Zingiber officinale Roscoe) plant extracts. The vitamin uptake was quantified via HPLC-MS, and bioefficacy was assessed via gene expression analyses or the Griess assay for nitric oxide generation. Results: Micellization increased the uptake of vitamin D into buccal and intestinal cells, with vitamin D3 being more efficient than vitamin D2 in increasing the expression of genes involved in calcium transport. The micellization of vitamin E acetate increased its uptake and conversion into biologically active free vitamin E in intestinal cells only. The vitamin K2 uptake into buccal and intestinal cells was increased via micellization. Plant extracts increased the uptake of select micellated vitamins, with no plant extract being effective in combination with all vitamins. The curcuma extract increased the uptake of vitamins D2/D3 but not their bioefficacy. Black pepper and ginger extracts increased the uptake of vitamin E acetate into intestinal cells but failed to increase its conversion into free vitamin E. The ginger extract augmented the uptake of vitamin K2 and increased NO generation additively. Conclusions: Our data substantiate the positive effects of micellization on fat-soluble vitamin absorption and bioefficacy in vitro. While the application of plant extracts in addition to micellization to further increase bioefficacy is an interesting approach, further studies are warranted to understand vitamin-specific interactions and translation into increased bioefficacy.

Does Systematic Use of Small Doses of Vitamin D Have Anti-Inflammatory Effects and Effectively Correct Deficiency Among Healthy Adults?

BACKGROUND

Calcitriol, beyond its well-established role in calcium and phosphate homeostasis, contributes to immunological processes. No known vitamin D dosage regimen effectively corrects the deficiency while accounting for immunoregulatory effects. Therefore, the purpose of this assessment was to determine whether regular administration of low doses of vitamin D might correct deficiency and have immunoregulatory effects.

METHODS

A total of 35 healthy volunteers were asked to supplement with vitamin D daily at a dosage of 500 or 1000 IU, depending on the degree of deficiency, for 12 months. At the beginning of the study and after the end of the supplementation period, concentrations of 25(OH)D; PTH; total calcium; inorganic phosphorus; and the inflammatory cytokines IL-17, IL-10, TGF-β, and IFN-γ were determined in all participants.

RESULTS

Correction of vitamin D deficiency was achieved with accompanying decreases in PTH and pro-inflammatory cytokine concentrations, while the concentration of anti-inflammatory cytokines remained stable.

CONCLUSIONS

Therefore, regular vitamin D supplementation, even in small doses, effectively corrected the deficiency and had immunomodulatory effects.

Melatonin and vitamin D as potential synergistic adjuvants for cancer therapy (Review)

Significant advancements have been made in cancer therapy; however, limitations remain with some conventional approaches. Adjuvants are agents used alongside primary treatments to enhance their efficacy and the treatment outcomes of patients. Modern lifestyles contribute to deficiencies in melatonin and vitamin D. Limited sun exposure affects vitamin D synthesis, and artificial light at night suppresses melatonin production. Both melatonin and vitamin D possess anti‑inflammatory, immune‑boosting and anticancer properties, rendering them potential adjuvants of interest. Studies suggest melatonin and vitamin D supplementation may address antioxidant imbalances in lip, oral and pharyngeal cancers. Moreover, promising results from breast, head and neck, brain, and osteosarcoma research indicate potential for tumor growth inhibition, improved survival, and a better quality of life of patients with cancer. The radioprotective properties of melatonin and vitamin D are another exciting area of exploration, potentially enhancing radiotherapy effectiveness while reducing side effects. For its part, the sleep‑promoting effects of melatonin may indirectly benefit patients with cancer by influencing the immune system. Thus, the prevalence of vitamin D and melatonin deficiencies highlights the importance of supplementation, as lower levels can worsen side‑effects from cancer treatments. The present review explores the potential of combining melatonin and vitamin D as synergistic adjuvants for cancer therapy. These agents have shown promise individually in cancer prevention and treatment, and their combined effects warrant investigation. Therefore, large‑scale controlled trials are crucial to definitively determine the optimal dosage, safety and efficacy of this combination in improving the lives of patients with cancer.

Understanding the Genetic Architecture of Vitamin Status Biomarkers in the Genome-Wide Association Study Era: Biological Insights and Clinical Significance

Vitamins play an intrinsic role in human health and are targets for clinical intervention through dietary or pharmacological approaches. Biomarkers of vitamin status are complex traits, measurable phenotypes that arise from an interplay between dietary and other environmental factors with a genetic component that is polygenic, meaning many genes are plausibly involved. Studying these genetic influences will improve our knowledge of fundamental vitamin biochemistry, refine estimates of the effects of vitamins on human health, and may in future prove clinically actionable. Here, we evaluate genetic studies of circulating and excreted biomarkers of vitamin status in the era of hypothesis-free genome-wide association studies (GWAS) that have provided unprecedented insights into the genetic architecture of these traits. We found that the most comprehensive and well-powered GWAS currently available were for circulating status biomarkers of vitamin A, C, D, and a subset of the B vitamins (B9 and B12). The biology implicated by GWAS of measured biomarkers of each vitamin is then discussed, both in terms of key genes and higher-order processes. Across all major vitamins, there were genetic signals revealed by GWAS that could be directly linked with known vitamin biochemistry. We also outline how genetic variants associated with vitamin status biomarkers have been already extensively used to estimate causal effects of vitamins on human health outcomes, which is particularly important given the large number of randomized control trials of vitamin related interventions with null findings. Finally, we discuss the current evidence for the clinical applicability of findings from vitamin GWAS, along with future directions for the field to maximize the utility of these data.

Does higher serum 25-hydroxyvitamin D levels will harm bone mineral density?: a cross-sectional study

OBJECTIVE

Vitamin D plays a critical role in the prevention and management of osteoporosis. However, there is an ongoing debate regarding the most effective vitamin D supplementation strategies for maintaining optimal bone mineral density (BMD) levels in adults. This study sought to establish the correlation between serum 25-hydroxyvitamin D [25(OH)D] levels and total BMD in a substantial population sample.

METHODS

Data from the National Health and Nutrition Examination Survey (NHANES) for the 2011-2018 cycles, encompassing 11,375 adult participants, were analyzed. The primary variables of interest were serum 25(OH)D levels and BMD. A multivariable logistic regression model was utilized to account for relevant variables associated with these correlations.

RESULTS

A U-shaped relationship between serum 25(OH)D levels and BMD was observed. In males, a significant positive association was identified for 25(OH)D levels below 84.8 nmol/L (p < 0.0001), while levels above this threshold showed no significant correlation (p = 0.3377). In females, those with 25(OH)D levels below 31.4 nmol/L exhibited a significant positive association with BMD (p = 0.0010), but this association weakened and became marginally significant above this threshold (p = 0.0650).

CONCLUSIONS

For adult males, the optimal serum 25(OH)D level is 84.8 nmol/L, beyond which higher levels do not lead to increased BMD. A deficiency threshold for adult females should be above 31.4 nmol/L, as lower 25(OH)D levels are not conducive to BMD. These findings underscore the importance of maintaining appropriate vitamin D levels for bone health in both genders.

Effects of an 8-week high-dose vitamin D supplementation on fatigue and neuropsychiatric manifestations in post-COVID syndrome: A randomized controlled trial

AIM

This study evaluated the effectiveness of high-dose vitamin D supplementation in alleviating fatigue and neuropsychiatric symptoms in post-COVID syndrome.

METHODS

In an 8-week, double-blind, randomized, placebo-controlled trial, 80 patients with post-COVID fatigue or neuropsychiatric symptoms were enrolled. Participants were randomly assigned to receive either 60,000 IU of vitamin D weekly (n = 40) or a placebo (n = 40) for 8 weeks. Clinical outcomes were assessed using the 11-item Chalder Fatigue Scale (CFQ-11); 21-item Depression, Anxiety, and Stress Scale (DASS-21); Pittsburgh Sleep Quality Index (PSQI); Addenbrooke's Cognitive Examination III (ACE); and Trail Making Test A and B (TMT-A and TMT-B). Baseline and 8-week measurements of inflammatory markers, including interleukin 6 (IL-6) and C-reactive protein (CRP), were also collected.

RESULTS

Significant improvements were found in the vitamin D group for CFQ (coefficient -3.5, P = 0.024), DASS-anxiety (-2.0, P = 0.011), and ACE (2.1, P = 0.012). No significant differences were observed in PSQI, DASS-depression, TMT, IL-6, or CRP levels. The incidence of adverse events was comparable between groups, with no serious adverse events reported.

CONCLUSION

High-dose vitamin D supplementation may benefit patients with post-COVID syndrome by reducing fatigue, alleviating anxiety, and improving cognitive symptoms, with minimal side effects.

Serum vitamin D concentrations in rabbits (Oryctolagus cuniculus) are more affected by UVB irradiation of food than irradiation of animals

Rabbits kept under ultraviolet B (UVB)-irradiation respond with increasing serum vitamin D (25(OH)D) concentrations, but it is unknown whether irradiation of the animals or their feed contributes more. Twenty-four New Zealand White rabbits were divided into three groups for a four-week period: the control group (C) received no UVB-exposure and non-irradiated hay (ergocalciferol (vitamin D2) concentration 2.22 µg/100 g dry matter). The direct exposure group (D) was provided with 12 h of UVB-irradiation daily and fed the same hay as group C in shaded areas to prevent UVB-irradiation thereof. The indirect exposure group (I) did not receive direct UVB-irradiation but was fed hay of the same batch that was exposed to 12 h of UVB-irradiation (vitamin D2 6.06 µg/100 g dry matter). Serum 25(OH)D2, 25(OH)D3, ionised calcium, total calcium, phosphorus, and magnesium concentrations were measured weekly. There was no systematic effect on serum mineral concentrations. The serum 25(OH)D2 concentrations were significantly higher in group I compared to groups C and D from the second week onwards. 25(OH)D3 concentrations increased only in group D, with significant differences to both other groups from the third week onwards, yet at lower magnitudes than the noted increase of 25(OH)D2 in group I. Total 25(OH)D concentrations were highest in group I, intermediate in group D and lowest in group C. Serum total 25(OH)D concentration was more affected by UVB-irradiation of rabbits' feed than by direct irradiation of the animals themselves. If rabbit serum total 25(OH)D concentrations should be managed, diet manipulation rather than animal UVB-exposure appears to be more effective.

An Overview of Different Vitamin D Compounds in the Setting of Adiposity

A large body of research shows an association between higher body weight and low vitamin D status, as assessed using serum 25-hydroxyvitamin D concentrations. Vitamin D can be metabolised in adipose tissue and has been reported to influence gene expression and modulate inflammation and adipose tissue metabolism in vitro. However, the exact metabolism of vitamin D in adipose tissue is currently unknown. White adipose tissue expresses the vitamin D receptor and hydroxylase enzymes, substantially involved in vitamin D metabolism and efficacy. The distribution and concentrations of the generated vitamin D compounds in adipose tissue, however, are largely unknown. Closing this knowledge gap could help to understand whether the different vitamin D compounds have specific health effects in the setting of adiposity. This review summarises the current evidence for a role of vitamin D in adipose tissue and discusses options to accurately measure vitamin D compounds in adipose tissue using liquid chromatography tandem mass spectrometry (LC/MS-MS).