Reviewed By
Overview
SCIENTIFIC SCORE
Possibly Effective
Based on 6 Researches
7
USERS' SCORE
Good
Based on 12 Reviews
8
Supplement Facts
Serving Size: 1 Softgel
Amount Per Serving
%DV
Vitamin D3 (as Cholecalciferol)
50 mcg (2,000 IU)
250%
Top Medical Research Studies
8
We explored the connection between vitamin D levels and upper respiratory tract infections (URTIs) among military recruits during their training. This observation spanned across different seasons and included over 1,600 recruits. Our aim was to understand how achieving sufficient vitamin D levels could potentially impact the frequency and severity of colds among physically active individuals.
In an additional phase of the research, we conducted a randomized controlled trial with 250 male recruits. They received either a placebo, simulated sunlight exposure, or oral vitamin D3 supplements during winter. This comparison allowed us to see if these methods effectively increased vitamin D levels to a sufficient status of 25(OH)D at 50 nmol/L or higher.
Notably, our findings showed that only 21% of recruits had adequate vitamin D during winter, yet those who did were 40% less likely to suffer from URTIs. Furthermore, both vitamin D supplementation strategies similarly helped nearly all participants achieve sufficient levels. Vitamin D supplementation notably reduced the severity of URTI symptoms by 15% and the number of days with URTIs by 36% compared to placebo.
While the supplementation strategies did not significantly alter other immune factors, such as salivary secretory immunoglobulin A, the overall reduction in respiratory infections indicates a beneficial effect of maintaining vitamin D sufficiency during military training.
In an additional phase of the research, we conducted a randomized controlled trial with 250 male recruits. They received either a placebo, simulated sunlight exposure, or oral vitamin D3 supplements during winter. This comparison allowed us to see if these methods effectively increased vitamin D levels to a sufficient status of 25(OH)D at 50 nmol/L or higher.
Notably, our findings showed that only 21% of recruits had adequate vitamin D during winter, yet those who did were 40% less likely to suffer from URTIs. Furthermore, both vitamin D supplementation strategies similarly helped nearly all participants achieve sufficient levels. Vitamin D supplementation notably reduced the severity of URTI symptoms by 15% and the number of days with URTIs by 36% compared to placebo.
While the supplementation strategies did not significantly alter other immune factors, such as salivary secretory immunoglobulin A, the overall reduction in respiratory infections indicates a beneficial effect of maintaining vitamin D sufficiency during military training.
Read More
8
We explored how 25-hydroxyvitamin D3 (25OHD), a form of vitamin D, influences upper respiratory tract infections (URTIs), commonly known as colds. In a carefully designed clinical study, we followed 428 participants aged 45 to 74 over a 16-week period. They were randomly assigned to receive either 10 μg of 25OHD daily or a placebo, all while maintaining a double-blind setup to ensure accurate results.
Our findings revealed that those who took 25OHD had reduced duration and severity of their cold symptoms. Participants reported improvements in their overall quality of life during the bouts of URTI. By tracking the health of the participants through surveys designed to measure cold symptoms, we gathered valuable data that indicates vitamin D3 could play a helpful role in managing colds.
This suggests that incorporating vitamin D3 into our diets may be beneficial when we catch a cold, potentially leading to a quicker recovery. It’s a promising avenue for anyone looking to ease the discomfort and duration of these frustrating infections.
Our findings revealed that those who took 25OHD had reduced duration and severity of their cold symptoms. Participants reported improvements in their overall quality of life during the bouts of URTI. By tracking the health of the participants through surveys designed to measure cold symptoms, we gathered valuable data that indicates vitamin D3 could play a helpful role in managing colds.
This suggests that incorporating vitamin D3 into our diets may be beneficial when we catch a cold, potentially leading to a quicker recovery. It’s a promising avenue for anyone looking to ease the discomfort and duration of these frustrating infections.
Read More
7
We evaluated the impact of high-dose vitamin D supplementation, specifically doses exceeding the standard 400 IU, on preventing colds and other infections in children under five years of age. Our analysis included seven studies, involving a total of 5,748 children, which looked into how effective vitamin D might be in reducing the incidence of upper respiratory tract infections.
Interestingly, while our findings showed no significant benefit of high-dose vitamin D on the prevention of upper respiratory tract infections as a whole, we did observe a noteworthy reduction in specific illness occurrences. We noted a 57% reduction in colds, a 56% reduction in coughs, and a 59% decrease in fever rates with daily doses exceeding 1,000 IU.
However, we must approach these findings with caution, as the evidence supporting the reduction in cough and fever was of lower certainty. No significant effects were observed regarding other conditions such as bronchitis or otitis media. Overall, while high-dose vitamin D may help with colds specifically, further research is needed to solidify these conclusions.
Interestingly, while our findings showed no significant benefit of high-dose vitamin D on the prevention of upper respiratory tract infections as a whole, we did observe a noteworthy reduction in specific illness occurrences. We noted a 57% reduction in colds, a 56% reduction in coughs, and a 59% decrease in fever rates with daily doses exceeding 1,000 IU.
However, we must approach these findings with caution, as the evidence supporting the reduction in cough and fever was of lower certainty. No significant effects were observed regarding other conditions such as bronchitis or otitis media. Overall, while high-dose vitamin D may help with colds specifically, further research is needed to solidify these conclusions.
Read More
Most Useful Reviews
10
Preventing illness
For several years, vitamin D has been our preferred supplement during the off-season. Adults take courses of 5000 IU, whilst children take 2000 IU. We can hardly remember the last time we suffered from colds, and our family has entirely avoided the well-known illness that is often discussed. All good health! Vitamin D is our favourite!
Read More
9
Fewer colds
Excellent! We take it on the recommendation of a doctor, with a prophylactic dose of 2000 units all year round. We've noticed a significant reduction in illness; we used to take sick leave at least once every season. Now, even if a cold does strike, it resolves very quickly and mildly. The vitamin has convenient small capsules with no unpleasant taste or smell, though the packaging runs out quickly.
Read More
9
No more colds
It's easy to adjust since it’s 2000 IU. I take it to boost my immunity. The small softgel is easy to swallow. I trust 21st Century supplements as they are tested with safe ingredients. Since taking vitamin D3, I've not caught a cold and feel much healthier. I typically take 3-4 tablets of 6000-8000 IU daily.
Read More
Medical Researches
SCIENTIFIC SCORE
Possibly Effective
Based on 6 Researches
7
- All Researches
8
We explored the connection between vitamin D levels and upper respiratory tract infections (URTIs) among military recruits during their training. This observation spanned across different seasons and included over 1,600 recruits. Our aim was to understand how achieving sufficient vitamin D levels could potentially impact the frequency and severity of colds among physically active individuals.
In an additional phase of the research, we conducted a randomized controlled trial with 250 male recruits. They received either a placebo, simulated sunlight exposure, or oral vitamin D3 supplements during winter. This comparison allowed us to see if these methods effectively increased vitamin D levels to a sufficient status of 25(OH)D at 50 nmol/L or higher.
Notably, our findings showed that only 21% of recruits had adequate vitamin D during winter, yet those who did were 40% less likely to suffer from URTIs. Furthermore, both vitamin D supplementation strategies similarly helped nearly all participants achieve sufficient levels. Vitamin D supplementation notably reduced the severity of URTI symptoms by 15% and the number of days with URTIs by 36% compared to placebo.
While the supplementation strategies did not significantly alter other immune factors, such as salivary secretory immunoglobulin A, the overall reduction in respiratory infections indicates a beneficial effect of maintaining vitamin D sufficiency during military training.
In an additional phase of the research, we conducted a randomized controlled trial with 250 male recruits. They received either a placebo, simulated sunlight exposure, or oral vitamin D3 supplements during winter. This comparison allowed us to see if these methods effectively increased vitamin D levels to a sufficient status of 25(OH)D at 50 nmol/L or higher.
Notably, our findings showed that only 21% of recruits had adequate vitamin D during winter, yet those who did were 40% less likely to suffer from URTIs. Furthermore, both vitamin D supplementation strategies similarly helped nearly all participants achieve sufficient levels. Vitamin D supplementation notably reduced the severity of URTI symptoms by 15% and the number of days with URTIs by 36% compared to placebo.
While the supplementation strategies did not significantly alter other immune factors, such as salivary secretory immunoglobulin A, the overall reduction in respiratory infections indicates a beneficial effect of maintaining vitamin D sufficiency during military training.
Read More
8
We explored how 25-hydroxyvitamin D3 (25OHD), a form of vitamin D, influences upper respiratory tract infections (URTIs), commonly known as colds. In a carefully designed clinical study, we followed 428 participants aged 45 to 74 over a 16-week period. They were randomly assigned to receive either 10 μg of 25OHD daily or a placebo, all while maintaining a double-blind setup to ensure accurate results.
Our findings revealed that those who took 25OHD had reduced duration and severity of their cold symptoms. Participants reported improvements in their overall quality of life during the bouts of URTI. By tracking the health of the participants through surveys designed to measure cold symptoms, we gathered valuable data that indicates vitamin D3 could play a helpful role in managing colds.
This suggests that incorporating vitamin D3 into our diets may be beneficial when we catch a cold, potentially leading to a quicker recovery. It’s a promising avenue for anyone looking to ease the discomfort and duration of these frustrating infections.
Our findings revealed that those who took 25OHD had reduced duration and severity of their cold symptoms. Participants reported improvements in their overall quality of life during the bouts of URTI. By tracking the health of the participants through surveys designed to measure cold symptoms, we gathered valuable data that indicates vitamin D3 could play a helpful role in managing colds.
This suggests that incorporating vitamin D3 into our diets may be beneficial when we catch a cold, potentially leading to a quicker recovery. It’s a promising avenue for anyone looking to ease the discomfort and duration of these frustrating infections.
Read More
7
We evaluated the impact of high-dose vitamin D supplementation, specifically doses exceeding the standard 400 IU, on preventing colds and other infections in children under five years of age. Our analysis included seven studies, involving a total of 5,748 children, which looked into how effective vitamin D might be in reducing the incidence of upper respiratory tract infections.
Interestingly, while our findings showed no significant benefit of high-dose vitamin D on the prevention of upper respiratory tract infections as a whole, we did observe a noteworthy reduction in specific illness occurrences. We noted a 57% reduction in colds, a 56% reduction in coughs, and a 59% decrease in fever rates with daily doses exceeding 1,000 IU.
However, we must approach these findings with caution, as the evidence supporting the reduction in cough and fever was of lower certainty. No significant effects were observed regarding other conditions such as bronchitis or otitis media. Overall, while high-dose vitamin D may help with colds specifically, further research is needed to solidify these conclusions.
Interestingly, while our findings showed no significant benefit of high-dose vitamin D on the prevention of upper respiratory tract infections as a whole, we did observe a noteworthy reduction in specific illness occurrences. We noted a 57% reduction in colds, a 56% reduction in coughs, and a 59% decrease in fever rates with daily doses exceeding 1,000 IU.
However, we must approach these findings with caution, as the evidence supporting the reduction in cough and fever was of lower certainty. No significant effects were observed regarding other conditions such as bronchitis or otitis media. Overall, while high-dose vitamin D may help with colds specifically, further research is needed to solidify these conclusions.
Read More
7
We explored the impact of vitamin D and B12 deficiencies in children experiencing primary Raynaud phenomenon (RP), which causes temporary blood flow changes often triggered by cold or stress. Our study aimed to identify how common these vitamin deficiencies are in pediatric patients and whether they influenced the severity of Raynaud symptoms.
Out of 40 young participants, a significant portion—41.5% for vitamin B12 and 39% for vitamin D—showed low serum levels of these vitamins. After providing supplementation, we observed improved symptoms in many cases, particularly through warming techniques. However, it's important to note that while vasodilator treatment needs were generally unchanged regardless of vitamin B12 levels, those who had vitamin D deficiencies and subsequently received vitamin D treatment required significantly less vasodilator therapy.
Overall, while some positive effects of vitamin D were noted, further research is necessary to conclusively determine its role in managing primary RP symptoms and its effectiveness in combating cold-induced episodes.
Out of 40 young participants, a significant portion—41.5% for vitamin B12 and 39% for vitamin D—showed low serum levels of these vitamins. After providing supplementation, we observed improved symptoms in many cases, particularly through warming techniques. However, it's important to note that while vasodilator treatment needs were generally unchanged regardless of vitamin B12 levels, those who had vitamin D deficiencies and subsequently received vitamin D treatment required significantly less vasodilator therapy.
Overall, while some positive effects of vitamin D were noted, further research is necessary to conclusively determine its role in managing primary RP symptoms and its effectiveness in combating cold-induced episodes.
Read More
7
Vitamin D reduces cold symptoms
We explored the effects of 25-hydroxyvitamin D (25OHD) on individuals experiencing upper respiratory tract infections (URTIs), commonly known as colds. In a well-structured study, participants with low vitamin D levels received either a daily dose of 10 micrograms of 25OHD or a placebo for a span of 16 weeks. The participants' symptoms were assessed using the Wisconsin Upper Respiratory Symptom Survey-21, focusing on how the vitamin impacted their cold symptoms.
Our findings showed that those taking 25OHD reported significant reductions in physical symptoms such as runny noses, sneezing, and head congestion compared to those on the placebo. Additionally, the quality of life scores improved for most symptoms, except for ease of breathing. However, it’s important to note that there was no significant difference in the total number of cold events or how often participants used medications like antibiotics or pain relievers.
Collectively, these results suggest that adequate intake of vitamin D can help ease cold symptoms, particularly those affecting the nose, and might enhance overall well-being when a cold strikes. This indicates that vitamin D may play a positive role in managing the discomfort associated with upper respiratory infections.
Our findings showed that those taking 25OHD reported significant reductions in physical symptoms such as runny noses, sneezing, and head congestion compared to those on the placebo. Additionally, the quality of life scores improved for most symptoms, except for ease of breathing. However, it’s important to note that there was no significant difference in the total number of cold events or how often participants used medications like antibiotics or pain relievers.
Collectively, these results suggest that adequate intake of vitamin D can help ease cold symptoms, particularly those affecting the nose, and might enhance overall well-being when a cold strikes. This indicates that vitamin D may play a positive role in managing the discomfort associated with upper respiratory infections.
Read More
User Reviews
USERS' SCORE
Good
Based on 12 Reviews
8
- All Reviews
- Positive Reviews
- Negative Reviews
10
Preventing illness
For several years, vitamin D has been our preferred supplement during the off-season. Adults take courses of 5000 IU, whilst children take 2000 IU. We can hardly remember the last time we suffered from colds, and our family has entirely avoided the well-known illness that is often discussed. All good health! Vitamin D is our favourite!
Read More
9
Fewer colds
Excellent! We take it on the recommendation of a doctor, with a prophylactic dose of 2000 units all year round. We've noticed a significant reduction in illness; we used to take sick leave at least once every season. Now, even if a cold does strike, it resolves very quickly and mildly. The vitamin has convenient small capsules with no unpleasant taste or smell, though the packaging runs out quickly.
Read More
9
No more colds
It's easy to adjust since it’s 2000 IU. I take it to boost my immunity. The small softgel is easy to swallow. I trust 21st Century supplements as they are tested with safe ingredients. Since taking vitamin D3, I've not caught a cold and feel much healthier. I typically take 3-4 tablets of 6000-8000 IU daily.
Read More
10
Miracle results
Every day has been amazing! Since taking these vitamins, my son has improved his studies and activities! We have also forgotten about colds! It's truly miraculous! Thanks for this life-enhancing vitamin supplement!
Read More
8
Prevents viruses
I find the vitamin D3 excellent — 250 capsules is ample for a long duration, and they’re easy to swallow. This brand is one of my favourites. We take them throughout the year, except in summer, and as prescribed by our doctor, it helps protect against colds and other viruses.
Read More
Frequently Asked Questions
10
Preventing illness
For several years, vitamin D has been our preferred supplement during the off-season. Adults take courses of 5000 IU, whilst children take 2000 IU. We can hardly remember the last time we suffered from colds, and our family has entirely avoided the well-known illness that is often discussed. All good health! Vitamin D is our favourite!
9
Fewer colds
Excellent! We take it on the recommendation of a doctor, with a prophylactic dose of 2000 units all year round. We've noticed a significant reduction in illness; we used to take sick leave at least once every season. Now, even if a cold does strike, it resolves very quickly and mildly. The vitamin has convenient small capsules with no unpleasant taste or smell, though the packaging runs out quickly.
6
Effective for colds
Small capsule with a good dosage. The brand on Ayherb is well-known, so I decided to give it a go. I've nearly completed the jar. My husband and I take one capsule daily, but during colds, I increase it to two. The capsules are odourless and easy to swallow, though they taste a bit like gelatin, which I haven't chewed on.
7.5
Less prone
I purchased vitamin D for my 15-year-old child. I administered 1 capsule daily, and I am very pleased with the results — the child is less prone to colds.
7.5
Strong immunity
Vitamin D3 is crucial nowadays. From infancy, children are given it in drops to prevent rickets, and older children need it for calcium absorption and robust immunity. Recent studies confirm that those with severe D deficiency face more severe and prolonged illness. Our pediatrician recommends a dose of 2000 IU from October to April when sunlight is limited, and people wear closed clothing during the cold. My son takes 1000 IU daily in summer. The small capsules are easy to swallow, taken with food. It invigorates some of us. A large supply lasts throughout the cold season. Highly recommended!
9
No more colds
It's easy to adjust since it’s 2000 IU. I take it to boost my immunity. The small softgel is easy to swallow. I trust 21st Century supplements as they are tested with safe ingredients. Since taking vitamin D3, I've not caught a cold and feel much healthier. I typically take 3-4 tablets of 6000-8000 IU daily.
5
We explored the effects of vitamin D supplementation on respiratory infections, particularly colds, in children under six years old. By examining various studies published until February 2023, we observed diverse findings, with some studies reporting benefits while others found no significant advantage. Overall, eight studies were included, with a total of 2,189 children assessed.
While a few studies indicated that low vitamin D levels might be linked to an increased risk of respiratory infections, only one study specifically noted that children who took 800 IU of vitamin D daily for three months experienced fewer mild respiratory symptoms and recovered more quickly. However, a significant number of studies showed no notable differences in the rates or severity of colds when vitamin D supplementation was used.
In essence, the evidence regarding vitamin D's role in preventing or effectively treating colds in young children is still unclear. We did find some indications that certain doses, like 80 IU/kg/day, may help reduce acute respiratory infection risks, but most research highlighted only minor benefits, such as quicker recovery rather than preventing infections. Variability in study design and supplementation protocols contributed to these inconclusive results, highlighting the need for further research.
While a few studies indicated that low vitamin D levels might be linked to an increased risk of respiratory infections, only one study specifically noted that children who took 800 IU of vitamin D daily for three months experienced fewer mild respiratory symptoms and recovered more quickly. However, a significant number of studies showed no notable differences in the rates or severity of colds when vitamin D supplementation was used.
In essence, the evidence regarding vitamin D's role in preventing or effectively treating colds in young children is still unclear. We did find some indications that certain doses, like 80 IU/kg/day, may help reduce acute respiratory infection risks, but most research highlighted only minor benefits, such as quicker recovery rather than preventing infections. Variability in study design and supplementation protocols contributed to these inconclusive results, highlighting the need for further research.
7
We evaluated the impact of high-dose vitamin D supplementation, specifically doses exceeding the standard 400 IU, on preventing colds and other infections in children under five years of age. Our analysis included seven studies, involving a total of 5,748 children, which looked into how effective vitamin D might be in reducing the incidence of upper respiratory tract infections.
Interestingly, while our findings showed no significant benefit of high-dose vitamin D on the prevention of upper respiratory tract infections as a whole, we did observe a noteworthy reduction in specific illness occurrences. We noted a 57% reduction in colds, a 56% reduction in coughs, and a 59% decrease in fever rates with daily doses exceeding 1,000 IU.
However, we must approach these findings with caution, as the evidence supporting the reduction in cough and fever was of lower certainty. No significant effects were observed regarding other conditions such as bronchitis or otitis media. Overall, while high-dose vitamin D may help with colds specifically, further research is needed to solidify these conclusions.
Interestingly, while our findings showed no significant benefit of high-dose vitamin D on the prevention of upper respiratory tract infections as a whole, we did observe a noteworthy reduction in specific illness occurrences. We noted a 57% reduction in colds, a 56% reduction in coughs, and a 59% decrease in fever rates with daily doses exceeding 1,000 IU.
However, we must approach these findings with caution, as the evidence supporting the reduction in cough and fever was of lower certainty. No significant effects were observed regarding other conditions such as bronchitis or otitis media. Overall, while high-dose vitamin D may help with colds specifically, further research is needed to solidify these conclusions.
8
We explored the connection between vitamin D levels and upper respiratory tract infections (URTIs) among military recruits during their training. This observation spanned across different seasons and included over 1,600 recruits. Our aim was to understand how achieving sufficient vitamin D levels could potentially impact the frequency and severity of colds among physically active individuals.
In an additional phase of the research, we conducted a randomized controlled trial with 250 male recruits. They received either a placebo, simulated sunlight exposure, or oral vitamin D3 supplements during winter. This comparison allowed us to see if these methods effectively increased vitamin D levels to a sufficient status of 25(OH)D at 50 nmol/L or higher.
Notably, our findings showed that only 21% of recruits had adequate vitamin D during winter, yet those who did were 40% less likely to suffer from URTIs. Furthermore, both vitamin D supplementation strategies similarly helped nearly all participants achieve sufficient levels. Vitamin D supplementation notably reduced the severity of URTI symptoms by 15% and the number of days with URTIs by 36% compared to placebo.
While the supplementation strategies did not significantly alter other immune factors, such as salivary secretory immunoglobulin A, the overall reduction in respiratory infections indicates a beneficial effect of maintaining vitamin D sufficiency during military training.
In an additional phase of the research, we conducted a randomized controlled trial with 250 male recruits. They received either a placebo, simulated sunlight exposure, or oral vitamin D3 supplements during winter. This comparison allowed us to see if these methods effectively increased vitamin D levels to a sufficient status of 25(OH)D at 50 nmol/L or higher.
Notably, our findings showed that only 21% of recruits had adequate vitamin D during winter, yet those who did were 40% less likely to suffer from URTIs. Furthermore, both vitamin D supplementation strategies similarly helped nearly all participants achieve sufficient levels. Vitamin D supplementation notably reduced the severity of URTI symptoms by 15% and the number of days with URTIs by 36% compared to placebo.
While the supplementation strategies did not significantly alter other immune factors, such as salivary secretory immunoglobulin A, the overall reduction in respiratory infections indicates a beneficial effect of maintaining vitamin D sufficiency during military training.
7
Vitamin D reduces cold symptoms
We explored the effects of 25-hydroxyvitamin D (25OHD) on individuals experiencing upper respiratory tract infections (URTIs), commonly known as colds. In a well-structured study, participants with low vitamin D levels received either a daily dose of 10 micrograms of 25OHD or a placebo for a span of 16 weeks. The participants' symptoms were assessed using the Wisconsin Upper Respiratory Symptom Survey-21, focusing on how the vitamin impacted their cold symptoms.
Our findings showed that those taking 25OHD reported significant reductions in physical symptoms such as runny noses, sneezing, and head congestion compared to those on the placebo. Additionally, the quality of life scores improved for most symptoms, except for ease of breathing. However, it’s important to note that there was no significant difference in the total number of cold events or how often participants used medications like antibiotics or pain relievers.
Collectively, these results suggest that adequate intake of vitamin D can help ease cold symptoms, particularly those affecting the nose, and might enhance overall well-being when a cold strikes. This indicates that vitamin D may play a positive role in managing the discomfort associated with upper respiratory infections.
Our findings showed that those taking 25OHD reported significant reductions in physical symptoms such as runny noses, sneezing, and head congestion compared to those on the placebo. Additionally, the quality of life scores improved for most symptoms, except for ease of breathing. However, it’s important to note that there was no significant difference in the total number of cold events or how often participants used medications like antibiotics or pain relievers.
Collectively, these results suggest that adequate intake of vitamin D can help ease cold symptoms, particularly those affecting the nose, and might enhance overall well-being when a cold strikes. This indicates that vitamin D may play a positive role in managing the discomfort associated with upper respiratory infections.
References
- Marusca LM, Reddy G, Blaj M, Prathipati R, Rosca O, et al. The Effects of Vitamin D Supplementation on Respiratory Infections in Children under 6 Years Old: A Systematic Review. Diseases. 2023;11. 10.3390/diseases11030104
- Carboo JA, Dolman-Macleod RC, Malan L, Lombard MJ. High-dose oral vitamin D supplementation for prevention of infections in children aged 0 to 59 months: a systematic review and meta-analysis. Nutr Rev. 2024;82:579. 10.1093/nutrit/nuad082
- Kisla Ekinci RM, Taskin Karacay IE, Celik U. Serum vitamin B12 and D levels in children with Primary Raynaud Phenomenon: a retrospective cohort study. Eur J Clin Nutr. 2022;76:1615. 10.1038/s41430-022-01151-0
- Harrison SE, Oliver SJ, Kashi DS, Carswell AT, Edwards JP, et al. Influence of Vitamin D Supplementation by Simulated Sunlight or Oral D3 on Respiratory Infection during Military Training. Med Sci Sports Exerc. 2021;53:1505. 10.1249/MSS.0000000000002604
- Shimizu Y, Ito Y, Uotsu N, Yui K. Intake of 25-Hydroxyvitamin D May Reduce the Severity of Upper Respiratory Tract Infection: Post hoc Analysis of a Randomized, Double-Blind, Placebo-Controlled, Parallel Group Comparison Study. Nutrients. 2020;12. 10.3390/nu12123769
- Shimizu Y, Ito Y, Yui K, Egawa K, Orimo H. Intake of 25-Hydroxyvitamin D3 Reduces Duration and Severity of Upper Respiratory Tract Infection: A Randomized, Double-Blind, Placebo-Controlled, Parallel Group Comparison Study. J Nutr Health Aging. 2018;22:491. 10.1007/s12603-017-0952-x
