Vitamin D During Pregnancy: Protecting Children's Respiratory Health? Latest Evidence on Vitamin D and Pediatric Asthma/Wheezing

1. What's the News?

On August 15, 2025, the German medical journal ÄrzteZeitung reported **"The potential of vitamin D supplementation during pregnancy to prevent wheezing and asthma in children". The source is a **new systematic review by Cochrane. The full article is for members only, but the main points are **"There is a preventive signal for supplementation during pregnancy / The effect is uncertain when administered to infants."AerzteZeitung.de

2. What the Cochrane Review Said (Key Points)

Cochrane's summary for the general public states the following:

• Supplementing with "high doses" of vitamin D during pregnancy is likely to reduce wheezing in children (moderate-certainty).

• The effect of direct vitamin D administration to infants is uncertain and may not lead to a clear reduction in asthma or wheezing.

• The preventive effect on a definitive diagnosis of "asthma" has not yet been sufficiently demonstrated.
  This message is repeated in various commentaries and news.CochraneNews-Medical

3. Historical Context: Why Focus on "During Pregnancy"?

The background involves the hypothesis that maternal vitamin D status can affect fetal immune and airway development, and RCTs such as VDAART and COPSAC have been conducted since the 2010s. For example, in VDAART, vitamin D3 at 4,400 IU/day during pregnancy (+ the usual 400 IU) was administered to explore the reduction of asthma and recurrent wheezing up to age 3, but the effect size was limited, and the clear difference diminishes in long-term follow-up (up to age 6), reporting "mixed signals."JAMA NetworkUniversity of Rochester Medical Center

4. What We Know and Don't Know

• What We Know

  • High-dose vitamin D supplementation during pregnancy is likely to reduce "wheezing" in children. (Moderate certainty)Cochrane

  • The definitive preventive effect on the disease unit of "asthma" is not yet confirmed.Cochrane Library

  • The preventive effect of supplementation to the infant is uncertain.Cochrane

• What We Don't Know Yet

  • Which dosage, timing, and background (such as maternal baseline 25(OH)D concentration) are most effective. Some analyses suggest the greater benefit for mothers with lower baseline values, but it is not definitive.ajcn.nutrition.org

  • The duration of the effect (beyond infancy to school age) and differences due to race/diet/sunlight exposure.Respiratory Therapy

5. The Matter of Dosage: Caution with Newsworthy "High Doses"

The "high doses" used in research include settings that exceed the typical Japanese tolerable upper intake level (UL) = 100 μg/day (4,000 IU) (e.g., VDAART's 4,400 IU/day ≒ 110 μg/day). This is under strict monitoring in RCT conditions and should not be imitated without professional guidance.Foundation for the Promotion of Longevity ScienceJAMA Network

6. Japanese Standards and Practical Approaches

• AI (Adequate Intake): In the latest Japanese summary, the AI for adults is generally 9.0 μg/day (as per the 2025 edition for the general public).Foundation for the Promotion of Longevity Science

• Tolerable Upper Intake Level (UL): 100 μg/day (for adults). It is generally considered the same during pregnancy.Foundation for the Promotion of Longevity Science

• Securing through diet: Focus on sunlight + fish and mushrooms, aiming first for a food-based approach. Supplements should be considered to "fill in the gaps" safely.Lion Dental Research Institute

In summary, "Maintaining an appropriate vitamin D status during pregnancy" is reasonable, but it cannot be definitively said that "high-dose supplements can reliably prevent asthma", which is the current reasonable stance.Cochrane

7. The Atmosphere on Social Media (Excerpts)

• Cochrane's public page clearly states the message **"High doses during pregnancy may reduce wheezing" and "Evidence is uncertain for infant administration."** This has been disseminated by medical accounts and news media.Cochrane

• Representative Post:

  • "Children of women given high doses of vitamin D during pregnancy are less likely to develop wheeze," as introduced in a post (Nottingham Eczema).“Children of women given high doses of vitamin D during pregnancy are less likely to develop wheeze.” (Original text)X (formerly Twitter)

  • News Medical's official guide also spreads the summary **"Positive during pregnancy, uncertain effect for infant administration."**X (formerly Twitter)News-Medical

• Tone of Reactions:

  • Clinicians and Researchers: Generally, a cautious stance of "Hopeful but too early to recommend."

  • General Users: **There is a lot of positive interest in "Is it okay during pregnancy?," while understanding is spreading that "

    it might be better to wait before giving it directly to babies.

8. Practical Solutions for "How to Act"

1. Understand your vitamin D status (sunlight, diet, and if necessary, blood evaluation).

2. The basic approach is to aim for AI through food + sunlight, and adjust any deficiencies with supplements.

3. Always consult with your primary care physician (obstetrician) before introducing or increasing supplements. Especially high doses should only be under medical supervision.

4. Supplementation for infants for preventive purposes is "pending conclusion". At present, there is not enough certainty to recommend it.Cochrane

9. The Next Steps for the Research Side

• Refinement of target groups##HTML_TAG