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New evidence

Vitamin C (500 mg/day) to pregnant smokers was linked to DNA methylation changes at 5 CpG sites that statistically explained a significant portion of the supplement's benefit on children's lung function at age 5 — but only in this specific clinical trial of 137 mother-child pairs.

This is the first strong hint that vitamin C might improve lung function in children through epigenetic changes, but with only 4 prior studies on the pairing and mixed results overall, we are far from a general recommendation — the finding needs replication.

In a double-blind trial, pregnant smokers who took 500 mg of vitamin C daily had children with better lung function at age 5 compared to placebo. The study found that the vitamin altered DNA methylation at several sites, and statistical analysis showed that changes at 5 of those sites accounted for a meaningful part of the lung function improvement. However, the effect was observed in a specific clinical population (smoking mothers), the sample was modest, and the broader body of evidence on vitamin C and lung function is still mixed (2 beneficial, 2 neutral) — so this is an intriguing lead, not a settled benefit.

Where this fits in the evidence

Pillser has synthesized 4 studies on Vitamin C for Improved Lung Function — overall evidence strength: Low.

Across 4 studies, 2 reported beneficial effects (one moderate-sized and statistically significant), while 2 found neutral effects. The predominant effect direction is mixed (beneficial and neutral), with effect sizes ranging from small to moderate. The most-studied population is clinical (pregnant smokers and individuals with asthma or COPD), and the evidence from the highest-quality study (RCT, n=137) showed a moderate beneficial effect at 500 mg/day on lung function, though this finding comes from a single study and was not replicated in larger meta-analyses.

The study

Vitamin C supplementation to pregnant smokers alters asthma- and allergy-associated CpGs in child buccal DNA at 5 years of age.

  • Randomized Controlled Trial (RCT)
  • n = 137
  • 2025-10-03
  • Clinical epigenetics
More on Vitamin CMore on Improved Lung Function

This is a plain-language summary of a research finding, not medical advice. Pillser surfaces research signals to help you decide what's worth investigating — always consult a qualified professional before changing what you take.

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