Author: Dr. Stephen Chaney
What do the experts say about vitamin D helping to prevent asthma attacks? You’ve seen the headlines. Vitamin D is no longer just for healthy bones. It has become the latest “miracle” nutrient. If you believe everything you read, vitamin D can prevent or cure everything from multiple sclerosis to diabetes, heart disease, and cancer. Unfortunately, the evidence for many of those claims is weak.
However, the effect of vitamin D on the severity of asthma symptoms appears to be an exception. That relationship appears to be on much more solid ground.
A review published last year(S.K. Bantz et al, Annals of Pediatrics and Child Health, 3: pii: 1032, 2015) concluded “We emphasize that all children, especially those who are asthmatic, should be assessed to ensure adequate intake or supplementation with at least the minimum recommended doses of vitamin D. The simple intervention of vitamin D supplementation may provide significant clinical improvement in atopic disease, especially asthma.” [Note: Atopic disease refers to diseases characterized by a hyperallergenic response, such as eczema, hay fever, and asthma.]
That was followed by the recent publication of a Cochrane Review that concluded “Vitamin D is likely to offer protection against severe asthma attacks”. To understand the significance of that statement you need to understand that this is not just another clinical study or another review. Cochrane Reviews are conducted by an international group of experts and are considered the “Gold Standard” for evidence-based medicine.
You may remember that famous commercial: “When E.F. Hutton speaks, people listen.” In this case: “When Cochrane Reviews speak, doctors listen.”
Let’s look briefly at how the review was conducted, and then examine exactly what the review said, and what it didn’t say.
Does Vitamin D Help Prevent Asthma Attacks?
One of the characteristics of Cochrane Reviews that set them apart from many of the other reviews that you find in the literature is that they include only the highest quality clinical studies in their analysis. This is one of the things that gives them such credibility.
This particular Cochrane Review included seven trials involving a total of 435 children and two trials involving a total of 658 adults. Most trial participants had mild to moderate asthma. The duration of the trials ranged from four to 12 months. All studies were placebo controlled and used close to RDA recommended doses of vitamin D.
The results were pretty clear cut:
- Vitamin D supplementation reduced the average number of severe asthma attacks requiring treatment with oral steroids by 36%. This conclusion was based on 3 high-quality studies involving 680 participants. Here, these studies clearly show vitamin D does help prevent asthma attacks.
- Vitamin D supplementation reduced the number of acute asthma attacks requiring emergency room visits and/or hospitalizations by 50%. This conclusion was based on 7 high-quality studies with 963 participants. These studies also show vitamin D helps prevent asthma attacks.
- None of the studies reported any severe adverse effects from vitamin D supplementation. (Compare that with all warnings associated with those ads for asthma medications you see on TV.)
However, they did not see any effect of vitamin D supplementation on day-to-day asthma symptoms.
What Does This Study Mean For You?
This study strongly suggests that vitamin D supplementation in the RDA range (600 IU for ages 1-70 and 800 IU for adults over 70) significantly reduces the risk of severe asthma attacks requiring steroids or hospitalization. Thus, if you or your child have asthma, vitamin D supplementation in the RDA range just makes sense.
However, this study also suggest that vitamin D is not a panacea that will make all asthma symptoms disappear.
Also, even Cochrane Reviews have limitations.
- None of the studies included in this review looked at vitamin D status prior to the study. We simply don’t know whether vitamin D supplementation might be effective at reducing day-to-day asthma symptoms in individuals who were vitamin D deficient.
- The studies included in this review did not include asthma sufferers with severe symptoms. Again, we don’t know whether vitamin D supplementation might make day-to-day symptoms more tolerable and easily controlled for people with severe asthma symptoms
One final thought: Blood levels of 25-hydroxy-vitamin D are the best indicators of vitamin D status. For reasons that we don’t understand, not everyone consuming RDA levels of vitamin D ends up with optimal levels (50-75 nmoles/L). For that reason, it is a good idea to get your blood levels of 25-hydroxy-vitamin D tested as part of your annual physical exam.
If you are already getting RDA levels of vitamin D and your 25-hydroxy-vitamin D levels are not in the optimal range, you may want to supplement with extra vitamin D. Just be sure to monitor your 25-hydroxy-vitamin D levels on a regular basis to make sure they don’t exceed the optimal range.
So, according to the Cochrane Review, vitamin D does help prevent asthma attacks.
The Bottom Line
- A recent Cochrane Review concluded that vitamin D supplementation in the RDA range (600 IU for ages 1-70 and 800 IU for adults over 70) significantly reduces the risk of severe asthma attacks requiring steroids or hospitalization in both children and adults. This is significant because Cochrane Reviews are considered the Gold Standard for evidence-based medicine.
- Thus, if you or your child have asthma, vitamin D supplementation in the RDA range just makes sense.
- However, blood levels of 25-hydroxy-vitamin D are the best measure of vitamin status, and not everyone consuming RDA levels of vitamin D ends up with optimal levels (50-75 nmoles/L). If you are already getting RDA levels of vitamin D in your diet and your 25-hydroxy-vitamin D levels are not in the optimal range, you may want to supplement with extra vitamin D. Just be sure to monitor your 25-hydroxy-vitamin D levels on a regular basis to make sure they don’t exceed the optimal range.
- This Cochrane Review did not find any effect of vitamin D supplementation on day-to-day asthma symptoms.
- However, even Cochrane Reviews have limitations.
- None of the studies included in this review looked at vitamin D status prior to the study. We simply don’t know whether vitamin D supplementation might be effective at reducing day-to-day asthma symptoms in individuals who were vitamin D deficient.
- The studies included in this review did not include asthma sufferers with severe symptoms. Again, we don’t know whether vitamin D supplementation might make day-to-day symptoms more tolerable and easily controlled for people with severe asthma symptoms
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.