Clinical Consultation: The respiratory benefits of vitamin E supplements

The respiratory benefits of vitamin E supplements Is vitamin E supplementation useful in the prevention and treatment of allergic rhinitis or upper respiratory tract infections?

Vitamin E has been evaluated for the treatment and prevention of several different chronic diseases in numerous clinical trials over the past 2 decades. However, only a limited number of studies have investigated the potential therapeutic or prophylactic effect of vitamin E on allergic rhinitis and respiratory infections. In contrast to trials on cardiovascular disease, which have failed to demonstrate a benefit from vitamin E supplementation,^1,2 there is mounting evidence that this essential vitamin may be useful for prevention of the common cold and treatment of allergic rhinitis.

Allergic rhinitis

A double-blind, placebo-controlled, randomized study evaluated the effect of vitamin E (800 mg/d) on seasonal allergic rhinitis.³ In this study, 112 patients with documented allergic rhinitis received vitamin E or placebo during the pollen season in addition to their regular allergy treatment. Patients treated with high-dose vitamin E had reduced nasal symptom scores but no change in ocular symptoms. There was no reduction in the percentage of days that patients had serious symptoms or in the percentage of days that medications were used to control allergy symptoms.

While this study suggests a potential benefit of vitamin E supplementation for patients with allergic rhinitis, the lack of an effect on serious symptoms and medication use suggests that the benefits may not be of sufficient magnitude to warrant the routine use of vitamin E supplementation in this setting. Given this study's relatively small sample size, a larger, carefully designed trial is warranted to see whether supplementation produces more clinically meaningful results.

Respiratory infections

Placebo-controlled, double-blind trials have demonstrated that vitamin E supplementation can improve immune response, including delayed-type hypersensitivity and response to vaccines, in elderly persons.^4,5 In one study, the incidence of infection (primarily respiratory infection) was 30% lower among healthy elderly persons who received a 6-month course of vitamin E than among those who received placebo.⁵ Although these findings were provocative, infections were self-reported and the study was not powered to demonstrate statistical significance.

Consequently, a follow-up study was carried out to determine the effect of vitamin E supplementation on objectively documented respiratory infections in the elderly.⁶ In this study, 617 elderly (aged 65 years and older) nursing home residents were randomized to receive 200 IU/d of vitamin E or placebo for 1 year. Nurses collected information weekly, using symptom and physical examination checklists, focused on the respiratory system. Standardized clinical definitions were used to characterize the types and duration of respiratory infections.

The results indicated no statistically significant effect of vitamin E on the incidence or number of days with infection for all, upper, or lower respiratory tract infections; allergic rhinitis; or antibiotic use.⁶ However, 13% fewer persons in the vitamin E group acquired 1 or more respiratory infections, while 19% fewer acquired upper respiratory tract infections. Subgroup analysis revealed a 20% lower incidence of common colds in the vitamin E group, and 21% fewer persons in the vitamin E group acquired 1 or more colds. There were no adverse effects from vitamin E supplementation, including no effect on mortality.

While this study failed to show a protective effect of vitamin E supplementation on lower respiratory tract infections, there was a reduction in upper respiratory tract infections, especially the common cold. In contrast, previous studies of vitamin E and infection in the elderly have demonstrated mixed results.

A double-blind, placebo-controlled study using a dose and duration of vitamin E supplementation similar to that in the above-mentioned study showed that supplementation had no effect on respiratory infection in independently living elderly persons.⁷ Differences in study design and outcome definitions may account for the apparent lack of a protective effect of vitamin E in the latter study.

A recent meta-analysis found that high-dose vitamin E (at least 400 IU/d) increased all-cause mortality by 4% (risk ratio, 1.04; confidence interval, 1.01 to 1.07).⁸ While this slight increase in mortality is worrisome, a number of concerns have been raised regarding this meta-analysis, including its restrictive inclusion criteria,^9,10 modeling artifact,¹¹ publication bias,¹² and other methodologic issues.^9-14 Consequently, it is premature to state definitively that high-dose vitamin E supplementation increases mortality, but future trials must monitor mortality to determine whether there is any risk.

Conclusions

While the finding that vitamin E may be protective against the common cold has important implications, it should be noted that this only applies to the elderly and not to younger populations. Additional randomized trials are needed to validate these findings. There is still insufficient evidence to warrant routine use of vitamin E for the management of allergic rhinitis, and further research is needed.

References:

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