Manipulating antioxidant intake in asthma: a randomized controlled trial.
What this study found
Increasing fruit and vegetable intake improved asthma outcomes, but tomato lycopene capsules did not add benefit. After 14 days, the low-antioxidant diet had lower %FEV1 and %FVC than the high-antioxidant diet, and by trial end the low-antioxidant group was 2.26 times as likely to exacerbate (95% CI 1.04, 4.91; P = 0.039). Among low-antioxidant diet participants, tomato extract and placebo showed no differences in airway or systemic inflammation or clinical outcomes, although log plasma CRP change per visit differed (0.03 [0, 0.06] vs -0.01 [-0.08, 0.06]; P = 0.010). Overall, the findings…
- Study & population
- Randomized controlled trial in adults with stable asthma recruited from an asthma clinic in New South Wales, Australia.
- Intervention
- Tomato extract (Lyc-o-Mato) capsules provided 15 mg lycopene per capsule, taken 1 capsule 3 times daily for a total of 45 mg/day during the supplementation phase.
- Key limitation
- Single-center trial in adults with stable asthma, which limits generalizability.
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Open PDFOriginal abstract
BACKGROUND Antioxidant-rich diets are associated with reduced asthma prevalence in epidemiologic studies. We previously showed that short-term manipulation of antioxidant defenses leads to changes in asthma outcomes. OBJECTIVE The objective was to investigate the effects of a high-antioxidant diet compared with those of a low-antioxidant diet, with or without lycopene supplementation, in asthma. DESIGN Asthmatic adults (n = 137) were randomly assigned to a high-antioxidant diet (5 servings of vegetables and 2 servings of fruit daily; n = 46) or a low-antioxidant diet (≤2 servings of vegetables and 1 serving of fruit daily; n = 91) for 14 d and then commenced a parallel, randomized, controlled supplementation trial. Subjects who consumed the high-antioxidant diet received placebo. Subjects who consumed the low-antioxidant diet received placebo or tomato extract (45 mg lycopene/d). The intervention continued until week 14 or until an exacerbation occurred. RESULTS After 14 d, subjects consuming the low-antioxidant diet had a lower percentage predicted forced expiratory volume in 1 s and percentage predicted forced vital capacity than did those consuming the high-antioxidant diet. Subjects in the low-antioxidant diet group had increased plasma C-reactive protein at week 14. At the end of the trial, time to exacerbation was greater in the high-antioxidant than in the low-antioxidant diet group, and the low-antioxidant diet group was 2.26 (95% CI: 1.04, 4.91; P = 0.039) times as likely to exacerbate. Of the subjects in the low-antioxidant diet group, no difference in airway or systemic inflammation or clinical outcomes was observed between the groups that consumed the tomato extract and those who consumed placebo. CONCLUSIONS Modifying the dietary intake of carotenoids alters clinical asthma outcomes. Improvements were evident only after increased fruit and vegetable intake, which suggests that whole-food interventions are most effective. This trial was registered at http://www.actr.org.au as ACTRN012606000286549.