Fiber
Andrianasolo et al. 44 studied multiple types of
dietary fiber intake in association with reported asthma control
(assessed at 6 months longitudinal intervals) as indicated by the Asthma
Symptom Score and the Asthma Control Test score. They noted that higher
quintiles of dietary fiber intake (total, soluble, insoluble fibers from
cereals, fruit and seeds) was associated with lower Asthma Symptom Score
(0.73, 95 % CI 0.67-0.79 in women; and 0.63, 95 % CI 0.55-0.73 in men,
both p<0.001) compared to participants in the lowest quintile
of total dietary fiber intake, indicating that higher fiber intake was
associated with fewer reported asthma symptoms. Higher total fiber
intake, mostly insoluble fiber and fiber from cereals was also
associated with lower odds of an ACT score indicating impairment (OR
0.72, 0.55-0.95, p=0.01 for women, OR 0.45, 0.26-0.79, p=0.01 for men).
Bseikri et al.45 noted no overall association between consumption of
a high fiber nutritional supplement bar (CHORI-bar) and pulmonary
function testing, ACT score and PedsQoL Am score, although they did note
that among treatment-compliant subjects with non-eosinophilic asthma, 8
weeks of CHORI-bar consumption was associated with increased FVC, FEV-1,
and FEF-25-75. McLoughlin at al.46 noted that a 7 day trial of inulin (12g per day)
supplementation was associated with improved Asthma Control
Questionnaire score exceeding the minimal important difference, though
not associated with objective parameters of improved lung function, but
they noted a subgroup effect among those with the poorest asthma control
in that the inulin supplementation was associated with decreased
eosinophilic airway inflammation, and better overall control among those
with eosinophilic vs. non-eosinophilic asthma.
Saeed et al. 47noted an association between low dietary fiber intake and increased odds
of reported asthma among US respondents on the NHANES survey. They noted
increased odds of asthma with lower fiber intake (lowest vs. highest
reported quartile, OR, 1.4; 95% CI 1.0– 1.8; P = 0.027) with
significant interactions between fiber and both sex and race/ethnicity,
in particular among women and non-Hispanic white adults. Lowest quartile
fiber intake was associated with increased odds of reported wheeze (OR,
1.3; 95% CI, 1.0–1.6; P = 0.018) and cough (OR, 1.7; 95% CI,
1.2–2.3; P = 0.002).
Two Australian studies looked at the effects of fiber during pregnancy.
Grieger et al.48 noted that, after adjusting for total energy
intake, pregnant women with uncontrolled asthma had higher intakes of
fiber (OR 1.07, 1.03-1.13, p=0.003). Pretorius et
al.49 noted that higher reported maternal dietary
intake of resistant starch was associated with reduced odds of doctor
diagnosed wheezing in the infant (aOR 0.68 (95% CI 0.49-0.95, p =
0.02).