# Diet and Asthma: A Narrative Review
## 4 Diet and Asthma
### Dairy Products  
The 2015-2020 Dietary Guidelines for Americans recommend consuming three cups of dairy per day [63]. However, a case-control study compared children in the highest quartiles of dairy intake (Q3-4; OR = 1.72, 95% CI 1.19; 2.49) with children in the lowest quartiles (Q1-2; OR < 1), and found a positive association between frequent dairy consumption and odds of developing asthma (OR = 1.93, 95% CI 1.32; 2.84) [69].  
A different study demonstrated that early life exposure to unpasteurized milk seems to exert a protective effect on asthma [93; 94], that may be related to its bacterial composition [93] or protein components [94].  
A community-based cross-sectional study of Australian young adults found that drinking whole milk was negatively associated with increased odds of doctor-diagnosed asthma (OR = 0.73, 95% CI 0.54; 0.99), while consumption of low-fat cheese was found to be positively associated (OR = 1.50, 95% CI 1.03; 2.19). Similarly, ricotta cheese intake was positively associated with current asthma (OR = 1.94, 95% CI 1.18; 3.19) [95].  
Although the mechanisms by which dairy products may influence the development of asthma are unknown, there was a positive association observed between dairy consumption and concentrations of pro-inflammatory IL-17F. The authors suggest the existence of an IL-17F-dependent inflammatory pathway that can play a role in the development of asthma [69].  
Table 6 summarizes the results of research on dairy intake on asthma.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Dairy** & & & \\
**Author, Year,** & **Sundy Design** & **Sample, Age** & **Dietary Assessment/Intervention** & **Results** \\ \hline \multirow{4}{*}{[PERSON], et al., 2015, Case-control [69]} & A total of 678 children, with & & Dietary intake was estimated \\  & 351 asthmatics. & & using a 75-item questionnaire on \\  & Mean age: & & the child’s food consumption, \\  & controls: 10.5 \(\pm\) 2.7 y. & & including dairy, in the prior week. \\ \cline{1-1}  & asthma: 10.0 \(\pm\) 2.6 y. & & \\ \hline \hline \end{tabular}
\end{table}
Table 6: Studies evaluating effects of dairy intake on asthma.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Salt** & & \\ \hline
**Author, Year,** & **Sample, Age** & **Dietary Assessment/Intervention** & **Results** \\ \hline \multirow{4}{*}{Systematic Review [91]} & Studies included in the systematic review & & Dietary salt reduction: \\  & (\(n\) = 6). & Salt intake. & (\(=\)) symptoms of \\  & Six RCTs were included in the review. & & allergic asthma. \\ \cline{1-1}  & Studies included in the systematic review & & \\  & (\(n\) = 9): & & \\ \cline{1-1}  & nine RCTs in relation to sodium & & Dietary salt reduction: \\ \cline{1-1}  & manipulation and asthma, of which five were & Salt intake. & (\(+\)) lung function; \\ \cline{1-1}  & in people with asthma (318 participants), and & & (\(+\)) symptoms of asthma. \\ \cline{1-1}  & four in people with exercise-induced asthma & & (63 participants). \\ \hline \hline \end{tabular} Notes: Age is described as mean age \(\pm\) standard deviation (SD) in years, unless stated otherwise. N/R, Not reported; and RCTs, Randomized control trial. (\(+\)) stands for significant and positive effects on asthma outcomes; (\(=\)) stands for no significant effects on asthma outcomes; and (\(-\)) stands for negative effects on asthma-related outcomes.  
\end{table}
Table 5: Studies evaluating effects of salt intake on asthma and asthma- related outcomes.