The DASH Diet for Adults With Uncontrolled Asthma

Dietary intervention efficacy trials are distinctly lacking in asthma research. This pilot study aims to provide effect size estimates and justification, clinical trial and intervention feasibility data, and procedural materials for a full-scale randomized controlled trial that will determine the efficacy and mechanisms of action of the Dietary Approaches to Stop Hypertension (DASH)-a recommended dietary pattern based on proven cardiovascular benefits-as adjunct therapy to standard care for adults with uncontrolled asthma. Eligible, consenting participants (n=90) will be randomized to receive usual care alone or combined with a DASH intervention. Follow-up assessments will occur at 3 and 6 months. By evaluating a dietary pattern approach to improving asthma control, this study could advance the evidence base for refining clinical guidelines and public health recommendations regarding the role of dietary modifications in asthma management.

Inclusion criteria

• Ethnicity: All ethnic groups
• Body mass index (BMI) 18.5-39.9 kg/m2
• Suboptimally controlled asthma:
• Diagnosis of asthma on the current medical problem list
• Currently prescribed at least 1 medication for the treatment of asthma
• Physiological evidence of asthma with demonstrable reversibility of airway obstruction, or a specialist's confirmation of asthma diagnosis based on chart review
• Documented history of high asthma-related emergency and/or inpatient encounters or reliever medication usage
• Asthma Control Test: total score <20 or item score <3 for any of the first 4 questions regarding symptoms (3-6x/week or more), nighttime awakening (1x/week or more), interference with normal activity (at least some of the time), and rescue medication use for symptom relief (2-3x/week or more)
• Kaiser member for ≥1 year
• PCP approval of study screening
• Able and willing to enroll and provide written informed consent

Exclusion criteria

• Intermittent asthma, defined as either seasonal asthma or (daytime asthma symptoms <2x/week and nocturnal symptoms <2x/month and no use of long-term control medications)
• Primary diagnosis of COPD (emphysema or chronic bronchitis) on the current medical problem list or suggested by baseline spirometry and smoking history
• Previous diabetes (other than during pregnancy) or diabetes diagnosed as a result of fasting blood glucose or hemoglobin A1c levels obtained at screening
• Previous cardiovascular disease: e.g., coronary heart disease, cerebrovascular disease, peripheral vascular disease, heart failure, or aortic aneurysm
• Diagnosis of cancer (other than non-melanoma skin cancer) that is/was active or treated with radiation or chemotherapy within the past 2 years
• Inflammatory bowel disease, colostomy, malabsorption, or major gastrointestinal resection
• Diagnosis of bipolar or psychotic disorder or hospitalization for psychological or emotional problems within the last 2 years
• Diagnosis of a terminal illness and/or in hospice care
• Fasting LDL cholesterol >190 mg/dL, triglycerides >500 mg/dl, fasting blood glucose >125 mg/dl
• Significant liver enzyme abnormality as indicated by AST or ALT more than 2 times the upper limit of normal or a clinical diagnosis of hepatitis
• Renal insufficiency (GFR<60 ml/min)
• Current use of insulin or oral hypoglycemic agents
• Use of oral corticosteroids >5 days/month on average
• Current use of medications for treatment of psychosis or manic-depressive illness
• Current use of prescription or non-prescription weight-loss products or any dietary/herbal supplements and unwillingness to discontinue;
• Inability to speak, read, or understand English at the 6th-grade level or above
• Inability to perform pulmonary function tests by spirometry in a consistent manner
• DASH concordance index >60%
• Unwillingness to modify current diet
• Current or planned participation in a structured program that overtly focuses on diet and nutrition
• Planning to undergo bariatric surgery during the study period
• Actively attempting to lose weight, or weight change >15 lbs during prior 3 months
• Consumption of >21 alcoholic drinks per week, or >=6 drinks on one occasion twice or more per week, or alcoholism as determined by the Alcohol Use Disorders Identification Test
• Pregnant, lactating, or planning to become pregnant during the study period
• No longer a Kaiser patient or planning to transfer care out of Kaiser or to move out of the area during the study period
• Family/household member of another study participant or of a study staff member
• Enrolled or planning to enroll in another research study that would limit full participation in the study or confound the interpretation of the study's findings
• Investigator discretion for safety or protocol adherence reasons