- If one volunteer consumed breakfast more than three days a week, their daily caffeine intake was over 500 mg caffeine, was taking medication, their psychological state was strongly influenced by some exogenous factor (e.g. moving to a new house, new job, divorce e.t.c.), was on hypocaloric diet for weight loss, was smoking more than five cigarettes a day, was an athlete with very vigorous physical activity (> 4 hours vigorous exercise a day), had a history of gastrointestinal disorders (e.g. gastroesophageal reflux disease (GERD), irritable bowel syndrome, diarrhea, ulcers e.t.c.), depression, diabetes, kidney disease, hypertension, blood disorders, liver disease, unregulated hyper - or hypothyroidism, arrhythmia, heart disease, cancer, vascular disease, recent surgery, or severe psychiatric disorders was automatically excluded from the study.