Some embodiments comprise dietary supplements for treating or preventing traveler's diarrhea comprising: (a) about 1000 mg green tea extract comprising at least 90% (w/w) catechins; (b) about 4 g partially hydrolyzed guar gum (PHGG); (c) about 100 mg L-theanine; and (d) about 5 g non-sugar sweetener, wherein the sweetener does not contain a polyol. Some embodiments comprise dietary supplement for treating or preventing traveler's diarrhea comprising: (a) from about 250 mg to about 1,500 mg green tea extract comprising at least 90% (w/w) catechins; (b) from about 1 g to about 8 g partially hydrolyzed guar gum (PHGG); and (c) from about 15 mg to about 250 mg L-theanine. Some embodiments comprise methods for treating or preventing traveler's diarrhea, the method comprising: administering to a subject in need therefore a dietary supplement comprising (a) from about 250 mg to about 1,500 mg green tea extract comprising at least 90% (w/w) catechins; (b) from about 1 g to about 8 g partially hydrolyzed guar gum (PHGG); and (c) from about 15 mg to about 250 mg L-theanine.