Taking Vitamin D supplements isn’t likely to keep you from catching colds and other upper respiratory tract infections (URTIs), a study published Wednesday in the Journal of the American Medical Association finds.

Researchers enlisted a total of 322 healthy adult New Zealanders for an 18-month study to determine whether substantial doses of Vitamin D would affect the number of URTIs people experienced or the severity of those illnesses.

Half the participants were administered large monthly oral doses of Vitamin D3 (the form of Vitamin D that the body produces when exposed to sunlight); the other half were administered placebo drugs resembling the vitamin supplements. Over the year-and-a-half study period, which encompassed two mild flu seasons, 593 people receiving Vitamin D3 and 611 receiving placebo contracted URTIs; the study authors say that difference isn’t statistically significant. There were no significant differences between the two groups in the severity or duration of illness or the number of workdays missed due to URTIs.

Vitamin D has been studied in recent years for its potential role in protecting against not just colds but other illnesses and conditions ranging from cancer to multiple sclerosis. The authors of the new study note that it’s still possible that Vitamin D supplementation might benefit some people, such as those who, unlike the people who entered this study, have a Vitamin D deficiency.