Do you know which foods naturally contain the most vitamin D? Bread or milk may be the first thing that comes to mind, but these foods are typically enriched with the nutrient, rather than naturally containing it. In fact, few foods are organic sources of vitamin D.

If that weren’t discouraging enough, new research has demonstrated that the consumption of vitamin D-rich foods of any kind has dropped in the past three decades.

A study published in the Journal of the American Dietetic Association found that between 1980 and 2009, daily vitamin D consumption from food-based sources decreased by 15 percent among men and 5 percent among women.

Without regular vitamin D intake, bone and respiratory health can be seriously impaired, as can any number of cellular processes within the body, the Office of Dietary Supplements reports.

Foods that naturally contain vitamin D include eggs, fish and mushrooms.

Without adequate food sources of the nutrient, individuals may wish to consider taking dietary supplements or multivitamins in order to maintain their health and well-being.