You may have a skewed understanding of this "vitamin".
First know this: Vitamin D is not actually a vitamin, but a hormone.
The best way to supply yourself with all the D you need is to expose your skin to sunlight—moderately and responsibly, of course. Esteemed nutrition expert Marion Nestle lobbied the U.S. Food and Drug Administration (FDA) three years ago against including Vitamin D on its new Nutrition Facts panel, arguing that because it is a hormone, it doesn’t belong.
She went on to explain to the FDA, that D “is found naturally in very few foods, (e.g., fish); in them, it is present in small amounts. It is present in most foods as a result of fortification.”
She says because D supplements and foods fortified with Vitamin D are taken orally, they don’t produce the same benefits as sunlight on skin.
Other experts point to studies that suggest Vitamin D regulates calcium absorption, keeping teeth and bones healthy. It may also help guard against cancer and diabetes, some experts say. Fatty fish like salmon, mackerel, and sardines, and organ meats are among the best food sources for naturally occurring Vitamin D.
“Many scientific debates about hormone Vitamin D are as yet unresolved,” Nestle notes in her letter to the FDA. “The lack of compelling research has permitted Vitamin D to become ‘trendy.’ It is advertised on boxes of fortified cereals, has its own pro-supplement advocacy group, and generates millions in annual supplement sales … In the absence of stronger evidence for possible adverse consequences, the FDA should not contribute to further commercialization of this misnamed hormone by permitting it to be listed on food labels.”
The FDA ultimately chose to include Vitamin D on its nutrition labels, to be launched by July 2018.