What it is
Vitamin D is a fat-soluble vitamin and a steroid hormone
What it does
As a steroid hormone, the discrete functions of vitamin D are too numerous to list. Most cells contain vitamin D receptors, allowing vitamin D to affect gene transcription in most cells. But, some of the most noteworthy effects of vitamin D include promoting calcium absorption, regulating glucose metabolism, and impacting neuromuscular and immune function.
The recommended intake for vitamin D is 15mcg per day for most younger men and women. Recommended vitamin D intake increases to 20mcg per day for adults over 70 years old.
The safe upper limit for vitamin D intake is 100mcg per day under most circumstances.
Likelihood of tracking completeness: Very high in the US, and low in most other places.
Nutrition labels in the US are required to list vitamin D content. So, the vast majority of American foods in the MacroFactor database should contain vitamin D information, making it easy to accurately track your vitamin D intake with consistent food logging.
However, in the EU, Australia, Canada, and many other countries, vitamin D is a nutrient that is only reported on a voluntary basis. Many food manufacturers do not voluntarily list vitamin D content on nutrition labels, so many branded products in the MacroFactor database from outside the US and Canada lack vitamin D information. So, if you’d like to accurately track your vitamin D intake, you’ll need to make a point of mostly tracking “common foods,” which come from research-grade databases that have full nutrient reporting.
For more on when you can track using branded foods versus common foods when you’re trying to accurately monitor your intake of particular nutrients, you should check out this article.
Likelihood of insufficient intake: Moderate
Many adults don’t consume adequate amounts of vitamin D, according to current intake recommendations. However, your body can also produce vitamin D when exposed to the sun, so vitamin D intake isn’t always a reliable indicator of vitamin D status. In the US, about 20-25% of adults have blood levels of vitamin D indicating inadequate or deficient vitamin D status. Melanin content and latitude are predictors of inadequate or deficient vitamin D status. All else being equal, if you live at higher latitudes (further from the equator) and have darker skin, your body synthesizes less vitamin D for a given level of sun exposure, so your vitamin D intake needs tend to be higher.
For more on nutrients with a greater likelihood of insufficient or excessive intake, you should check out this article.
Signs of deficiency
The primary sign of vitamin D deficiency is bone malformation as a result of incomplete mineralization, leading to soft bones and skeletal deformities. This condition is called rickets in children, and osteomalacia in adults. Muscle spasms and seizures are also common.
Good sources of vitamin D include mushrooms, fatty fish, dairy products (many of which are also fortified with vitamin D), eggs, plant-based dairy replacements that have been fortified with vitamin D, and pork products.
Most food sources of vitamin D are animal products, so many vegans (especially vegans who don’t consume a lot of mushrooms) benefit from vitamin D supplementation.
If you’d like to learn more about micronutrients generally, there’s a five-part series on the MacroFactor website you might enjoy.