Most of your vitamins and nutrients come from the food you eat: The banana and peanut butter you have for breakfast with your coffee, the leftover casserole you heated up for lunch, and the spaghetti and meatballs you swirled around your fork at dinner all provide valuable macro and micronutrients to fuel you through the day.
Vitamin D, however, is unique. While other vitamins and naturally occur in a food, vitamin D needs sunlight to be synthesized. Ultraviolet rays trigger vitamin D synthesis when it contacts the skin of humans or animals, according to the National Institutes of Health. For this reason, your ability to meet the recommended daily allowance (RDA) of vitamin D may depend on your sun exposure and proximity to the sun.
The recommended amount of vitamin D is 600 IU (international units) per day for ages 1 to 70, regardless of your gender or whether you’re pregnant or not. After age 70, experts recommend an increase to 800 IU of vitamin D a day.
Unfortunately, most people do not reach this RDA for vitamin D. In a one study, average vitamin D intake for men was just 204 to 288 IU per day; for women, it was 144 to 276 IU per day.
Symptoms of a vitamin D deficiency may be subtle. While two serious conditions associated with vitamin D deficiency are rickets and osteomalacia, both known for weak bone tissue, these aren’t very common in America today. The boom of rickets in the late 19th century resulted in the fortification of milk, bread, and breakfast cereals with vitamin D. These days, you’re far more likely to experience symptoms of vitamin D deficiency like muscle weakness and fatigue, bone fractures, and difficulty thinking.
To reach your RDA of vitamin D, add these top food sources into your diet:
Brown or cremini mushrooms: 1110 IU in 1 cup
Salmon: 570 IU in 3 oz
Cod liver oil: 450 IU in 1 tsp
Canned tuna: 228 IU in 3 oz
Vitamin D-fortified skim yogurt: 127 IU in 1 cup
Vitamin D-fortified soy milk: 119 IU in 1 cup
Vitamin D-fortified skim milk: 115 IU in 1 cup
Vitamin D-fortified whole grain wheat flake cereal: 100 IU in ¾ cup
As a general rule, experts recommend getting all your vitamins and minerals from whole, fresh foods as opposed to supplements. However, some doctors and nutritionists think vitamin D may be the exception, depending on your sun exposure, skin tone, and proximity to the equator. (FYI, sunbathing is not the answer here. Experts still want you to follow proper sun damage and skin cancer prevention guidelines, even if your vitamin D levels are low.)
Be sure to monitor your vitamin D levels with your doctor—and maybe start adding mushrooms to everything. Try this spaghetti bolognese recipe with mushrooms to get you started.