How much vitamin D do we need a day?

This article has been written and reviewed by a Registered Dietitian, Samantha Cassetty.

Vitamin D needs vary by age. Adults require 600 IUs per day until age 70. After that, the requirement increases to 800 IUs per day.
How much vitamin D do we get from the sun?
Although your skin manufactures vitamin D when exposed to the sun, the process isn’t always efficient. For instance, if you’re wearing sun protection or it’s cloudy, the activation process is less effective. However, the risks of sun exposure outweigh the benefits of vitamin D activation, so it’s better to focus on food and supplements than spending time in the sun without adequate sun protection.
What foods are high in Vitamin D?
Vitamin D is in very few foods.
Salmon is probably the top source of vitamin D. A 3-ounce serving of cooked, farmed Atlantic salmon supplies about 450 IUs of this nutrient. Plus, you’ll get much-needed omega-3 fatty acids as well as a quality source of protein. 
2 eggs have 82 IUs, which is concentrated in the yolk. Eggs are also an easy source of protein
1 tin of sardines provides 178 IUs of vitamin D, as well as omega 3 fatty acids. Sardines are somewhat polarizing, but if you like them, they’re very nutritious!
1 cup of milk has 117 IU since milk is traditionally fortified with vitamin D. So, if you’re using a dairy alternative, it’s a good idea to check labels to find a substitute that’s fortified with vitamin D, as well as calcium. You’d be surprised at how many dairy-free milk products aren’t fortified!
Sometimes cereal is fortified with vitamin D, and if this is the case, you can meet about 15 percent of your daily needs between a serving of cereal and a half cup of milk. Check labels to see if your favorite cereal is fortified, and keep in mind that the healthiest cereals have a whole grain as the first ingredient and have less than 6 grams of added sugar per serving.
Do we need to eat anything else for vitamin D to be absorbed?
Healthy people absorb vitamin D well through food or supplements. Vitamin D is a fat-soluble vitamin, so in theory, you need some fat in your gut, but you don’t need to overthink it. As long as you eat fatty foods throughout the day (think nuts, seeds, avocados, and extra virgin olive oil), you shouldn’t have a problem absorbing vitamin D through food or supplements. In terms of supplements, vitamin D3 is the preferred form since it’s slightly better absorbed than vitamin D2.
If someone isn’t getting out in the sun or eating enough vitamin D rich foods - should they take supplements?
Most health organizations discourage sun exposure because of the risk of skin cancer. Therefore, the advice is to get vitamin D through foods and supplements. Since it’s not widely available through food, most people benefit from a supplement to meet their needs.
I usually suggest 1,000 to 2,000 IUs of vitamin D for healthy people. However, certain people are more vulnerable to deficiency. For instance, older people, those with darker skin, and those with certain GI conditions, such as celiac or Crohn’s disease, may be at higher risk for vitamin D deficiency. People who meet the clinical definition of obese are also considered at higher risk. If you fall into an at-risk population, the best thing to do is talk to your doctor about getting a simple blood test to measure your vitamin D status. If your levels are low, your healthcare provider can suggest the amount you should take. We know that a lot of people require 3,000 IUs a day, or even more, to bring their vitamin D status to a healthy level.
What are some vitamin D deficiency signs to look out for?
Since vitamin D is involved in promoting calcium absorption, inadequate intake may result in thin, weak bones, which may ultimately lead to osteoporosis. But vitamin D has other roles in the body that you may not be familiar with. For instance, it’s involved in regulating inflammation in our immune response, which may be why low levels are linked to higher rates of viruses and auto-immune disorders. Vitamin D deficiency has also been linked to type 2 diabetes. You might experience vague symptoms, like fatigue, or you might not have any symptoms. That’s why it’s smart to get your levels checked periodically and to take a supplement.