The current Recommended Daily Allowance of Vitamin D is only 200 International Units (IU) for people up to age 50. Ages 51-70 is 400IU and ages 71 and over is 600IU.
Experts are telling us about their research which has shown that we need a lot more than the current RDA to prevent Vitamin D Deficiency, perhaps 10 times that or even more. They say intake should be higher in the winter and for those living at higher latitudes. I live in the southwest and I am currently taking 4000IU daily as a maintenance dose. I may need to take more this winter. Some medical conditions, additional body fat and some medications may inhibit the ability to absorb and convert Vitamin D.
Lots of foods have some Vitamin D in them but it is tough to get enough from diet alone. We also need safe sun exposure when we can get it but most of us are going to need to take Vitamin D3 supplements to prevent Vitamin D Deficiency. Looking at the table below, you can see how difficult it would be to get enough every day without taking supplements.
Food Serving Size Vitamin D Content
IUs in each serving
Cod Liver Oil 1 Tablespoon 1360
Some researchers caution that Vitamin A content may be too high and could lead to Vitamin A toxicity.
Sockey Salmon 3 ounces cooked 794
Mushrooms 3 ounces, UV-B 400
Only when grown/exposed to UV-B light to increase Vitamin D
Mackerel 3 ounces cooked 388
Tuna 3 ounces canned 154
in water and drained
Milk 1 cup, vitamin D 115-124
Yogurt 6 ounces, vitamin 80 and higher with
D fortified additional fortification
Margarine 1 tablespoon
vitamin D fortified 60
Egg 1 whole egg with 25
Cheese, swiss 1 ounce 6