Vitamin D is an important nutrient that is also considered to be a hormone. This vitamin/hormone can be difficult to get through the diet, but can be synthesized by your skin when you are exposed to high quality sunlight. If you are someone who lives in a location far north or south of the equator, you are probably not getting sufficient levels of vitamin D through the sun. So, it is important to know there are at least 10 foods high in vitamin D. (post contains affiliate links)
Vitamin D is a fat soluble vitamin, which means it is absorbed better with foods containing fat. This also means that vitamin D is stored in the fat in your body. As a result, vitamin D can be potentially toxic when high doses are taken in supplemental form. This is why you shouldn’t take a high dose supplement unless you’ve had your levels checked first.
I am going to briefly discuss how vitamin D is measured and reported on food labels. This will hopefully alleviate some of the confusion you have when trying to decide if you are getting sufficient amounts in your diet or multivitamin.
Firstly, vitamin D is measured in two ways:
- Using IU, which stands for “International Units.”
- Using mcg (micrograms).
A microgram is equivalent to one millionth of one gram. In contrast, 1 IU is the biological equivalent of 0.025 mcg cholecalciferol, the active form of vitamin D (D3). Note that an International Unit is a measure of biological activity and is different for each substance. So, you can’t use this formula for converting retinol or beta-carotene, for example. (Dietary Supplement Data Base)
Secondly, keep in mind that different vitamin manufacturers use different units of measure.
For example, we have two different multi-vitamins currently in our house. One of them, Kirkland Signature Daily Multi for adults, shows 10 mcg vitamin D (400 IU) and says it has 50% of the US RDA. On the other hand, Centrum chewables for adults contains 400 IU vitamin D, claiming this is 100% of US RDA.
So which one is correct? It depends on who you ask. However, since the US RDA for vitamin D varies by age, it is not that simple.
Thirdly, research shows that almost 50% of people are deficient in vitamin D.
This is a controversial topic, with some doctors believing that a blood level of 50 nanograms/milliliter (ng/ml) is the optimal level to shoot for. In contrast, other doctors believe over 50 ng/ml to be potentially toxic.
For example, when my vitamin D was low some years ago, I had to take 10,000 IU a day to get it above 50 ng/ml which is what my doctor at the time recommended. My current doctor, however, is part of the second crowd, bless his little heart. He’s a great doctor, otherwise, but we don’t always see eye-to-eye on these things.
The Vitamin D council, which specializes in vitamin D research, is in the first group, and I’m with them. However, It is important to note there are two different blood measurements of vitamin D. Thus, it is advised that you check with your doctor to help you decipher your results.
It is important to get your vitamin D checked to make sure that it isn’t too low OR too high.
If it is low, you will need a higher dose than the US RDA. If it is within normal levels, then you will probably do fine with 1000 IU per day. However, if you have any of the symptoms of low vitamin D, (even if your levels are 30-40 ng/ml) then speak with your doctor about a higher dose.