Vitamin D: Do I take a supplement??
There is a lot of controversy that surrounds Vitamin D supplementation, mostly because Vitamin D helps your body to absorb and adhere calcium to your bones (you need one to have the other help), but the BEST source of vitamin D is from UV B exposure. 4 minutes of unexposed sunlight (for a light skinned person) gives about 1000IU of Vitamin D3 (the US RDA for the average person is around 600IU/day and 800IU/day for elderly and pregnant women and for EU/Australia it is closer to 200-400IU/day or 5-10 micrograms). So what is the big controversy? Some HCP's tell patients to take up to 4000IU a day of Vitamin D, but do we really need high doses of Vitamin D and should we encourage supplementation. There are health detriments to both too much Vitamin D and too little!
What is Vitamin D all about?
Vitamin D is a fat soluble vitamin, which means that it is stored in your fat, so unlike, for example, Vitamin C, you don't just pee out the excess, your body stores all of the Vitamin D you ingest in your fat. (Vitamin A, D, E, & K are all fat soluble FYI.) It is created in the skin after exposure to UVB rays, then transported to the liver and converted into calcidiol, then into calcitrol where it works as part of your immune system AND when circulating in the bloodstream it helps to regulate calcium and phosphate in the blood and assists in growth and remodeling of bone. It also has some neurological functions as it helps in the growth and life cycles of cells, and decreases inflammation. There have been studies that look at the role of Vitamin D and prevention of cancer, but the studies all seem to have conflicting outcomes and nothing really points at the specific role of Vitamin D. Also, a study from The Journal of Steroid Biochemistry and Molecular Biology found that abnormal levels (high or low) are related to premature aging and abnormal cell functioning.
What can too much Vitamin D lead to?
Too much Vitamin D can lead to hypercalcemia (too much circulating calcium) and in pregnant women, this can cause mental retardation and/or various deformities in the fetus. Other signs of too much Vitamin D are anorexia, pruritus (itchy skin), nausea, vomiting, nervousness, muscle twitching, and calcifications in the kidneys that can lead to kidney failure. It has been shown that 50,000IU/day of Vitamin D can cause these problems over the timeframe of a few months, but certain medical conditions could cause it to happen faster.
What about to little Vitamin D?
Most notably, Vitamin D deficiencies cause rickets in children, which causes deformities of the long bones and osteomalacia, which is a thinning of the bones which causes muscle weakness and easily broken bones. Osteomalacia can also lead to chronic muscle/bone pain and is usually present only in adults. There is a theory that low Vitamin D levels can lead to susceptibility of the flu virus. Low levels of vitamin D can also be associated with cardiovascular disease, in the form of peripheral artery disease (PAD) and in a study from Johns Hopkins and Emory it showed that people with lower calcium levels had an 80% higher rate of PAD.
What foods have Vitamin D?
Mushrooms (besides UVB) are the only vegetarian friendly form of Vitamin D and will give you 14 IU per serving.
Cod Liver oil (1 tablespoon): 1360 IU
Salmon (3oz): 764 IU
Mackerel (3oz): 388 IU
Tuna (canned 3oz): 154 IU
Milk (fortified 1 cup) : 115-124 IU
OJ (fortified 1 cup): 100 IU
Yogurt (fortified 6 oz): 80 IU
Margarine (fortified 1 tablespoon): 60 IU
Sardines (2): 46 IU
Beef Liver (3.5 oz): 46 IU
Cereal (fortified 1 cup): 40 IU
Egg (whole - Vitamin D is in yolk): 25 IU
Swiss Cheese (1 oz): 6 IU
How does Sunblock effect its absorption?
First off, darker skinned people need 20-30 minutes more exposure time to sunlight to get the same amount of Vitamin D that light skinned people make in 4 minutes of exposure. So, how does sunblock work on this end? Well, most sunblocks claim to block 99% of UVB rays, which is what we need to make Vitamin D and what we need to prevent to stave off skin cancer....ugh! What it actually does is decrease your ability to make Vitamin D by around 95%. So, for light skinned people that need to be unexposed in the UVB rays for 4 minutes that are now wearing sunblock you need to increase that time to around 8 minutes, but the problem therein is for darker skinned people who have to spend around 20-30 minutes in the UVB rays to generate enough Vitamin D and with sunblock now need to spend closer to an hour in the sun to make the same amount of Vitamin D; this puts us at a higher risk for skin cancer.
There are detrimental health effects from too much and too little Vitamin D, its almost like being Goldilocks and finding the right amount and what is best for you. The BEST way to absorb is from UVB light, and from food sources, as supplements aren't usually absorbed as well for viable use by the body. If you are worried about how much Vitamin D you have, or thinning bones (especially if you already have osteoporosis) talk to your HCP about you best plan of care and how much Vitamin D you need. Also talk about sunlight exposure and risk of skin cancer....this problem is clearly multi faceted and no one seems to have the 'right' answer, so work with your HCP to find the best plan for you!
Yours in Good Health