Did I say that we would be taking a much briefer look at vitamin D? HA! In my mind I thought that the more extensive research done on vitamin D (as opposed to B12) and its prevalence in medical thought of the moment would make it easier to write about. I was wrong, wrong, wrong. There is so much information that we will be taking a much less comprehensive look at vitamin D, and I will provide sources for your further research; otherwise, One is Hungry will begin to look like a medical treatise rather than a helpful, easily understood food blog!
What is vitamin D, and why on earth does it matter?
Vitamin D is a fat soluble vitamin that may be obtained in two ways. The first, and most effective, is produced cutaneously, or by the skin, after exposure to UVB radiation (the sun). The second means of obtaining vitamin D is orally, either through foods or supplements. Though there are many types of vitamin D, the two thought to be most beneficial to humans are D2, which is primarily vegetal, and D3, which is produced in the skin and can be found in some food sources. Below is a chart of the blood test numbers, and how they translate for you.
|<30||<12||Associated with vitamin D deficiency, leading to rickets in infants and children and osteomalacia in adults|
|30–50||12–20||Generally considered inadequate for bone and overall health in healthy individuals|
|≥50||≥20||Generally considered adequate for bone and overall health in healthy individuals|
|>125||>50||Emerging evidence links potential adverse effects to such high levels, particularly >150 nmol/L (>60 ng/mL)|
* Serum concentrations of 25(OH)D are reported in both nanomoles per liter (nmol/L) and nanograms per milliliter (ng/mL).
** 1 nmol/L = 0.4 ng/mL
Vitamin D is widely recognized for its importance to bone health. Properly processed vitamin D is necessary to the body’s healthy absorption and use of both calcium and phosphate. In children insufficient vitamin D, and thereby calcium, can show up as rickets and improper skeletal development. In adults brittle bones are a common outcome.
What is not as widely discussed is the effect vitamin D has on our health at large. Current research links vitamin D to healthy body weight, immune function, brain development and maintenance, respiratory health, diabetes, cancer prevention, and heart health! A few studies are even linking vitamin D deficiency to chronic migraines.
Who is at risk?
Those with limited sun exposure due to inclination, culture, or climate. The sunscreen message has gotten across to the public, and as skin care routines get better, vitamin D levels get lower. In most cultures, our strict adherence to covering our bodies with clothing is a point against cutaneous vitamin D production :) . There are also geographic locations in which the amount of UVB radiation available at certain times of year is insufficient to our needs. Darker skinned ethnic groups are more susceptible to a vitamin D deficiency as the increased melanin in their skin does not allow for the same levels of vitamin D production after exposure to UVB radiation. Finally, as we age our bodies produce less vitamin D through sun exposer.
Also at risk are those with limited oral intake, and those with impaired intestinal absorption (Celiac sufferers, Crohns, and the like). Infants being breastfed by women without sufficient vitamin D stores are at great risk for vitamin D deficiency. Gastric bypass surgery patients and those following extremely low-fat diets are very likely candidates as well.
How do you treat it?
My personal choice is move to the tropics and live a life of naked, un-sunscreened happiness! However, as that is not an option for 99.99% of us, what else can be done? Limited, sun-screen free exposure to the sun was the first thing my doctor recommended. 10-20 minutes a day (depending on skin sensitivity and climate) in the summer months is ideal. For those with a strong family or personal history of skin cancer, extreme northerly and southerly climates, and winter-dwellers everywhere outside the tropics: the answer is supplements.
My fist question to my doctor was: can I try to manage this with diet? She tilted her head and said, “Sure,you can try”. According to the Mayo Clinic, her response should be interpreted as “No”. The following excerpt is from a Mayo Clinic Study published by the N.I.H.
Many patients and physicians think that adequate vitamin D intake can be obtained via diet alone. This assumption is erroneous. With the exception of fatty fish, the vitamin D content of most foods, including fortified dairy products, is relatively low to nonexistent. Even some dairy products in the United States are not fortified, making it important to read food labels to ensure the vitamin D content of foods.
The only absolutely reliable source of vitamin D that all experts seem to agree on is oral supplements. As there is an opposite risk of vitamin D toxicity, it is recommended that the average adult not take over 800 to 1000 IU/ per day. Your personal dosage is best determined with your doctor!
So, what foods have vitamin D?
This list is going to look surprisingly similar to that for B12 . Fatty fish are the number one dietary source of vitamin D. After that, meats, eggs, fortified dairy, cereals and soy products make up the remainder. The list below, like the list for the B12 entry, is from the N.I.H. In the source materials at the bottom of this article is a link to an extended food list from Self, and one from World’s Healthiest Foods.
|Food||IUs per serving*||Percent DV**|
|Cod liver oil, 1 tablespoon||1,360||340|
|Swordfish, cooked, 3 ounces||566||142|
|Salmon (sockeye), cooked, 3 ounces||447||112|
|Tuna fish, canned in water, drained, 3 ounces||154||39|
|Orange juice fortified with vitamin D, 1 cup (check product labels, as amount of added vitamin D varies)||137||34|
|Milk, nonfat, reduced fat, and whole, vitamin D-fortified, 1 cup||115-124||29-31|
|Yogurt, fortified with 20% of the DV for vitamin D, 6 ounces (more heavily fortified yogurts provide more of the DV)||80||20|
|Margarine, fortified, 1 tablespoon||60||15|
|Sardines, canned in oil, drained, 2 sardines||46||12|
|Liver, beef, cooked, 3 ounces||42||11|
|Egg, 1 large (vitamin D is found in yolk)||41||10|
|Ready-to-eat cereal, fortified with 10% of the DV for vitamin D, 0.75-1 cup (more heavily fortified cereals might provide more of the DV)||40||10|
|Cheese, Swiss, 1 ounce||6||2|
* IUs = International Units.
** DV = Daily Value. DVs were developed by the U.S. Food and Drug Administration to help consumers compare the nutrient contents among products within the context of a total daily diet. The DV for vitamin D is currently set at 400 IU for adults and children age 4 and older. Food labels, however, are not required to list vitamin D content unless a food has been fortified with this nutrient. Foods providing 20% or more of the DV are considered to be high sources of a nutrient, but foods providing lower percentages of the DV also contribute to a healthful diet.
The U.S. Department of Agriculture’s Nutrient Database Web site lists the nutrient content of many foods. It also provides a comprehensive list of foods containing vitamin D. A growing number of foods are being analyzed for vitamin D content. Simpler and faster methods to measure vitamin D in foods are needed, as are food standard reference materials with certified values for vitamin D to ensure accurate measurements .
Let’s wrap it up
If you have made it this far, thanks for sticking with me. Remember that chart at the top listing vitamin D serum levels in blood, and what those levels mean? Well, 30 and below is considered deficient; I came in at 23 or 24 (I’ve lost the paper I wrote it down on :S). So, my doctor told me to get some sun, and take 1000 IU per day. She did not specify between D2 and D3, so for the moment I’ve chosen D3. I’m going to talk to her about it further at my three month check-up. It is still too early for me to say positively what effect the B12 shots and vitamin D supplements are having. For the first full month I had bronchitis; I just took my second shot a few days ago, and am on a steady routine with the supplements. My migraines have not gone away entirely, but, at the moment, I’m no longer experiencing them every day. Progress! I’m also sleeping more deeply than I can ever remember doing, but as it is winter, and I’ve been sick, I don’t know if it is the med.s or just hibernation.
Remember, if you are using this article for your own health education, it is a very broad overview. Please see the sources listed below for more information, and definitely consult your G.P.
Coming up soon we will finally be getting back to recipes (HOORAY) and a big update on the condo situation! See you soon.