If you’re following the health news, you know that vitamin D currently is in the media spotlight, and rightly so. Will Brink just did a great podcast “Vitamin D3 – scam or panacea?“, giving an overview on the importance vitamin D. In this article I will expand upon some key points taken up in the podcast, and back up the case with a solid reference list of recent studies on the topic. I will also present some revealing prevalence stats on vitamin D insufficiency, in order to convince you to get your blood levels checked to find out your vitamin D status.
Vitamin D is interesting for several reasons:
1. The role of vitamin D for health promotion has undergone a paradigm shift.
While traditionally thought to only be important for development and maintenance of strong bones, an impressive body of scientific research has accumulated over the past decade, showing that adequate vitamin D levels are necessary to prevent many diseases, especially cardiovascular disease, high blood pressure, endothelial dysfunction, diabetes (both type-1 and type-2), the metabolic syndrome, chronic inflammation, cancer, osteoporosis (including falls and fractures), muscle weakness, cognitive dysfunction and mental illness, autoimmune diseases (e.g. multiple sclerosis, rheumatoid arthritis), infectious diseases, as well as infertility and adverse pregnancy and birth outcomes [1-24].
Vitamin D deficiency/insufficiency is associated with all-cause mortality , and supplementation has been shown to decrease mortality rates [25, 26]. It has been estimated that doubling vitamin D levels in the general population (from 21 ng/mL to 44 ng/mL) would reduce vitamin D-related disease mortality rate by 20%, and increase life expectancy with about 2 years .
2. Insufficient levels of vitamin D also have direct implications for fitness enthusiasts and athletic performance, due to the importance of vitamin D for muscle function (I will cover this in much more dept in an upcoming article) [28-39].
3. In contrast to other vitamins, vitamin D deficiency/insufficiency is very common (more on that below).
4. The vitamin D requirement for health promotion and protection against the mentioned diseases and muscle dysfunction is much higher than the dietary recommendations (RDA) for bone health [4, 40-45].
Having heard about all the vitamin D benefits you might wonder what is the optimal vitamin D level? How low is too low and how high is too high? How much vitamin D does one have to consume to reap all the benefits?
Let’s find out…
What are the blood level thresholds indicating vitamin D insufficiency?
The form of vitamin D that is measured in blood and used to indicate vitamin D status is called 25-hydroxy-vitamin D (abbreviated 25[OH]D) [9, 46]. So when I talk about blood vitamin D levels in this article, it is 25-hydroxy-vitamin D I am referring to (it’s easier for most people to think in terms of vitamin D levels than 25[OH]D or 25-hydroxy-vitamin D).
There is no official consensus about what is the optimal vitamin D level, and it is possible that different endpoints require different optimal vitamin D levels. However, based on the currently available data, prominent vitamin D researchers and authorities have presented the following guidelines:
Vitamin D status thresholds as defined by blood 25-hydroxy-vitamin D (25[OH]D) levels.
|ng/mL||nmol/L||Vitamin D status||Reference|
Risk for toxicity
[18, 22, 41, 47, 48, 50-58]
[4, 9, 22, 28]
[9, 46, 59]
* Severe deficiency that causes softening of the bones occurs with levels below 10 ng/mL (25 nmol/L) .
* Blood (serum) levels of 25(OH)D are reported in either nanograms per milliliter (ng/mL) and nanomoles per liter (nmol/L).
* 1 ng/mL = 2.5 nmol/L
Traditionally, government issued health guidelines have stated that vitamin D levels of 20 ng/mL are sufficient. However, in light of new data prominent vitamin D researchers now recommend vitamin D levels in the range of 50-60 ng/ml, for both health promotion and athletic/physical performance [4, 9, 28]. As indicated in the table, even though this new recommended level is 2-3 times the old recommendation, it is far below the risk for intoxication and is thus a safe target to aim for in order to achieve all the vitamin D related health benefits (which is will cover in dept in upcoming articles).
How common is vitamin D insufficiency?
Low vitamin D status, i.e. vitamin D deficiency or insufficiency, is far more common than previously thought.
When looking at stats, it’s important to distinguish vitamin D deficiency from insufficiency. While severe vitamin D deficiency isn’t as prevalent, vitamin D insufficiency is:
* 36% of the US population is deficient, with vitamin D levels below 20 ng/ml .
* In a study on subjects characteristic of the US white population, it was found that only 18% have a vitamin D level over 30 ng/ml . Thus, a whopping 82% are insufficient in vitamin D!
Similar results were found in the 2004 National Health and Nutrition Examination Survey (NHANES)  and in other analyses .
* To make things worse, data from (NHANES) showed that the number of persons with a vitamin D level below 30 ng/mL nearly doubled between the 1994 and 2004 .
Bearing in mind that the desired range as recommended by vitamin D research experts, is 50-60 ng/ml, these stats are alarming and underscore the fact that vitamin D insufficiency exists in epidemic proportions in the US. This vitamin D insufficiency epidemic spans across the globe .
How should I get my vitamin D?
|Salmon, fresh wild caughtSalmon, fresh farmedSalmon, cannedSardines, canned Mackerel, canned Tuna, canned Egg yolk Fortified milk||600–1,000 IU/3.5 oz vitamin D3100–250 IU/3.5 oz vitamin D3300–600 IU/3.5 oz vitamin D3300 IU/3.5 oz vitamin D3 250 IU/3.5 oz vitamin D3 236 IU/3.5 oz vitamin D3 20 IU/yolk vitamin D3 or D2100 IU/8 oz, usually vitamin D3|
Thus, unless you eat oily fish every day (which would carry risk for toxicity from environmental contaminants), you cannot rely on your diet to cover your vitamin D needs.
Another source, the safety of which is controversial, is sunlight exposure. This is why vitamin D is called the “sunshine vitamin”. Because vitamin D can be produced by the skin upon sun exposure, it is actually not a vitamin in the traditional sense (per definition, vitamins are essential because they cannot be produced by the body). In fact, vitamin D is a pre-hormone to the hormone calcitriol (which is the active hormonal from of vitamin D that exerts effects on different tissues in the body). However, as said above, it is the vitamin D metabolite 25-hydroxy-vitamin D (25[OH]D) that is used to indicate vitamin D status and to guide supplementation needs.
Even though sun exposure theoretically is an effective vitamin D source, it cannot safely be relied on. A recent study showed that vitamin D supplementation is actually more effective than advised sunlight exposure for treating vitamin D deficiency . The inferiority of sunlight exposure to improve and keep optimal vitamin D status is supported by findings of prevalent vitamin D insufficiency even in sunny Florida . This was also underlined in a study of tanned prototypic “surfer dudes” (mean age 24 years) who overall reported an average of 22.4 hours per week of unprotected sun exposure . Despite this abundant sunshine exposure, the mean blood vitamin D level was only 31 ng/mL (79 nmol/L), and 51% had a level below the recommended ideal 30 ng/mL (75 nmol/L) cutoff for sufficiency .
Also, the capacity to produce vitamin D in the skin is lower in dark skinned people, and diminishes as we get older [67, 68]. The darker skin types (III–VI) and the oldest people (>59 yr) are at the highest risk for not making enough vitamin D3 during the year from everyday outdoor exposures, even with a 2–3 week summer vacation . People living in northern latitudes are especially at risk of not getting enough vitamin D producing UVB radiation from the sun [68, 69].
Another issue with sun bathing is the consequence of skin aging and risk of skin cancer. Unfortunately, the UVB radiation that produces vitamin D in the skin, is also the culprit causing skin cancer and wrinkling [70, 71]. This is a legitimate reason to not attempt to cover your vitamin D requirements by sun exposure. And even if sun exposure was a safe and reliable way to cover vitamin D needs, in today’s society with hectic work schedules most people don’t have much time to be out in the sun. It has been established that most adult Americans do not go outside enough to meet their minimum vitamin D3 needs all year .
Vitamin D supplements come as either vitamin D2 (ergocalciferol) or vitamin D3 (cholecalciferol) [4, 72] and in over-the-counter dosages of up to 10,000 IU. In the past there was a scientific “D-bate” over the efficiency of D2 vs. D3. However, a recent systematic review and meta-analysis of all studies published to date concluded that vitamin D3 is more effective at raising blood levels of vitamin D (i.e. 25-hydroxy-vitamin D) . More specifically, vitamin D3 is approximately 87% more potent in raising and maintaining 25-hydroxy-vitamin D levels, and produces 2- to 3-fold greater body storage of vitamin D than does vitamin D2 . Given its greater potency and lower cost, the vitamin D3 form should be the preferred supplement choice to elevate and maintain health promoting vitamin D levels.
Now you know the importance of finding out your vitamin D level. Either ask your doctor to check it, or order a vitamin D blood test online without a doctor’s prescription if you don’t have health insurance. Life Extension offer great blood testing services, including vitamin D testing. Get your 25-Hydroxy-vitamin D Blood Test now!
If your blood level of 25-hydroxy-vitamin D shows that you are insufficient in vitamin D (which most folks are), you will need to get a vitamin D3 supplement to reap all the health and performance benefits from this multi-functional pre-hormone. Vitamin D supplementation is the fail-proof way to go in order to safely and effectively get your vitamin D level to the optimal 50-60 ng/mL range. Adequate vitamin D supplementation and sensible sunlight exposure to reach optimal vitamin D status are among the front line factors of prophylaxis for a spectrum of commons diseases.
In the next article I will explain that there is no clear cut vitamin D dose-response relationship because of the considerable variation in how individuals respond to vitamin D supplementation. The response to treatment varies with baseline vitamin D levels, body fatness, differences in activities of vitamin D metabolizing enzymes, skin pigmentation (race), season and geographic location (latitude). This is why it is so important that you check your baseline level and also keep monitoring it regularly, e.g. every 6 months, to see how you respond to vitamin D3 supplementation. In the next article I will cover supplemental vitamin D “loading” and maintenance dosages to raise your level fast and keep it there. I will also present studies that have reported mega-dosages of vitamin D intake, to give you a perspective, and cover safety and toxicological aspects. Stay tuned!
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