I occasionally get letters from people who are taking 5,000 IU per day and their vitamin D levels are still less than 50 ng/ml 3 months later. While poor absorption, genetics, obesity, and season of the year may all play a role, another possible cause is that the vitamin D supplement you take may contain little or no vitamin D at all.
A recent Finnish study, which is apparently in the Finnish language, found that only a third of the vitamin D supplements in Finland were within 20% of what was claimed on the bottle. Some contained no vitamin D at all.
However, thanks in part to ConsumerLab.com, the same problem appears to be less common in the USA, at least with the vitamin D brands they choose to test. ConsumerLab.com tests several dozen vitamin D supplements on a somewhat regular basis, finding very few with less than their label reported and none without any vitamin D. However, two were contaminated with lead: AlgaeCal Plus and Pure Essence Labs Ionic-Fizz Super D-K Calcium Plus.
In the United States, ConsumerLab.com is a company that routinely tests a sample of dietary supplements. The Vitamin D Council will keep you up to date if there are any problem vitamin D supplements that ConsumerLab.com tests. However, hundreds of vitamin D supplements are available, so relatively speaking, they did not test very many vitamin D supplements.
The other organization that certifies vitamin purity and content, NSF, certifies purity and amounts claimed via unannounced purchases. They also make unannounced visits to the factories producing the supplements to verify that the various ingredients are pure and not contaminated. Such certification is expensive and seldom done. Professional athletes must take an NSF certified product or risk failing drug testing. To my knowledge, few vitamin D supplements are NSF certified, the one I designed for professional athletes by Purity Products.
However, one does not need worry if your vitamin D is both pure and contains what it says it does on the label. Just continue your membership to the Vitamin D Council, and we will alert you to any problems with of the Consumerlab.com tested vitamin D supplements. On the other hand, you can use one of our sponsor’s vitamin D, Bio Tech Pharmacal or Stop Aging Now. We appreciate it when you patronize our sponsors, and you will appreciate the quality and price of either company.
It is also a good idea to test your 25(OH)D at least once or twice a year and you can do it in the privacy of your own home thanks to another one of our sponsors, ZRT. If your level is less than 50 ng/ml, despite taking 5,000 IU per day, switch supplements and take the new one with your largest meal of the day. If that does not work, you may be one of the people that need 10,000 IU/day due to body weight or genetics. We don’t recommend that you exceed 10,000 IU per day except if you know what you are doing and get regular 25(OH)D tests.