Response to an Article in German Journal FITBOOK

The article entitled: “Amazing effect of vitamin D supplementation on metabolism” discusses a recent study that according to the author of the FITBOOK article suggests supplementing 3320 IU of Vitamin D per day. Let’s clarify first that the study entitled: “Modifiers of the Effects of Vitamin D Supplementation on Cardiometabolic Risk Factors: A Systematic Review and Meta-Analysis” has been published in the journal of Engineering and is a meta-analysis, not a new research study.

To motivate the article, the author of the FITBOOK article, Martin Lewicki, points us to a study by the Robert Koch-Institut in Germany, which claims that 30% of adults in Germany have insufficient Vitamin D levels. Looking at the article, it becomes apparent that this study used nmol/L levels to categorize sufficiency. They categorize >= 50 nmol/L of Calcifediol as sufficiency. When comparing this to the levels that others find sufficient D Levels, we see that levels below 75 nmol/L are typically associated with an insufficiency. That means that in 2016, more than 50% of persons measured in Germany were clearly deficient in Vitamin D. The unfortunate selection of the >=50 nmol/L cutoff doesn’t allow us to understand whether even a single person had sufficient Vitamin D levels.

Lewicki calls Germany a Vitamin D Mangelland (deficient country), which, due to its temperate climate, is obvious. Lewicki could have been more precise in pointing out that Vitamin D is produced in the skin with the help of UVB radiation, but he remains a bit vague, saying it is produced in the body with UV light. There is no way to produce sufficient Vitamin D by any amount of sun exposure in the winter in Germany unless you are in snow-covered mountain areas. In that case, you are at risk of sunburn, which you should diligently avoid. But putting sunscreen to do so will block UVB and Vitamin D production. All in all, Fitbook tested ten random subjects in Germany, and 90% were deficient. Which levels they applied is unclear.

With the motivation for the article out of the way, Lewicki introduces the study above, which shows the metabolic effect of Vitamin D. Before discussing the article; he points us to former articles in FACEBOOK that tell us about the benefits of Vitamin D (I might have a look some other time). He closes that section by claiming that 100-200 grams of fatty fish (salmon) should be sufficient to cover the daily Vitamin D need. Salmon has only about 500 IU per 100g, so to reach the 3320 IU that is suggested by the article, much more than 200g per day is needed. Also, the 500IU is probably only valid for wild catches, not farmed salmon. The phrase: “A kilo of salmon per day keeps the doctor away” might not catch on anytime soon, and with the heavy metals found in fish nowadays, might also be ill-informed.

Finally, Lewicki introduces the study, which considered 99 randomized controlled trials (RCT) with a total of ~17500 participants. However, where did Lewicki get the strange number 3320 IU Vitamin D per day from? For that, we need to look at the cited article, and in its abstract, we see that from the 99 RCTs the median Vitamin D dose was 3320 IU. The range in the RCT was from 40 to 120.000 IU per day. Why they included studies with 40 IU into the list is unclear to me as there cannot be any measurable effect at such levels. I would exclude anything below 1000 IU per day, for sure. Apparently, the researchers’ ideas seem to be aligned with mine, and they created two groups for further analysis, < 3320 IU per day and >= 3320 IU per day. In the latter group, positive effects on various metrics can be found. How Lewicki translates this to 3320 IU being the optimal dose is unclear to me. To me, this is misinformation! Mind you, the >= 3320 IU group also includes studies with 120.000 IU Vitamin D per day.

Some obvious results are that effects are higher in persons who were previously deficient (really worth mentioning?). Effects were also hither in non-western participants. Now, this needs to be delineated. We don’t know enough about the RCTs to do that, though. I think it is safe to assume that most of them were done in Western countries (Europe, USA, Canada). These are temperate areas where people with darker skin are at a disadvantage, considering the innate production of Vitamin D. Under this premise, we can understand why so-called non-western participants benefitted more from Vitamin D supplementation. Why participants with lower body-mass-index benefitted more is also not directly obvious. Since supplementation typically uses Cholecalciferol, it is associated with chylomicrons. These are then often taken up by fat cells, and the more and larger fat cells are available, the more Vitamin D is sequestered into them, leaving less to increase blood levels. Overall, there is no exciting news.

Lewicki then suggests how much Vitamin D we need per day. His first suggestion is to have a Calcifediol (25-hydroxy Vitamin D) test to determine the blood levels, which is very good. He then fabulates about previous FITBOOK articles and insignificantly low doses such as 800 IU. Basically, he ignores the article he discussed above and points us to alleged toxicity above 5000 IU (according to the BfR in Germany). Looking back at the study he mentioned, About half of the participants must have been far above the toxicity level (120.000 IU is 60 times higher). Try to pass such RCT studies by ethical committees if 5000 IU were indeed toxic. BTW, if I sunbathe in Germany in the summer, I will produce far more than 5000 IU, so am I then intoxicating myself? Another point Lewicki makes that Vitamin D blood levels above 100 ng/ml are not easily reached is, of course, nonsense. I can attest to that with a blood level above 200 ng/ml (fear not I reduced my daily intake after the measurement).

Overall, the article by Lewicki is more targeted at connecting previous FITBOOK articles to the current study than anything else. Whether he read beyond the abstract and if he actually understood the study he mentions in this article is open to discussion. The amazing effects were only briefly mentioned and did not leave me awestruck.

• Critizism
• FITBOOK
• Vitamin D
• D3
• Sufficiency
• Blood Levels
• Calcifediol
• Metabolism
• D3 Toxicity