Response to an Article in German Journal FITBOOK

I commented earlier on another article in FITBOOK concerning the Amazing effect of vitamin D supplementation on metabolism. Now, we need to talk about another article in FITBOOK. The article entitled: “Effect of vitamin D on brain function” discusses a study on Brain Vitamin D Forms, Cognitive Decline and Neuropathology in Community-dwelling Older Adults. The article by Friederike Ostermeyer discusses a recent study examining the relationship between Vitamin D levels in the brain and cognitive function. While Vitamin D is undoubtedly important for overall health, her article exaggerates the findings of the study and misrepresents key points, leaving readers with more hype than substance.

Unfortunately, the original article is also uninspiring and has quite a few shortcomings that I discuss in a different blog post.

Let’s break this down.

Overgeneralization of Study Findings

The FITBOOK article suggests a direct and causative link between Vitamin D levels and improved brain function or reduced risk of dementia. However, the cited study only identifies an association between brain Vitamin D levels and cognitive function without establishing causation. This nuance is entirely overlooked in the FITBOOK article. The study acknowledges that dementia is multifactorial, and the mechanisms through which Vitamin D might influence brain health remain unclear. FITBOOK fails to communicate these important limitations.

Exaggerated Claims

The article sensationalizes the potential benefits of Vitamin D, calling it “Wunderstoff” (miracle substance). FITBOOK refers to Vitamin D as a “miracle substance,” which is scientifically inappropriate and misleading. Their claim, a “rapid reduction of dementia risk by 33%”, is a statistic based on observed correlations in the study and does not imply that Vitamin D supplementation will directly lower dementia risk by this percentage (or at all).

Misrepresentation of Study Scope

The FITBOOK article does not explain that the study analyzed postmortem brain tissue from 209 individuals, which limits its ability to address Vitamin D’s active role in living populations or its dynamic effects over time. The absence of mechanistic exploration in the study, such as how Vitamin D influences cognitive processes, is not mentioned in FITBOOK’s review. FITBOOK is content in cherry-picking data from the original article that can be exaggerated, it seems.

Insufficient Understanding of Vitamin D Metabolism

The original article fails to discuss the complexities of Vitamin D metabolism. For example, the active form of Vitamin D (Calcitriol): FITBOOK does not clarify that only Calcitriol (not calcifediol) binds to Vitamin D receptors (VDRs). The study itself had difficulty quantifying Calcitriol levels in the brain, making the relevance of measured Vitamin D levels unclear. This oversight creates confusion about what the findings actually mean. The original article does not consider whether the brain converts calcifediol into Calcitriol locally, a critical factor in understanding the study’s implications. FIBOOK has several articles on Vitamin D and discusses these points in some of them. Why does FITBOOK not critically acclaim the original article?

Omission of Study Shortcomings

FITBOOK does not critically assess the cited study’s limitations such as the participants’ Vitamin D Status. Many participants were likely Vitamin D insufficient, which limits the generalizability of the findings. The study is cross-sectional, meaning it cannot determine whether higher Vitamin D levels prevent cognitive decline or are merely correlated with better function in healthier individuals.

Misleading Health Advice

FITBOOK provides incomplete and sometimes inaccurate health recommendations. The FITBOOK article highlights concerns about Vitamin D toxicity, yet the cited study includes participants who consumed far higher doses without reported adverse effects. This fear-mongering is unwarranted and detracts from a balanced discussion. While FITBOOK suggests measuring Vitamin D levels, it does not clarify what levels are optimal for cognitive health, leaving readers without actionable guidance. Different opinions exist on optimal blood levels. Some of them are listed here.

Verdict

The FITBOOK article on Vitamin D’s impact on brain health overstates the study’s findings, lacks critical engagement with its limitations, and provides vague or misleading health advice. While Vitamin D is undoubtedly an important nutrient, this article serves more as a vehicle for promoting previous FITBOOK content than as a reliable source of information. Recommendation Readers should seek evidence-based, scientifically grounded discussions of Vitamin D’s role in cognitive health. The detailed critique of the study mentioned in the article will follow in a separate blog post.

• Critizism
• FITBOOK
• Vitamin D
• D3
• Brain Levels
• Blood Levels
• Calcifediol
• Dementia
• D3 Toxicity
• Alzheimer
• Neuropathology