Library.

“Low vitamin B levels, low vitamin D levels, and low iron levels can contribute to symptoms that may be mistaken for depression.”

The evidence supports the claim’s core point. Low iron, low vitamin B levels—especially B12 and folate—and low vitamin D can be associated with fatigue, cognitive slowing, low mood, and related symptoms that overlap with depression. The main caveat is that this does not prove these deficiencies directly cause depressive disorder in every case.

“Taking 5,000 IU of vitamin D daily does not cause side effects for most people.”

Most adults are unlikely to develop side effects from 5,000 IU of vitamin D daily, and several studies found it was generally well tolerated. But the claim overstates the evidence: 5,000 IU is above the usual adult upper limit of 4,000 IU, and review-level evidence shows a small but real increase in some adverse events at nearby doses. A safer wording would be that side effects are uncommon, not absent.

“A meta-analysis published in 2023 found that taking 3,200 to 4,000 International Units (IU) of vitamin D daily is associated with a higher risk of hypercalcemia.”

The cited 2023 meta-analysis did report that long-term vitamin D supplementation at 3,200-4,000 IU/day was associated with a higher risk of hypercalcemia. The pooled estimate showed a statistically significant increase versus control. Important context is that the absolute excess risk was small and reported cases were often asymptomatic or reversible.

“Vitamin K helps vitamin D absorption for bone health.”

The evidence does not show that vitamin K helps the body absorb vitamin D. What reliable sources do support is that vitamins D and K can work together in bone health through different roles: vitamin D helps regulate calcium and induces certain proteins, while vitamin K activates some of those proteins. That makes the claim directionally related to a real interaction, but wrong in its stated mechanism.

“Vitamin D deficiency is widely overdiagnosed in clinical practice.”

Strong evidence shows vitamin D testing is widely overused — with studies finding 57–77% of tests lack clinical justification — but the claim conflates overtesting with overdiagnosis. Overtesting means ordering tests without guideline indications; overdiagnosis means incorrectly labeling healthy people as deficient. While contested diagnostic thresholds may inflate deficiency labels in some populations, global data also show substantial true deficiency prevalence with meaningful health associations. The unqualified assertion that deficiency is "widely overdiagnosed" overstates what the clinical literature supports.