We’ve long associated vitamin D deficiency with rickets, but autism? Schizophrenia? Depression? The past decade of research has cast light on a new role for the sunshine vitamin and there’s a growing consensus: vitamin D deficiency doesn’t just harm developing bones—it harms the developing brain.

Known as the sunshine vitamin because its primary source in humans is UVB radiation, Vitamin D is an essential nutrient that aids in calcium and phosphorus absorption, bone formation, and immunity. Without adequate Vitamin D, an infant can develop rickets, a softening of the bones. His immune system can be compromised. And, as recent critical reviews suggest, any number of more subtle effects may be occurring inside his developing nervous system.

In the brain, vitamin D is a neurosteroid thought to be widely distributed. It’s a master-controller of gene expression, regulating that of a large number of genes, with direct effects on many proteins as well.

For obvious reasons, the effects of vitamin D deficiency in the brain are difficult to study in humans. Instead, scientists are looking to animal and cellular models of deficiency. While many questions remain unanswered, research on the topic is hot. Turns out vitamin D may be every bit as important as the other heavy-hitting neuroactive steroids — estrogen, testosterone, glucocorticoids — for brain development and function.

Here’s just a few of the processes critical to brain development for which vitamin D is now thought to be important:

• Cellular differentiation — it helps tell cells what to become as they develop.
• Proliferation — it helps control when cells divide and grow in number.
• Apoptosis — it helps guide programmed cell death, such as in neurons that are no longer needed.
• Dopamine production and metabolism — it helps shape the dopamine system, important for motor and reward pathways.
• Reactive oxygen species buffering — it helps protect the brain from oxidative stress.
• Neurotrophic factor expression — it modulates nerve growth factor (NGF) expression, for instance, which helps neurons grow, survive, and migrate.
• Regulation of hippocampal L-type voltage-sensitive calcium channels — it may be important for learning and memory.

So what effects might vitamin D deficiency have on the developing brain?

It’s hard to tell. Vitamin D deficiency early in development has been associated with several neuropsychiatric disorders, including schizophrenia and autism — but at this time the evidence linking these to vitamin D is at best mixed and preliminary.

The role for vitamin D in hippocampal and dopamine system development suggests effects on learning and memory and motor and/or reward systems may be possible. But longitudinal studies in humans are needed to fully address this question. These take time, so it may be years before we get the complete picture. Even with such studies, given the breadth and complexity of its roles in the brain, the sub-clinical effects of vitamin D deficiency may be subtle, diffuse, and difficult to detect. This is particularly the case in the more moderate form of deficiency common in the US and other developed countries.

That being said, until then it’s probably safe to assume that vitamin D deficiency isn’t an ideal state for the developing brain.

References

Eyles DW, Burne TH, & McGrath JJ (2012). Vitamin D, effects on brain development, adult brain function and the links between low levels of vitamin D and neuropsychiatric disease. Frontiers in neuroendocrinology PMID: 22796576

Wagner CL, Taylor SN, Dawodu A, Johnson DD, & Hollis BW (2012). Vitamin D and its role during pregnancy in attaining optimal health of mother and fetus. Nutrients, 4 (3), 208-30 PMID: 22666547

Kesby JP, Eyles DW, Burne TH, & McGrath JJ (2011). The effects of vitamin D on brain development and adult brain function. Molecular and cellular endocrinology, 347 (1-2), 121-7 PMID: 21664231

Image via Serg64 / Shutterstock.