Examining Vitamin D's Effect on the Brain
10 of 12 in Series: The Essentials of Vitamin D Benefits
Recent studies suggest that vitamin D may play a role in brain development and brain health from birth to old age. Interesting new associations link high vitamin D status to the prevention of certain psychiatric conditions and in the development of Alzheimer’s disease.
Vitamin D may play a role in various developmental stages and disease states, including autism, Alzheimer’s disease, Parkinson’s disease, depression, and seasonal affective disorder.
Vitamin D and normal brain development
The first question researchers asked is whether there is any reason that vitamin D could be affecting the brain. They did these studies in isolated cells and in studies of animals that have brain function similar to humans. Consider some of the evidence:
Vitamin D receptors and the enzyme that converts 25-hydroxyvitamin D into calcitriol are present throughout the brain.
Calcitriol alters the expression of many genes in brain cells. This includes neurotrophins, proteins in the brain that help nerve cells survive and become more specialized.
Calcitriol helps nerve cells turn into the specialized cells that are needed throughout the brain.
The brains of animals that were born to vitamin D–deficient mothers show abnormal growth and development. Severe vitamin D deficiency in animal models may cause abnormal brain development indirectly because of calcium deficiency.
Evidence of the important role vitamin D plays in the development of the brain continues to accumulate, but more study is needed. The remainder of this article provides a look at the evidence for vitamin D in conditions that affect the brain.
Vitamin D and autism
The origin of autism is unknown, but the incidence of this disease has increased significantly over the last 30 years. Autism now affects 1 in every 110 children. Certain evidence suggests that vitamin D could play a role in its onset.
Autism is a mental disorder that begins in the first three years of life. It has the following characteristics:
The child doesn’t develop or is slow to develop communication skills.
The child doesn’t interact with other children.
The child performs repetitive actions, like flapping the hands or continually stacking objects.
The child doesn’t make eye contact.
As the child gets older, he may have severe tantrums.
Up to 10 percent of those with autism have unusual talents, like amazing memorization ability.
The suggestion that vitamin D might play a role in the development of autism comes from a number of observational studies:
Autism is more common in areas with less sun. Children born in winter are much more likely to develop it than children born in summer.
Autism is more common in African-American children, whose mothers tend to have the lowest levels of vitamin D.
Active vitamin D prevents the production of cytokines in the brain that have been associated with autism.
Maternal consumption of vitamin D during pregnancy has been associated with reduced symptoms of autism in the child.
Scientists will need to establish a firmer connection before any recommendations can be considered for using vitamin D to prevent or diminish autism in children.
Vitamin D and Alzheimer’s disease
Alzheimer’s disease is another brain disease that seems to be increasing rapidly in prevalence. It now affects more than five million Americans. Whereas diseases like strokes, heart disease, and cancer are declining, the number of people affected with Alzheimer’s disease is expanding.
This fact may have to do with the aging population, but maybe there’s more to it than that. Some data even point to a possible role for vitamin D in the onset of Alzheimer’s disease. But for now, the evidence for recommending vitamin D supplementation in Alzheimer’s disease is not strong.
Alzheimer’s disease (AD) is a gradual loss of mental faculties that usually begins after age 65 but can occur earlier. Most people die an average of 7 years after the disease begins. Fewer than 5 percent live longer than 14 years.
Consider some of the major signs and symptoms, in the order in which they generally occur:
Loss of recent memory
Loss of language
Loss of long-term memory
Loss of control of body functions
As the disease progresses, the patient goes from being independent to being completely dependent upon caregivers. Memory deteriorates to the point that the person may not recognize children and spouse any longer. The patient is apathetic and can’t feed or care for himself. Often Alzheimer’s patients eventually die of an infection like pneumonia or from infected bed sores.
Some of the evidence that Alzheimer’s disease may be a vitamin D deficiency disease, at least in part, includes the following:
Alzheimer’s disease is found much more often in temperate than in tropical climates.
Patients with AD have lower levels of vitamin D in their blood than the normal population.
Among patients with Alzheimer’s disease, those with higher levels of vitamin D perform better on tests of knowledge.
It may be, however, that low serum 25-hydroxyvitamin D levels are a reflection of the poor health, diet, and lack of outdoor physical activity of people with dementia and not that lack of vitamin D leads to dementia. That’s not a subtle point — if the low vitamin D status comes after the disease, then giving more vitamin D won’t have any impact on their neurological disease.
Vitamin D and Parkinson’s disease
Parkinson’s disease (PD) is a brain disease that affects motor skills instead of learning, knowledge, and memory. Currently, about one million people in the United States are believed to have Parkinson’s disease, but an additional three to four million people don’t know they have it.
The connection between Parkinson’s disease and vitamin D is about as strong as the link between vitamin D and Alzheimer’s disease. Researchers have found some promising associations.
Parkinson’s disease begins over the age of 50. The condition is believed to result from the loss of dopamine-producing brain cells. Dopamine is a brain chemical that is essential to the transmission of impulses from one nerve to another.
Consider the major symptoms of Parkinson’s disease:
Trembling of the hands, arms, legs, jaw, and face. The tremor occurs when the patient is at rest and disappears when the limb moves.
Stiffness of the arms, legs, and trunk. The patient may feel pain in the joints; when they’re moved, they have a stop/go feel to them.
Slowness of movement. The patient shuffles along and has difficulty executing any complex movement.
Impaired balance and coordination. The patient tends to fall, especially in the late stages of the disease.
Several drugs can help reduce the signs and symptoms, but nothing is curative. If drug therapy is inadequate, surgery can be performed either to produce lesions in certain parts of the brain or to do deep brain stimulation to send impulses into the brain.
Experts don’t understand just how vitamin D might play a role in PD. Some of the suggested explanations include the following. Vitamin D
Protects nerves by preventing oxidation that kills nerve cells.
Decreases immune damage to nerve tissue.
Improves nerve conduction.
Decreases damage to nerve cells that produce dopamine by toxins.
Unfortunately, there is also a lot of conflicting data related to vitamin D and PD that make it hard to fully embrace the relationship. Still, the evidence shows that it may be important to keep your serum 25-hydroxyvitamin D levels higher than 20 ng/ml or 50 nmol/L — the same amount recommended to protect bone health.