There’s a reason I took a detour to cover circadian rhythm disorders that don’t revolve primarily around vitamin D levels. The role sunlight plays in our biological clocks, which are directly tied to our physiological rhythms and thus, ultimately, to how we feel—sleepy or alert, hungry or full, hot or cold, and so on
—reinforces the importance of sunlight in our lives. But now let’s turn to how vitamin D plays directly into our mental health, starting with some interesting recent findings about vitamin D and dementia.
Dementia is among the most feared conditions of old age. No one wants to end up in a catatonic state characterized by the inability to communicate with others, recall memories, do simple math, recognize family members, and have a grasp on the goings-on in the world. Recently, two studies looked at the role of vitamin D in maintaining brain function. One examined evidence linking vitamin
D deficiency to brain dysfunction, and the other explored the role of vitamin D in preventing the collapse of mental performance. Taken together, many of these reports lay the groundwork for the hypothesis that vitamin D can reduce the risk of dementia.
The term dementia is a bit misleading because it’s not necessarily a single disease. Rather, dementia encompasses a spectrum of brain-related diseases, including Alzheimer’s disease, vascular dementia, Lewy body disease, and what’s known as frontotemporal dementia. The distinction between Alzheimer’s, a progressive, degenerative disease of the brain that causes impaired memory, thinking, and behavior and is probably the most commonly thought-of brain disease of old age, and vascular dementia is somewhat blurred. As many as 45 percent of those with dementia may have mixed dementia, or a combination of Alzheimer’s and vascular dementia. Vascular dementia is typically characterized by previous strokes, heart disease, hypertension, and diabetes.
The multifaceted nature of dementia means that there is no single, defined path to dementia—there are many, from inflammation and oxidative stress (otherwise known as free-radical damage) to small strokes and the death of neurons in the brain. And there are just as many risk factors or conditions that often precede dementia, including cardiovascular diseases, diabetes, depression, osteoporosis, and even dental cavities and periodontal disease. Not only do all of these increase the risk of dementia later in life, but notice that they are all associated with low levels of 25-vitamin D. The laboratory evidence includes several findings on the role of vitamin D in protecting the brain and reducing inflammation. People with Parkinson’s and Alzheimer’s, for example, have been found to have lower levels of 25-vitamin D.
It’s not that boosting levels of 25-vitamin D will reverse or cure dementia (though I would strongly suggest that patients already diagnosed with dementia keep their 25-vitamin D levels in the healthy range); the goal here is to maintain adequate 25-vitamin D levels to reduce the risk of the pathways that lead to dementia—namely, the ones I just mentioned.
A study done by University of Manchester scientists in collaboration with colleagues from other European institutions compared the cognitive performance of more than three thousand men between the ages of forty and seventy-nine years at eight test centers. This study, published in the Journal of Neurology, Neurosurgery, and Psychiatry, wound up being quite remarkable because it was the first to look specifically at the relationship between vitamin D and cognitive performance (for example, how fast you can multiply two times two). In
studying this large population sample, the researchers took into account potential interfering health and lifestyle factors, such as depression, education, and level of physical activity—all of which can affect mental ability in older adults. They found that the middle-aged and older men with the higher levels of 25-vitamin D showed the best mental agility. In fact, the men with higher levels of 25-vitamin D performed consistently better in a simple and sensitive neuropsychological test that documents an individual’s attention and speed of information processing.
The most unexpected finding of the study was that increased vitamin D and faster information processing were more strongly associated in men over the age of sixty, although the biological reasons for this remain unclear. The scientists concluded that vitamin D appears to have extraordinarily positive effects on the brain. The study also raises the possibility that vitamin D could minimize aging-related declines in cognition. We don’t know exactly how vitamin D and mental agility may be connected, but it wouldn’t surprise me to see future studies demonstrate vitamin D’s role in increasing certain hormonal activity or other biological reactions that ultimately protect neurons and that confer healthier brains.
It’s common for people with dementia to suffer disturbances in circadian rhythm, too, because of the damage occurring to their brains. A vicious cycle often begins, with the dementia-induced circadian rhythm disturbances exacerbated by indoor confinement and lack of exercise, both of which contribute to circadian rhythm disorders. A person with dementia typically has problems sleeping through the night and may wander out of bed and be confused. Sedatives have traditionally been used to treat circadian rhythm symptoms associated with dementia, but they are not particularly effective and have significant side effects. A number of studies have proven that bright-light treatments can be extremely helpful. As you can deduce on your own by now, bright-light therapy helps people with various forms of dementia by resetting their biological clocks, helping them become more alert during the day so they go on fewer night wanderings. In addition, recent research has shown that reducing circadian rhythm disturbances using bright-light treatments can improve the mental function of people with early stages of dementia.
From Womb to Older Age
This brain protection actually beings in utero—in the womb. Living at higher
latitudes has been shown to increase the risk of schizophrenia, the roots of which may take hold in a developing baby’s brain long before symptoms emerge in young adulthood. In fact, one of the causal links that have been made between schizophrenia and vitamin D is based on the theory that vitamin D deficiency in utero alters brain development. This helps explain schizophrenia’s odd characteristic of occurring more frequently in those born in winter or early spring. Dr. John McGrath, professor of pediatrics, biochemistry, and molecular biology at the Medical University of South Carolina, stated it perfectly when he said that vitamin D deficiency during pregnancy not only is linked to a mother’s skeletal preservation and her baby’s skeletal formation, but also is vital to the fetal “imprinting” that may affect chronic disease susceptibility later in life as well as soon after birth. That is to say, the vitamin D status of a pregnant woman directly impacts whether or not her child develops certain illnesses and diseases, from diabetes as an adolescent to osteoporosis and dementia as an elder.
To think that prebirth vitamin D determines our bone health for life and even our risk for cancer and autoimmune diseases, among a litany of other illnesses, is amazing. The connection wouldn’t normally leap out at you, but the mounting evidence is clear and persuasive. Even a child’s lungs are affected by a mother’s vitamin D levels. Asthma, a common childhood problem, has been linked to vitamin D deficiency in mothers. When the journal Clinical and Experimental Allergy in 2009 published an article entitled “Childhood Asthma Is a Fat-Soluble Vitamin Deficiency Disease,” laypeople and doctors alike took notice. The paper outlined a strong link between vitamin D and childhood asthma. (I’ll be going into much more detail about pregnancy and vitamin D in chapter 10.)
Given this deluge of new information, it’s no surprise that people often have more than one vitamin D-sensitive disease during their lives. The question you’re likely asking yourself now is, how bad is your deficiency?