Vitamin D Is Full of Surprises
Vitamin D May Improve Mood
and Cognition in the Elderly
Deficiency of the “sunshine vitamin” during winter months
may also explain seasonal nature of the flu
By Richard P. Huemer, M.D.
Whoever wishes to investigate medicine properly
should proceed thus: in the first place to
consider the seasons of the year . . .
he curtain of blackness which has overfallen the outer world has also descended upon the inner world of our souls,” wrote the Arctic explorer Frederick Cook in 1898. “Around our tables … men are sitting about sad and dejected, lost in dreams of melancholy. For brief moments some try to break the spell by jokes, told perhaps for the 50th time. Others grind out a cheerful philosophy; but all efforts to infuse bright hopes fail.”
© iStockphoto.com/Johan Swanepoel
The interminable darkness of Arctic nights does not concern most Americans, but many are nonetheless sensitive to the shorter hours of daylight in wintertime. It’s called the “winter blues” or, in medspeak, seasonal affective disorder (SAD). It often produces weight gain and sleepiness as well as depression, and it afflicts more women than men. The main cause appears to be light deprivation, so it’s not surprising that a common therapy is exposure to sunlight or bright artificial light.
Why Sunshine Matters
The mechanism of SAD is somewhat of a mystery, but it appears to involve a disruption in the hormonal regulation of the normal day/night cycle, which affects sleep and mood, among other things. There is, however, another possible explanation, perhaps complementary to the hormonal hypothesis. It involves a deficiency of vitamin D caused by insufficient exposure to sunlight during winter.
As vitamins go, D is an odd duck. Most notable is that it’s not even considered to be a vitamin when we’re exposed to sunshine fairly regularly, because the sun provides all the vitamin D we need by synthesizing it in our skin. When we’re chronically sunshine-deprived, however, as during the winter months in northern climes (and under other circumstances as well), we must obtain our vitamin D from food or supplements. (For more on the oddities of vitamin D, see the sidebar.)
When Is a Vitamin Not a Vitamin?
When we’re out in the sun, soaking up the rays, that’s when. Even brief exposure to sunlight on our arms and legs—as little as 10 minutes three times a week—is sufficient to produce, in our skin, all the vitamin D our body needs. Thus, since we can make our own vitamin D, it can’t be a vitamin, can it? By definition, vitamins are essential organic micronutrients that can be obtained only from an external source: food.
What happens, however, when we don’t bag enough rays for our own good—during winter months in northern latitudes, e.g., or when we stay indoors all the time, or when we’re outdoors but are either overly clothed or near-naked but slathered in sunscreen? Or what if we’re getting old and our skin doesn’t make vitamin D as well as it used to? In all these circumstances, we may be deficient in vitamin D, so we must obtain it from food. Presto—it’s now a vitamin!
The oddity of vitamin D doesn’t stop there, however. Even when it’s a vitamin, it’s technically not a true vitamin, because it has no biological activity! This “almost” vitamin can be converted, however, to something that is biologically active. Let’s see how that works.
Solar ultraviolet radiation striking your skin converts a cholesterol derivative called 7-dehydrocholesterol to a compound called cholecalciferol, aka vitamin D3.* This compound enters your circulation and is converted in your liver to a derivative compound. That compound is converted in your kidneys (mainly) to a second derivative compound, called 1,25-dihydroxycholecalciferol, or 1,25(OH)2D3 for short. And that compound has the biological activity we loosely ascribe to “vitamin D”: it regulates various aspects of calcium uptake and metabolism, among other things, and it’s vital for the health of your bones and teeth. Chronic vitamin D deficiency produces rickets in children and osteomalacia in adults.
Considering how important it is, you’d think that 1,25(OH)2D3 would have a nickname, but it doesn’t, unless you count "1,25(OH)2D" or “1,25-dihydroxyvitamin D” as nicknames. So what happened to the 3? Any vitamin D term using just-plain-D is understood to mean that the compound in question could be either D3 or D2, or a combination of the two. That’s because both can be converted to a 1,25(OH)2D compound, and those two compounds have equivalent biological activities. As a supplement, however, vitamin D3 is preferable to vitamin D2 because it’s considered to be safer when taken in large amounts.
But where does vitamin D2 come from, anyway? It’s made in small quantities in some plants, but most is produced synthetically from its plant precursor, ergosterol, yielding ergocalciferol (vitamin D2). By contrast, our food sources of vitamin D3 are animal in origin, mainly fatty fish and fish liver oils. (We also get vitamin D from fortified milk and cereals.)
Both vitamin D3 and vitamin D2 are steroid derivatives called secosterols, and 1,25(OH)2D from either source is also a secosterol. Because its biochemical properties are steroidal, however, 1,25(OH)2D is called a steroid—a steroid hormone, in fact. Hormones are secreted by endocrine glands, whence they circulate throughout the body to perform their functions in various organs and tissues. Because 1,25(OH)2D is produced mainly in the kidneys, they can be considered to be endocrine glands in this case.
To summarize, vitamin D is an almost vitamin some of the time and not a vitamin the rest of the time. It’s an almost steroid and an almost hormone that has no biological activity, but it turns into an almost steroid that’s a real hormone with real biological activity. (You can’t make up stuff like this—it’s too weird.)
Vitamin D Is Involved in Brain Function
About one-quarter to one-half of all adults over age 60 are thought to be vitamin D-deficient, but little is known about whether they’re more likely to suffer from depression than those with healthy vitamin D levels. Vitamin D deficiency has, however, been implicated in various psychiatric and neurologic disorders, including SAD and depression. There is some evidence that supplemental vitamin D enhances wintertime mood in healthy subjects and that it can produce better results than those of bright-light therapy in treating SAD patients.
A growing body of literature suggests that vitamin D is involved in brain development and function, and a deficiency of the vitamin might be related to age-related neurodegenerative diseases. The elderly make only about 25% as much vitamin D in their skin as do 20-year-olds, and elderly women with Alzheimer’s disease have a higher incidence (74%) of vitamin D deficiency than the elderly population as a whole (they also have reduced bone mass, which could be related to vitamin D deficiency).
Vitamin D Deficiency Is Associated with Low Mood and Poor Cognition
Because vitamin D deficiency is a significant problem in the elderly and is easily treatable, researchers at the Washington University School of Medicine in St. Louis decided to assess vitamin D status in a group of community-dwelling older adults and to examine how it’s related to mood and cognition. They recruited 80 participants, of whom 40 had mild Alzheimer’s disease (AD) and 40 had normal cognitive function. They assessed mood and cognitive function by means of standard neuropsychiatric tests as well as clinical diagnosis, and they used a physical performance test to assess the patients’ overall functional status.
The researchers found that 58% of the participants had clinical vitamin D deficiency and that this was significantly associated with low mood and poor performance on two of the four tests of cognitive function. One of these tests was a sensitive screening tool for dementia, and the other was a strong predictor of progression to overt AD in those in whom the diagnosis is uncertain. There was no relation between vitamin D level and physical performance.
The authors emphasized the need for caution in embracing the association of poor cognitive performance with vitamin D deficiency, inasmuch as two of their tests did not support it. Moreover, the sample size was small, and it was not known whether vitamin D levels were fluctuating. Nonetheless, the study gave further support to the idea that low vitamin D levels are associated with impaired cognition and mood disorders in older adults.
Vitamin D Boosts Immune Function
Vitamin D’s apparent association with brain function should not be surprising. Almost all vitamins have multiple functions in the body, so a recital of a particular vitamin’s actions sounds like a carnival barker’s spiel for a patent medicine. Among the many actions that can be claimed for vitamin D are strong and varied effects on the immune system, and it has recently been suggested that vitamin D may underlie a certain seasonal variation in our immune-system function, just as with mood and cognition.
The subject is influenza; ironically, it was a psychiatrist, not an immunologist, who detected the apparent link with vitamin D. Dr. John J. Cannell had been giving high doses of vitamin D to virtually all the patients in his ward in California’s Atascadero State Hospital, an all-male, maximum-security prison for the criminally insane. When influenza struck the institution in 2005, ultimately afflicting 10% of the inmates, none of Cannell’s 32 patients caught it. A few months later, serendipitously, he read that UCLA researchers had found vitamin D to be a potent inducer of cathelicidins, a class of endogenous (made within ourselves) antibiotics. Light bulb!—it occurred to Cannell that vitamin D might have given his patients their flu resistance.
Vitamin D Deficiency May Be the Flu’s Seasonal Stimulus
Cannell’s insight had been foreshadowed in 1981 by Dr. R. Edgar Hope-Simpson, a renowned British general practitioner and self-taught epidemiologist. A keen observer of obscure facts, Hope-Simpson had noticed some curious geographic patterns in the global incidence of flu epidemics. They suggested to him that sunlight produced a “seasonal stimulus” that profoundly affected the course of the flu—but he had no idea what it was.
© iStockphoto.com/Rich Harris
Marshalling a large array of diverse and impressive evidence from the scientific literature, Cannell and his colleagues have now suggested that vitamin D could be Hope-Simpson’s long-sought seasonal stimulus.* Their hypothesis has elicited excitement, controversy, and, most importantly, a spate of new studies to try to resolve the matter. If it’s confirmed, it could be another example of a simple, inexpensive solution to a major health problem (unlike, say, flu vaccines, which are complex and costly). Examples of similarly cost-effective treatments abound in the realm of natural medicine.
Meanwhile, it seems as though our parents were right when they made us take nasty-tasting, vitamin D3-rich cod liver oil. If only we had known that we were absorbing “liquid sunshine”! (OK, we would still have hated it.) It probably spared us a respiratory infection or two, and it may even have made us a little less bratty.
It’s easy to agree with John Denver, who had an intuitive grasp of sunshine’s vitamin D-mediated effects, even if he may never have heard of cholecalciferol. He sang, “Sunshine on my shoulders makes me happy, sunshine in my eyes can make me cry. Sunshine on the water looks so lovely, sunshine almost always makes me high.” Amen.
- Wilkins CH, Sheline YI, Roe CM, Birge SJ, Morris JC. Vitamin D deficiency is associated with low mood and worse cognitive performance in older adults. Am J Geriatr Psychiatry 2006 Dec;14(12):1032-40.
- Raloff J. The antibiotic vitamin: deficiency in vitamin D may predispose people to infection. Science News, Nov 11, 2006, pp 312+317.
- Cannell JJ, Vieth R, Umhau JC, Holick MF, Grant WB, Madronich S, Garland CF, Giovannucci E. Epidemic influenza and vitamin D. Epidemiol Infect 2006 Dec;134(6):1129-40.
Dr. Richard P. Huemer received his M.D. from UCLA and did postdoctoral research in cancer immunology at CalTech. He has specialized in orthomolecular medicine for most of his career, has written and lectured extensively on alternative medicine, and has served on the editorial boards of professional journals. His published books include The Roots of Molecular Medicine: A Tribute to Linus Pauling and, with coauthor Jack Challem,
The Natural Health Guide to Beating the Supergerms.