Grey skies over Basingstoke.
In Britain, we do not get an awful lot of sun. From October to April the sun is not high enough in the sky for us to make Vitamin D from it, even if it were visible. There are vitamin D receptors in virtually all the cells in our body and it is becoming increasingly clear that vitamin D is as important to our health as omega 3 – and its shortage contributes to many ills. Rather than write several thousand words in an attempt to cover all of vitamin D’s glory, this blog will look at vitamin D and the brain and how shortage of the vitamin is being linked to impaired foetal brain development, development of PMS, SAD, part of the cause of Alzheimers, age-related cognitive decline, greater incidence of schizophrenia and a possible link to depression.
There are vitamin D receptors in at least 6 parts of the brain and collectively these areas cover attention, planning, language, memory formation, movement, motivation, circadian rhythms and hormone release. (( The areas concerned are prefrontal cortex, hippocampus, cingulate gyrus, thalamus, hypothalamus and substantia nigra))
There have been a couple of studies both reported in Scientific American on mental decline in relation to vitamin D deficiency. ((One was conducted by David Llewellyn, University of Cambridge, but I cannot trace its publication. The other is Lee DM, Tajar A, et al. Association between 25-hydroxyvitamin D levels and cognitive performance in middle-aged and older European men. J Neurol Neurosurgery Psychiatry 2009;80:722-729)) The study on 1,700 men and women, conducted by David Llewellyn, found that those severely deficient in D were more than twice as likely to have impaired mental function than those with optimum D levels. The other study conducted on 3,000 men across Europe also found that low D levels were associated with a slower information processing speed, especially in those over 60 years. When it comes to developing Alzheimers, the first place that symptoms are seen are in the hippocampus. ((The hippocampus is where memories are forged. It talks to the cortex and signals go back and forth between the two whilst memories become permanent. The hippocampus is also responsible for navigation and for finding short cuts etc – apparently London cab drivers have a very large right hippocampus)) Now the hippocampus has many receptors for the stress hormones and for Vitamin D and there is in-vitro evidence of cross-talk between the two. When under prolonged stress, the hippocampus is prone to shrinking. Many investigators consider D to be a neurosteroid – ie it reduces inflammation in the brain. So to keep the brain – and particularly the hippocampus healthy, then it would be good to keep optimal levels of D throughout life. (See footnote 4 for reference)
There is a very interesting review of studies by Elizabeth Bertone-Johnson ((Bertone-Johnson E R. Vitamin D and the occurrence of depression: causal association or circumstantial evidence. Nutr. Rev. 2009 Aug; 67(8):481-492. )) She was looking principally at evidence linking low D levels to depression – and her findings were mixed. However she did find that there is good evidence that low maternal levels of D were linked to poor brain development that persisted even into adulthood. And that children born during the winter and spring were more susceptible to schizophrenia, again this being linked to low maternal levels during pregnancy. Supplementation during early life may reduce this risk. The take home message is that if thinking of getting pregnant or already pregnant, supplementing with Vitamin D will build a better baby.
In 2005, Bertone-Johnson looked at the results of the Nurses Health study II, Harvard University and found that those with a higher intake of D from food sources had a 41% lower risk of developing PMS over the next 2-4 years compared with the women with the lowest intake. Now since food is not a particularly good source of D, then it would be very interesting to find out what would happen if women with PMS took good levels of D supplementation. A few pills will definitely be better than the monthly grumps. To back this up, another review on PMS found that women with PMS had significantly lower levels of D than the controls without PMS symptoms ((Thys-Jacobs S. Micronutrients and the premenopausal syndrome: the case for Calcium. J Am coll. nutr 2000; 19:220-7. By pre-menopausal, the term refers to women of child bearing age – ie before any menopause symptoms start. This study found levels of calcium and magnesium were also important.))
The jury is mixed on whether D helps alleviate SAD – seasonal affected disorder. The footnoted study compared vitamin D supplementation with photo-therapy given at a dose high enough to raise D levels. ((Gloth FM 3rd, Alam W, Hollis B. vitamin D vs broad spectrum photo-therapy in the treatment of SAD. J Nutr Health 1999; 3(1):5-7)) It found that D supplementation increased levels by 74%, whilst the photo-therapy increased it by 36% and the D supplementation group felt less depressed after the 1 month of therapy and the photo-therapy group felt no different. Although I regard repeating Charles Poliquin as a bit feeble, he did say that the risk of skin cancer from sunbeds was negligible if D levels were already high. So it seems that D supplementation is safer and more effective than sunbeds if SAD is a problem and it is desired to stop suffering from it.
Dosage is argued about, of course. Bertone-Johnson says in her review, footnote 4, that
in fact toxicity has not been observed with daily intakes [of vitamin D] up to 10,000 IU per day.
This is a high dose and, particularly in places far from the equator like the UK, it is a good idea to supplement with D throughout the year. Vitamin D has many more excellent effects on us than on only our brains. Just make sure the supplement is a natural D3 and not D2 which has poor bioavailability nor a man made D3. The best source of D in food is oily fish – but oily fish carries problems of heavy metal contamination and still cannot beat reliable bursts of sunlight – or high quality supplementation.
So it seems to me that although findings may be mixed about whether a shortage of vitamin D causes depression, low levels are associated with various other mental problems. If we just think about where the D receptors are found in the brain – and these areas are responsible for things like motivation, sleep wake cycles, hormone production, movement, memory etc then a shortage of this vitamin can only lead to decreased mental performance and increased aging in the brain. After all, what goes on in our noggins is still something of a mystery.