A study released from the cold Finland shows that baby boys given vitamin D supplements had a reduced risk of schizophrenia (a form of psychosis). Interestingly, the same benefit was not observed in the girls. The boys were given 2,000 units of vitamin D (eight times the U.S. RDA for vitamin D for kids). This further reinforces the fact that all children need vitamin D supplements if they are not exposed to sunshine, especially breast fed babies as there really isn't any significant quantity of usable vitamin D in breast milk.
When you live in cold, far northern countries like Finland you really don't have any practical options to get vitamin D the way God designed you to get it, by exposing your skin to sunshine. If you are in a similar situation and need a vitamin D supplement, cod liver oil is clearly your best choice as it is balanced with natural vitamin A and that decreases any potential vitamin D toxicity.
If you have any of the following conditions though:
Then you will want to consider a high-quality vitamin D supplement to improve your vitamin D levels, like the vitamin D we use in our office. It is emulsified and much better absorbed than vitamin D capsules. If you use this though it is very important that you monitor your levels with vitamin D testing.
Following is an exclusive interview that we recently conducted with Dr. John McGrath, the lead researcher of this study. He discusses the role of vitamin D in health and offers some keen insights into the study findings.
Schizophrenia Research April, 2004;67(2-3):237-45
Dr. John McGrath
Did the study participants who did not receive vitamin D supplementation have their vitamin D levels measured, and if so, were they found to be vitamin D deficient?
No, alas they did not directly measure 25 hydroxyvitamin D in either the supplement nor nonsupplemented groups. Based on the relatively high rates of hypovitaminosis in North Finland, we could assume that the proportion of nonsupplemented kids who had hypovitaminosis D would be HIGHER than the supplemented kids (i.e. nonsupplement becomes a proxy marker of hypovitaminosis D).
Was there any association between a reduced risk of other mental disorders beyond schizophrenia and vitamin D supplementation?
No, we looked at other disorders and found no association with vitamin D supplementation.
Would vitamin D supplementation later in life, perhaps during later childhood or early teenage years, provide any protection against schizophrenia?
We have no evidence one way or the other on this issue. Our initial hypothesis related to prenatal vitamin D only, but based on recent animal experiments we wonder if the first year of life is also a critical window (during which low vitamin D may adversely impact on brain growth). So, the Finnish study was useful to help us look at the first year post-natal.
I also am attracted to the idea that optimal vitamin D levels in the first year of life may 'rescue' children who had prenatal hypovitaminosis D. We have no evidence for this, but it is an interesting speculation. We give children vitamin K at birth to reduce the risk of a rare bleeding disorder--maybe we should think about vitamin D as well.
Would people with schizophrenia benefit from taking vitamin D supplements?
I do not believe that hypovitaminosis D during adult life increases the risk of developing the disorder, nor do I think that people with established schizophrenia would have improved mental state if their vitamin D levels were optimized. However, many patients with schizophrenia have poor nutrition anyway, and may also have low vitamin D. While it may not help their mental state, it may help other health outcomes (reduced risk of osteoporosis, reduced risk of various types of cancer, etc.).
Why do you think there was no association found in females?
I think that this is a feature of the low power of this study. Thus, the finding is INCONCLUSIVE, rather than negative. Schizophrenia comes on later in women, and thus the members of the cohort have not gone through enough of their period of risk in order to develop the illness.
The study was driven by a directional, a priori hypothesis, and has a reasonable degree of biological plausibility. However, the findings are very 'fragile' due to low power (low number). Thus, while the findings are very interesting, it is much too soon to be making any recommendations from a public health perspective.
How does low vitamin D during early life increase the risk of schizophrenia?
Low prenatal vitamin D leads to increased cell division and reduced cell death during brain development. In animal experiments, we have found that prenatal hypovitaminosis D leads to different shaped brains, larger ventricles, and major changes in various growth factors (e.g. nerve growth factor). This PDF article from Neuroscience reports these findings.
Is vitamin D supplementation during the first year of life something you would recommend to most people to reduce the risk of schizophrenia?
No--not to most people. In many countries sunlight exposure is more than enough to make vitamin D. In women living at high latitudes, I would recommend they consider vitamin D supplements during winter and spring. For dark skinned women at high latitudes, or women who are veiled, they would need supplements all year around. There are dangers in taking too much vitamin A if one relies on multivitamins. We really need pure vitamin D supplements with adequate does (e.g. 2000 IU per day).
Would people living in regions exposed to more intense sunlight tend to benefit less from vitamin D supplementation during the first year of life as compared to the participants who lived in Northern Finland?
Yes, exactly. It may not be relevant in other climates.
What type of vitamin D supplement was used in the study? What kind do you believe is most beneficial? As far as I know, most got pure cholecalciferol (D3). They were told to give 2000 IU per day, which was probably the correct dose (they dropped the dose in later years).
Are any other studies planned to further explore this finding?
Yes, we have lots of work to do. We have looked in banked maternal sera (PDF), but this finding was inconclusive. We hope to look at other samples in the years to come.
Dr. John McGrath received his medical degree from the University of Queensland. He is a professor with the Department of Psychiatry, University of Queensland, and also has an adjunct position with the School of Biomolecular and Biomedical Sciences, Griffith University. He has won several national and international awards including the Premier's Award for Medical Research in 2002. In 2003 he was given a Centenary Medal for 'distinguished contribution to mental health research and support'. He is on the editorial boards of several international journals. Over the last 10 years he has published over 100 papers, books and book chapters and attracted over $3.8 million from competitive, peer-reviewed funding agencies. Research interests include risk-factor epidemiology, the primary prevention of schizophrenia, and the neurobiology of schizophrenia.