Continued from above:
What’s New
In 2020, a systematic review and metaanalysis that looked at 25 controlled studies found that vitamin D had a positive effect on depression and anxiety (Depress Anxiety. 2020 Jun;37(6):549-564).
Now, a systematic review and meta-analysis of 41 controlled studies, that included 53,235 people, has found that vitamin D reduces depression (Journal of Clinical Nutrition. 2022;nqac107).
Overall, vitamin D had a moderate positive effect in people with clinically relevant depressive symptoms. When the results were broken down, vitamin D did not seem to help people who were not depressed, but it significantly helped people with major depressive disorder. It also had a large and significant effect on depression during and after pregnancy.
The significant difference was greater in studies that excluded antidepressant drugs.
Studies using 2,000IU a day seem to be slightly more effective than studies using less, and taking over 4,000IU a day was more effective than taking less. For some reason, vitamin D seemed to perform better in people who are 65 years old or younger.
Vitamin D also provided a significant additional benefit when it was added to antidepressant drugs.
In studies that measured the antidepressant effect on the frequently used Beck Depression Inventory, vitamin D had a significant effect.
Vitamin D & Dementia: What We Knew
The first hints that vitamin D might be associated with cognition appeared in the research around the same time that the depression research started coming out.
Men between 40 and 79, it was found, have slower speed of information processing when they have lower levels of vitamin D (J Neurol Neurosurg Psychiatry 2009;80:722-729).
In seniors, low levels of vitamin D are associated with increased risk of cognitive impairment. People over 65 who have the lowest levels of vitamin D are more than twice as likely to suffer cognitive impairment than people with the highest levels (J Geriatr Psychiatry Neurol 2009;22(3):188- 95). And a study of 498 women over 75 found that the risk of Alzheimer’s is 77% lower in women who got the most D in their diet than it is in the women who get the least (J Gerontol A Biol Sci Med Sci 2012;67:1205-11).
Although there is less research, the same may be true for younger adults. An intriguing study found that both older and younger adults are at greater risk of cognitive impairment if their vitamin D levels are low (Neuropsychiatr Dis Treat. 2015; 11: 2217–2223).
All of this research led a summit of international experts to conclude that low vitamin D increases the risk of cognitive decline and dementia in older adults (J Intern Med. 2015 Jan;277(1):45-57).
A 2019 meta-analysis of 8 studies found that insufficient vitamin D was associated with a 9% greater risk of dementia and a 19% greater risk of Alzheimer’s. Vitamin D deficiency was associated with a 33% greater risk of dementia and a 31% greater risk of Alzheimer’s (Nutr Neurosci. 2019 Nov;22(11):750-759).
What’s New
In a very large, first of its kind study of vitamin D and brain health, researchers were able to look, not only at the association of vitamin D with brain health and dementia, but, for the first time, at the causal effect of increasing vitamin D.
They found that low vitamin D is associated with increased risk of dementia. People with vitamin D levels of 25 nmol/L (deficient) had 54% higher odds of dementia compared to people with levels of 50 nmol/L (optimal). They say that means that up to 17% of dementias could be prevented by increasing vitamin D to optimal levels of 50 nmol/L (Journal of Clinical Nutrition. 2022;nqac107).
Vitamin D & Autism: What We Knew
Vitamin D deficiency can contribute to autism, and supplementing vitamin D has been shown to significantly improve symptoms, especially for younger children (Nutr Neurosci 2017;20(5):284- 290).
Recent research has also suggested that vitamin D can improve hyperactivity and, when combined with omega-3 EFA’s, irritability in children with autism (J Steroid Biochem Mol Biol. 2019 Mar;187:9-16).
So, how much evidence is there for vitamin D?
What’s New
For the first time, researchers have conducted a meta-analysis of placebocontrolled studies to see if supplementing vitamin D can improve symptoms in kids with autism spectrum disorder. The systematic review included three studies that measured improvement on the Social Responsiveness Scale and the Child Autism Rating Scale. The news was good.
They found that after taking vitamin D, outcome scores were “dramatically elevated” in kids who took vitamin D compared to the control group. The difference in improvement was significant.
Encouragingly, the researchers concluded that “vitamin D supplementation improves the typical symptoms of autism spectrum disorder” and that it “is beneficial for children with autism spectrum disorder” (Clin Psychopharmacol Neurosci 2020;18(2):203-213).
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