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Blog #9 What is Vitamin D?

In my previous blog, I introduced a study from Canada regarding physical exercise, cognitive training, and vitamin D intake. According to the study, vitamin D intake didn’t affect the participants’ cognitive function*1.

Vitamin D is probably most known for its role in bone health. Moreover, it is an anti-inflammatory, antioxidant, and neuroprotective. But to be honest, I didn’t know much about the association between vitamin D and cognitive impairment. I was lucky enough to find this very comprehensive review on an overview of its association *2. According to this article, in conclusion,

1)Animal or cellular studies suggested that vitamin D has multiple functions in the central nervous system. 2)Cross-sectional studies (studies that examine the data of a specific population in a specific time) report that vitamin D concentrations are lower in people with cognitive impairment and dementia. However, reverse causality can be a possibility (because the person developed Dementia, which affected their diet, that’s why their vitamin D level is low, not vice versa). 3)Association of low vitamin D with an increased risk of cognitive decline still has no answer. 4)Trials examining the effect of vitamin D supplementation on cognitive outcomes, have produced mixed findings. 5) No consensus over the dosage of vitamin D and no optimal age of treatment for people at risk are identified. 6)More studies are needed! Indeed, we still don’t have definitive answers regarding the relationship between vitamin D and cognitive decline.

The lack of improvement results of vitamin D in the study in my previous blog, might be related to the fact that there were only 4 participants who were severely deficient in vitamin D while others were not deficient in vitamin D, as the authors mentioned in the study.

In the US, according to the National Institutes of Health *3, average daily recommended amounts of vitamin D are; if one is between 14 and 17 years old, they need to take 15 µg (micrograms). And, if one is older than 71 years, they should be taking 20 µg. A blood test can measure the amount of a form of vitamin D, called 25-Hydroxyvitamin D. If the levels are below 30 nmol/L (nanomoles per liter), they are too low, and if the levels are above 125 nmol/L, they are considered as too high. Both cases (too high/too low) might affect your health in very negative ways. Whether or not vitamin D levels affect our cognition, insufficient levels of vitamin D, for example, can increase the risk of fractures due to osteoporosis especially among the elderly population.

Of course, it is a good idea to pay attention to one’s own levels of vitamin D— both too much and too little are not good for our health. But, if a person’s level is among the normal range, I think that it is wise to just keep getting vitamin D from your consistent healthy diet, and not from the dietary supplements. Vitamin D rich foods are, for example, fatty fish such as salmon, some mushrooms, eggs, milk, soy milk, and so on. And it’s also vital not to forget to regularly spend some time in the sun since our body makes vitamin D when our skin gets exposed to sunlight. I live under the gray skies of Washington State, so whenever the sun comes out, I make sure to apply some sunscreen and go directly outside!!

*1 Montero-Odasso M, Zou G, Speechley M, et al. Effects of Exercise Alone or Combined With Cognitive Training and Vitamin D Supplementation to Improve Cognition in Adults With Mild Cognitive Impairment: A Randomized Clinical Trial. JAMA Netw Open.2023;6(7):e2324465. doi:10.1001/jamanetworkopen.2023.24465

*2 Sultan S, Taimuri U, Basnan SA, Ai-Orabi WK, Awadallah A, Almowald F, Hazazi A. Low Vitamin D and Its Association with Cognitive Impairment and Dementia. J Aging Res. 2020 Apr 30;2020:6097820. doi: 10.1155/2020/6097820. PMID: 32399297; PMCID: PMC7210535.

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