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Study under review: Effects of vitamin D3 supplementation on cognition and blood lipids: a 12-month randomised, double-blind, placebo-controlled trial
Introduction
Dementia is characterized by the inability to perform daily activities due to a decline in memory, reasoning, and thinking[1]. This condition affected 47 million people in 2015[2] and is expected to almost triple in prevalence by the year 2050. One major risk factor for dementia is mild cognitive impairment (MCI)[3], which indicates some problems with cognition that are unexpected for the person’s age, but that don’t strongly impact daily life. Many people with MCI remain stable or even improve, but over half go on to develop dementia.
While there is currently no effective drug treatment for the condition,early detection and changes in lifestyle[4] or diet[5] could help slow progression. Early intervention could also involve supplementation, such as with the fat-soluble vitamin D, which has demonstrated a role in brain health and function[6]. Vitamin D appears to influence[7] neurotransmission, vascularization, and amyloid-beta and tau protein accumulation, all of which can play a role in Alzheimer’s-related dementia. Moreover, vitamin D deficiency is associated with a more than two-fold increased risk[8] of developing dementia, suggesting a role for vitamin D in the prevention of neurodegenerative disease[9]. However, the mechanism is still unclear and results have been inconclusive[10] regarding the role of vitamin D[7] supplementation for cognition.
Another aspect of dementia related to lifestyle and nutrition that may be of interest is blood lipids. Almost all major classes of lipids have some correlation[11] with Alzheimer’s disease pathogenesis, the leading cause[12] of dementia among elderly people. Individuals with cognitive impairments appear to have higher[13] serum total and LDL-cholesterol than sex- and age-matched non-demented peers, while decreased risk of dementia has been associated[14] with higher plasma HDL-cholesterol, suggesting predictive potential for risk of dementia, although there’s also evidence against this[15].
While cholesterol and vitamin D share a common 7-dehydrocholesterol pathway in the liver[16], which is sketched out in Figure 1 and is consonant with vitamin D’s possible influence on blood lipids, the role of vitamin D in lipid metabolism is controversial. A meta-analysis of 12 RCTs[17] examining vitamin D supplementation showed no significant changes for triglycerides, total cholesterol, and HDL-cholesterol. In addition, how these all come together to influence dementia risk is unclear.
The authors of the study under review aimed to investigate the potentially preventive effects of vitamin D on cognitive decline and blood lipids in a randomized, double-blind, placebo-controlled trial of elderly participants with MCI.
Dementia is characterized by the inability to perform daily activities due to a decline in memory, reasoning, and thinking. With a rapidly rising prevalence and no effective treatment, intervening during early warning signs such as mild cognitive impairment (MCI) may help slow progression. Recently, vitamin D research has suggested prevention against neurodegeneration and blood lipids might correlate with mental decline, but interactions between the two and their influence on cognition is unclear. The authors of the study under review aimed to investigate the potential prevention of cognitive decline attributed to vitamin D and any changes in blood lipids in a randomized, double-blind, placebo-controlled trial.
Who and what was studied?
What were the findings?
What does the study really tell us?
The big picture
Frequently asked questions
What should I know?
Other Articles in Issue #48 (October 2018)
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Mini: Vitamin D, dementia, and lipids: the ApoE connection
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