Cognitive Decline and Vitamins

Abstract

Dementia and cognitive decline are concerning conditions, especially because they coincide with great uncertainty and have no cure. Scientists continue to explore these conditions in order to better understand their causes and identify potential treatments. Numerous interventions have been studied, from various diets to medications, supplements, and vitamins. There are many scientific and nonscientific articles that discuss what may lead to these conditions and how to address them. However, researchers are still trying to understand the actual and complex causes of dementia and cognitive decline; the available medications primarily focus on symptoms but do not “cure” the conditions (and also come with their own controversies); and much of the nonscientific literature contains recommendations that are not supported by strong empirical evidence. This article briefly reviews the data about how vitamin B and E in dementia and cognitive decline.

“A meta-analysis of 95 randomized controlled trials suggested that vitamin B supplementation is associated with slowing the rate of cognitive decline.”

Introduction

The rising prevalence of dementia is concerning, and both health care providers and members of the general population are actively searching for ways to prevent, mitigate, and treat this condition. Dementia is considered to be an umbrella term that includes cognitive, functional, and behavioral symptoms that are caused by specific conditions. The most common disease causing dementia is Alzheimer’s disease (AD), and other conditions which lead to dementia include vascular dementia, frontotemporal lobar degeneration, and lewy body dementia. Additionally, cognitive decline is not synonymous with dementia; the driving factor of dementia must be underlying progressive neurodegenerative disease. ¹ Understanding the differences between these conditions, whose names are often used interchangeably, is key when diving into the research regarding causes, treatments, and factors that can potentially prevent or mitigate these conditions and their symptoms.

There are many scientific and nonscientific articles available that discuss what may lead to dementia and how to address it. However, researchers are still trying to understand the actual and complex causes of dementia and cognitive decline; the available medications primarily focus on symptoms but do not “cure” the conditions (and also come with their own controversies); and much of the nonscientific literature contains recommendations that are not supported by strong empirical evidence. The most common causes of dementia that are potentially modifiable include: a lack of knowledge or education; hypertension; hearing impairment; smoking; obesity; depression; physical inactivity; diabetes; low social contact; excessive alcohol consumption; traumatic brain injury; and air pollution. Studies have also shown that diet and nutritional deficits are linked with developing dementia. ² Various studies analyze the effects of lifestyle interventions, including modifications to diet, and the impact of certain nutrients and vitamins on addressing dementia. Most of the studies focus on AD, and this article briefly summarizes some of the research regarding the efficacy of various nutrients and vitamins in the prevention or treatment of AD.

A systematic review was completed to study the “efficacy of using vitamin supplements in the diet as a solution to nutritional deficiencies and the prevention of dementia and mild cognitive impairment.” ³ In the 27 articles that met the inclusion criteria, the interventions that were reviewed were B complex vitamins, vitamin D, and vitamin E. The authors concluded that this systematic review suggests that vitamin B complex may delay and prevent risk of cognitive decline; vitamin E and ascorbic acid showed positive outcomes, but the number of studies were too low to reliably draw that conclusion; and the studies regarding vitamin D were too varied to make any findings. ³ In most of the systematic reviews that have been completed, the authors have found that different studies show differing results, and therefore additional research is needed to make definitive conclusions and recommendations. This article will briefly delve into B complex vitamins and vitamin E.

Vitamin B Complex Vitamins

One of the risk factors associated with dementia is elevated homocysteine levels, and studies have shown that vitamin B can reduce homocysteine levels. There are eight B vitamins including B1 (thiamin), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folate [folic acid]), and B12 (cobalamin). The B vitamins associated with dementia and cognitive decline include B1, B6, B9, and B12.

A meta-analysis of 95 randomized controlled trials suggested that vitamin B supplementation is associated with slowing the rate of cognitive decline. The analysis further suggested the following specific findings: vitamin B was especially beneficial when utilized as an early intervention; positive outcomes associated with vitamin B intake were stronger when used for a longer duration; and higher intake of dietary folate lowered the risk of incident dementia in the non-dementia age population. ⁴ In another systematic review and meta-analysis of cohort studies examining B vitamin status and risk of dementia, authors found that there is not sufficient to make recommendations for vitamin B. ⁵

In general, vitamin B from foods or even supplements are considered safe, and adverse effects are rare. Rare concerns include the risk of potentially masking B12 deficiency if an individual ingests high amounts of folic acid, as well as masking the risk of neuropathy with long-term, very high doses of B6.

Vitamin E

Vitamin E is a fat-soluble vitamin that is considered to be an antioxidant. It is found in plant based oils, nuts, seeds, fruits and vegetables. Various studies have explored the role of vitamin E in treating medical conditions including cardiovascular disease, neurodegenerative diseases, age-related macular degeneration, non-alcoholic fatty liver, and cancer. Most studies have concluded that there is not enough high quality evidence to draw conclusions about health outcomes related to vitamin E, and that there is a need for further research. ⁶

In AD, it is vitamin E’s antioxidant, anti-inflammatory, and immune-modulating properties that provide a theoretical basis for its beneficial role. Reduced circulating vitamin E levels have been linked to increased AD risk, and dietary intake of foods containing vitamin E may slow disease progression. ⁷ The Prevention of Alzheimer’s Disease by Vitamin E and Selenium (PREADVise) was a randomized trial in which 7540 men were given: 1) vitamin E; 2) selenium; 3) vitamin E and selenium; or 4) a placebo. They were evaluated for dementia with a 2-stage screen. The incidence of dementia (325 of 7338 men [4.4%]) was not different among the 4 study arms and it was concluded that neither selenium nor vitamin E supplementation prevented dementia in asymptomatic men. ⁸ In the Women’s Health Study—which was a randomized, double-blind, placebo-controlled trial—39 876 healthy women were given either vitamin E supplementation or a placebo. This large-scale study also found that there was no cognitive benefit associated with vitamin E supplementation. ⁹ As is the case with other vitamin and supplement studies, while there are smaller studies that do show potential benefits, further research is needed before health care providers can conclusively recommend vitamin E in the treatment or prevention of AD.

In general, vitamin E that is obtained from natural sources does not have toxic effects. People who are healthy and take supplements that contain vitamin E generally do not experience adverse effects; however there is a risk of excessive bleeding at doses of greater than 1000 mg daily and in people who are taking anticoagulants. ¹⁰

Additional Vitamins and Supplements

The list of vitamins and supplements that have been evaluated for dementia, cognitive health, and Alzheimer’s is extensive. This article briefly reviewed the data about vitamins B and E. There is potential benefit associated with some of these supplements. For example, within this journal as well as in many articles, omega-3 fatty acids have also been extensively evaluated, with research showing that supplements containing omega-3 fatty acids may have positive benefits for people experiencing early cognitive decline.^11,12 Other supplements which have been studied include ginkgo biloba and curcumin, neither of which have been conclusively shown to prevent or treat AD.

Conclusion

Dementia and cognitive decline are concerning, especially because they are associated with so much uncertainty and have no cure. Scientists continue to explore these conditions in order to better understand their causes and identify potential treatments. Numerous interventions have been studied, from various diets to medications, supplements, and vitamins.

As more research is conducted and published, we will better understand what role these vitamins and supplements truly play in treating AD and cognitive decline. In general, it is well established that a diet including these various vitamins and minerals has positive overall health outcomes, but more evidence is needed to truly determine which vitamins can be given as supplements and in what doses to treat or prevent dementia and cognitive decline. In the meantime, healthcare professionals can continue to provide evidence-based recommendations. If recommending supplements and vitamins, it is imperative that health care providers obtain a full medical and medication history to evaluate for deficiencies, toxicities, and interactions.