With the changing demographics of the U.S. population there is growing concern that complications primarily seen in the elderly will become an overwhelming health problem. Cognitive decline, with Alzheimer’s disease (AD) representing an advanced form, represents a substantial societal burden.
An intriguing question is “Can dietary interventions or supplementation affect the cognitive and mental problems associated with aging, by either preventing or delaying the problems?” There have been a series of recent publications to suggest, especially in the early stages, that indeed there are significant benefits to supplementation or dietary intervention.
The most recent study by Tan et al., 1 addressed the impact of dietary omega-3 fatty acids (the fish oils), particularly those rich in docosahexanoic acid (DHA). DHA levels in red blood cell membranes reflect dietary intake and these levels were compared to brain volume, as measured by MRI, and performance on cognitive tests. It was noted that individuals with the lowest levels of DHA in red blood cell membranes had significantly greater brain atrophy or shrinkage, and they performed significantly worse on tests for logical recall, verbal and visual memory, abstract reasoning, and attention and executive function.
The magnitude of the changes in the study by Tan et al., were dramatic 1. Essentially, those individuals with the lowest quartile of DHA levels had brains that were the equivalent of being two years older in mass and function. These results were independent of other factors that have known influences on brain structure and function e.g., homocysteine levels, physical inactivity and high body mass, and traditional vascular risk factors. In other words, DHA levels in blood was correlated with brain mass and function independently of other risk factors.
This investigation was conducted in middle-aged and elderly subjects free of clinical stroke and dementia, but yet at risk. What is less well appreciated is the effectiveness of omega-3 fatty acids in more advanced forms of the disease.
The conclusion that there is a functional correlation between diet and brain volume and cognition is supported by other studies assessing nutrient profiles. Bowman et al., noted that cognitive performance and brain size were favorable in individuals with high omega-3 fatty acids 2. Whereas high levels of trans fats were associated with compromised mental performance and brain atrophy.
Bowman et al., also noted that individuals with high plasma levels of B vitamins (B1, B2, B6, folate, B12) also displayed larger brain volumes and superior performance on cognitive tests 2. This relationship between B vitamins and mental health has been addressed in specific interventional studies with dietary supplementation with high dose B vitamins for two years (about 10x the current DV) 3, 4. In studies conducted at Oxford University, supplementation with B vitamins suppressed the rate of brain atrophy by a third and like brain volume in conjunction with improved cognitive function 3,4. In the Beyond Ageing Project 5, supplementation with folic acid and vitamin B12 for two years improved cognitive functioning in the elderly. Improved mood and psychological performance has been noted with a high dose B vitamin complex in males between the ages of 30-55 years, suggesting that these benefits are not limited to an aged population 6.
It is also important to note that the dose of B vitamins required for the lowering of homocysteine levels is substantially above the DV, suggesting supplementation is critical. It does appear that the effectiveness of B vitamin supplementation is minimal in subjects where cognitive decline has progressed to the point of diagnosis of Alzheimer’s disease 7,8. This indicates that these nutritional interventions need to be in place as preventative measures and not as a treatment for advanced disease.
Does the same mechanism account for the benefits of omega-3 fatty acids and B vitamins? It appears unlikely although both appear to exert positive outcomes by an action on the vasculature. In the Tan et al. study 1 the benefits were independent of homocysteine levels, whereas B vitamins work by lowering homocysteine levels, converting homocysteine to the amino acids methionine or cysteine. Additionally, the benefits of B vitamins are substantially greater in individuals with high plasma homocysteine levels 2,3. In other words, B vitamins are most effective in subjects with high homocysteine levels and the effectiveness of DHA is independent of homocysteine.
In conclusion, there are intense efforts to develop pharmaceutical interventions to treat dementia and cognitive decline, but unfortunately effective options are not currently available. On the other hand, it appears that maintaining cognitive health for as long as possible can be achieved with simple cost-effective dietary supplementation with omega-3 fatty acids like DHA, and B vitamins.
- Tan Z.S. et al., Red blood cell omega-3 fatty acid levels and markers of accelerated brain aging. Neurology 2012; 78: 658-664.
- Bowman G.L. et al., Nutrient biomarkers, cognitive function, and MRI measures of brain imaging. Neurology 2012; 78; 241-249.
- Smith A.D. et al., Homocysteine-lowering by B vitamins slows the rate of accelerated brain atrophy in mild cognitive impairment: a randomized controlled trial. PLoS One 2010; 5; e12244
- De Jager C.A. et al., Cognitive and clinical outcomes of homocysteine-lowering B-vitamin treatment in mild cognitive impairment: a randomized controlled trial. Int J Geriatr Psychology 2011; DOI: 10.1002/gps.2758
- Walker J.G., et al., Oral folic acid and vitamin B-12 supplementation to prevent cognitive decline in community-dwelling older adults with depressive symptoms – Beyond Agein Project: a randomized control. Am J Clin Nutr 2012: 95; 194-203.
- Kennedy D.O., et al., Effects of high-dose vitamin complex with vitamin C and minerals on subjective mood and performance in healthy males. Psychopharmacology (Berl) 2012: 211; 55-68.
- Aisen P.S. et al., High-dose B vitamin supplementation and cognitive decline in Alzheimer disease: a randomized controlled trial. JAMA 2008: 300; 1774-1783.
- Van Dyck C.H. et al., Cognitive and psychiatric effects of vitamin B12 replacement in dementia with low serum B12 levels: a nursing home study. Int Psychogeriatr 2009: 21; 138-147.