A number of nutrients and dietary ingredients have been researched for their potential cognitive health benefits, including the long-chain omega-3 polyunsaturated fatty acids EPA and DHA, vitamins C and E, B vitamins, and antioxidants, wrote Dr Pascale Barberger-Gateau from the University of Bordeaux in France and author of the new review in the European Journal of Clinical Nutrition.
However, many of the randomized clinical trials using nutritional supplements have been “disappointing” so far, said Dr Barberger-Gateau, which may be due to “intrinsic limitations” in study designs or a lack of an effect of the supplements.
“Despite the disappointing results of nutritional interventions on cognition so far, there is considerable room for improvement and more evidence-based knowledge on the link between nutrition and cognitive decline in older persons,” she wrote. “Trials with nutritional supplements should learn from RCTs with drugs regarding biomarkers of disease progression for inclusion criteria and outcomes.”
Three new nutrients highlighted by Dr Barberger-Gateau for increased attention are DPA and vitamins D and K.
“[Omega-3] DPA is mainly found in fatty fish and could contribute to the apparently protective effect of fish consumption against cognitive decline,” she wrote. “The metabolism and biological functions of DPA are still poorly understood. Supplementation with pure n-3 DPA induced a significant rise in the proportions of EPA and DHA in plasma triacylglycerides, suggesting that DPA may act as a reservoir of the major long-chain n-3 PUFA in humans.
“In healthy humans under their spontaneous diet, n-3 DPA is found in non-negligible amounts in cerebrospinal fluid (CSF) and positively correlated with total plasma n-3 PUFA.”
The link between vitamin D and brain health is not new. Indeed, a 2008 review by Bruce Ames and Joyce McCann from the Children's Hospital and Research Center Oakland highlighted the role of the vitamin in maintaining brain health, noting the wide distribution of vitamin D receptors throughout the brain.
According to the review (FASEB Journal, Vol.22, pp. 982-1001), the vitamin has been reported to affect proteins in the brain known to be directly involved in learning and memory, motor control, and possibly even maternal and social behavior. Depression in the elderly is highly prevalent and can increase the risk of medical illnesses, worsen the outcome of other medical illnesses, and may increase mortality.
“Several RCTs assessing the impact of vitamin D on cognition, either as primary or a secondary outcome, are in progress,” noted Dr Barberger-Gateau. “If ongoing RCTs yield more positive results with higher doses of vitamin D, improvement of cognitive function would be a beneficial side-effect of systematic vitamin D supplementation in deficient individuals.”
Vitamin K is the last of the three nutrients listed in the review, which noted that some vitamin K-dependent proteins contribute to brain function, “notably Gas6 which is expressed in the hippocampus of adult rat and contributes to survival of neurons and microglia”. Despite this, studies exploring the role of vitamin K in cognition are lacking, she said.
Better targeting and technology
Dr Barberger-Gateau noted that some of the “disappointing” results from clinical trials may be due to a lack of sensitivity for the outcomes, while selecting suitable biomarkers could enhance the studies.
“The considerable development of omics technologies will give new insight into the potential metabolic pathways involved in the link between nutrition and brain functioning and provide new integrative biomarkers that will help understand their effects,” she wrote.
“For example, lipidomic profiling recently identified a set of 10 lipids in plasma that predicted short-term conversion to [amnestic mild cognitive impairment] or [Alzheimer’s disease] with a very high accuracy in healthy elderly persons. These phospholipids have essential structural and functional roles in cell membranes, suggesting that their peripheral blood levels could be an early correlate of neurodegeneration in [Alzheimer’s disease]. Moreover, this specific lipid profile could be used as inclusion criteria in more efficient RCTs of nutritional interventions with lipids for the prevention of cognitive decline.”
‘Not enough people are talking about nutrition and cognition’
A recent review in Nutrition by Hasan Mohajeri, PhD, Barbara Troesch, PhD, and Peter Weber, MD, PhD, from DSM Nutritional Products Ltd. (Basel, Switzerland) noted that many members of the general population consume inadequate amounts of various vitamins and omega-3s, even in industrialized countries, which may increase the risk of mild cognitive impairment (and subsequently increase the risk of developing Alzheimer’s disease).
Brain health ingredients
To view NutraIngredients-USA’s gallery of the top ingredients for cognitive health, please click HERE.
Commenting on the paper, Dr Michael McBurney, PhD, VP Science, Communication & Advocacy – DSM Nutritional Products, told NutraIngredients-USA last month that "not enough people are talking about nutritional status and brain function".
“The pathogenesis of cognitive loss and dementia is not understood and needs to be. The brain is very active metabolically. Vitamins serve as co-factors of glucose metabolism and antioxidants, quenching free radicals to prevent peroxidation of polyunsaturated acids, e.g. docosahexaenoic acid (DHA),” said Dr McBurney.
Source: European Journal of Clinical Nutrition
Published online ahead of print, doi: 10.1038/ejcn.2014.177
“Nutrition and brain aging: how can we move ahead?”
Authors: P. Barberger-Gateau