According to The World Alzheimer Report 2011, three-quarters of the estimated 36 million people with dementia worldwide do not have a formal diagnosis. Understanding the condition and its key symptoms are therefore paramount for early diagnosis and intervention. As such, the theme for World Alzheimer’s Day 2011 is ‘Faces of dementia’ which aims to promote increased awareness of the condition whilst also highlighting the need for support and care for people with dementia and their carers. Certainly, preventing or postponing the onset of dementia and delaying or slowing its progression would lead to a consequent improvement of health status and quality of life in older age.
Whilst the dramatic increase in the prevalence of dementia over the last century is in part due to an increase in average lifespan, it is also, interestingly, associated with specific areas of diet, including changes in our dietary fat intake. Increased intake of saturated fatty acids is believed to have negative effects on age-related cognitive decline and mild cognitive impairment. In contrast, present, epidemiological evidence suggests that there is a possible association between fish consumption, monounsaturated fatty acids and polyunsaturated fatty acids (PUFA; in particular, omega-3 PUFA) and a reduced risk of cognitive decline and dementia. As such, adopting a Mediterranean-type diet – low in saturated fat and high in mono and polyunsaturated fats – may be key dietary changes that can help to protect the brain from decline.
Omega-3 fatty acids found in oily fish and fish oils play a vital role in brain growth and development. The incorporation of long-chain fatty acids into neuronal membranes lowers the total cholesterol fraction, leading to increased membrane fluidity, which is essential to maintain the normal nerve function and neurotransmission crucial for learning, memory and other complex cognitive processes. Further to this, alterations in gene expression induced by these fatty acids influence the normal lifespan of our neurones and a higher intake of long-chain omega-3 fatty acids has been shown to be associated with increased overall brain gray matter volume.
It is easy to think of dementia as a normal part of growing old. It is well established however, that dementia is not necessarily a stage of life associated with increasing age. Diet, and especially food choices made in our early and mid years, plays a direct role in influencing the complex mechanisms that are involved in normal brain structure and function. Approximately 50% of neuronal membranes are composed of fatty acids, with the content of the protective myelin sheath as much as 70%. The molecule and fatty acid content of membranes play an important role in fluidity; for example, high membrane cholesterol content significantly reduces the fluidity index affecting neuronal function. Myelin integrity is also significant and long-chain polyunsaturated fatty acids are directly and centrally involved in the active phase of myelin synthesis; deficiencies can result in dysfunction in the myelination process.
Reduced dietary intake of specific nutrients and micronutrients is believed to not only increase the risk of early-onset dementia and more severe forms of dementia, but also to exacerbate existing dementia symptoms. Dietary inclusion of specific nutrients such as long-chain omega-3 in the form of highly purified supplements may not only provide an alternative and early intervention approach to dementia risk, but also may limit further developmental damage, such as cognitive loss, and improve long-term therapeutic outcomes in those individuals with early-onset dementia, as well as dementia in its most progressive stages.
Solfrizzi V, Panza F, Frisardi V, Seripa D, Logroscino G, Imbimbo BP, Pilotto A. Expert Rev Neurother. Diet and Alzheimer’s disease risk factors or prevention: the current evidence. Expert Rev Neurothe 2011 11:677-708.