What We Know About Alzheimer's Disease and Nutrition

Julia Bird

June 15, 2018

Alzheimer’s Disease is globally the most common form of dementia in older people. The disease is characterized by a slow decline in cognitive function: the first sign of Alzheimer’s Disease is normally loss of memory, particularly of recent events [1]. Later on, the ability to make decisions, use language and write are impaired [1]. Patients cannot care for themselves in the final stages of the disease and are totally dependent on others. These cognitive and functional decreases mirror changes in the brain. Total brain volume shrinks, and there is a gradual breakdown in the brain tissue firstly in areas responsible for memory, then through the rest of the brain.  

Prevalence 

Alzheimer’s Disease and other related dementias currently affect around 24 million people worldwide. The number of cases have shown a steady increase over the past decades, and dementia now the global number 4 cause of death  in the world [2]. Due to the chronic nature of the disease, healthcare costs for treating patients are considerable, exceeding those from cancer or cardiovascular disease in high-income countries such as the United States [3].  

Risk Factors 

Unfortunately, we still do not know the exact underlying causes of Alzheimer’s Disease [4]. A complex combination of genes and environment determine the onset and progression of the disease. There is no cure, and current medication can only slow the progression of the disease or treat certain symptoms [5]. However, certain genetic and lifestyle factors are known to affect the risk of developing the disease [6]. It seems that there is overlap in many of the risk factors for diabetes, cardiovascular disease, and Alzheimer’s Disease. For example, smoking, physical inactivity and obesity tend to increase risk, while the use of statin medication (a first-line treatment for high cholesterol levels) could decrease risk according to several meta-analyses [7,8]. In addition, it seems that low social interactions, poor sleep, and a history of head injuries can increase risk, while engaging in intellectually stimulating activities can decrease the risk of developing Alzheimer’s Disease [6].  

Diet and Nutrition 

Diet and nutrition are also thought to play a modest role in the risk of developing Alzheimer’s Disease. For example, people with type II diabetes are at greater risk of Alzheimer’s Disease, and the development of diabetes is related in part to dietary intakes of energy-dense foods. Currently, risk of Alzheimer’s Disease is lowest in people who have a healthy dietary pattern, such as in the Mediterranean [9] or Dietary Approaches to Stop Hypertension (DASH) diets [10]. These diets follow standard dietary guidelines and contain plenty of fruit and vegetables, healthy fats from nuts and fish, are high in fiber and contain limited sugar [11]. On the other hand, the Western diet, containing higher intakes of red and processed meat, refined grains and sugar was associated with an increased risk of Alzheimer’s Disease [11].  

It is difficult to identify specific nutrients that affect risk of Alzheimer’s Disease. Ultimately, the total nutrient content of the diet seems to be important rather than specific components. Even so, several nutrients have been identified as potential influences of some of the processes that underlie Alzheimer’s Disease [12]. For example, the two antioxidant vitamins C and E may support antioxidant defences, which could protect the brain from oxidative stress in the highly metabolically active brain [12]. Vitamin C, along with folate, are found in higher concentrations in the brain [13,14], and researchers believe this may protect DNA in cells in the brain from damage [12]. Many of the B-vitamins are involved in the production of energy in cells, which is particularly important in the brain where energy needs are much higher than in other organs [15]. Deficiencies in thiamine, riboflavin, niacin, pantothenic acid, vitamin B6, biotin, vitamin B12 and folate impair the way that cells make their energy [12]. It is prudent to avoid deficiencies in the B-vitamins, for general health, and also the health of the brain.  

This Alzheimer’s and Brain Health Awareness month, think about how to nourish your brain by choosing a healthy lifestyle and diet.  

References

  1. Joubert, S.; Gour, N.; Guedj, E.; Didic, M.; Gueriot, C.; Koric, L.; Ranjeva, J.P.; Felician, O.; Guye, M.; Ceccaldi, M. Early-onset and late-onset Alzheimer's disease are associated with distinct patterns of memory impairment. Cortex 2016, 74, 217-232. 10.1016/j.cortex.2015.10.014.
  2. Collaborators, G.B.D.C.o.D. Global, regional, and national age-sex specific mortality for 264 causes of death, 1980-2016: a systematic analysis for the Global Burden of Disease Study 2016. Lancet 2017, 390, 1151-1210. 10.1016/S0140-6736(17)32152-9. 
  3. Kelley, A.S.; McGarry, K.; Gorges, R.; Skinner, J.S. The burden of health care costs for patients with dementia in the last 5 years of life. Ann Intern Med 2015, 163, 729-736. 10.7326/M15-0381.
  4. Jack, C.R., Jr.; Bennett, D.A.; Blennow, K.; Carrillo, M.C.; Dunn, B.; Haeberlein, S.B.; Holtzman, D.M.; Jagust, W.; Jessen, F.; Karlawish, J., et al. NIA-AA Research Framework: Toward a biological definition of Alzheimer's disease. Alzheimers Dement 2018, 14, 535-562. 10.1016/j.jalz.2018.02.018. 
  5. Sahoo, A.K.; Dandapat, J.; Dash, U.C.; Kanhar, S. Features and outcomes of drugs for combination therapy as multi-targets strategy to combat Alzheimer's disease. J Ethnopharmacol 2018, 215, 42-73. 10.1016/j.jep.2017.12.015.
  6. Reitz, C.; Mayeux, R. Alzheimer disease: epidemiology, diagnostic criteria, risk factors and biomarkers. Biochem Pharmacol 2014, 88, 640-651. 10.1016/j.bcp.2013.12.024. 
  7. Hersi, M.; Irvine, B.; Gupta, P.; Gomes, J.; Birkett, N.; Krewski, D. Risk factors associated with the onset and progression of Alzheimer's disease: A systematic review of the evidence. Neurotoxicology 2017, 61, 143-187. 10.1016/j.neuro.2017.03.006.
  8. Xu, W.; Wang, H.F.; Wan, Y.; Tan, C.C.; Yu, J.T.; Tan, L. Leisure time physical activity and dementia risk: a dose-response meta-analysis of prospective studies. BMJ Open 2017, 7, e014706. 10.1136/bmjopen-2016-014706. 
  9. Cao, L.; Tan, L.; Wang, H.F.; Jiang, T.; Zhu, X.C.; Lu, H.; Tan, M.S.; Yu, J.T. Dietary Patterns and Risk of Dementia: a Systematic Review and Meta-Analysis of Cohort Studies. Mol Neurobiol 2016, 53, 6144-6154. 10.1007/s12035-015-9516-4.
  10. Pistollato, F.; Iglesias, R.C.; Ruiz, R.; Aparicio, S.; Crespo, J.; Lopez, L.D.; Manna, P.P.; Giampieri, F.; Battino, M. Nutritional patterns associated with the maintenance of neurocognitive functions and the risk of dementia and Alzheimer's disease: A focus on human studies. Pharmacol Res 2018, 131, 32-43. 10.1016/j.phrs.2018.03.012. 
  11. Hu, N.; Yu, J.T.; Tan, L.; Wang, Y.L.; Sun, L.; Tan, L. Nutrition and the risk of Alzheimer's disease. Biomed Res Int 2013, 2013, 524820. 10.1155/2013/524820.
  12. Fenech, M. Vitamins Associated with Brain Aging, Mild Cognitive Impairment, and Alzheimer Disease: Biomarkers, Epidemiological and Experimental Evidence, Plausible Mechanisms, and Knowledge Gaps. Adv Nutr 2017, 8, 958-970. 10.3945/an.117.015610. 
  13. Hyland, K.; Shoffner, J.; Heales, S.J. Cerebral folate deficiency. J Inherit Metab Dis 2010, 33, 563-570. 10.1007/s10545-010-9159-6.
  14. May, J.M. Vitamin C transport and its role in the central nervous system. Subcell Biochem 2012, 56, 85-103. 10.1007/978-94-007-2199-9_6. 
  15. Porter, K.; Hoey, L.; Hughes, C.F.; Ward, M.; McNulty, H. Causes, Consequences and Public Health Implications of Low B-Vitamin Status in Ageing. Nutrients 2016, 8. 10.3390/nu8110725.