Diet and dementia risk – the evidence

There is growing evidence that a healthy diet is important for brain health and may help reduce the risk of developing dementia.  In particular, avoiding saturated fat and including unsaturated fats, fruits and vegetables and fish may be important for brain health.

Several prospective studies have found that high intakes of saturated and transunsaturated (hydrogenated) fats are associated with increased risk of dementia, while higher intake of polyunsaturated and monounsaturated fats is associated with reduced risk of dementia [1].

The omega 3 fatty acids contained in fish oils are thought to reduce inflammation in the brain and promote neurogenesis.  Results are conflicting as to whether omega 3 protects against dementia [2], but several studies have shown an association between higher fish consumption and lower dementia risk.

Antioxidants may help protect against oxidative damage, considered part of the pathology of Alzheimer’s disease.  Lower levels of antioxidants have been observed in people with Alzheimer’s in cross-sectional studies [3].  Prospective studies provide some evidence of lower dementia risk for higher intake of specific antioxidants, but results are conflicting [3]. 

Several studies have found a lower risk of dementia is associated with higher intake of fruit and vegetables and higher adherence to the Mediterranean diet [4].

Folate and vitamin B12 deficiencies have been associated with cognitive impairment and dementia.  However, whether increasing intake or using supplements of folate or vitamin B12 reduces the risk of developing dementia is as yet unknown [5].  Deficiencies or elevated homocysteine should be treated.

There is insufficient evidence to promote a specific diet for reducing dementia risk.  However, the Australian Dietary Guidelines recommend avoiding saturated fat and eating plenty of fruits and vegetables [6].  This general healthy diet is likely to help reduce the risk of dementia, in addition to cardiovascular disease and other health conditions.

References

1. Solfrizzi V, et al (2005) Dietary fatty acids intake: possible role in cognitive decline and dementia. Experimental Gerontology, 40:257-270
2. Issa AM (2006) The efficacy of omega–3 fatty acids on cognitive function in aging and dementia: a systematic review. Dement Geriatr Cogn Disord, 21:88-96
3. Scalco MZ & van Reekum R (2006) Prevention of Alzheimer disease. Encouraging evidence. Can Fam Physician, 52:200-207
4. Lee Y, et al (2009) Systematic review of health behavioral risks and cognitive health in older adults. Int Psychogeriatr, doi:10.1017/S1041610209991189
5. Woodward M, et al (2007) Dementia risk reduction: the evidence. Alzheimer’s Australia, Canberra
6. NHMRC (2003) Dietary guidelines for Australian adults. Commonwealth of Australia, Canberra