Memory loss is a symptom of dementia while Alzheimer’s disease (AD) is the most common cause of dementia. AD has been a social and economic burden worldwide. Unfortunately, there is no drug or treatment can cure or slow down the progression of AD so far. Evidence suggests that diets rich in protein, dietary fibre, vitamins, flavonoids or phenolics could enhance human’s memory and reduce the risk of AD through direct effects on amyloid beta (Aβ, a hallmark of AD) and consequently influence AD pathogenesis. This paper has reviewed the pathology, mechanisms of Aβ mediated toxicity, contributing factors, diagnosis and therapeutics of AD. The diets which are beneficial to reduce AD risk have also been discussed in detail to provide a health advice.