Figure 2.

Proposed factors involved in the negative effects of a vegan diet in Alzheimer’s disease (AD). A vegan diet can easily lead to a deficiency in vitamins B12 and D if unsupplemented. Vitamin B12 deficiency accelerates cognitive decline, while a lack of vitamin D increases oxidative stress and Aβ and tau pathology. An insufficient intake of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on the other hand, reduces brain glucose utilization. These factors can lead to the worsening of AD. Furthermore, these vitamin deficiencies lead to an increased risk of AD, both directly and indirectly (increase in plasma homocysteine levels).