How do you stop amyloid build up?

Get plenty of omega-3 fats. Evidence suggests that the DHA (Docosahexaenoic Acid) found in these healthy fats may help prevent Alzheimer's disease and dementia by reducing beta-amyloid plaques. Food sources include cold-water fish such as salmon, tuna, trout, mackerel, seaweed, and sardines. You can also supplement with fish oil

Avoid certain foods

Complex carbohydrates, including pasta, cakes, white sugar, white rice, and white bread cause spikes in insulin production and can contribute to the formation of toxic proteins associated with Alzheimer's. 

Diet: Foods high in sugar or carbohydrates are more likely than other foods to raise blood sugar levels. Lack of physical activity: A sedentary lifestyle can cause spikes in blood sugar levels. On the other hand, high intensity exercise can lead to physical stress, which is also a trigger for blood sugar spikes (look up diabetic dementia).

People, in general, are now eating less white sugar, white rice and white bread so dementia cases are decreasing. Right? Wrong.

How can I reduce tau protein in my brain naturally?

A 2013 study from UC Santa Barbara implicated that the chemical epicatechin might be able to prevent the build up of tau protein tangles in the brains of people with Alzheimer's.

Epicatechin is found naturally in apples, blackberries, broad beans, cherries, grapes, pears, raspberries, cocoa, and tea leaves.

Eating too much red meat, which raises brain levels of iron, may heighten the risk of developing Alzheimer's disease, researchers from the Semel Institute for Neuroscience and Human Behavior at UCLA reported in the Journal of Alzheimer's Disease and, as we get older, more iron ‘gets dumped’ in the brain anyway.