The bad news is that one in nine people age 65 and older in America has Alzheimer's, and about one-third of people 85 and older have it. (ref)
The good news is that studies are showing ways to decrease your risk of becoming one of those people.
One of these, the Zutphen Elderly Study, found that those with the highest total fat intake had a 240 percent higher risk of developing dementia. High saturated fat intake increased risk 90 percent and high cholesterol intake increased risk 70 percent.
Examples of foods with saturated fat are: fatty beef, pork, chicken with its skin, cheese, butter, and of course, various processed foods.
A later study showed that carbohydrates, not fat, are the bigger culprit of obesity leading to heart disease that leads to Alzheimer's. In the American diet, the biggest sources of carbs are: grain-based desserts (cakes, cookies etc) and yeast breads. Another very large source is soda pop. Sugar is a known cause of memory loss. (ref)
The easiest way to avoid the "bad stuff" is to follow the WYBIWYG rule. It's very similar to "What You See Is What You Get" or WYSIWYG. The only difference is that it warns: "What You Buy Is What You Get." What we don't have in our refrigerator or cabinet, won't show up on our table.
For most of us, what we see IS what we get! At the grocery, just remember the cow who says, "Eat more vegetables!"