Don’t get me wrong: animal studies like these are
incredibly valuable. Thanks to these studies, we have some
clues as to why people who adhere more closely to the high-
sugar, high-fat Standard American Diet tend to have smaller
hippocampi—the structure in the brain that processes our
memories.^37 These studies also tell us that the combination
of sugar and saturated fat (common in fast food) can drive
inflammation and drain BDNF from the brain.^38
The problem is, this nuance is often lost when the media
reports on these findings, resulting in misleading headlines
such as “How a High-Fat Diet Could Damage Your
Brain”—which was the title of a widely circulated article
posted on one well-known publisher’s site.^39 (The food used
in the mouse study that the article was reporting on was 55
percent saturated fat, 5 percent soybean oil, and 20 percent
sugar.) Unless readers went out of their way to find the
original study, assuming they’d even have access to it and
didn’t glaze over from the jargon, they could easily interpret
this as a strike against high “healthy fat” diets—those that
are low in processed carbohydrates and polyunsaturated oils
and high in omega-3 fats, nutrient-rich vegetables, and the
relatively small amount of saturated fat found in properly
raised animals’ products.
The question that remains is how much saturated fat
should be consumed in a brain-optimal diet. While the
evidence warning us to avoid saturated fat is, and has
always been, shaky at best, there is also scant evidence to
suggest that chasing saturated fat has any benefit to the
brain (unlike, for example, monounsaturated fat, which is