Four Days of High-Fat Food Primed Mice for Worse Skin Inflammation, a UCSF Study in Nature Finds

A few days of rich food may be enough to change how the immune system reacts, at least in a mouse. Researchers at the University of California, San Francisco report in Nature that lean mice fed a high-fat diet for just four days developed severe skin inflammation when later challenged with an irritant, about as bad as in obese mice, according to Medical Xpress. The paper was published on 28 October.

It is a mouse study, and the people who ran it say so. But it points at a question nutrition science has mostly asked over months and years rather than days.

What did the mouse experiment show?

The team raised mice on low-fat or high-fat pellets and applied imiquimod, an irritating cream that causes inflammation, to one ear. Normal-weight mice switched to high-fat food for four days, then challenged three days later, developed severe ear inflammation similar to that of obese mice on a high-fat diet. Going the other way, obese mice moved to normal food for four days had milder inflammation, News-Medical reported.

So in this model, what the animals had eaten in the last few days mattered about as much as their body weight. The researchers saw a similar heightened response to irritation in the lungs after a few days of high-fat feeding.

How could four days of food prime the immune system?

The proposed mechanism has two steps. First, high-fat feeding drew rapid-response immune cells into the skin, which amplified the reaction. Second, after the inflammation faded, memory T cells stayed behind in the ear, leaving the tissue primed. When normal-weight mice were returned to low-fat food and the same ear was challenged again weeks later, the skin responded more strongly than before.