I have just come across the labels used in Chile to signal to the consumer that products may contain high levels of various things like saturated fats, sodium, sugars and so on. Looking on Google images I find lots of images of the labels but it is always alto. But if it is on a food substance which is feminine should there not be a parallel set of labels Alta en ...?
Note I have seen the question ¿Qué tipo de palabra es «alto»? about alto as an interjection meaning stop but that does not seem to fit here where I am sure it means high.
Just in case it is the slightest relevance I am reviewing an article about the effect of the law which introduced them but my question here is pure curiosity.