Safari pages using huge amount of memory
I have seen this some years ago, but I thought it was getting better. My wife goes to lots of web sites using Safari, mostly about cooking. She leaves lots of tabs open. After a week or two, the computer becomes very sluggish, and I see in Activity Monitor that there are many web pages that are using over 1 GB of memory. Is there any way to stop these web pages in Safari from using this huge amount of memory? We bought this MacBook Pro with 16 GB of RAM that was the most possible at the time, but it should not become unusable by simply opening web pages in Safari.
MacBook Pro 15″, macOS 10.14