The rest of the post is mostly Paltrow talking about how she saw a "functional medicine practitioner" who essentially put her on a diet to alleviate the inflammation. It's basically an ad for his book, as well as for a bunch of other stuff, but Paltrow claims that it all makes her feel better, which is fine.
But — and this is important! — the best prevention and treatment having to do with COVID-19 has nothing to do with, say, "keto and plant-based but flexible" fasting techniques. Listen to doctors, not Gwyneth — who, while respectable in her own right, is not a doctor.
There are safety precautions you can take in your everyday life to prevent getting or giving COVID-19: wear a mask, practice social distancing, and get tested when necessary. Head to the CDC's website for information about how to get a COVID-19 test in your state.