What is Holistic
If someone offered you a pill that had been shown to prevent and reverse heart disease and type 2 diabetes, lower cholesterol, blood pressure, and body weight; significantly reduce your risk of getting multiple types of cancer; extend your lifespan; and make you look and feel great, would you hesitate to take it?
It may not come in a bottle, but whole foods, plant-based diet has been shown to do all these things.
The South African statesman and philosopher, Jan Smits, who is credited with coining the term “holism” (without the “w” wrote that reality consists of a “great whole” that comprises “small natural center (s) of wholeness” within the great whole of which is the mitochondria.
The body is the great whole and the process by which by which the body digests food is a smaller center of wholeness within the body. (Nutrition is one perspective on the wholeness of the body.) You can apply this content to refer also to a human being as DNA, and other blobs you studied in high school biology are small, natural centers that are also a whole unto themselves.
In either direction, you can continue as far as observation and then your imagination can take you. From the macrocosmic universe to the microcosmic ones, there is, philosophically speaking, a hierarchy of wholes, with each whole having parts that themselves are wholes.