Water chestnut is a Green food. Green foods are safe to eat as a regular part of a diet.
Guideline related quotes related to Non-Starchy and Green throughout Geoff Bond's publications.
Eat at least 2 3/4 lbs of mixed salad and vegetables per day, consisting of "Green-Green” and “Green” foods. Of these, at least 3/4 lb should be mixed salad. Also include at least 5 cups of “Green-Green” leafy vegetables or 2 1/2 cups of other vegetables per week. ~Paleo in a Nutshell p.102
Specific references to Water chestnut throughout Geoff Bond's publications.
Not all underground vegetables are starchy. For example, turnip and radish, which both originated in Asia, are non-starchy, as are bulbs such as onion and garlic from Asia and the leek from the Middle East. Corms such as Chinese water chestnut are also non-starchy. Unlike the starchy roots, they mostly get their bulk from another com pound called "inulin." ~Deadly Harvest p.56