Stinging Nettle Under a Walnut Tree

Presently, I am growing Urtica dioica, for my own consumption, under a black walnut tree, which is fairly large. I have been told that the juglone the tree produces may affect some types of flora. In your opinion, am I in danger of ingesting this poison? It certainly doesn't appear to affect the nettle. They are large and healthy. The extension service in Lansing, Michigan were quite doubtful.

It is commonly said that walnut trees produce juglone which is supposed to act as a kind of chemical warfare antidefoliant to suppress the growth of other plants. We have never noticed this effect around walnut trees growing on our property over the past twenty years, so we are doubtful of just how significant any such effect may really be. It does not surprise us that your nettle plants are doing fine under it. We have found a wide variety of herbs grow well under walnut trees as long as they can stand the shade. We have a beautiful two metre high Siberian ginseng bush growing under a eight metre walnut tree, for example.
Supposing that there is some level of juglone present in the soil around your tree, it is an open question whether the juglone is of any significance to your health. There is no research that I know of that directly answers your question. Nor have I heard of any health problems arising when ingesting neighbouring plants.
I suppose we might take some guidance from the fact that walnut is itself a medicinal herb that is taken internally. The bark, leaves and the rind of the fruit are used, mainly as an astringent for sore throat, tonsils and diarrhea, and as laxative and digestive aid – depending on the species. What this says about the possible danger of juglone is unclear to me, but taken together with the fact that I have not heard of any problems, I suspect that there is little danger of using herbs such as nettles that are growing nearby walnut trees. But that's just a guess and you may wish to make further inquiries before making your decision on whether or not to use your plants.