The vrat food list, with the numbers

In most households a phalahar vrat permits fruit, milk and curd, the non-cereal flours — kuttu, singhara, rajgira and samak — plus sabudana, makhana, potato and other permitted tubers, nuts, and sendha namak in place of ordinary salt. What is set aside is grains, pulses, table salt, onion and garlic. Every part of that varies by family, region and community.

It is very widely eaten during fasts, and the usual reasoning is that it is not a grain. Some households set it aside. This is a matter of family and sampradaya practice.

Paneer, at 18.3 g per 100 g, where a household permits it. Among the flours, rajgira leads at 13.3 g per 100 g. Sabudana carries essentially none — 0.2 g per 100 g — which is why a fast built on it runs short.

Because it is unrefined and unprocessed, which is the customary reasoning. It is a religious and cultural practice rather than a nutritional one, and its details differ between households.