The doctors who got a Nobel Prize for their work discovering Nitric Oxide do not recommend Maca Extract.
They do recommend mainly foods that boost nitric oxide and also just enough L-Argenine + L-Citruline to then reach 100% Nitric Oxide as measured by inexpensive saliva test strips. They warn about not taking more than 5,000mg L-Argenine. I only take 750mg daily to boost my Nitric Oxide to 100%. I plan to cut that in half next week and rely more on the foods.