Yes it's OK to eat buckwheat everyday and it's healthy.
Buckwheat is very healthy for you and your heart and could prevent heart disease, heart attacks, strokes, blood clots etc.
Buckwheat is very healthy just like oatmeal is.
Just avoid eating too much buckwheat because it could lead to constipation in some people when eaten in excess.
Yes buckwheat can cause constipation if you eat too much of the buckwheat.
Buckwheat contains a lot of fiber content which can cause constipation when eaten in excess.
However the fiber in buckwheat or anything else can help relieve constipation and help keep your bowels and colon healthy.
That is as long as you eat the buckwheat in moderation.
Just don't eat too much buckwheat otherwise it's possible to get constipated from eating buckwheat which has happened to me before.