If he has a thyroid problem then kelp can help or hinder it depending on if his thyroid has too much or too little iodine/
What his thyroid problem is
He could try this test.
How to Self-Test for an Iodine Deficiency
If he has enough iodine he should stop the kelp until he checks with the doctor about it.
I have heard that alfalfa sprouts are not good I don't know about them in supplement form