Truly mentioned. It has also been seen that the constipation, i.e. accummulation of multiple days' faecal matter in the large intestine and rectum triggers headache as the fermentation and too much storage of faecal matter strains the bowel movement. In some cases, it is also seen that after the patient is relieved of constipation through yoga therapy or shatkarmas (detoxification techniques of yoga) or enema, they are relieved of headaches.
Even I have seen that most of the diseases arise only due to chronic constipation. That's why in naturopathy, it is usually said that if the middle region of the body is ok, all regions of body are ok, interpreting that if any body is careful of his diet and daily defecation, then there will be no health issues. Even treatment of any chronic disorder or disease starts from enema and abdominal mud pack in nature cure hospital as this process eliminates the waste and toxic material from the body as well as cools down the intestines of the body. We have cured very drastic chronic diseases only with the principle of elimination of toxins from the body and proper nutrition to the body.