Low-impedance headphones are in the range 16 to 32 ohms and high-impedance headphones are about 100-600 ohms. As the impedance of a pair of headphones increases, more voltage (at a given current) is required to drive it, and the loudness of the headphones for a given voltage decreases.
Yes, taking to much Vitamin D can cause some people to get diarrhea. Some others may experience constipation from to much Vitamin D.
Vitamin D is soluble and can be stored in the body for many months. Too much vitamin D in the body can cause elevated levels of calcium in the blood. It is called hypercalcaemia. High levels of calcium in the blood can cause constipation. So, the answer to her question is yes, vitamin D can cause constipation. However, taking the supplement at the recommended dose should not cause any problems. You can take up to 1000 IU of vitamin D3 a day without any side effects. If you are vitamin D deficient, your doctor may recommend a higher dose.