When a change in the position of a person’s head results in a sudden spinning sensation, it’s a condition known as benign paroxysmal positional vertigo. For 86 percent of people afflicted with it, daily life can be interrupted, including missing work. Treatment usually involves a doctor or health practitioner performing a series of movements to the patient’s head that shift particles in the ears, but scientists in South Korea have found another simple solution: 400 international units of vitamin D and 500 milligrams of calcium daily. In a study of 957 people published in Neurology, 445 in an intervention group were given supplements if vitamin D levels were less than 20 nanograms per milliliter. The 512 people in the observation group did not get supplements. After a year, the supplement-takers had 24 percent fewer episodes, and those with very low vitamin D levels at the start experienced a 45 percent reduction.