Most people don’t need to take extra vitamin D and calcium supplements — and taking too much can actually be harmful. This is because both vitamin D and calcium can build up in the body, causing serious health problems. Vitamin D is fat-soluble, which means that it is stored in the fat cells of the body and can thus accumulate to toxic levels over time, causing nausea, fatigue, deafness and bone loss. Likewise, too much calcium in the body can impair kidney function and lead to constipation, nausea and even a coma.
More about calcium and vitamin D:
For the most part, people who eat a normal diet and spend at least 10-15 minutes a day in the sun have enough vitamin D, especially because more and more foods are being fortified with the vitamin. Vitamin D toxicity can occur in as little as a few months in adults and in as little as a few days in children.
Research has shown that the only group of people not getting enough calcium in their diets is adolescent girls. Many postmenopausal women are getting too much calcium and are putting themselves at risk for kidney stones.
The amount of vitamin D in many supplements is almost 10 times the daily recommended dosage for adults.