Vitamin D overconsumption can only occur by supplements as it is relatively impossible to consume such a large amount of fatty fish. Prolonged exposure to the sun also does not lead to overproduction of vitamin D because the thermal activation of provitamin D3 leads to the formation of other inactive forms, thus preventing high concentrations.
Excessive concentration of vitamin D leads to high absorption of calcium in the gastrointestinal tract, causing hypercalcemia in the body.
Hypercalcaemia, in turn, can lead to nausea, vomiting, muscle weakness, neuropsychiatric disorders, pain, loss of appetite, dehydration, polyuria, excessive thirst and kidney stones.
In extreme cases, vitamin D toxicity causes kidney failure, calcification of soft tissues throughout the body (including coronary arteries and heart valves), heart arrhythmias and even death.
Serious cases of vitamin D toxicity have only been reported by:
- Consumption of dietary supplements containing excessive amounts of vitamin D due to manufacturing errors
- supplements taken in excessive amounts or incorrectly prescribed by doctors