What is the right dose of vitamin D and could higher amounts do harm to our bodies?
What dose of vitamin D is the right amount; 400 international units (IU) per day or 4,000 IU per day or 10, 000 IU per day?
A clinical trial in Canada has found that taking vitamin D at high dosages is worthless and could even reduce bone density.
Some signs of taking too much vitamin D include:
- dehydration,
- fatigue,
- nausea,
- muscle weakness,
- thirst,
- and constipation.
Our skin makes vitamin D from exposure to sunlight and during the summer it only takes 15 minutes to get enough vitamin D for the day.
During winter time people in many countries such as Canada can’t get enough sunlight so the advice is to take a vitamin D supplement.
Our body needs vitamin D to absorb calcium for healthy bones, immune function, and mental health.
The Canadian study focuses on the necessity for vitamin D supplementation regarding bone density and bone strength.
They conducted a 3-year study on 311 healthy adult aged 55 to 70.
One group received 400 IU of vitamin D3 daily, the other 4,000 IU per day, and the third 10,000 IU per day.
Calcium and vitamin D together are important for bone health, therefore, the research team also provided participants a calcium supplement of 1,200 mg daily.
Health Canada recommends a dosage of 600 IU to 800 IU of vitamin D per day for a healthy adult aged 70+.
Osteoporosis Canada’s recommendation for vitamin D daily intake is 400 to 2,000 IU to avoid the bone loss disease.
Moreover, some individuals taking even a higher amount due to a vitamin D deficiency or a medical condition.
Therefore, it brings us back to this question of what is the right amount and what dosage of vitamin D can be harmful.
The study examined participants’ bone mineral density (BMD) by measuring levels of calcium and other minerals in the bone.
The risk of breaking a bone increases when the bone density is lower.
The BMD examinations showed that bone loss was significantly different between the three dosage of vitamin D groups.
Over the 3-year study, people on 10,000 IU of vitamin D saw a 3.6 percent reduction in their BMD while for the 4,000 IU group the reduction was 2.6 percent, and for the 400 IU group a 1.4 percent drop.
In short, the findings contradicted the hype about higher doses of vitamin D helping to increase bone density and build strong bones.
In this study, those who were on 10,000 IU vitamin D per day had the biggest decrease in bone density, suggesting a higher dosage can cause damage to the bones.
Professor Steven Boyd, the study’s co-author, said:
“with XtremeCT, the latest in bone imaging technology, we were able to find dose-dependent changes over the three years.
However, we were surprised to find that instead of bone gain with higher doses, the group with the highest dose lost bone the fastest.
That amount of bone loss with 10,000 IU daily is not enough to risk a fracture over a three-year period, but our findings suggest that for healthy adults, vitamin D doses at levels recommended by Osteoporosis Canada (400-2000 IU daily) are adequate for bone health.”
In addition, the study found that vitamin D supplements at higher doses, when taken for a long period, could increase risk of developing hypercalciuria, high amounts of calcium in the urine which can cause kidney stones.
The study was published in the Journal of the American Medical Association (Burt et al., 2019).
