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RCT suggests seniors need 4,000 IU vitamin D daily for disease prevention

Posted on: July 28, 2017   by  Missy Sturges


As we age, our bodies contain less vitamin D precursor in the skin, thereby decreasing the body’s efficiency of producing adequate vitamin D from the sun. Additionally, elderly individuals often lead an indoor lifestyle and do not receive adequate vitamin D education, placing these individuals at an increased risk for vitamin D deficiency.  

Research has shown that low vitamin D status is associated with cognitive decline, a decreased ability to perform activities of daily living and mortality. Furthermore, vitamin D supplementation has been shown to reduce the occurrence of acute respiratory tract infections by nearly 50% and improve survival rate after hip surgery.  These are only a few of health conditions associated with vitamin D.

Research indicates that maintaining healthy vitamin D levels is a crucial component in preserving the health of senior citizens. However, vitamin D deficiency remains highly prevalent among the elderly. Therefore, researchers conducted a randomized double blind placebo controlled trial (RCT) to determine the dosage of vitamin D required to maintain optimal levels.

A total of 305 individuals at at least 65 years of age were included in the study. The participants were ambulatory, living independently and were not supplementing with more than 400 IU vitamin D3 per day prior to enrolling in the study. At baseline, the participants were randomly assigned to receive 4000 IU D3 (n = 102), 2000 IU D3 (n = 102) or placebo (n = 101) daily for one year.  

A nurse on the research team visited the participants in their home at baseline and months 6 and 12 of the study. The nurse recorded the participant’s medical history, blood pressure and risk factors for heart disease and fractures. The participants had their blood drawn and received a series of physical tests to evaluate heart health and physical performance. In addition, the researchers randomly selected one-third of the participants to receive an additional blood draw at 1 month to evaluate how quickly vitamin D levels were improved.

Here is what the researchers found:

  • Average baseline vitamin D status was 20 ng/ml.
  • After 12 months, vitamin D levels increased to 55 ng/ml in those who supplemented with 4,000 IU, 40.8 ng/ml among those who supplemented with 2,000 IU (p < 0.0001). The placebo group’s vitamin D levels remained the same.
  • Vitamin D levels significantly improved within one month of vitamin D supplementation in both supplement groups (p < 0.05).
  • Between 6 and 12 months, the average 25(OH)D levels increased by 4.4 ng/ml and 2 ng/ml in the 4,000 IU and 2,000 IU supplement groups, respectively.
  • Of the participants who were supplementing with vitamin D, the overall improvement in vitamin D status was decreased by ⅓ among overweight individuals and ⅔ in obese participants compared to those who were a normal weight.
  • Both vitamin D supplement doses were well tolerated with no cases of hypercalcemia or kidney stones.
  • Vitamin D supplementation did not impact heart health or physical function.

This study possessed several strengths. The participants were deficient at baseline, the study duration was long and the dosage enabled the participants to reach optimal vitamin D status (40-60 ng/ml). The primary limitation of this study is that most of the participants were Caucasian, thereby decreasing the generalizability of their findings. Additionally, participant’s compliance decreased over time, a common challenge of long-term trials.

The researchers concluded,

“After taking account of the typical average 70% compliance observed in long-term trials of vitamin supplements for disease prevention, the results of the present study suggest that daily doses of 4000 IU of vitamin D3 may be required to achieve the high plasma levels of 25(OH)D associated with the lowest risks of mortality in the observational studies.”


Sturges, M. & Cannell, JJ. RCT suggests the elderly need 4,000 IU vitamin D daily for disease prevention. The Vitamin D Council Blog & Newsletter, 7/2017.


Hin, H. et al. Optimum dose of vitamin D for disease prevention in older people: BEST-D trial of vitamin D in primary care. Springer, 2016.

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