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High-Dose Vitamin D Supplements in Older Adults


This Phase II study will test high-dose oral vitamin D compared to a standard dose for treating vitamin D insufficiency in a diverse group of older adults. The effects of the different doses on cognitive function will also be assessed to gather data for a potential future trial in older adults at risk for dementia.

Minimum Age Maximum Age Gender Healthy Volunteers
65 Years 90 Years All Yes
March 18, 2019
March 30, 2022

  • Low vitamin D status, as measured at screening
  • Fluent in English or Spanish
  • Willingness to be randomized to high-dose or standard dose vitamin D
  • Education-adjusted scores between 12 to 30 on the Montreal Cognitive Assessment
  • Diagnosis of no cognitive impairment, mild cognitive impairment, or mild Alzheimer's disease, as determined by cognitive and memory tests
  • Alzheimer's medications, such as donepezil and memantine, are allowed if doses have been stable for more than 6 weeks, and no changes are anticipated; experimental Alzheimer's therapies, such as anti-amyloid or anti-tau treatments, will be excluded.

  • Lacks adequate vision, hearing, or literacy to complete psychometric tests
  • Liver insufficiency, defined by either albumin less than 3.3 g/dL or by a value more than 2 times the upper limit of normal (ULN) in either alanine aminotransaminase or bilirubin, or more than 3 times the ULN for aspartate aminotransaminase
  • Kidney insufficiency, defined by either serum creatinine greater than 1.7 mg/dL or glomerular filtration rate less than 30 mL/min/1.73 m2
  • Current serious or unstable medical illnesses including heart, liver, kidney, gastroenterologic, lung, endocrinologic, neurologic, psychiatric, immunologic, or blood disease and other conditions that could interfere with participant safety
  • Life expectancy of less than 4 years
  • History of recurrent kidney stones
  • Unable to undergo magnetic resonance imaging (MRI), such as pacemaker, metallic implants, or severe claustrophobia
  • History of chronic psychiatric illness (e.g., schizophrenia or bipolar disorder), major depression within last 2 years, current Global Depression Scale score greater than 6, or any recent suicide attempts or suicidal ideation
  • History within the last 5 years of a serious infectious disease affecting the brain (including neurosyphilis, meningitis, or encephalitis), or head trauma resulting in loss of consciousness for more than 10 minutes or any persistent cognitive deficit
  • History of chronic alcohol or drug abuse/dependence within the past 5 years
  • History within the last 5 years of a primary or recurrent malignant disease with the exceptions of resected cutaneous squamous cell carcinoma in situ, basal cell carcinoma, cervical carcinoma in situ, or non-metastatic prostate cancer with a normal prostate-specific antigen post-treatment
  • Poor venous access such that multiple blood draws would be prevented
  • Prohibited medications: regular use of benzodiazepines, antipsychotics, narcotics, cholinesterase inhibitors, memantine, or anti-epileptic drugs. Stable doses of SSRI or SNRI antidepressants will be allowed if dose does not change throughout the study.
  • No additional supplements containing vitamin D will be allowed

Participants will be randomly assigned to take either a high-dose tablet of vitamin D3 (4,000 IU) or a standard-dose tablet (600 IU) daily for 3 years. Vitamin D levels will be measured every 6 months through blood draws. Researchers will measure changes in cognitive function and brain structure through cognitive tests and MRI scans.

Name City State Zip Status Primary Contact
University of California, Davis Alzheimer's Disease Center
Walnut Creek California 94598 Recruiting Maria Levallois

University of California, Davis

  • National Institutes of Health (NIH)
  • National Institute on Aging (NIA)

Name Role Affiliation
John Olichney, MD Principal Investigator UC Davis Alzheimer's Disease Center

Name Phone Email
Maria Levallois 916-734-5245
Hongzheng Zhang 925-357-6914


Phase II RCT of High-dose Vitamin D Supplements in Older Adults