About Vitamin D

Vitamin D is important for strong bones, but most Americans have levels that are too low for ideal bone health. People with low vitamin D levels also have greater risk of obesity, high blood pressure, depression, sleep problems and some infections, including COVID-19 and influenza. Vitamin D levels tend to be lower in people who do not get sun year-round, or are Black, LatinX or South Asian.

It is recommended that most adults take 600-800 international units (IU) of vitamin D daily for bone health. However, we don’t know if these doses recommended for bone health can prevent COVID-19 and influenza, or the other health conditions associated with low vitamin D levels.

Prompted by evidence that vitamin D supplements reduce viral respiratory infections and that people with low vitamin D levels are more likely to test positive for and develop severe COVID-19, researchers at the University of Chicago and Rush University are conducting two studies to learn if daily vitamin D supplements can reduce the risk and severity of COVID-19.

Even with more people vaccinated and falling COVID-19 rates, taking more vitamin D may be important. Vaccines are not fully protective and likely less effective over time, especially as new variants arise. Many people may also want to know if vitamin D can help them manage their weight, blood pressure, mood or sleep, or lower their risk of influenza and other infections.

You may be eligible to participate if you live in the US and are over age 18. You are also eligible even if you have been vaccinated. During the sign-up process, we will screen you for health conditions that increase your risks from taking vitamin D supplements.

Risks and Benefits

All research has some risk. Vitamin D supplements can increase blood calcium which can cause anxiety, confusion, heart problems, kidney problems, and muscle weakness with increased risk of falls. Personal information can be accidentally released. We reduce these risks by:

• Keeping vitamin D doses below those likely to cause high calcium
• Excluding people from the study who report any health condition that could increase the risk of taking vitamin D supplements
• Storing all data behind secure passwords and firewall protected computer networks
• Offering blood testing for vitamin D side effects in Study Option 2

Benefits of participating may include:

• Helping yourself and others by learning if vitamin D reduces the burden of COVID-19 and other health conditions
• Decreasing your risk of COVID-19 or severe COVID-19 or other health conditions that may be affected by vitamin D
• Improving your bone health
• Having vitamin D supplements mailed to your home at no cost
• Receiving 4 free COVID-19 antibody tests and lab testing for vitamin D safety (Study Option 1 below)
• Being able to participate completely from your home (Study Option 2 below)

Study Choices

We are offering two versions of our study so participants can choose the best option for them.

Study Option 1: Participants must live or work in Chicagoland (including Northern Indiana or Wisconsin). Participants will receive tablets to take daily containing either 400, 4,000 or 10,000 IU of vitamin D. You will have blood drawn for lab tests at the start of the study and every three months to assess for side effects of vitamin D. You will need to come to the University of Chicago medical campus in Hyde Park, the Ingalls medical campus or to the Rush medical campus for these blood tests. These lab tests will also check your blood to see if you have been exposed to COVID-19 (COVID antibodies). We will let you know if you are antibody positive. You may prefer this option if you want the opportunity to take 10,000 IU of vitamin D, are interested in knowing if you have COVID antibodies, or want to have blood tests for safety monitoring.

Study Option 2: Participants may live anywhere in the US. Participants will receive tablets to take daily containing either 400 or 4,000 IU of vitamin D. This study is no-contact and can be completed from your own home. You may prefer this option if you don’t live or work in Chicagoland, would rather take lower doses of vitamin D, do not want blood draws, or do not want to travel to lab test sites.

In both studies, you will complete an initial on-line screening survey to collect demographic and health information to determine your eligibility and where your vitamins will be sent or picked up. You will also complete a 15-minute follow-up survey every 3 months for a year. You will not know what level of vitamin D supplement you are given and have no financial responsibility for cost of the vitamin D supplements or lab tests where required.