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Frequently Asked Questions

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  • Vitamin D helps the body absorb calcium. It helps build bones, and it keeps them strong and healthy. Vitamin D is also important in other body functions, such as with hormones and blood sugar control. Vitamin D is either taken orally or produced in the body from exposure to sunshine.

  • The role of vitamin D in reproduction is an exciting area of research. Low levels of vitamin D are common in the U.S., especially among women with darker skin tones.
    • Low levels of vitamin D have been linked with a harder time getting pregnant.
    • One study reported that lower levels of vitamin D were linked to irregular and/or longer menstrual cycles.
    • Low levels of vitamin D were also shown to be linked to delayed ovulation (the releasing of eggs).
    How or why vitamin D has these effects is unknown.

  • Participants will be asked to conduct various study tasks. Some of these tasks include:
    • Attending three in-person visits at the Durham, NC NIEHS Clinic Research Unit (CRU).
    • Filling out daily and weekly online diaries among other surveys about your menstrual cycle.
    • Collecting daily urine samples.
    • Collecting other body fluid samples.

  • The inVitD trial is looking for a diverse group of women who:
    • are between the ages of 19-40
    • have menstrual (period) cycles that are less than 50 days apart
    • have an intact uterus and ovaries
    • are not currently using hormonal birth control
    • are not pregnant or planning to become pregnant in the next 5 months
    • have no illnesses that affect your menstrual cycle
    • are willing to complete study tasks and take vitamin D capsules
    • live in one of our study areas or are willing to travel to the areas for study visits:
      • Research Triangle Park (RTP), North Carolina or surrounding area

  • Study email address: info@invitedtrial.net
  • Study phone number: 800-945-2459 (Monday-Friday, 8am-5pm EST)

NIEHS Clinical Research Unit (CRU)


Alexander Njunge
Field Staff

Brittany Mosley
Field Staff

Catherine-Wild
Field Staff

Cindy Smith
Field Staff

Stefanie Vidal
Field Staff

Heidi Rogers
Field Staff

Lashawn Ruffin
Field Staff

Xiomara Hodge
Field Staff
info@invitedtrial.net
800-945-2459
Monday-Friday, 8am-5pm EST
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800-945-2459
Monday-Friday, 8am-5pm
info@invitedtrial.net
NIEHS-NIHlogos
DLH logo
NIEHS-NIHlogos
DLH logo