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Why higher vitamin D intake may be important for prediabetics

Woman with Vitamin D supplements

Many doctors recommend vitamin D serum levels of 20-30 nanograms per milliliter (ng/mL)—but for people with prediabetes, that may not be enough. A recent study found that vitamin D serum levels of 40 ng/mL or higher were linked to protective effects against the development of diabetes.1 To achieve an optimal level, higher doses of vitamin D may be needed, according to the study's authors. (Life Extension's optimal vitamin D range is 50 to 80 ng/mL.)

The study analyzed data from 2,362 prediabetic men and women who participated in a trial that examined the association between intake of 4,000 IU of vitamin D and the risk of developing diabetes. Serum 25-hydroxyvitamin D levels were measured prior to a 2.5-year median follow-up period and were repeated each year.

In addition to looking at vitamin D serum levels and diabetes, researchers set out to determine whether overweight or obese prediabetics and people of color with prediabetes have different associations between vitamin D levels and diabetes risk compared with normal weight or Caucasian prediabetics. The conclusion? While both groups benefited from vitamin D intake, Whites benefitted more. Caucasian and Black participants whose average annual vitamin D levels measured during the trial were 40 ng/mL or higher had significantly lower risks—58% and 49% lower, respectively—of developing diabetes than those whose levels were 20 ng/mL to less than 30 ng/mL. A serum vitamin D level of 40 ng/mL or more was also significantly protective for participants who had body mass indexes of less than <40 kg/m2. The findings were published on March 29, 2023, in the American Journal of Clinical Nutrition.

Similar findings in a recent review and meta-analysis published in the Annals of Internal Medicine suggested that high vitamin D levels may be optimal for diabetes prevention.2 The review found that vitamin D intake overall reduced the risk for diabetes by 15%. In those in the vitamin D group who maintained a serum 25-hydroxyvitamin D level of at least 50 ng/mL during the trial, compared with 20 to 29 ng/mL, relative risk of diabetes risk was reduced by 76%. Vitamin D intake conferred a 30% chance of restoring normal glucose regulation. Vitamin D was well-tolerated, with no increased risk of adverse events.


Apply What You’ve Learned: Vitamin D Intake

  • Studies have not established the amount of vitamin D needed to raise blood levels by a specified amount.3 It is suggested to have your blood tested for serum 25-hydroxyvitamin D [25(OH)D] to make sure your levels are within a healthy range and to increase intake of the vitamin as needed. Retesting can help determine whether your supplement regimen is adequate.
  • Insufficient vitamin D levels of less than 20 nanograms per milliliter (ng/mL) are not uncommon and should be corrected.4
  • Vitamin D is important for the bones, immune system, cancer prevention, healthy blood pressure, teeth, cardiovascular system, brain, and more.5-8
  • While exposure to the sun's ultraviolet (UV) rays is well known as a way of obtaining vitamin D, the American Academy of Dermatology does not recommend getting vitamin D from sun exposure or indoor tanning. Unprotected exposure to UV rays is a known risk factor for skin cancer, including potentially fatal melanoma.9


  1. Chatterjee R et al. Am J Clin Nutr. 2023 Mar 29;S0002-9165(23)46304-6.
  2. Pittas AG et al. Ann Intern Med. 2023 Mar;176(3):355-363.
  3. Ramasamy I. Clin Biochem Rev. 2020 Dec;41(3):103-126.
  4. Bouillon R et al. Best Pract Res Clin Endocrinol Metab. 2018 Oct;32(5):669-684.
  5. Khazai N et al. Curr Rheumatol Rep. 2008 Apr;10(2):110-7.
  6. Uwitonze AM et al. J Steroid Biochem Mol Biol. 2018 Jan;175:190-194.
  7. Mheid IA et al. J Am Coll Cardiol. 2011 Jul 5;58(2):186-92.
  8. Goodwill AM et al. J Am Geriatr Soc. 2017 Oct;65(10):2161-2168.
  9. “Vitamin D stats and facts.” American Academy of Dermatology.

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