Get your score

Should you take high-dose vitamin D?

What you hear: “Everyone should take 5,000 to 10,000 IU of vitamin D a day because it prevents cancer, heart disease, infections and depression.”

What the studies found

The VITAL trial gave 25,871 US adults 2,000 IU a day or a dummy pill for about 5 years and found no drop in cancer (hazard ratio 0.96) or major heart events (0.97). In the same trial, 18,353 people were tracked for depression, with no difference between groups (0.97). Australia's D-Health trial gave 21,315 people over 60 a monthly 60,000 IU dose and saw no fewer deaths (1.04). A 2025 pooled analysis of 40 trials (61,589 people) found no clear protection against chest and throat infections (odds ratio 0.94, not statistically significant). One small bright spot: in a pooled analysis of trials, daily (not monthly) doses went with 12% fewer cancer deaths, though the overall result across all trials was not significant. The Endocrine Society now advises against taking more than the standard daily amount to prevent disease in healthy adults under 75. Note that these trials used 2,000 IU a day or monthly doses; no large trial has tested 5,000 to 10,000 IU a day for disease prevention.

Take care: Big doses can backfire: in 2,256 older women, one yearly 500,000 IU dose led to 15% more falls and 26% more fractures, and 10,000 IU a day for 3 years slightly lowered bone density compared with 400 IU.

What you could do

Take vitamin D if you are low, older than 75, pregnant or advised by your doctor, at standard doses rather than megadoses.

See it in the habit library, with what it means for your own longevity score.

Not medical advice. General information from published studies, not a diagnosis or a treatment plan. Talk with your doctor before starting a supplement or changing a medicine, especially if you are pregnant, take other medicines or have a health condition.

How we judged it

Doesn't hold up: Good studies looked and found no benefit, or the claim is plainly false. We judge the claim as it is usually said online, not the habit itself. Trials assign people at random, so they can show cause; observed studies follow people and show a link, not proof. Last checked: October 2026.

The studies, in their own words

1. Manson et al. N Engl J Med 2019 (VITAL)

   During a median follow-up of 5.3 years, cancer was diagnosed in 1617 participants (793 in the vitamin D group and 824 in the placebo group; hazard ratio, 0.96; 95% confidence interval [CI], 0.88 to 1.06; P=0.47). A major cardiovascular event occurred in 805 participants (396 in the vitamin D group and 409 in the placebo group; hazard ratio, 0.97; 95% CI, 0.85 to 1.12; P=0.69).

2. Okereke et al. JAMA 2020 (VITAL-DEP)

   Risk of depression or clinically relevant depressive symptoms was not significantly different between the vitamin D3 group (609 depression or clinically relevant depressive symptom events; 12.9/1000 person-years) and the placebo group (625 depression or clinically relevant depressive symptom events; 13.3/1000 person-years) (hazard ratio, 0.97 [95% CI, 0.87 to 1.09]; P = .62)

3. Neale et al. Lancet Diabetes Endocrinol 2022 (D-Health)

   The HR of vitamin D3 effect on all-cause mortality was 1.04 [95% CI 0·93 to 1·18]; p=0·47)

4. Jolliffe et al. Lancet Diabetes Endocrinol 2025

   For the primary comparison of any vitamin D versus placebo, the intervention did not statistically significantly affect overall ARI risk (OR 0·94 [95% CI 0·88-1·00], p=0·057; 40 studies; 61 589 participants; I2=26·4%).

5. Sanders et al. JAMA 2010

   Among older community-dwelling women, annual oral administration of high-dose cholecalciferol resulted in an increased risk of falls and fractures.

6. Kuznia et al. Ageing Res Rev 2023

   Subgroup analyses revealed a 12 % lower cancer mortality in the vitamin D3 group compared with the placebo group in 10 trials with a daily dosing regimen (RR [95%CI]: 0.88 [0.78-0.98])

7. Demay et al. J Clin Endocrinol Metab 2024 (Endocrine Society guideline)

   The panel suggests against empiric vitamin D supplementation above the current DRI to lower the risk of disease in healthy adults younger than 75 years.

8. Burt et al. JAMA 2019

   treatment with vitamin D for 3 years at a dose of 4000 IU per day or 10 000 IU per day, compared with 400 IU per day, resulted in statistically significant lower radial BMD

More claims, checked

• Doesn't hold upYou need 8 glasses of water a day
• Doesn't hold upSkipping breakfast makes you gain weight
• Doesn't hold upVibration plates melt fat
• Backed by trialsA 10-minute walk after meals
• Partly trueIntermittent fasting and time-restricted eating
• Partly trueApple cider vinegar before meals

See all 50 claims