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Head-to-head evidence comparison — which supplement is right for you?
Chlorella vs Vitamin D3: Vitamin D3 has the stronger overall evidence (7.5 vs 6.5/10); they're alternatives for support immune system — the best pick depends on your goals. Take the 60-second quiz for a pick tailored to your goals.
Vitamin D3 wins 2 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Too few graded studies
Top outcomes
Verdict
Probably helps
7 of 14 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (1)
Outcomes where both Chlorella and Vitamin D3 have evidence — compare verdict strength side-by-side.
3-10g daily
Before meals for detox, With food if GI sensitive, Away from medications (may bind)
Broken cell wall chlorella powder or tablets
2000-4000 IU daily
Morning with breakfast
D3 (cholecalciferol) softgel or liquid
and 1 more not shown
4-8 weeks
4-8 weeks
8-12 weeks
First 1-2 weeks
4-8 weeks
4-8 weeks
2-4 weeks
4-8 weeks
Identifying immunostimulatory herbal supplements that may flare autoimmune skin diseases: a systematic scoping review
Lupus science & medicine (2025) · Review
Scoping review screening 11,819 articles, of which 469 studies met inclusion criteria, identified 227 herbal supplements with immunostimulatory properties.
Effect of supplementation with Chlorella vulgaris on lipid profile in adults: A systematic review and dose-response meta-analysis of randomized controlled trials
Complementary therapies in medicine (2022) · Meta analysis · n=539
Meta-analysis of 10 RCTs with 539 adults (264 given Chlorella vulgaris, 275 controls).
Dietary Interventions in the Management of Fibromyalgia: A Systematic Review and Best-Evidence Synthesis
Nutrients (2020) · Systematic review
It is estimated to have a worldwide prevalence of 1.78%, with a predominance in females.
Vitamin D supplementation vs. placebo and incident type 2 diabetes in an ancillary study of the randomized Vitamin D and Omega-3 Trial
Nature communications (2025) · Rct · n=22220
Ancillary analysis of VITAL: 22,220 adults without T2D randomized to vitamin D3 2000 IU/day or placebo, with a meta-analysis of 3 additional trials.
Vitamin D Supplementation for Patients with Dysmenorrhoea: A Meta-Analysis with Trial Sequential Analysis of Randomised Controlled Trials
Nutrients (2024) · Meta analysis · n=687
TSA revealed that the current RCTs provide sufficient information.
Vitamin D and respiratory tract infections
BMJ (2017) · Meta analysis · n=11321
25 RCTs, 11 321 participants aged 0 to 95 years. Vitamin D reduced acute respiratory tract infection overall (adjusted OR 0.88, 95% CI 0.81 to 0.96).
At 1.5 g a day for 8 weeks, a double-blind trial in 84 adults with type 2 diabetes found no change in blood lipids (PMID 33532874). At 5 g a day for 4 weeks, two double-blind trials found an effect: in 63 mildly hypercholesterolaemic adults total cholesterol changed -1.6% versus 0.03% on placebo (PMID 24920270), and in 34 adults eating three eggs a day LDL-C rose 1.7% versus 14.3% on placebo (PMID 27177615). At 15 g a day for 14 days, total and LDL cholesterol fell in 80 healthy adults (PMID 37049486), but uric acid rose and iron and selenium status fell. The meta-analyses disagree on dose: one found reductions at doses above 4 g a day (PMID 29037431), another found the LDL-C reduction at doses up to 1,500 mg and not above (PMID 35331862). No trial compared doses, so the curve is flat above 5 g and no minimum, optimal or safe ceiling is set.
Both points come from a meta-analysis of double-blind cholecalciferol trials in people aged 60 and over (PMID 15886381). Trials at 700 to 800 IU a day cut hip fracture risk by 26% (RR 0.74) and non-vertebral fractures by 23%, plotted at 800 IU. Trials at 400 IU a day showed no benefit (hip fracture RR 1.15), and the WHI trial of 400 IU with 1,000 mg calcium did not significantly reduce hip fracture (PMID 16481635). Most of these trials also gave calcium, and the Cochrane review found vitamin D alone unlikely to prevent fractures while vitamin D with calcium gave a small reduction (PMID 24729336). Doses above 800 IU were not compared, so no optimal dose or ceiling is set.
AI-estimated from published studies. Interpret as directional guidance.
Vitamin D3 has a higher evidence score (7.5/10 vs 6.5/10) and wins in 2 of 3 categories.
For support immune system, Vitamin D3 has a higher relevance score (92 vs 60).
No documented interaction was found in the data searched. This does not establish that this exact combination is safe.
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The right pick depends on your goals. Answer a few quick questions for a personalised recommendation — or dig into the full evidence on each.