What are the unexpected pitfalls in choosing vitamin D supplements? Test, choose, and make it effective. How to take vitamin D in a "result-oriented form."

Introduction: What Everyone Is Overlooking Now

Vitamin D is crucial for bones and immunity, especially during seasons with less sunlight, making supplements essential. However, "Which Vitamin D to Choose" Can Change the Outcome——a new systematic review (meta-analysis of randomized controlled trials) highlighting this "unexpected pitfall" has been published, covered by AOL, and sparked discussions on social media. The review reports a consistent pattern that taking plant-derived Vitamin D2 (ergocalciferol) lowers the body's D3 (cholecalciferol) levels. The implication is that D2 and D3 do not "work the same way." An explanatory article by EatingWell (published on October 6, 2025) also clearly organizes this summary.EatingWell

What's "Unexpected": D2 and D3, Different Behaviors Despite Being the Same "Vitamin D"

The review narrowed down RCTs from literature between 1975 and 2023, integrating 11 trials. The findings showed that D3 decreased by an average of about 18 nmol/L in the D2 group (difference at the end of the trials). While both have the effect of raising total Vitamin D (25(OH)D), the implication that D3 is superior in terms of maintaining D3 levels has strengthened. The mechanism of why D3 decreases with D2 is unexplained and remains a subject for future research.EatingWell

Implications for Real Life: The Number After "D" on the Label Affects Efficacy

• Choose D3 as the First Option for Supplements: Based on the review's conclusion and practical sense, D3 is the safer choice for stable maintenance of body levels. **Vegan-friendly D3 (lichen-derived)** is also available, providing an option for those avoiding animal-derived products.EatingWell

• Limited Intake from Food: D is naturally present in few foods, limited to fatty fish, egg yolks, and UV-exposed mushrooms. Most come from **"fortified foods" like milk, plant-based milk, and cereals**. The idea of supplementing what's lacking makes sense.EatingWell

• Basic Knowledge from Public Information: Comprehensive basic information on effects, recommended amounts, safety ranges, and interactions is available in the NIH (National Institutes of Health) ODS fact sheet.ods.od.nih.gov

Atmosphere on Social Media: D2 Advocates, D3 Advocates, and Vegan D3 Advocates Intersect

After the AOL/EatingWell release, links spread on X (formerly Twitter), Facebook, and Reddit. The reactions generally converged into the following three types.

1. "It's Definitely D3" Group: Voices supporting D3 superiority based on past small-scale studies or personal blood test experiences. Comments like "D3 is the only choice" followed EatingWell's official posts.X (formerly Twitter)

2. "D2 Worked for Me Too" Group: Voices pointing out individual differences, dosage, and duration, citing effective cases of D2. Discussions also considered the point that many fortified foods contain D2.EatingWell

3. "Vegans Can Use D3 Too" Group: Introducing options for lichen-derived D3, seeking a balance between ethics and efficacy. On Reddit, the D2/D3 debate reignited using the AOL article as a source.Reddit

In summary, a realistic choice that reconciles the "triangle of ethics/preferences (vegetarianism), availability (D2 in fortified foods), and efficacy (D3 superiority)" is being explored even on social media.

A "Smart Choice" Checklist to Avoid Mistakes

The supplement industry is not as strictly regulated as pharmaceuticals, so deciphering labels and checking third-party certifications are crucial. The following points are recommended by nutrition media as general "smart supplement purchasing tips."EatingWell

1. Type of Ingredients: Choose Vitamin D3 (cholecalciferol) as the top option. For vegans, lichen-derived D3 is available.EatingWell

2. Appropriate Dosage: Stay within the tolerable upper limit (consult with a healthcare provider along with blood levels).ods.od.nih.gov

3. Third-Party Testing: Verify purity and content with certification marks like USP/NSF.EatingWell

4. Interactions and Medical History: Always check for interactions with medications and diseases (e.g., accumulation of fat-soluble vitamins).ods.od.nih.gov

5. Form and Absorption: Consider practical aspects that enhance absorption, such as oil-based soft gels or taking after meals.EatingWell

Quick Answers to Common Questions

• Q. Fortified plant milk contains a lot of D2, but is it useless?
  A. It's not useless. However, from the perspective of maintaining D3, D3 is superior. A realistic approach is a "combination technique" of diet + sunlight + D3 if necessary.EatingWell

• Q. Is it difficult to get D3 as a vegan?
  A. Lichen-derived D3 is commercially available and can be chosen.EatingWell

• Q. I had sufficient increase with D2, though?
  A. It varies with individual differences, dosage, and duration. Blood tests are the most reliable.ods.od.nih.gov

Steps for Practice

1. Current Status Assessment: Check 25(OH)D with tests. Supplement only when necessary.ods.od.nih.gov

2. Product Selection: Choose D3 (lichen-derived for vegans) + those meeting third-party certification.EatingWell

3. Combine with Lifestyle: Avoid excess or deficiency by combining with sunlight, diet, and exercise.EatingWell