Why Sample Size Matters in Clinical Trials

When you see a product claim like “Clinically shown to improve skin texture in 4 weeks,” do you ever wonder how many people actually tested it? Was it 10? 100? The answer lies in a detail that most consumers never notice, but researchers and regulators definitely do: sample size.

Far from being a background statistic, sample size can make or break the credibility of a clinical trial. For brands in the supplement, skincare, superfood, or pet wellness industries, getting this right is essential, not just for science, but for sales.

What Is Sample Size in Clinical Trials?

Sample size refers to the number of participants enrolled in a clinical study. It determines how confidently researchers can draw conclusions about a product's effectiveness. A trial with too few participants may produce unreliable or non-reproducible results, while one with an adequate sample size provides the statistical power needed to back up product claims with confidence.

Why Sample Size Is Crucial in the Wellness Industry

1. Statistical Significance and Credibility

The bigger the sample (to a point), the more likely your findings are to be statistically significant, not just a fluke. This matters when making specific, quantifiable claims like “reduces fine lines by 20%.”

2. Marketing Transparency and Consumer Trust

Today’s consumers are savvy and skeptical. Being able to say your product was tested on 100 people in a randomized, double-blind study gives your marketing real weight, and sets your brand apart.

3. Regulatory and Legal Risk Management

While the FDA isn’t involved in most non-drug consumer trials, the FTC requires that any marketing claim be supported by “competent and reliable scientific evidence.” A robust sample size is part of that equation.

How to Determine the Right Sample Size

The optimal sample size depends on:

• The product type (topical, ingestible, etc.)

• The expected size of the effect

• Outcome variability

• Study design (randomized, placebo-controlled, etc.)

• Desired confidence levels (typically 95% or higher)

Small pilot studies may start with 20–30 participants, while full-scale trials often require 100–200+ depending on the desired statistical power.

Sample Size vs. Budget: Finding the Balance

Clinical trials are a significant investment, especially for startups or indie wellness brands. But there are ways to optimize without cutting scientific corners:

• Use crossover designs, where each subject receives both the test and control treatment.

• Narrow your outcome measures for greater sensitivity.

• Explore decentralized clinical trials (DCTs) to reach broader demographics while reducing site costs.

The Link Between Sample Size and Claim Language

Not all claims are created equal, and neither are the sample sizes needed to support them. There’s a big difference between saying:

• “Clinically tested on 15 people” and

• “Clinically validated in a 100-person randomized, double-blind study”

The former is vague and often unimpressive. The latter communicates scientific rigor. The larger and more methodologically sound your study, the bolder and more specific your claims can be, with a solid defense against scrutiny from regulators, partners, or consumers.

Sample Size in Decentralized Clinical Trials (DCTs)

As decentralized clinical trials continue gaining traction, particularly in the post-pandemic landscape, they offer an opportunity to reach more diverse and representative samples. This has a direct impact on sample size and statistical power, more accessible trials mean greater participation, faster recruitment, and stronger data.

For consumer health brands, especially those targeting niche or underserved demographics, DCTs can help boost sample size while improving real-world relevance and inclusivity.

The Science of Smart Study Design

Sample size may seem like a dry statistic, but it's actually a core ingredient in building scientific trust and brand authority. Whether you're running a study on collagen supplements, anti-aging creams, or probiotic pet treats, the size of your sample can either elevate your claims, or cast doubt on them.

In an era where consumers expect proof, not just promises, the right sample size can be your most powerful marketing asset.

Curious about how to structure your study? Try our free tool, CitrusMatch, and get a detailed study breakdown in under two minutes!