Researchers tested whether a supplement made from brown algae called fucoidan could help people build muscle and get stronger when combined with weight training. Twenty healthy adults took either fucoidan or a fake pill while doing resistance exercises for six weeks. Both groups got stronger, but the fucoidan group showed better results for quick, explosive movements and gained more muscle while losing more body fat. This suggests that fucoidan might be a helpful addition to a workout routine, though more research with larger groups is needed to confirm these findings.

The Quick Take

  • What they studied: Whether a brown algae supplement called fucoidan could help people build muscle, get stronger, and improve their body composition when combined with weight training exercises.
  • Who participated: Twenty healthy adults (9 men and 11 women) with no serious health conditions. Half received fucoidan supplement and half received a placebo (fake pill) while both groups did the same six-week weight training program.
  • Key finding: Both groups improved their strength equally, but the fucoidan group showed significantly better results for explosive power movements and gained more lean muscle while losing more body fat compared to the placebo group.
  • What it means for you: If you’re doing weight training, fucoidan supplementation may help you see better results in muscle gain and fat loss, though the strength gains appear similar to training alone. This is promising but needs confirmation in larger studies before making it a standard recommendation.

The Research Details

This was a randomized controlled trial, which is considered one of the strongest types of scientific studies. Researchers randomly assigned 20 participants into two equal groups: one received 1 gram of fucoidan supplement daily, and the other received an identical-looking placebo pill. Neither the participants nor the researchers knew who was getting the real supplement (called double-blind), which prevents bias. Both groups completed the exact same six-week resistance training program with measurements taken before and after the study period.

The researchers measured several important outcomes: how much weight participants could lift in a back squat (maximum strength), their explosive power using a special test called the Wingate test, their body composition (muscle versus fat), and various blood markers. This comprehensive approach allowed them to see if fucoidan affected different aspects of fitness and health.

The double-blind, placebo-controlled design is important because it eliminates the placebo effect—the tendency for people to feel better or perform better simply because they believe they’re receiving treatment. By keeping both participants and researchers blinded to the treatment assignment, the study ensures that any differences between groups are due to the supplement itself, not expectations or bias. The combination of strength testing, power testing, and body composition analysis provides a complete picture of how the supplement affects different fitness outcomes.

This study has several strengths: it used a proper control group with placebo, employed blinding to prevent bias, and measured multiple relevant outcomes. However, the main limitation is the very small sample size of only 20 people, which makes it harder to be confident in the results. The study lasted only six weeks, so we don’t know if benefits continue longer or if they’re sustainable. The participants were apparently healthy adults, so results may not apply to older adults, people with health conditions, or athletes. Published in Scientific Reports, a reputable peer-reviewed journal, which adds credibility to the findings.

What the Results Show

Both the fucoidan and placebo groups significantly increased their back squat strength (the maximum weight they could lift one time) after six weeks of training, with no meaningful difference between groups. This shows that resistance training itself is very effective for building strength, and the supplement didn’t add extra strength benefits beyond what training alone provides.

However, when measuring explosive power—the ability to produce force quickly, tested using a Wingate test—the fucoidan group showed significantly greater improvements compared to the placebo group. This suggests the supplement may specifically help with quick, powerful movements rather than maximum strength.

For body composition, the fucoidan group showed better results: they gained more lean muscle mass and lost more body fat percentage compared to the placebo group. This is particularly interesting because it suggests the supplement may help the body build muscle more efficiently and reduce fat storage while training.

Blood measurements were taken to assess metabolic health, and the fucoidan group showed improvements in body composition markers, suggesting the supplement may positively affect metabolism. The study also tracked safety, with no adverse effects reported in either group, indicating fucoidan appears to be safe at the tested dose of 1 gram daily.

Previous research in mice showed that fucoidan improved aerobic capacity and increased muscle size and strength. This human study partially confirms those findings—the body composition improvements align with the mouse studies. However, the lack of additional strength gains in humans differs from the mouse research, suggesting that fucoidan’s effects may work differently in humans than in laboratory animals. The explosive power improvements in humans represent a new finding not previously documented in animal studies.

The study’s biggest limitation is its small size—only 20 participants makes it harder to be confident the results would apply to larger populations. The six-week duration is relatively short; we don’t know if benefits continue, plateau, or fade over longer periods. All participants were apparently healthy adults, so results may not apply to older adults, people with chronic diseases, or competitive athletes. The study didn’t track diet or overall activity outside the training program, which could have influenced results. Finally, the study used a specific fucoidan blend at a specific dose, so different products or amounts might produce different results.

The Bottom Line

Based on this research, fucoidan supplementation at 1 gram daily may be worth considering if you’re doing regular resistance training and want to optimize muscle gain and fat loss (moderate confidence level). However, it doesn’t appear to provide additional strength gains beyond training alone. The supplement appears safe with no reported side effects. More research with larger groups and longer duration is needed before making strong recommendations.

This research is most relevant to people actively doing resistance training who want to maximize muscle gain and fat loss. It may be particularly interesting for those focused on explosive athletic movements. People with brown algae allergies or sensitivities should avoid it. Those taking blood thinners should consult their doctor, as some seaweed products may have mild blood-thinning effects. Pregnant or breastfeeding women should consult healthcare providers before starting any new supplement.

Based on this study, you might expect to see measurable changes in body composition (muscle gain and fat loss) within 4-6 weeks of combining fucoidan supplementation with consistent resistance training. Improvements in explosive power may appear within similar timeframes. However, individual results vary, and benefits may take longer or be less noticeable depending on your starting fitness level, diet, and training consistency.

Want to Apply This Research?

  • Track weekly measurements of body composition (weight, body fat percentage if possible), explosive power performance (vertical jump height or similar quick-movement tests), and subjective energy/recovery ratings. Record supplement adherence daily to ensure consistent intake.
  • Set a daily reminder to take the fucoidan supplement at the same time each day, ideally with a meal. Pair this with a structured resistance training schedule (3-4 sessions weekly) and track workouts in the app to ensure consistency, since the supplement’s benefits depend on regular training.
  • Measure and log body composition weekly using the same method and time of day. Track maximum lift weights monthly for major exercises. Assess explosive power monthly through consistent tests (like vertical jump). Monitor energy levels and recovery quality daily. Set a 6-week checkpoint to evaluate whether you’re seeing the expected improvements in muscle gain and fat loss.

This research summary is for educational purposes only and should not replace professional medical advice. While this study suggests fucoidan supplementation may be safe and potentially beneficial when combined with resistance training, the evidence is based on a small sample size and short duration. Before starting any new supplement, especially if you have existing health conditions, take medications, are pregnant or breastfeeding, or have allergies to seaweed products, consult with your healthcare provider or registered dietitian. Individual results vary, and supplements are not regulated the same way as medications. This summary reflects the findings of one study; more research is needed for definitive recommendations.