Highlights: 

  • Seaweed extract increases the strength of middle-aged and older adults. 
  • Seaweed extract and anabolic steroids similarly elevate testosterone in old mice to reach levels largely equal to young mice. 
  • Muscle mass is also increased in old mice to similar levels as young mice with both seaweed extract and anabolic steroids. 

Sarcopenia — age-associated muscle and strength loss — can lead to bone fractures, falls, and even death. Therefore, maintaining muscle mass and strength with resistance exercise and other potential interventions is of vital importance for longevity — increasing one’s lifespan. 

Now, researchers from Jeju National University in Korea report in Aging and Disease that seaweed consumption reduces age-associated muscle loss. In humans, Hyun and colleagues show that seaweed extract increases strength. In mice, they show that seaweed extract increases testosterone and muscle size. These findings suggest that consuming seaweed could counteract sarcopenia by providing functional nutrients — nutrients with medicinal value. 

 “Functional nutrients should be supplemented through routine dietary seaweed consumption to prevent muscle loss,” say the authors. “Functional nutrient supplementation is safe with few side effects, and it can be used in patients with an inherent risk of muscle weakness.”

Seaweed Counteracts Sarcopenia and Elevates Testosterone 

To determine the effect of seaweed on sarcopenia, Hyun and colleagues gave 100 mg/kg of seaweed extract (from Ishige okamurae brown algae) to adults aged 50 to 85 with relatively low muscle mass. Before and after 12 weeks of supplementation, the participants performed knee extensions while strapped to a chair and connected to a device that measures torque to assess muscle strength. After supplementation, seaweed extract was shown to increase muscle strength, particularly in the right quadricep — the largest group of muscles in the body, located in the thigh. 

(Hyun et al., 2023 | Aging and Disease) Seaweed Extract Increases Strength in Humans. Left: Quadricep muscle strength was measured by the torque exerted by knee extensions. Right: Compared to the placebo group (Con), males and females supplemented with seaweed extract (Test) saw an increase in right leg (R) quadricep strength.

To determine how seaweed supplementation could be increasing the muscle strength of older humans, Hyun and colleagues compared old mice (12 months, equivalent to 44 human years) to young mice (4 months, equivalent to 25 human years). The old mice were fed varying doses of seaweed extract for 6 weeks. As a result, the old mice that were given at least 100 mg/kg of seaweed extract had similar testosterone levels to young mice. 

“Testosterone is a powerful androgenic hormone that promotes muscle growth,” said the authors.  

(Hyun et al., 2023 | Aging and Disease) Seaweed Extract Increases Testosterone in Mice. Compared to young mice (YM), old mice (OM) had lower testosterone levels. However, OM treated with 100 or 200 mg/kg of Ishige okamurae seaweed extract (IO) had testosterone levels largely equal to young mice. Moreover, 50 mg/kg of the anabolic steroid oxymetholone (Oxy) increased testosterone to similar levels as 100 or 200 mg/kg of IO in OM.

Hyan and colleagues next assessed the muscle mass and strength of old mice treated with seaweed extract. They found that doses ranging from 50 to 200 mg/kg increased the calf muscle size of old mice, reaching similar levels to young mice. Additionally, grip strength was increased by the same dose range but did not reach similar levels to young mice. These findings suggest that seaweed extract can increase muscle size, at least in old mice.

(Hyun et al., 2023 | Aging and Disease) Seaweed Extract Increases Muscle Size in Mice. Compared to young mice (YM), old mice (OM) had lower calf muscle weights (Gastrocnemius weight). However, these weights largely equaled young mice when the OM were given 100 or 200 mg/kg of Ishige okamurae seaweed extract (IO). Moreover, 50 mg/kg of the anabolic steroid oxymetholone (Oxy) increased muscle weight to similar levels as 100 or 200 mg/kg of IO.

Supplementing with Seaweed to Slow Aging 

A compound called fucoidan — abundant in brown algae seaweed — has been shown to improve the memory of mice inflicted with inflammation-induced brain aging. Considering that brown algae seaweed has now been shown to slow muscle aging, seaweed extract could potentially be a potent anti-aging supplement. 

Furthermore, it may be possible to obtain the benefits of seaweed extract by adding whole seaweed to one’s diet. The authors conclude, 

“A consistent seaweed diet may assist in the prevention of age-related diseases. However, large-scale studies are required to further elucidate the protective function of seaweeds against sarcopenia caused by aging.”

Seaweed has not traditionally been associated with the American diet. However, this nutrient-dense food can be found at local grocery stores, especially near the coast, and at some specialty food stores or Asian markets. Furthermore, dried seaweed sheets can be found at places like Target, Wal-Mart, and Costco.