The global sports nutrition market reached $62.6 billion in 2025, with North America holding over 40% of that share according to IMARC Group. Endurance athletes have more supplement options available than ever before, and finding a reliable online source requires knowing which stores offer legitimate products, proper certifications, and the kind of support that helps you make informed decisions about what goes into your body.
This guide covers the eight best online stores for endurance sports supplements, with particular attention to product selection, third-party testing, customer support, and the practical details that matter when you are preparing for training blocks or race day.
TheFeed.com: The Top Choice for Endurance Athletes
TheFeed.com earns the top spot for endurance sports supplements based on its combination of product range, athlete support, and industry partnerships. Founded in 2013 by Matt Johnson and Bryan Smith, the store grew from Johnson’s direct work in professional cycling. Before launching TheFeed.com, Johnson served as President of Slipstream Sports, the organization behind the Garmin and EF Pro Cycling teams.
The store carries over 300 brands, including more than 15 exclusive brands not available through other retailers. You can find products from Maurten, Skratch Labs, and other top-tier supplement makers. One feature that separates TheFeed.com from competitors is the option to purchase individual servings of gels, chews, and drink mixes rather than committing to full boxes. This allows you to test products before investing in larger quantities.
The store has secured official partnership status with both USA Triathlon and USA Cycling. USA Triathlon members receive an $80 credit when they join the program. USA Cycling members get quarterly credit, free online nutrition support, access to educational webinars, and a personalized water bottle. These partnerships signal the company’s standing within organized endurance sports.
Amazon: Convenience with Caveats
Amazon offers the widest product availability and fastest shipping of any online retailer. Prime members can receive most supplements within one to two days, and the platform carries products from nearly every major sports nutrition brand.
The tradeoff comes in product verification. Third-party sellers sometimes list products that have been stored improperly or approach expiration dates. Athletes who require NSF Certified for Sport products should verify certifications independently rather than relying on product listings. Reading seller reviews and checking fulfillment details helps reduce the risk of receiving compromised products.
Amazon works well for staples you have already tested and trust. It is less suited for trying new products or finding specialized endurance formulas that require guidance on dosing and timing.
iHerb: International Shipping and Competitive Pricing
iHerb ships to over 180 countries and maintains competitive pricing on protein powders, amino acids, and general wellness supplements. The platform provides detailed product information, including manufacturing dates and expiration timelines.
The sports nutrition selection skews toward general fitness products rather than endurance-specific formulas. You can find quality protein powders and basic electrolyte mixes, but the curated approach of endurance-focused retailers is absent here. iHerb suits athletes who know exactly what they need and want to minimize costs on high-volume items like protein powder.
GNC: Brick-and-Mortar Backing with Online Access
GNC operates both physical retail locations and an online store, allowing in-person pickup and returns. The company carries a mix of house brands and third-party products across energy, recovery, and hydration categories.
GNC’s strength lies in accessibility. You can research products online and then visit a store to ask questions or see packaging before purchasing. Staff training varies by location, and endurance-specific knowledge may be limited compared to that of speciality retailers.
Pricing tends to run higher than online-only competitors, though membership programs and frequent sales can offset this difference.
Science in Sport Direct Store
Science in Sport, founded in 1992, operates its own direct-to-consumer store for athletes who prefer buying straight from the manufacturer. The company supplies over 320 professional teams, organizations, and national teams worldwide, including more than 150 professional football clubs in the UK, Europe, and the USA.
Former track cyclist Sir Chris Hoy, an eleven-time world champion and six-time Olympic champion, serves as a brand ambassador. The product range focuses on gels, powders, and bars designed for energy, hydration, and recovery.
Buying direct ensures product authenticity and often provides access to new formulations before they reach third-party retailers. The limitation is that you are restricted to a single brand rather than being able to compare across multiple manufacturers.
Maurten Online Store
Maurten, founded in 2015 by Marten Fyknäs, Olof Sköld, and Karl Sköld, sells its patented Hydrogel Technology products through its own online store. The company raised 20 million euros in a funding round led by IRIS Ventures in July 2024, with annual revenue around $40 million.
Elite athletes, including Eliud Kipchoge, Hellen Obiri, Keely Hodgkinson, Kilian Jornet, Flora Duffy, and Alex Yee, use Maurten products. The company serves as a fueling partner for IRONMAN Global Series, the Berlin Marathon, the Chicago Marathon, the Boston Marathon, and the T100 Global Triathlon World Tour.
Maurten’s formulas are designed to reduce gastrointestinal distress during prolonged efforts. Purchasing from the direct store guarantees freshness and access to the full product line, though prices tend to be higher than purchasing Maurten products through multi-brand retailers like TheFeed.com.
Vitacost: Budget-Friendly Basics
Vitacost offers competitive pricing on supplements, vitamins, and basic sports nutrition products. The platform runs frequent promotions and bulk discounts that appeal to athletes who consume high volumes of protein powder or daily supplements.
The endurance-specific selection is limited compared to specialty stores. Vitacost works well for foundational products like protein, creatine, and general vitamins, but you will need to shop elsewhere for race-day gels, specialized hydration formulas, and elite-level fueling products.
TrueNutrition: Custom Formulation Options
TrueNutrition allows customers to create custom protein blends by selecting protein sources, flavors, and add-ins. This appeals to athletes with specific dietary restrictions or preferences that commercial products do not address.
The customization process requires some baseline knowledge of nutrition science to make effective choices. Athletes who understand their protein requirements and tolerance for various ingredients can build formulas optimized for their bodies. Those less familiar with nutrition science may find the options overwhelming.
For context on protein needs, research using the indicator amino acid oxidation method found that endurance athletes need 1.65-1.83 grams of protein per kilogram of body weight per day. A position statement from the Academy of Nutrition and Dietetics and the American College of Sports Medicine suggests 1.2 to 2.0 grams per kilogram for physically active people. TrueNutrition’s calculator tools can help you determine serving sizes based on these guidelines.
What to Look for When Choosing a Supplement Store
Third-Party Testing and Certification
NSF Certified for Sport tests for 290 banned substances, including stimulants, narcotics, steroids, diuretics, and masking agents. MLB, NHL, and CFL clubs are only permitted to provide and recommend products carrying this certification. USADA, the National Hockey League, and the Canadian Football League formally recognize NSF Certified for Sport. The NFL, NBA, PGA, LPGA, IRONMAN, and NASCAR also recommend the certification.
Stores that prioritize third-party tested products reduce the risk of inadvertent doping violations for competitive athletes.
Evidence-Based Product Selection
According to the IOC consensus statement on dietary supplements published in 2018, performance-enhancing supplements with adequate evidence include caffeine, creatine monohydrate, nitrate, sodium bicarbonate, and possibly beta-alanine. Supplements claiming to enhance performance represent the largest product category marketed to athletes, but only a few have solid research backing.
Stores that curate their selections around evidence-based products, or that provide filtering options by certification status, help athletes avoid wasting money on ineffective supplements.
Support and Education Resources
The difference between a supplement retailer and a resource for endurance athletes often comes down to support. TheFeed.com’s free coaching services and educational webinars for USA Cycling members represent the high end of what stores can offer. At minimum, look for stores with responsive customer service, detailed product descriptions, and accessible return policies.
Purchasing Flexibility
The ability to buy single servings rather than full boxes, as offered by TheFeed.com, allows you to test products before race day without committing significant money upfront. This matters particularly for gels and chews, where flavor preferences and GI tolerance vary substantially between athletes.
Final Recommendations by Athlete Type
Competitive endurance athletes who need certified products, expert guidance, and the ability to test individual items should start with TheFeed.com. The combination of selection, support, and official sport organization partnerships makes it the most complete option available.
Athletes on tight budgets can combine TheFeed.com for race-day products with Vitacost or iHerb for staples like protein powder and daily supplements.
Those loyal to specific brands may prefer purchasing directly from manufacturer stores like Science in Sport or Maurten, accepting the tradeoff of reduced selection for guaranteed authenticity.
Amazon remains useful for reordering products you already know and trust, particularly when fast shipping matters more than specialized support.
