Researchers in Germany examined whether long-term DHA plus whey protein supplementation improved erythrocyte omega-3 status, modulated hematological markers relevant to oxygen transport, and translated to performance or menstrual symptom benefits in female athletes.
“This study contributes further evidence that 4 months of DHA supplementation in semi-professional female soccer players robustly increases the HS-O3I and may have induced remodeling of erythrocyte membranes,” the researchers wrote in the journal Frontiers in Nutrition.
Omega-3s and endurance in female athletes
Omega-3 fatty have been shown to benefit recovery, adaptation, inflammation and oxygen transport. They may also help regulate exercise-induced inflammation, although the optimal dose and the individual effects of EPA and DHA remain unclear. Combining DHA with whey protein has also been shown to provide additional benefits by supporting both membrane changes and muscle recovery.
These effects may be particularly relevant for female athletes, the researchers of the new study noted, as omega-3 supplementation has been linked to reduced premenstrual symptoms, suggesting they may offer benefits for both performance and female-specific health. However, most research has focused on clinical populations rather than athletes, they noted.
Previous research has reported relatively low omega-3 status among athletes, with female athletes showing omega-3 index levels (HS-O3I) values of around 4–5%. The authors noted that these levels are below the 8–11% range proposed as a target based on clinical research. However, whether increasing omega-3 status improves athletic performance remains uncertain, they added.
DHA and improved endurance performance
Researchers enrolled 27 semi-professional female soccer players aged 18–35 to receive 1,000 mg/day of DHA (DHA FlexP 20) and 12 g/day of Nutri Whey Isolate protein, both supplied by FrieslandCampina, or to serve as an unsupplemented reference group.
Researchers assessed the athletes at baseline, two months and four months. They tracked menstrual cycles using daily symptom and temperature records, cervical signs and urinary tests. They also assessed premenstrual symptoms using the Premenstrual Symptoms Screening Tool (PSST).
At each assessment, researchers collected fasting blood samples to measure omega-3 status, erythrocyte membrane composition, hematological markers, inflammatory cytokines, and hormones. During assessment, athletes completed football-specific performance tests, including a 30 m sprint, countermovement jump and progressive running tests. Researchers used lactate and heart-rate measurements to determine the individual anaerobic threshold and other endurance indicators.
Results showed that DHA and whey supplementation significantly increased the HS-Omega-3 Index from 5.3% to 9.1% over four months, while the reference group remained unchanged. Researchers observed changes red blood cell size and volume, and reticulocyte hemoglobin (the hemoglobin inside newly produced, immature red blood cells). However, most blood markers remained unchanged.
The intervention did not improve sprint, jump or anaerobic threshold performance. However, higher omega-3 status was associated with better endurance. Menstrual symptoms and hormone levels also showed no significant changes.
The researchers suggested that changes in red blood cell membranes could help explain the link between omega-3 status and better endurance performance.
“Improved erythrocyte deformability, which has been linked to enhanced microvascular perfusion and tissue oxygenation, may constitute a physiological mechanism through which elevated omega-3 status could support endurance performance,” they noted.
“Future research should explore whether combined EPA and DHA supplementation offers greater functional benefits than DHA alone and identify the omega-3 threshold at which erythrocyte adaptations enhance oxygen transport and performance.”
Source: Frontiers in Nutrition. doi: 10.3389/fnut.2026.1886305. “Four months of DHA and whey protein supplementation in semi-professional female soccer players: a prospective non-randomized controlled study of omega-3 status, hematological outcomes, and physical performance.” Authors: Nolte, S. et al.
