Soccer is one of the most popular sports in the world and it has been growing at a fast pace in the US over the last several decades. In 2018, the number of soccer players in U.S. high school programs hit an all-time high, with more than 850,000 participants, including 370,000 females.
The structural growth in women’s soccer has been accompanied by unparalleled interest in the game. Yet, as the number of those participating in soccer increases, so does the risk of negative brain health outcomes.
Several studies have demonstrated that concussion rates in soccer are comparable to, and often exceed, that of other contact sports. In fact, as many as 22% of all soccer injuries are concussions. Furthermore, evidence indicates that women exhibit more widespread evidence of microstructural damage in similar sports compared to men, suggesting biological sex differences in brain responses to repetitive microtrauma.
New research suggests proactive steps can be taken to protect the long-term cognitive health of female soccer players, so they can stay in the game.
Brain Health Risks Innate to Soccer
Head injury in soccer can occur via player-to-player collisions, falls, or heading (e.g., where players purposefully use their heads to control and/or advance the ball). Although contact with another player is the leading cause of concussions in soccer, accounting for over 51%, studies indicate that heading the ball plays a big role, too, accounting for over 30% of concussions in middle-school and high-school female soccer players alone.
Still, researchers believe these statics don’t capture the complete picture, and that many young players who likely sustained a concussion are not examined by a qualified professional and, therefore, are not accurately diagnosed or accounted for.
To make matters more complicated, the exact definition of a concussion continues to evolve. A widely accepted definition is a brain injury traumatically induced by a biomechanical force to the body, most often directly to the head, resulting in temporary impairment of normal neurological function.
But you don’t need a full-blown concussion to negatively impact neurological health. A subconcussion, or subconcussive impact (SCI), is a traumatic biomechanical force most commonly applied to the head that does not result in a known or clinically diagnosed concussion.
Subconcussive events, or repetitive subconcussive head impacts (RSHI), pointing to repeated events often experienced in sports such as soccer, rugby, football, or boxing, still lead to short and long-term cognitive consequences. For example, studies have revealed that cumulative heading over one year is associated with poorer neurocognitive performance and microstructural alteration of brain white matter, similar to traumatic axonal injury. The primary concern of the cumulative effect of RSHI is the long-term effects on athletes’ brains and mental health.
Sex Differences in Head Injury Risk and Outcomes
Research has shown that female athletes are at greater risk for poor outcomes after concussions. Although concussion numbers are higher in men due to greater participation in sports, women are more likely to have persistent post-concussion symptoms (1, 2, 3, 4).
While many theories have been bounced around for these sex differences, including subjective reporting variance, evidence provides objective data demonstrating biological differences in brain health outcomes. For example, one prospective cross-sectional study, which included 49 men and 49 women, found that with similar exposure to heading, women are more sensitive to repetitive subconcussive head impacts at brain tissue microstructure levels compared to men.
A few possible explanations have been suggested for these sex differences. One is that the standard ball size used for men’s and women’s soccer is the same regardless of physiological differences. Some argue that the relative impact of the ball on head and neck size may play a role.
Computer models have demonstrated the relative effects of head-ball collisions for different head masses in the past and concluded that a lighter ball should be used for children to reduce head-injury risk. Therefore, the same approach might be considered for women’s soccer since the head mass of women is 15% smaller than that of men.
Moreover, women’s neck muscles tend to be weaker, and evidence indicates that neck strength is vital for reducing the effects of head impacts and, therefore, concussion risk. Consequently, it’s possible that playing with a smaller ball and educating female soccer players on the importance of neck strength might close the disparity between negative outcomes of RSHI in sport. However, there might be more a female athlete can do to protect her cognition.
Omega-3 Role and Status Among Women Soccer Players
Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are omega-3 fatty acids that play essential roles in modulating inflammatory processes within the body. EPA and DHA may benefit the athletic population through several means, including enhanced muscle recovery, reduced exercise-related oxidative stress, and anti-inflammatory properties, which are potentially neuroprotective against RSHI. DHA, in particular, is an important structural component of neuronal cell membranes, accounting for approximately 10% of the total lipid content in the brain.
Even more so, omega-3s have been found to decrease the likelihood of concussions and improve recovery following traumatic head impact. In fact, research shows that when the brain is mechanically injured, omega-3s are released from neuronal membranes and used to reduce inflammation, lowering the omega-3 content in the brain tissue. This means that maintaining adequate Omega-3 Index could provide some protection for athletes who experience head trauma.
The Omega-3 index is a stable biomarker of omega-3 tissue status, and low Omega-3 Index levels have been observed in male and female athlete populations. For example, a 2020 study that assessed the dietary intake and Omega-3 Index of more than 1,500 participants, 49% female, found that only 6% of athletes met the Academy of Nutrition and Dietetics recommendation to consume 500 mg of DHA + EPA daily.
Moreover, the average Omega-3 Index was well below the recommended 8% — with the average hovering around 4.3%.
More recently, a 2023 study assessed 35 elite international-level female athletes participating in team-based sports and found that none of the athletes met the Omega-3 Index target of 8%, with only 8 of the 35 athletes consuming >250mg of DHA + EPA daily.
Prior Evidence demonstrates that declines in the Omega-3 Index are common, especially with increased training loads during a competitive soccer season. However, until recently, no study has accounted for the impact of heading frequencies on omega-3 status throughout a soccer season.
New Evidence Find Omega-3 Index is Negatively Associated with Heading Frequency
A study published in May 2023 was the first to explore the relationship between red blood cell (RBC) omega-3 status (i.e., Omega-3 Index) and heading frequencies in soccer players during a competitive season.
Sixteen players from a Division 1 NCAA soccer team completed the study. Their Omega-3 Index was measured pre- and post-season, bi-weekly electronic surveys were conducted to quantify header frequency, gameplay minutes were collected, and dietary assessment of habitual omega-3 dietary intake was measured using a food frequency questionnaire (FFQ).
The researchers found that preseason diet and Omega-3 Index were positively correlated; however, this correlation disappeared post-season. Furthermore, while gameplay minutes did not correlate with the post-season Omega-3 Index, they observed that the Omega-3 Index was negatively associated with heading frequency throughout the season.
Finding that despite no change in intake, post-season Omega-3 Index did not correlate with omega-3 intake suggests that soccer-related factors, such as frequent impacts to the head, may negatively influence omega-3 status.
The outcomes of this preliminary study indicate that increased dietary intake of omega-3s may be required for soccer players who frequently head the ball to maintain omega-3 status. Furthermore, these findings highlight the importance of educating young athletes on the importance of omega-3 status for player brain health in sports with repetitive head impacts.
Considering that soccer is the most popular sport in the world, the long-term consequences of soccer-related concussive and subconcussive brain trauma may represent a public health concern. More research is needed, especially those with longitudinal designs, to clarify the clinical significance of heading as a cause of brain injury.
Furthermore, as concussion and SCI diagnosis protocols continue to evolve, educating susceptible populations on the importance and potential protective properties of maintaining an adequate Omega-3 Index may help shield those who play the game.
The most effective way to increase the Omega-3 Index is to increase the dietary intake of omega-3 fatty acids EPA and DHA. Common dietary sources include fatty fish and seafood, fish oil, or algal oil supplementation. Regularly checking your Omega-3 Index can help ensure you are on the right track or are sustaining an Omega-3 Index that provides the most significant health benefits.