Published on March 16, 2022

A randomized controlled trial demonstrates a positive relationship between the Omega-3 Index (specifically EPA levels) and increased strength among athletes supplementing with omega-3 fish oils

Key Points

  • Omega-3s have been shown to help improve muscle strength, range of motion (ROM), and delayed onset muscle soreness (DOMS), as well as upper arm circumference and muscle quality
  • A new randomized controlled trial found that athletes taking the fish oil supplements for 8 weeks increased their Omega-3 Index by 73% (from an average of 4.58% to an average of 7.94%), EPA levels by 332%, DHA levels by 64%, and handgrip strength significantly by 9.1%, and this increase was positively correlated with changes in EPA (greater increases in EPA levels were associated with greater increases in strength)
  • Vitamin D has also been shown to improve skeletal muscle function, normal coordination and balance

Studies have shown how omega-3 supplementation and a higher Omega-3 Index can positively impact athletic performance and recovery. Muscle stiffness, soreness, and loss of range of motion (ROM) are common negative effects of a new or strenuous exercise routine, which have shown to be reduced or prevented with fish oil supplements. Specific outcomes among those supplementing with omega-3 fish oils and/or with a higher Omega-3 Index include the prevention of loss of muscle strength, decreased ROM, and delayed onset muscle soreness (DOMS), as well as increased upper arm circumference and decreased muscle echo intensity (an indicator of muscle quality).

Study Shows 8 Weeks of Omega-3 Supplementation Increased Muscle Strength and Omega-3 Index

A randomized, double-blind, placebo-controlled study (RCT) by Heileson et al. looked at the effects of long-chain omega-3 fatty acids on athletic performance by measuring changes in body composition, strength, and power among a group of athletes taking fish oil supplements. The study enrolled 27 collegiate athletes, 15 of whom took fish oil supplements consisting of 1.75 g EPA plus 1.1 g DHA (taken daily for 8 weeks), and 12 who received placebo supplements. Omega-3 status was measured using a blood spot test for the Omega-3 Index, EPA and DHA levels.

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Among the athletes taking the fish oil supplements

  • The Omega-3 Index increased by 73% (from an average of 4.58% to an average of 7.94%)
  • EPA levels increased by 332%
  • DHA levels increased by 64%
  • Handgrip strength increased significantly by 9.1%, and this increase was positively correlated with changes in EPA (greater increases in EPA levels were associated with greater increases in strength)

None of the above changes were observed among those taking the placebo, and there were no significant differences between the supplementation group and the placebo group for changes in body composition. However, power (measured by vertical jump height) did improve in the fish oil group while it declined slightly in the placebo group, although this finding was not statistically significant.

Vitamin D is Important for Muscle and Bone Health Too

Vitamin D has been shown to improve skeletal muscle function, normal coordination and balance.  Studies have shown that maintaining a vitamin D level of at least 40 ng/ml (100 nmol/L) resulted in a decreased risk of bone fracture and stress fracture. Fast-twitch muscle fibers have been shown to be especially sensitive to vitamin D levels, which are important for burst activities and fall avoidance. Overall, cumulative research has shown that peak musculoskeletal performance may occur with a vitamin D level of at least 50 ng/ml.

Could Your Omega-3 and Vitamin D Levels be Improved? Measure them At-Home Today!

Are your vitamin D and omega-3 levels supportive of an active lifestyle? Make sure you know your Omega-3 Index (target of at least 8%) and your vitamin D level (target of 40-60 ng/ml or 100-150 nmol/L), and are taking daily steps to keep both within range. Testing is essential, as there is a large amount of variability in the omega-3 status for different people with the same intake amount (similar to vitamin D!). For example, a GrassrootsHealth analysis showed that the range of response with 1000 mg of EPA+DHA per day was 5.7% to 10.2%. Therefore, it is recommended that individuals measure their Omega-3 Index and determine a personalized dose using the Omega-3 calculator to achieve a minimum Omega-3 Index of 8%.

Having and maintaining healthy vitamin D levels and other nutrient levels can help improve your health now and for your future. Choose which additional nutrients to measure, such as your omega-3s and essential minerals including magnesium and zinc, by creating your custom home test kit today. Take steps to improve the status of each of these measurements to benefit your overall health. With measurement you can then determine how much is needed and steps to achieve your goals.  You can also track your own intakes, symptoms and results to see what works best for YOU.

Enroll in D*action and Test Your Levels Today!

What Does it Take YOU to Get Your D to 40 ng/ml (100 nmol/L)?

Did you know your health could be greatly affected by making sure you have a vitamin D level of at least 40 ng/ml (100 nmol/L)? Help us help you.

STEP 1 - Do you know what your vitamin D level is? If not, be sure to test today to find out.

STEP 2 – Determine your target level. Are you at your target level? Experts recommend a level of at least 40-60 ng/ml (100-150 nmol/L).

STEP 3 – Need to boost your level? Use the D*calculator to see how much vitamin D it may take to reach your target. Opt for the Loading Dose for a quicker boost.

STEP 4 – Optimize how your body absorbs and utilizes vitamin D with co-nutrients and these simple steps.

STEP 5 – Re-Test! This is an important step to make sure you have reached your target level, and to ensure you are not taking too much! Re-testing after 3-4 months is recommended.

STEP 6 – Adjust, Repeat…

Give your immune system the nutrients it needs to support a healthy you and protect yourself from unnecessary diseases, especially COVID-19.


The first Randomized Controlled Trial on vitamin D and COVID-19 has shown a 96% lower risk of ICU admission for those receiving vitamin D (as 25(OH)D to quickly boost vitamin D blood levels) along with the standard treatment, compared to those receiving standard treatment alone.

These results support many previous observational studies showing a relationship between vitamin D levels and intake and COVID-19 severity.

Review the Latest Nutrient Research for COVID-19

GrassrootsHealth Nutrient Research Institute has launched the new Immune Boost project with the use of our myData-myAnswers nutrient health system that nearly 15,000 people are already using for their health. Specific markers that influence immune health are suggested for testing as part of this project including:

  • Vitamin D
  • Omega-3 Index
  • Essential elements magnesium, selenium, and zinc
  • hsCRP

Our goal is to demonstrate how one can use the Nutrient Research Model established by Dr. Robert Heaney to show the effect of vitamin D serum levels of at least 40 ng/ml (100 nmol/L) on risk reduction for all ethnicities in the population. Status and intake of other nutrients will also be analyzed for any type of relationship to immune status and symptom severity. Join the project today!

Please let us know if you're interested in helping sponsor this project.

CLICK HERE for updates and new information about the project.

Through GrassrootsHealth Nutrient Research Institute, you can also test your essential elements magnesium, copper, zinc and selenium, toxins such as lead, mercury and cadmium, as well as your omega-3 levels, inflammation levels and thyroid stimulating hormone (TSH) level. Find out your levels today! Log on to the test selection page (click the link below) to get your tests and see for yourself if your levels can be improved.

Make sure you track your results before and after, about every 6 months!

Click Here to Access the Test Page

How can I track my nutrient intake and levels over time?

To help you track your supplement use and nutrient levels, GrassrootsHealth has created the Personal Health Nutrient Decision System called

For each specific supplement, you can track what days you take it, how much, and many other details.  This will help you know your true supplemental intake and what patterns of use work for you to reach and maintain optimum nutrient levels. Check it out today!