Should Women Take BCAAs?

By Cassandra Forsythe, PhD, RD

Branched-chained amino acids (or BCAAs) are a popular pre- and during-workout supplement. As a woman who wants to optimize her training and nutrition to be healthy and strong and look as good as she feels, BCAAs, like creatine, could be a beneficial addition to your nutrition strategy.

What are BCAAs and what do they do?

Amino acids are the building blocks of protein, and some amino acids (like the three in BCAA supplements: leucine, isoleucine, and valine) are considered essential because the body cannot make them. Therefore, they must be obtained from the foods we eat, through supplementation, or through a combination of both. High-protein foods such as meats, dairy, and eggs are excellent dietary sources of BCAAs.

BCAAs are unique within the family of essential amino acids in that they themselves make up at least one-third of the amino acids found in lean muscle tissue.1 Within your muscle, they work together to help repair damaged muscle proteins, which is important in order to build and grow high quality muscle tissue, especially following exercise. Leucine itself is actually one of the main drivers of muscle protein synthesis.


They are also unique in their metabolism: unlike other amino acids, BCAAs are not metabolized to a large extent in the liver, like most amino acids are.2 Instead, they travel directly to skeletal muscle, where they are broken down to create acetyl-CoA (see image), turned into new proteins, or are used to make glucose via gluconeogenesis, which can stabilize blood sugar levels.

Interestingly, during fasting or long periods of low blood glucose and insulin levels, leucine levels rise in the blood and muscle, while the capacity of muscle to use leucine to make energy increases concurrently (via the Citric Acid Cycle) .2 This means that when you go long periods of time between meals, which can cause your blood glucose levels to fall (and insulin levels also decrease), or when you fast (which also results in low glucose and insulin), your body will use protein for energy and will take away the role leucine and the other BCAAs can play in building new muscle proteins.

Note: remember this relationship between glucose, insulin, and leucine because we are going to come back to it in a moment.

Why supplement with BCAAs?

The reason why BCAAs are a popular sport nutrition supplement in both endurance and strength sports is because research indicates that they can help you build more muscle following resistance exercise3, can help prevent fatigue during long-duration aerobic exercise4, and can reduce exercise-related muscle soreness.5

Most exercise and sports nutrition research is done with men, and the results are then assumed to be the same for women, which may not always be the case. Surprisingly, there are actually a few studies done with women to prove these points, and they do show that moderate BCAA supplementation can be beneficial.

First, researchers from Nagoya University in Japan studied 12 untrained women and had them perform a high-volume squat exercise protocol (7 sets of 20 reps with 30 seconds of rest between sets) with and without 100 mg/kg body weight (about 5.5 grams) BCAA in a 2:1:1 Leucine: Isoleucine: Valine ratio.5

Researchers followed the women’s reports of soreness and muscle force output for three days following these exercise sessions and found that those who had taken the BCAAs had significantly lower delayed-onset muscle soreness (DOMS) and a lesser decrease in force output from their leg muscles. These findings indicate that BCAAs may help you recover faster from exercise, have less soreness from new exercise, and maintain your strength from hard training sessions.

deepsquats-kneepain-molly-450x340Second, a study recently published in the Journal of Dietary Supplements showed that BCAA supplementation given to a group of female rats eating a high-fat diet with or without exercise was able to improve body composition over a period of 16 weeks.

Those rats taking the supplement along with exercise and either a control diet or a high-fat diet both saw an increase in muscle mass and a decrease in fat mass.6 Indeed, many women who take BCAAs have also reported similar changes in their body composition.

Finally, a mixed-gender study of 218 men and women participating in a 30-kilometer cross country race or a marathon, showed that a dose of approximately seven grams (shorter race) and 16 grams (marathon) of BCAAs helped runners feel less mentally fatigued after the race, as assessed by the Stroop Color and Word Test (CWT) and improved performance during the marathon for the “slower” runners.7

Overall, there is indication that BCAA supplements for women can help reduce soreness, improve body composition with exercise, and reduce mental and physical fatigue.

Abby Smith-Ryan, PhD, an Assistant Professor and the Director of the Applied Physiology Laboratory at the University of North Carolina Chapel Hill’s Department of Exercise and Sports Science, suggests that BCAAs are most beneficial for women during aerobic exercise to help reduce fatigue. In addition, BCAAs can help to minimize muscle loss while allowing body fat reduction for women with low calorie intake.

Too much of a good thing? BCAAs and Type 2 Diabetes

While all the information presented here so far might indicate that you stand to benefit from BCAA supplementation, there are some newer findings you should be aware of and take into consideration before you run out to the store.

In researching for this article, I came across recent publications that have indicated a strong association between high BCAA intake, and high BCAA levels in the blood and type 2 diabetes.

Most recently, in a study published in the International Journal of Epidemiology, researchers took data from the huge cohorts of people involved in the Nurses Health Study (NHS; women followed from 1980 to 2012), NHS II (women followed from 1991 to 2011); and the Health Professionals Follow-up Study (HPFS; men followed from 1986 to 2010).8 Using advanced statistical analysis with detailed dietary records, they calculated the total intakes of BCAAs in each person and the correlations between BCAA intake and protein intake. (Because high animal protein intake is often associated with higher BCAA intake, it had to be corrected for in the analyses.)

The researchers observed consistent associations of long-term consumption of BCAAs with increased risk of Type 2 diabetes.

These associations were independent of traditional diabetes risk factors, including BMI, and were separate from total meat and protein intake.

These finding are similar to results from several recent studies in which high blood levels of BCAAs were associated with increased diabetes risk, impaired fasting glucose, and insulin resistance. The reason for this association is that high concentrations of BCAAs in the blood reflect an early disturbance of protein and amino acid metabolism in these disease states, which may worsen if BCAA intake remains high.9

Now, remember the discussion above where low glucose and insulin resulted in increased leucine in the blood and leucine use for glucose stabilization? Well, Type 2 diabetes and insulin resistance are characterized by highs and lows of glucose and insulin in the blood. In the low times, leucine would be part of the solution for stabilizing blood glucose, and in high times, leucine would drop, except when normal protein metabolism is altered, like it is in these disease states. This would then lead to chronically elevated leucine and BCAA levels. And, as stated, if you supplement with BCAAs when you have this situation going on in your body, you are only going to make your health worse.

The good news is that if you improve your health by exercising regularly, which increases muscle metabolism and fuel utilization, and eating better, which naturally stabilizes your blood glucose and insulin levels and reduces body fat, you can lower your blood BCAA levels by increasing their metabolic breakdown and possibly concurrently reduce your risk of these diseases.10

Because of the possible association between high BCAA intake and development of type 2 diabetes, it’s important to approach supplementation conservatively, particularly if you tend to have a high dietary protein intake.

Should you supplement with BCAAs?

This article has hopefully helped you better understand the potential benefits and risks of taking BCAAs so that you can make an informed decision to include them or not as part of your strength and fitness supplement strategy. The data available to date shows that a reasonable dose of 100 mg/kg of bodyweight per day before or during your workout should be enough to help build or maintain muscle, and reduce fatigue and muscle soreness (that’s about 5 to 8 grams, for weight ranging from 110 to 180 pounds, respectively). More than the recommended dosage could lead to negative consequences for your health. So, like most things, more of a good thing is not always better.

Note from GGS: As with any supplement, always read labels carefully, consult with a healthcare provider, and stop taking if you notice an abnormal or adverse reaction.

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About the author:  Cassandra Forsythe, PhD, RD

Cassandra Forsythe, PhD, RD, CSCS, CISSN is an Assistant Professor at Central Connecticut State University (CCSU). She is a mother, entrepreneur, health and fitness enthusiast, and the author of The Modern Woman’s Guide To Good Nutrition. Cass is also on the advisory boards for Women’s Health magazine, and You can learn more about Cass on her website.


  1. Mero A. Leucine supplementation and intensive training. Sports Med 1999;27:347-358
  2. Groff & Gropper. Advanced Nutrition and Metabolism. Wadsworth Thompson Learning. 2000
  3. Dreyer HC, et al. Leucine-enriched essential amino acid and carbohydrate ingestion following resistance exercise enhances mTOR signaling and protein synthesis in human muscle. Am J Physiol Endocrinol Metab. 2008 Feb;294(2):E392-400. Epub 2007 Dec 4.
  4. Kreider, RB (1998). Central fatigue hypothesis and overtraining. In RB Kreider, AC Fry, & ML O-Toole (Eds.), Overtraining in Sport (pp. 309-331). Champaign, IL: Human Kinetics.
  5. Shimomura Y et al. Branched-chain amino acid supplementation before squat exercise and delayed-onset muscle soreness. Int J Sport Nutr Exerc Metab.2010 Jun;20(3):236-44.
  6. Platt KM et al. Branched-Chain Amino Acid Supplementation in Combination with Voluntary Running Improves Body Composition in Female C57BL/6 Mice. J Diet Suppl. 2016;13(5):473-86
  7. Blomstrand E et al. Administration of branched-chain amino acids during sustained exercise—effects on performance and on plasma concentration of some amino acids. Eur J Appl Physiol Occup Physiol. 1991;63(2):83-8.
  8. Zheng Y et al. Cumulative consumption of branched-chain amino acids and incidence of type 2 diabetes. Int J Epidemiol. 2016 Jul 13
  9. Lynch CJ, Adams SH. Branched-chain amino acids in metabolic signaling and insulin resistance. Nat Rev Endocrinol. 2014 Dec;10(12):723-36
  10. Shah SH, et al. Branched-chain amino acid levels are associated with improvement in insulin resistance with weight loss. Diabetologia. (2012)

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