Branched-chain amino acids (BCAAs) are essential nutrients vital for muscle metabolism and overall health. While BCAA supplements are popular among athletes and bodybuilders, recent research suggests that a diet low in BCAAs may offer unexpected benefits, particularly for metabolic health. However, it's crucial to understand both the potential advantages and risks associated with restricting BCAA intake.
Understanding BCAAs
The body can code for 20 different types of amino acids. However, some amino acids are considered to be essential whereby they cannot be synthesized in large enough quantities by the body. Therefore, they must be consumed as part of a balanced diet. Of the nine essential amino acids, leucine, valine, and isoleucine are referred to as branched-chain amino acids. These three BCAAs are so called because they have a branched molecular configuration (which brings back happy nerdy memories of drawing amino-acid diagrams during my nutrition degree!). BCAAs are hugely important for health because they make up one-third of muscle protein, can be used directly as fuel by the muscles, and can be converted into glutamine and alanine - two other important amino acids that are released in large quantities during aerobic exercise.
Sources of BCAAs
BCAAs are naturally occurring amino acids found in protein-rich foods. Anyone eating a plant-based diet may find BCAA supplements helpful for making up shortfalls in these essential amino acids, although care should be taken to also ensure a good overall intake of plant protein - from legumes, pulses, nuts, and seeds, for instance - to get all the amino acids required for health. Quality and active ingredients in supplements may vary widely from maker to maker. You can get branched-chain amino acids from these foods:
- Whey, milk, and soy proteins
- Corn
- Beef, chicken, fish, and eggs
- Baked beans and lima beans
- Chickpeas
- Lentils
- Whole wheat
- Brown rice
- Almonds, Brazil nuts, and cashews
- Pumpkin seeds
Potential Benefits of a Low BCAA Diet
Improved Metabolic Health
A new study in mice has suggested that counting calories might not be the only way to improve humans’ metabolic health. The study found that feeding obese, pre-diabetic mice a specialized diet low in the amino acids leucine, isoleucine and valine promoted leanness and improved the regulation of blood sugar. Importantly, mice in this study were free to eat as much of the low-BCAA food as they wanted, and thus did not experience overall calorie reduction.
Dr. Lamming said, “We’ve identified an unanticipated role for dietary BCAAs in the regulation of energy balance, and we show that a diet with low levels of BCAAs promotes leanness and good control of blood sugar." Researchers will next investigate whether reducing dietary BCAAs can improve the metabolic health of humans, and how the specific amino-acid composition of dietary protein regulates metabolic health.
Read also: In-Depth Look at BCAAs and Female Weight Loss
Elevated branched chain amino acids (BCAAs) are associated with obesity and insulin resistance. We demonstrate that the metabolic and lifespan costs of high BCAA: non-BCAA intakes, when paired with a high carbohydrate, low fat nutritional background, are not associated with increased hepatic mTOR activation, but rather, can be explained by their interactions with other key metabolically essential AAs leading to extreme hyperphagia.
Appetite Control and Weight Management
Long-term exposure to high BCAA diets leads to hyperphagia, obesity and reduced lifespan. These effects are not due to elevated BCAA per se or hepatic mTOR activation, but rather due to a shift in the relative quantity of dietary BCAAs and other AAs, notably tryptophan and threonine. Increasing the ratio of BCAAs to these AAs resulted in hyperphagia and is associated with central serotonin depletion.
The ratio among AAs in the non-BCAA complement were not identical between treatment diets offering the opportunity to disentangle non-BCAA effects. The intakes of three EAAs, Trp, Thr and methionine (Met), were maintained consistently across diet treatments. Supplementation of Trp or Thr, two metabolically essential AAs, but not Met, suppressed food intake on BCAA200 diets towards levels seen in control mice on the BCAA100 diet.
Potential Role in Longevity
Published in final edited form as: Nat Metab. 2019 Apr 29;1(5):532-545. How long-term dietary BCAAs impact late-life health and lifespan is unknown. Preventing hyperphagia on BCAA-supplemented diets by either 20% calorie restriction (CR) or pair-feeding reversed metabolic dysfunction and lifespan costs. Median lifespan of BCAA200 mice was reduced by ~10% when compared to the other dietary groups.
Potential Risks and Considerations
Muscle Growth and Recovery
The rationale behind supplementing with BCAAs is that these three amino acids promote muscle synthesis (anabolism) and help prevent muscle breakdown (catabolism). Leucine in particular has been shown time and again to play a unique role in stimulating muscle protein synthesis (MPS), with more recent studies finding an additive effect when all three BCAAs are taken together. Essential amino acids (EAAs) in general have been found to stimulate mechanistic target of rapamycin complex-1 (mTORC1) signaling.
Read also: Fuel Your Keto Diet with BCAAs
If you’re going to use for athletic performance, in practical terms, studies show that taking around 4-6 grams of BCAAs during and after exercise can help increase MPS by around 22%. However, greater increases in MPS have been seen with whey protein supplements taken after exercise that contain all essential amino acids including BCAAs.
BCAA supplementation may, however, offer particular benefits for improving MPS at rest, such as when a person is on bed rest or recovering from injury. And, BCAAs seem to be helpful in reducing muscle breakdown, damage, and soreness in endurance athletes, and delayed onset muscle soreness (DOMS) in general. Other studies suggest that BCAAs may help preserve muscle in people on low carbohydrate diets. BCAAs help to promote the use of fatty acids for energy and enhance glycogen synthesis in the liver, thereby sparing muscle from being broken down as an energy source.
Potential for Cancer Growth
There isn’t a definite answer as of yet, but some of the latest cancer and longevity research actually centers around amino acid restriction as a means of delaying aging and reducing the risk for cancers. Among the amino acids thought best to be consumed in limited amounts are the BCAAs as well as methionine and tryptophan, as these amino acids are thought to fuel the growth of cancer cells. For example, BCAAs cause activation of the mTORC1 pathway, which stimulates cells to grow and proliferate, including cancer cells, and amino acids like leucine have been isolated as carcinogenic in some animal models, as well as by longevity researchers like Dr. Valter Longo who is head of the Longevity Institute at the University of Southern California.
Also consider this study which showed that deprivation of leucine inhibits growth of breast cancer cells. Although we need some BCAAs in our diets, Dr. Longo’s research would seem to indicate that long term use of high dose BCAA supplements is probably a bad idea, and that these products should be reserved for performance athletes. The bottom line here is actually fairly straightforward - BCAA supplements are pro-growth, in both good ways and bad. The side effects are usually minimal and they can help with muscle growth and recovery, however, if you find Valter Longo’s research compelling, BCAA supplements could also increase the risk of cancer growth in some people as well.
General Safety and Side Effects
For the most part, BCAA supplements are safe and well tolerated, with few, if any, adverse effects. BCAA supplements are considered generally safe for use at the amount recommended (check product labels) but could reduce the absorption of other essential amino acids if taken in excess. Also, anyone with a kidney issue should consult a health care practitioner before taking BCAAs. People with type 2 diabetes should also consult a health care practitioner prior to taking BCAAs as they may affect how the body responds to insulin and uses glucose.
Read also: Guide to BCAA for Fat Loss
When taken up to 6 months, oral supplements of BCAAs have not often been linked with harmful side effects. However, side effects may include:
- Nausea
- Pain
- Headache
Interactions
BCAAs may interfere with blood glucose levels during and after surgery. You may also be at increased risk if you have chronic alcoholism or branched-chain ketoaciduria. Also, avoid using BCAAs if you are pregnant or breastfeeding. Talk with your doctor first if you are taking:
- Diabetes medications
- Parkinson's medications
- Corticosteroids
- Thyroid hormone
- Proglycem (diazoxide)
Tell your doctor about any supplements you're taking, even if they're natural. That way, your doctor can check on any potential side effects or interactions with medications or foods. They can let you know if the supplement might increase your risk.