Recent posts: Amino Acids

What are branched chain amino acids?

Amino acids are the building blocks of protein. Branched chain amino acids (BCAAs) are so called because of their structure, which includes a “side chain” of one carbon atom and three hydrogen atoms. There are three BCAAs: leucine, isoleucine, and valine. Of these, leucine is the most heavily researched, and appears to offer the biggest physiological benefit. (More on that below.)

For the science geeks, these hydrophobic (water-fearing) amino acids are referred to as “aliphatic” (from the Greek aleiphar, or oil), as their central carbon attaches to a branched non-cyclic, open carbon chain.

BCAAs provide the basis for protein synthesis and energy production (Harper AE et al 1984; Patti ME et al 1998; Xu G et al 1998; Anthony JC et al 2001). In fact, BCAAs can comprise up to one-third of muscle protein (Mero 1999). Because of their prevalence and involvement in protein synthesis and energy production, BCAAs are important to many metabolic processes.

However, if BCAAs are going to participate in these processes, they must be available to the body. This means we have to eat enough BCAAs, and at the right times, to enable such processes to occur.

Why is adequate BCAA intake so important?

The BCAAs are the only amino acids not degraded in the liver. All other amino acids are regulated by the gut and the liver before being circulated elsewhere in the body. However, BCAAs head directly into the bloodstream. This means that dietary intake of BCAAs directly influences plasma levels and concentrations in muscle tissue (Layman DK 2003). Interestingly, BCAAs are burned for energy (oxidized) during exercise, so they’re also an important exercise fuel.

Consuming BCAAs before training can increase uptake into muscle tissue (Mittleman KD et al 1998). This has many benefits:

1. BCAA supplementation may lower lactate levels after resistance training and improve muscular oxidation.
2. BCAAs may increase growth hormone (GH) circulation, which may be related to anabolic mechanisms causing muscle growth (De Palo EF et al 2001).
3. BCAA supplementation may decrease serum concentrations of the intramuscular enzymes creatine kinase and lactate dehydrogenase following prolonged exercise. This can decrease muscle damage and improve recovery (Coombes JS, McNaughton LR 2000).

Muscle is an important site of BCAA activity. There is an increased cell concentration and breakdown of BCAAs in muscle tissue (Layman DK 2003). BCAAs are continuously released from the liver and other internal organs to skeletal muscle so that the BCAAs can assist in maintaining blood sugar levels. Indeed, BCAAs may be responsible for up to 40% of blood sugar production during exercise (Ahlborg G et al 1974; Ruberman NB 1975; see also Layman DK 2003).

What you should know

Because BCAAs are so important to muscle tissue, and because they help maintain blood sugar levels, it’s important to get enough to support your workouts. Consuming a carbohydrate, protein, and amino acid beverage during and after training can induce an insulin response, which helps transport BCAAs into cells. However, availability of leucine is more important than insulin. Within the muscle cell there’s one particular regulatory pathway for protein synthesis that’s stimulated by insulin, but dependent on leucine (Anthony et al 2000). In other words, protein synthesis (and hence muscle rebuilding) depends on how much leucine is available. And since BCAA levels decline with exercise, it makes sense to supplement with them during and/or after workouts (Mero 1999).

Because it’s so important to have leucine available for protein synthesis, if you train in a fasted state, or don’t eat after exercise, you’re going to lose more protein than you rebuild. However, if you eat adequate BCAAs during this time, especially leucine, you’ll enhance protein synthesis.

For extra credit

For the body to make new proteins, it needs an estimated daily leucine intake of between 1 to 4 grams/day (FAO/WHO/UNU 1985). That minimum intake needs to be met before leucine will be able to impact the insulin signaling pathway. But that’s just a baseline. Actual metabolic use, especially by athletes and people doing heavy resistance training, may be upwards of 12 grams/day.

There is a theory that BCAAs can limit central fatigue with endurance athletes, but it doesn’t appear to be supported by current data.

BCAA content of foods (grams of amino acids/100 g of protein)

Whey protein isolate 26%
Milk protein 21%
Muscle protein 18%
Soy protein isolate 18%
Wheat protein 15%

Source: USDA Food Composition Tables

Summary and recommendations

BCAAs play an important role in:

• Synthesis of proteins in general
• Glucose homeostasis (i.e. keeping blood sugar levels constant)
• Direct regulation of muscle protein synthesis (via insulin signaling cascade)

BCAAs’ potential impact on the aforementioned processes depends upon availability and dietary intake.

Adequate consumption of BCAAs may help manage body fat, spare muscle mass, and regulate glucose/insulin balance.

How can you put this knowledge to use?

Try adding BCAAs into your workout drink at a rate of 5 g BCAA per hour of training.

During periods of lower calorie intake, try adding a BCAA supplement every 2-4 hours during the day.

References

What is glutamine?

Glutamine is the most abundant free amino acid in the human body, making up about 60% of the skeletal muscle amino acid pool. (For more on amino acids, see All About BCAAs and All About Protein sections.)

Glutamine is a conditionally essential amino acid, which means that normally our bodies don’t need it from our diet. Exogeneous glutamine (in other words, glutamine we supplement or consume in food) is essential only under certain conditions, which include stress, trauma, muscular dystrophy, and illness, which can decrease glutamine levels by up to 50% (in severe cases). Because glutamine is a precursor for the structural unit of DNA and RNA, rapidly dividing cells are most likely to suffer from a shortage.

When we aren’t experiencing stress, trauma, muscular dystrophy or illness, our body produces enough glutamine on its own to supply our needs. The major part of endogenously produced (in other words, stuff our body makes) glutamine comes from skeletal muscle. Vitamin B3 and B6 are necessary for the production of glutamine from glutamic acid.

Why is glutamine so important?

Glutamine is a vital fuel source for the intestines and immune system that helps to keep defenses up against microbes. By nourishing these cells, it maintains the integrity of the GI tract.

Since the immune system is necessary for recovery from stress, glutamine may help during intense bouts of training. It may play a role in:

• Normalizing growth hormone
• Promoting glucose uptake after workouts
• Enhancing the hydration state of a muscle
• Reducing acid buildup with exercise

Yet it doesn’t seem that exercise decreases glutamine concentrations enough to compromise regular immune functions. This makes sense, since those who consume adequate energy from their diet tend to have a high glutamine intake. However, some people whose training and diet causes physical stress may benefit, e.g. people who are eating less food than necessary to modify body composition (in other words, dieting) or people whose training is extremely strenuous (such as elite athletes).

What you should know about glutamine

Where to find it

Cabbage and beets contain high concentrations of glutamine. (Eastern European grandmothers everywhere, rejoice! You have one more reason to encourage your “too skinny” grandchildren to eat the buraczki, borscht and holubtsi!) Other food sources include fish, beans and dairy.

Glutamine supplementation and dose

Typically, the consumption of any solo amino acid in high doses may hinder the assimilation of other amino acids. High doses of single amino acids can also result in bloating and diarrhea since they have osmotic properties. Yet glutamine supplements appear to be absorbed adequately and don’t create GI distress.

Glutamine supplementation has become routine to promote gut health in those with GI disorders, or those with HIV/AIDS, cancer, and other severe illnesses. Because glutamine has a rapid turnover rate, even high amounts (up to 30 grams each day) can be given without side effects. Most people will have a normalized plasma glutamine concentration by adding 20-25 grams over a 24 hour period.

In studies, glutamine supplement dosages have varied, including:

• 18 to 30 grams per day, by mouth
• 10 grams three times per day, by mouth
• 0.6 grams per kg of body weight per day (thus a 100 kg/220 lb person would consume 60 g daily)
• 14 grams of glutamine per day in combination with arginine and HMB for up to 24 weeks

Glutamine side effects and long-term use

There is little data regarding long-term usage (more than a few weeks) of glutamine supplements. No reported adverse effects have been attributed to short-term supplementation at less than 30 grams per day. Still, in some studies using high-dose intravenous administration of glutamine, patients developed elevated liver enzymes (indicating liver stress).

Other groups at risk:

• Those with diabetes should use caution when supplementing with glutamine because they tend to metabolize glutamine abnormally.
• Those who are sensitive to MSG (monosodium glutamate) may want to avoid glutamine supplements, due to glutamate inter-conversion.
• Those with epilepsy or bipolar disorder should be extremely cautious if considering glutamine and discuss it with their doctor first. Many anti-seizure medications work to block glutamate stimulation in the brain. And since the body metabolizes glutamine to glutamate, glutamine may interact negatively with anti-seizure medication.

Summary

Will it harm you in doses of less than 30 grams per day? Probably not.

If all of your bases are covered with nutrition, exercise and recovery, and you have the money to spend each month on more supplements, then adding glutamine is good. If you are undergoing a period of food restriction, then glutamine supplementation may improve nitrogen retention, decrease infection, and promote recovery from illness. Other situations that may benefit from glutamine supplementation include GI disorders, HIV/AIDS, and cancer.

Extra credit

Glutamine is a precursor for arginine.

A supplement blend containing glutamine has been shown to lower body fat, increase muscle mass, and increase strength when combined with 12 weeks of resistance training.

References