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Healthy Eating for Women

Fuel: Understanding Amino Acids

To understand more about these critical nutrients and why you need them, let’s take a closer look.

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We all know that protein provides the building blocks for muscle. And it’s common knowledge that on the molecular level, amino acids provide the building blocks for protein. But not all aminos are the same, and the amounts of each you need vary based on overall protein consumption and the requirements of your fitness lifestyle. To understand more about these critical nutrients and why you need them, let’s take a closer look.

There are 20 proteinogenic amino acids that create proteins in the body to perform countless physiological and chemical processes, including muscular development and maintenance. These are categorized according to their need to be supplied in the diet or the body’s ability to manufacture sufficient amounts for health. The three categories are known as essential, nonessential and conditionally essential.

Essential Amino Acids

Eight amino acids are considered essential for adults in that they are required to be provided by food consumption. Your body requires these to synthesize proteins to support anabolic muscular growth and reduce catabolic muscle breakdown, yet it cannot manufacture them. The essential amino acids are L-isoleucine, L-leucine, L-lysine, L-methionine, L-phenylalanine, L-threonine, L-tryptophan and L-valine. In addition, two additional aminos are considered essential for infants only: L-arginine and L-histidine.

Nonessential Amino Acids

A second group of amino acids is known as nonessential. There are five in this group that can be manufactured by your body through ingestion of essential aminos and other protein compounds. Therefore, supplementation of these is not critical for health so long as you eat a balanced diet. The nonessentials include L-alanine, L-asparagine, aspartic acid, L-glutamic acid and L-serine.

Conditionally Essential Amino Acids 

Finally, there are six conditionally essential amino acids that cannot be produced by the body in sufficient amounts to meet specific demands, such as catabolic distress from crash dieting or high-intensity training. In addition, these are shown to provide significant health benefits through supplementation. The six in this category are L-arginine, L-cysteine, L-glutamine, L-glycine, L-proline and L-tyrosine.

Branched-Chain Amino Acids

Three of the essential amino acids noted above — leucine, isoleucine and valine — are unique in the way they are synthesized and used in the body. Known collectively as branched-chain amino acids, this trio helps produce energy within muscle tissue that is even more efficient than glucose (typical muscular fuel). In addition, they stimulate protein synthesis, which promotes muscular growth. Leucine specifically triggers an increase in mTOR activity, which activates anabolic growth. For this reason, BCAA supplements typically have ratios that include extra leucine versus isoleucine and valine (such as 4:1:1 or even 10:1:1).

Specific Benefits of Select Aminos 

Dietary protein assimilation is handcuffed by something known as the “limiting amino-acid factor.” In essence, this means that if any essential amino acid is not present in sufficient quantities compared to the others, it limits protein synthesis. This is why blends of plant-based proteins, which are deficient in various aminos, are more anabolic than individual ones. Of course, whey is considered the king of proteins because of its complete amino-acid profile.

Yet the benefits of amino acids extend beyond protein consumption and digestion. Extensive research shows that individual aminos provide specific health benefits that can be achieved through supplementation. Leucine and the BCAAs are an obvious example when it comes to building muscle, improving recovery and providing energy for exercise. But there are others with research-backed benefits. (See accompanying chart.)

Required Consumption of Aminos 

Because they are required to be provided via the diet or supplementation, the essential amino acids have specific requirements for daily ingestion. These easily should be met through a balanced diet consisting of about 30 percent of your caloric intake from complete protein (poultry, lean red meat, whey supplements, etc.). 

Here are the minimum daily needs for aminos, according to the Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids (The National Academies Press, 2002 and 2005):

Histidine: 14 mg/kg bodyweight per day

Isoleucine: 19 mg/kg

Leucine: 42 mg/kg

Lysine: 38 mg/kg

Methionine (plus cysteine): 19 mg/kg

Phenylalanine (plus tyrosine): 33 mg/kg

Threonine: 20 mg/kg

Tryptophan: 5 mg/kg

Valine: 24 mg/kg

To determine your basic needs, first calculate your bodyweight in kilograms. Do so by dividing by 2.2 (i.e., 100 pounds / 2.2 = 45.5 kilograms). Then multiply by the indicated number to obtain your basic need (for leucine it would be 42 x 45.5 = 1,911 milligrams). Incidentally, that’s not a whole lot of leucine for someone who exercises. For instance, use of BCAAs at 2.5 grams (2,500 milligrams), with 76 percent leucine (1,900 milligrams), have been shown to increase protein synthesis and reduce muscle breakdown. As a result, researchers have suggested increasing the average minimum requirement to 45 milligrams/kilograms or more — which would mean about 2,048 milligrams (45 milligrams x 45.5 kilograms). However, please note that this amount should be even greater for exercising individuals.

Obviously, this is only the beginning of a complex subject, but it will provide the basics to help you know more about amino acids. To get the most out of your training and be as fit as possible, amino supplementation is something to look at more closely.

Amino-acid benefits

  • L-arginine: Nitric-oxide production, stronger immunity, healthy hair, manage menopause symptoms, blood-sugar management
  • L-carnitine: Weight loss, preserve muscle, anti-aging antioxidant, blood-sugar management
  • L-cysteine: Stronger immunity, healthy hair, anti-aging antioxidant
  • L-glutamine: Stronger immunity
  • L-glycine: Healthy hair, digestive health, anti-inflammation, stronger immunity
  • L-histidine: Recovery, growth regulation, healthy skin, nerve health
  • L-isoleucine: Muscular growth, preserve muscle, muscular energy
  • L-leucine: Increased protein synthesis, anabolic muscular growth, muscle energy
  • L-lysine: Shorten cold-sore flair-ups, improve mood
  • L-methionine: Fight arthritis, healthy hair
  • L-phenylalanine: Mood improvement, concentration, memory
  • L-proline: Skin and nail health
  • L-threonine: Stronger immunity, liver health
  • L-tryptophan: Healthy sleep, improved mood
  • L-valine: Muscular growth, preserve muscle, muscular energy