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It is unfortunately true that, at some point in our lives, most of us will have to deal with a major health issue. This may be surgery, serious illness such as pneumonia, or chronic disease such as kidney disease. Muscle loss is accelerated in response to serious illness or injury, and that can have a direct impact on your recovery, which is why maintaining muscle mass when you’re sick is so very important. Essential amino acids can help reverse muscle loss associated with illness, injury, or high stress levels, and help accelerate recovery.
The consequences of muscle loss as a result of serious injury or illness can be severe and immediate. Muscle mass can be a direct contributor to survival during times of critical illness and can significantly contribute to the speed and extent of recovery. When we age, we lose muscle slowly and gradually, but when we are battling a serious illness or injury, muscle deteriorates so quickly that consequences can be evident in a matter of days or weeks.
Rapid muscle loss is called a catabolic state, which is part of an overall response that can be considered a physiological stress response. There are common aspects of the stress response regardless of the underlying cause (i.e., cancer, injury, surgery, etc.). The stress response not only involves losing muscle at a much faster rate, but also includes loss of appetite, as well as metabolic changes, such as reduced sensitivity to the action of the hormone insulin. The loss of appetite results in decreased nutritional intake at a time when demand for dietary nutrients, particularly protein, is increased. Interestingly, regardless of the clinical condition that causes the stress response, changes in muscle protein metabolism are basically the same. Therefore, the stress response can be discussed in a general context.
The rapid loss of muscle protein reflects an imbalance between the rates of protein synthesis and breakdown. This imbalance caused by the stress response is driven by a large increase in the rate of muscle protein breakdown.
When protein breakdown is accelerated, such as during illness, essential amino acids flood into muscle cells and stimulate muscle protein synthesis. Even under these conditions, the message sent by the availability of essential amino acids is to build muscle. However, the increased synthesis is still not enough to balance the dramatic increase in breakdown. The net result is a large increase in the loss of muscle protein because muscle protein synthesis just can’t keep up!
While free amino acids released from the muscle get reincorporated back into muscle, muscle protein synthesis is further stimulated only marginally (or not at all) by nutritional intake while the stress response is activated. The stress response kills the appetite so much that it is hard to eat enough food, and even when you do force down food or rely on traditional meal replacement beverages, you see little or no beneficial response. Food doesn’t have much of a beneficial effect due to the abundance of essential amino acids available in muscle. Accelerated protein breakdown has freed so many essential amino acids for protein synthesis that the rate of synthesis is already close to maximal.
Furthermore, the stress response causes severe anabolic resistance, which means eating dietary protein doesn’t increase muscle protein synthesis in times of injury and stress as it does in times of optimal health. The body absorbs essential amino acids from intact protein slowly and the extent of the increase in essential amino acids is not particularly large. Therefore, dietary protein is essentially rendered ineffective in stimulating protein synthesis because consuming it doesn’t induce enough of a change in essential amino acid concentrations in the muscle.
In order for muscle protein synthesis to be further increased in the stress response, there must be an activation of the intracellular molecules involved in initiating protein synthesis. The central factor in this process is an initiation factor of protein synthesis called mTOR. You can activate mTOR by fortifying your body with an essential amino acid supplement formulated with a high proportion of leucine. The leucine activates mTOR, and the available essential amino acids serve as precursors for newly synthesized protein. If enough essential amino acids are consumed, concentrations will rise high enough to inhibit muscle protein breakdown as well. The combination of activating mTOR and stimulating protein synthesis while inhibiting protein breakdown improves the net balance between protein synthesis and breakdown.
To recap: supplementing with a mixture of free essential amino acids high in leucine can slow the net loss of muscle protein, whereas consuming intact protein in a meal or a meal replacement beverage is ineffective during physiological stress.
Illness, injury, and surgery bring about inactivity. If you are in the intensive care unit, you are likely confined to bed. If you are over 65 years old, you may be confined to a hospital bed even when you are capable of walking due to concerns with stability and risk of a fall. After surgery, you are likely to be physically limited until incisions are healed and you show some degree of recovery. This is particularly true after orthopedic surgery. In all cases of serious illness, you probably don’t feel much like exercising. As a result, the metabolic effects of the stress response are usually coupled with the catabolic effects of inactivity.
A series of studies sponsored by the National Aeronautics and Space Agency (NASA) showed how inactivity amplifies the catabolic response to stress. Spaceflight offers a perfect model for experimentation. The lack of gravity during spaceflight reduces the physical work of movement drastically, and muscle loss during space flight can be severe. NASA has used strict bed rest as a model for the effects of zero gravity during space flight. Bed rest studies have been done on young, healthy subjects and older subjects. As you might expect, inactivity produces the opposite effects of exercise. Muscle mass and strength are reduced, and the rate of deterioration is faster in older individuals.
By itself, inactivity is detrimental to muscle mass and function. When coupled with stress, bed rest amplifies muscle loss. Consumption of a balanced essential amino acid mixture (15-gram doses) throughout bed rest slowed the loss of muscle mass and strength in both young and older subjects
Essential amino acids also have been shown in a blinded study of a large number of patients to speed recovery from hip or knee replacement, which inevitably involves a significant limitation in activity.
The acute stress response can be considered the most severe phase. The word “acute” implies a short time, but the severe phase of the stress response can last for months in some cases, such as cancer. During the acute response, body weight and muscle mass are rapidly lost. Decreased appetite complicates the metabolic response.
Essential amino acid supplements are uniquely suited for the acute phase because they can be formulated to elicit a stimulation of muscle protein synthesis, even in the state of anabolic resistance. Even when your appetite is flagging, it is possible to consume the necessary essential amino acids because of the small volume in which an effective dose can be dissolved.
The recovery phase still presents metabolic challenges, as many of the responses in the acute phase are slow to heal in the recovery phase. For these reasons, an essential amino acid supplement should be used as a supportive aid during the recovery phase. Essential amino acid intake is crucial to avoid replacing lost muscle with fat.
