[Effects of Leucine] A Complete Protein that Aids Muscle Synthesis

Hello, I am Jinny, a pharmacist.

As you age, muscle loss occurs. Consequently, even with a little movement, you quickly become fatigued, and due to reduced stability, it becomes easier to fall. Therefore, as you age, it's important to ensure an adequate intake of "protein," which is essential for muscle synthesis.

Koreans tend to have a carbohydrate-heavy diet, making it challenging to consume sufficient protein. Furthermore, as you age, reduced gastric acid secretion may lead to aversion to relatively hard-to-digest protein intake. As a result, it has been shown that around 31% of men and approximately 43% of women over the age of 60 have insufficient protein intake[1].
[1] Hyunji ham, kyungho ha. (2022). Trends in Dietary Protein Intake and Its Adequacy among Korean Adults: Data from the 2010 ~ 2019 Korea National Health and Nutrition Examination Survey (KNHANES). Korean J Community Nutr., 27(1), 47–60.

Of course, simply consuming more protein is not a magic solution. As mentioned earlier, with aging, the function of the stomach deteriorates, leading to reduced protein absorption. Therefore, it is crucial to consume proteins with high bioavailability that directly assist in muscle synthesis.

In this context, the substance I will introduce today is "Leucine Protein." It is known as a "complete protein" that is associated with improving muscle atrophy and enhancing muscle strength in the elderly and has gained the attention of the academic community. Now, I will explain through research papers how leucine protein intake affects muscle and strength improvement.

The human body is originally composed of about 600 muscles. However, as the aging process begins, the number of muscle fibers that make up these muscles decreases. Typically, muscle mass in the body starts to decline from the 30s, and by the age of 70, it can shrink to half its original level, a condition known as muscle atrophy.

With muscle atrophy, even simple tasks like getting up from a seated position become difficult, and walking speed can slow down to the point where it's challenging to cover even 1 meter in one second. Unfortunately, there is currently no specific treatment for muscle atrophy, making prevention and management critically important.

In this regard, there has been research indicating that leucine plays a significant role. In a study involving elderly individuals with muscle atrophy, when they consumed 6g/day of leucine for 13 weeks, it was found to significantly improve functional performance, such as walking time.

Falls are a common health issue among individuals aged 65 and over. Globally, about 35% of individuals aged 65 and over experience falls each year, and this percentage increases to 42% for those aged 70 and over. Additionally, 40% of fall experiencers are reported to fall repeatedly [2].
[2] Chang, I. S., & Park, E. O. (2013). The Experience of Falls and Related Factors in Community-Dwelling Elderly Persons. Journal of Korean Public Health Nursing, 27(1), 89–101.

These fall accidents can lead to various complications, increase mortality rates, and incur substantial time and costs for treatment and recovery. One of the major causes of such fall accidents is muscle weakness.

Therefore, maintaining muscle strength and consuming an adequate amount of protein for muscle growth is crucial. According to a review article published in the prestigious journal "Archives of Gerontology and Geriatrics" in 2022, it was confirmed that leucine protein intake significantly improved muscle strength.

Protein is indeed necessary for muscle synthesis, but it's not the case that all the protein you eat will turn into muscle just because you consume more. There is a limit to the amount that can be synthesized into muscle at one time. If you consume more than is needed, it can actually be stored as fat.

Therefore, it's not the quantity of protein that's important, but rather the ability of the protein you consume to be effectively synthesized into muscle. In this regard, a study published in 2021 in the prestigious journal Frontiers in Nutrition argued that leucine protein is more advantageous for muscle protein synthesis in the elderly.

So far, we have examined the benefits of leucine protein intake through research papers. According to the World Health Organization (WHO), it is recommended that healthy adults consume 39mg/kg of leucine[3].
[3] Rondanelli mariangela, nichetti mara, peroni gabriella, faliva milena anna, naso maurizio, gasparri clara, perna simone, oberto letizia, di paolo enrica, riva antonella, petrangolini giovanna, guerreschi giulia, tartara alice. (2021). Where to Find Leucine in Food and How to Feed Elderly With Sarcopenia in Order to Counteract Loss of Muscle Mass: Practical Advice. Frontiers in Nutrition, 7.

Leucine is generally considered safe, but excessive intake can lead to potential side effects such as serotonin reduction, brain damage, and liver damage. Therefore, it's important to be cautious and not exceed the recommended intake levels.

I hope you have a healthy day both physically and mentally. This was Jinny.