For athletes who "want to eat but can't"—amino acids: a way to streamline body building—

Athletes train every day, striving to build stronger bodies. However, for athletes who engage in high-intensity exercises such as basketball, handball, soccer, rugby, and American football, nutritional concerns are endless, such as "I need to eat a lot, but I can't" or "I eat a lot, but I can't build muscle..."

This time, we interviewed Professor Jun Yasuda of the Department of Health Management, Faculty of Health Sciences, Tokai University, who has been engaged in research and practical guidance on exercise and nutrition strategies for many years. He taught us about the use of amino acids to make body building more efficient while reducing the burden on the gastrointestinal tract. Taniyama, who is involved in product development of sports supplements at Ajinomoto Co., Inc., will delve into the scientific basis.

≪Contents of this article≫

• Common mistakes in body building that occur when relying too much on protein.
• The scientific reasons why you "can't eat" after high-intensity training.
• • A nutritional strategy using amino acids that are easy on the digestive system.
• • How essential amino acids such as leucine support muscle synthesis

Many student athletes face challenges with "physical conditioning."

Taniyama:I was an American football player in college, and many of my teammates struggled to eat properly after training, which made building their physique difficult. What kind of problems do the athletes that Professor Yasuda coaches face?

Yasuda:Many of the basketball, soccer, and American football players I watch generally want to gain weight, but because they train so much every day, they also need to eat more. Eating is part of training, but when training is high intensity, some players just can't eat enough, so I get a lot of requests for support from players who are struggling with this. To increase muscle mass, it's important to consume carbohydrates (sugars) as an energy source, but many players don't fully understand this importance, and I get the impression that many end up relying on protein supplements.

Taniyama:How do student athletes view protein?

Yasuda:Many athletes are fixated on protein, and it seems that the idea that "you can build muscle just by drinking protein" is becoming widespread. Supplements should ideally be used as a supplement, but many athletes believe they possess some kind of special power. I feel that these are the very athletes who struggle with gaining weight or controlling their weight.

Furthermore, after high-intensity exercise, athletes often feel unwell or lose their appetite, and some feel compelled to force themselves to drink protein shakes. As a result, they may feel even worse, leading some athletes to dislike protein shakes altogether.

The scientific reasons for decreased appetite after exercise

Taniyama:What are some reasons why appetite decreases after exercise?

Yasuda:Numerous studies have reported on decreased appetite after exercise. Physiologically, after exercise, insulin sensitivity in the body increases, promoting nutrient uptake into various tissues, including muscles. However, neurologically, the sympathetic nervous system becomes dominant during exercise. This slows down gastrointestinal activity, which is one reason for decreased appetite. In addition, decreased visceral blood flow and fluctuations in appetite-related hormones due to exercise also play a role.

Because the sympathetic nervous system remains dominant immediately after exercise, even if you consume solid foods such as rice balls or high-volume protein drinks, your digestive and absorptive functions may not work properly.

Instead of forcing yourself to eat when you have no appetite, your nutritional strategy should focus on minimizing the burden on your digestive system. Whether you choose to consume regular protein or more finely broken-down peptides and amino acids, these are all important strategic choices.

Taniyama:Considering the strain on the body, is the key to consuming nutrients that have been broken down into more complex forms?

Yasuda:Yes, that's what we think. We've also heard from the athletes that peptides and amino acids are easier to take, and that they put less strain on the body than drinking protein shakes.

Essential amino acids that activate muscle synthesis without putting a strain on the digestive system.

Taniyama:Are there any particular points to keep in mind when actually taking amino acids?

Yasuda:Basically, "essential amino acids" are crucial for building muscle. There are a total of 20 types of amino acids, and proteins are composed of 9 essential amino acids and 11 non-essential amino acids. If you eat a balanced diet, you can get the essential amino acids from your snacks, and your body can produce the remaining 11 non-essential amino acids. In other words, the theory is that if you get essential amino acids from your snacks, you will build muscle.

In particular, the essential amino acid "leucine" plays a role in activating muscle synthesis. Therefore, consuming amino acids, especially leucine, in conjunction with exercise makes perfect sense.

Taniyama:Should I choose an amino acid product that contains leucine?

Yasuda:There are amino acids available that are high in leucine. Research data has also been conducted to investigate how these leucine-rich amino acids affect muscle synthesis compared to regular whey protein. The report indicates that there was no difference in muscle synthesis between consuming whey protein and consuming leucine-rich amino acids.

Based on this data, it can be said that if you consume sufficient essential amino acids, you can definitely expect muscle hypertrophy. Therefore, "high leucine content" will likely remain an important keyword when choosing supplements in the future.

Taniyama:Finally, regarding the use of amino acids, could you give a message to students who are involved in sports?

Yasuda:Amino acids themselves are not always a panacea. Their usefulness depends on how they are used. While some athletes can get by with whey protein alone, student athletes and professional athletes who regularly engage in high-intensity training generally find themselves using amino acids more often. Perhaps reviewing your diet and considering a nutritional strategy that includes the use of amino acids would lead to a less stressful athletic life.

Summary | For athletes who "want to eat but can't"

• Appetite and digestive capacity tend to decrease immediately after high-intensity training.
• • Taking protein in that condition tends to put a heavy burden on the digestive system.
• Essential amino acids can reduce the burden on the digestive system and support muscle synthesis.
• • For efficient body building, consider incorporating essential amino acids into your routine.

<<Click here for functional amino acid materials related to this article>>
For those who want to enhance the effects of muscle training with "small amounts, high efficiency," try "EAA-rich whey protein."

Professor Jun Yasuda, Lecturer, Department of Health Management, Faculty of Health Sciences, Tokai University

PhD (Sports and Health Sciences), Registered Dietitian, NSCA-CSCS

After completing her doctoral studies at the Graduate School of Sport and Health Science, Ritsumeikan University, she worked as a researcher at the National Institute of Sports Science, among other positions, before assuming her current position in 2023. Her research focuses on maintaining and increasing muscle mass, encompassing exercise and nutritional strategies, and she implements evidence-based findings into nutritional support in competitive sports settings.

Masanao Taniyama, Marketing Group, Sports & Health Nutrition Department, Ajinomoto Co., Inc.

During his student years, he dedicated himself to American football, experiencing firsthand the importance of physical training and conditioning. After joining the company in 2013, he worked in sales of household products before assuming his current position in 2019. He is involved in the development of sports supplements, utilizing his knowledge from competitive sports and research in product design.