Branched-chain amino acids are safe, but they may be useless and even hinder muscle growth. Branched chain is one of several amino acids decomposed by protein. Amino acids decomposed by protein, such as meat, are divided into glutamic acid, branched chain amino acids and so on, and then recombine to form human protein according to human needs, and then form muscle. Therefore, branched-chain amino acids and other amino acids are necessary but not the only elements for muscle synthesis. I have studied a little nutrition, emphasizing that a chain can be saturated with amino acids at the same time. If one amino acid is in excess, other amino acids will line up and then combine with the chain. If there are too many branched-chain amino acids, the absorption space of other amino acids will be reduced at the same time, and the amount of amino acids required by protein molecules may be unbalanced. It leads to the slow speed of protein biosynthesis, which in turn affects muscle synthesis. So I suggest that if you take a single amino acid supplement such as branched-chain amino acid or glutamic acid, it is best to mix it with some grains containing plant protein to accelerate absorption. The absorption rate of plant protein is not high, but it is different from meat. Plant protein is mostly a single amino acid or a combination of several amino acids. For example, the amino acids of plant proteins contained in corn and peas are different and complementary. This unbalanced distribution will help you to take a single amino acid supplement, which is helpful.
In short, there is no harm, but improper use will affect the effect.