Shinya is also known for his claims about health benefits of enzyme supplementation. However, some of his claims in commercial advertisements have been criticized as deceptive.
Shinya has authored many books, of which the most well-known, Living without Disease: A Miracle Enzyme Determines Life (in Japanese: ‘病気にならない生き方 ミラクル・エンザイムが寿命を決める’), is said to have sold more than a million copies in Japan.
In advertisements, Shinya has recommended taking enzymes from consumed food. There he cites a medical paper that reports a decrease in the secretion quantity of three kinds of digestive enzyme (and bicarbonate) from the pancreas. The article speculates that this is due to aging, and does not discuss intake of nutrients, so it is irrelevant to his claim. He also says that in recent years vegetables are poorer sources of nutrients, and that it is difficult to obtain sufficient enzymes from consumed food alone. His evidence for this is a chart based on references for 1963 and 2008 which shows values of beta-carotene, vitamin C and iron found in spinach and carrot, from which he appears to infer a comparable enzyme deficit in all vegetable food sources.