Five regulatory dimensions of food: the body's regulatory mechanisms from boosting immunity to anti-aging

Functional substances in food can be categorized as follows: ① substances that enhance the body's immune function; ② substances that prevent and treat diseases; ③ substances that regulate the body's rhythms; ④ substances that prevent obesity; and ⑤ anti-aging substances. Functional substances that regulate the body differ from nutrients; even trace amounts can affect the body. Besides those already present in food, some substances with these effects are latent, meaning they only begin to manifest their function after being digested in the body. In addition, there are substances that indirectly regulate the body by stimulating hormone secretion.

Some substances are known to stimulate the lymphatic system, enhancing immunity and thus improving the body's disease resistance. PSK, isolated from *Armillaria truncata*, has been used as an anticancer drug. Furthermore, it has been found that mushroom polysaccharides in shiitake mushrooms, certain substances in *Schizophyllum* fungi, yeast glucan in baker's yeast, and polysaccharides found in various seaweeds also possess anticancer effects. Exogenous lectins found in plants such as lentils, sword beans, burdock, soybeans, and potatoes also have the effect of activating the immune system.

A food product low in phenylketonuria and without odor has been developed for patients. Furthermore, the importance of diet in the prevention and treatment of diseases such as diabetes, hyperlipidemia, and hypertension is self-evident. Milk contains substances that affect the body, such as thyroid-stimulating hormone, adrenocorticotropic hormone, and gonadotropins. Dietary fiber is now being used in practical applications. In addition, enzyme inhibitors such as amylase inhibitors in wheat and protease inhibitors in soybeans, because they can inhibit digestion, may be used to prevent obesity.

The pungent components of mustard can promote energy expenditure. Foods that may help prevent obesity, such as appetite suppressants, low-calorie oil substitutes, and non-natural, indigestible oil-like substances (mixed fats), are also under investigation. While the exact causes of aging are still unclear, a recent and compelling theory suggests that aging is caused by lipid peroxidation due to oxygen ions. It has been found that feeding animals with vitamin C, vitamin E, and substances that can "capture" oxygen ions can extend their lifespan.

Several new food processing technologies have been developed, enabling the stable extraction of easily decomposed functional substances. These include supercritical gas extraction, the application of high pressure in food processing, membrane treatment technologies such as ultrafiltration, fine filtration, reverse osmosis, and electrodialysis, freeze-drying and freeze-pulverizing of foods processed by extruders, and food freezing and ice-temperature storage. These new food processing and storage technologies are highly effective in preventing the decomposition of physiologically active substances in food. Functional foods are foods processed to fulfill their intended functions.

Although milk contains a variety of functional substances, it is an unprocessed food and therefore cannot be called a functional food. Furthermore, a functional food not only contains functional substances but must also be able to fully exert their functions. To manufacture functional foods, it is necessary to remove undesirable components (such as allergens), and to either add functional substances or stabilize them through processing. Adding functional substances involves two methods: one is concentrating the components already present in the food; the other is adding new components not originally present in the food.