Nutrition Physiology

The role of taste sensations in digestion

The taste of food is not only a subjective pleasure, but also a crucial physiological trigger. Taste sensations initiate a reflex from the oral cavity that signals food intake and naturally stimulates the neural centers responsible for digestion.

Amino acid balance directly depends on taste. With adequate taste stimulation, digestion proceeds normally: a complete mixture of amino acids is formed in the gastrointestinal tract, as exogenous (dietary) amino acids are supplemented by endogenous (body-secreted) ones. If food is tasteless, the secretion of endogenous amino acids does not occur.

This is precisely why eating exclusively "healthy" but tasteless food (e.g., unsalt vegetables, undercooked porridges, or completely fat-free cottage cheese) is a risk factor. It rapidly leads to a deficiency of essential nutrients and health disorders. At the same time, tasty food is capable of compensating for shortcomings in the qualitative composition of the diet for quite a long time.

Structure of daily energy expenditure

Daily physiological energy requirements consist of two major groups of energy expenditure: unregulated and regulated.

Unregulated energy expenditure includes:

1. Basal metabolic rate (BMR) is the minimum energy expenditure required to maintain the functioning of vital systems (respiratory, cardiovascular, excretory) in a state of complete rest. BMR is a strictly individual and relatively constant value. It depends on body weight, height, sex, age, climate, and the state of the endocrine system. To determine the basal metabolic rate, standard conditions must be met: measurements are taken in the morning on an empty stomach, in a lying position, at a comfortable microclimate, and in a state of absolute muscular and neuropsychic rest.
2. Specific dynamic action of food is the elevation of metabolism under the influence of food components. The mechanism includes the chemical impact of digestive products on assimilation processes and the reflex effect of the eating act itself. Proteins elevate metabolism the most, followed to a lesser extent by fats and carbohydrates. The intake of a regular mixed meal increases energy expenditure by 10–12% compared to the basal metabolic rate.

Regulated energy expenditure refers to the energy spent on any activity. During physical exertion, energy expenditure increases significantly. Mental activity also requires energy expenditure, but to a much lesser extent.

Physiological nutritional standards and PAL

Physiological nutritional standards are scientifically grounded indicators that fully cover the body's energy expenditure and provide it with nutrients in optimal proportions. These standards are dynamic: they are periodically revised due to new scientific data in nutritional hygiene and changes in the living and working conditions of the population.

The adult able-bodied population is divided into groups depending on daily energy expenditure (according to the 1991 standards, there are 5 groups for men and 4 groups for women). This gradation is based on the value of the basal metabolic rate and the physical activity level (PAL).

PAL is the ratio of daily energy expenditure to the basal metabolic rate. The more intense the energy expenditure, the higher this coefficient. For instance, if a person expends twice as much energy per day as their BMR, their PAL is 2.

Population group I by energy expenditure includes workers predominantly engaged in mental labor. Their PAL is 1.4. This category includes organizational executives, engineering and technical personnel, and physicians (except surgeons).

Class and exam questions

What else to study on this topic

• Structure of the functional system of nutrition according to Anokhin and Sudakov
• Food center: levels of organization and mechanisms of action
• Hypothalamic centers of hunger and satiety
• Hormonal regulation of metabolism
• Calorimetry methods for assessing energy expenditure

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