Why do people have a preference for sweet things from birth?

Physiologically, taste is generated by the interaction between taste substances and receptors and ion channels on the microvilli at the tips of taste receptor cells. The classical taste theory recognizes only four basic tastes: sweet, salty, sour, and bitter. Until recently, many experts in this field argued that umami is also one of the basic tastes. Thus, taste came to consist of five flavors: sweet, sour, salty, bitter, and umami. It is generally believed that the process of taste transmission involves receptors specifically detecting a certain chemical structure; once bound, these receptors convert taste signals into molecular second messengers such as cyclic nucleotide monophosphates (cNMPs) and inositol trisphosphate (IP3), which cause depolarization of taste cells and lead to changes in calcium ion levels, thereby transmitting the signal to nerve cells. Sweet substances are mostly sugars, such as lactose and mannose, including glucose produced by the breakdown of salivary amylase. Acidic substances are mostly hydroxyc acids, such as citric acid and acetic acid. Salty flavors are primarily derived from salts such as sodium chloride and potassium chloride. Bitter substances cover a wide range of compounds, including alkaloids and heavy metal salts. Umami is primarily derived from nitrogenous sources such as amino acids, and it includes two main categories: amino acid compounds like aspartic acid, and purine nucleotide compounds.

Of course, there are many exceptions, such as saccharin which is not a sugar but is sweet, and potassium iodide which is a salt but is bitter. Perhaps it’s a coincidence; for example, the artificial sweetener aspartame is a coincidence, or there might be another story behind it. But overall, the taste compounds associated with sweetness are calories and carbon atoms ； The acidity is directly evaluated to determine the degree of acidity of a substance ； Control of saltiness: regulation of salt intake, which is essential for the salt cycle necessary for biological survival ； The substance responsible for umami is a unique flavor component in biological nitrogen sources, and it is what determines the quality of proteins ； Bitter taste compounds are the most widespread and can be summarized as: non-essential substances that possess potential physiological reactivity. Of course, it is worth mentioning that, in terms of receptor mechanisms, both umami and sweet taste receptors belong to the first family of taste receptors, T1R. They share the same receptor, but their signal transduction pathways are different; therefore, umami and sweetness are often mentioned together. Shanghainese people believe that there is indeed scientific evidence supporting the idea that sweetness enhances umami flavor. From a survival perspective, the five tastes control distinct and separate intake modules. It also essentially explains the trend in people’s pursuit of different tastes: sweetness signifies the intake of energy and carbon sources, freshness represents high-quality nitrogen sources, while saltiness denotes the supplementation of salts – all of which are essential for the body, and the preference for these tastes does not tend to weaken significantly ； Acidity can be regarded as a regulator of the pH level in the body’s internal environment; this varies from person to person. (The concept of using antioxidants to eliminate free radicals and prevent aging applies only to socially intelligent species; for species as a whole, reproduction is far more important than extending individual lifespans.) ； Bitterness serves as a warning to the taste senses; it involves a wide range of components. Substances classified as bitter can at least bind to bitter receptors, indicating that there may be certain risks associated with their intake into the body, so caution should be exercised when consuming them. Therefore, a preference for sweet and salty flavors over bitter ones has actually nothing to do with the natural selection of human populations, as bitterness itself is a classification system established to control the intake of substances that pose risks. Genetically, the genes for sweet and salty flavors are very stable and ancient, representing the most fundamental tastes in biological evolution. Bitterness receptors belong to the second family of taste receptors, T2R; they have relatively poor genetic stability and have undergone certain levels of genetic selection. As a result, bitterness represents a defense system that continues to evolve and expand in terms of the chemical compounds it detects.