Sugar has become one of the main “villains” of modern times: reducing it as much as possible from the diet is a priority objective, as long as it is not naturally present in food. The World Health Organization recommends that consumption in the form of free sugars should not exceed 10% of the total daily caloric intake, both in adults and children, and also suggests a reduction to below 5% of caloric intake ( about 25 grams a day).
These free sugars are the sugars (refined or unrefined) added to foods and drinks by the manufacturer, the cook or the consumer, to which must be added those naturally present in honey, syrups, fruit juices and juice concentrates. Hence the study of its consumption is such a relevant topic in recent years.
However, many investigations still omit the form of ingestion – that is, whether they are free or intrinsic –, which could justify the contradictory data between them. It is true that experts emphasize the importance of avoiding free sugars, but the lack of consideration in some studies may contribute to the discrepancy in the results.
Diana Thomas, of the Center for Quantitative Obesity Research, in New Jersey, has pointed out this omission. A situation that affects, for example, the glucose, cholesterol and triglyceride tolerance test: sometimes there are no changes in these parameters and other times there are.
Given this lack of definition, the guidelines over the last decades have also been discrepant, since sometimes it was advised that sugar intake should not exceed 5% of the energy requirement, while other recommendations imply that even 25% of the Total energy could easily come from that dietary ingredient. The great enlightening study has not yet been given, but examining the issue through the prism of evolution can give us a clue to finding the truth.
Evolutionary physiology explores how organisms have changed over time to improve their fitness and survival. Their findings lead us to believe that evolution genetically adapted the metabolic physiology of our ancestors to deal with the intrinsic sugar of fresh fruits, since free sugar was non-existent.
In the Miocene era, between 24 and 5 million years ago, fruits were the main component in the hominid diet. According to Italian expert Riccardo Baschetti, four key findings bring an evolutionary perspective to the sugar debate:
Gastric emptying and intrinsic sugars. The speed with which food leaves the stomach is crucial for regulating blood sugar levels, since it passes to the intestine and is absorbed by the body. Glucose and intrinsic sucrose in food are emptied in a similar way.
Evolutionary adaptation to fresh fruits. It manifests itself in emptying, which becomes slower as the glucose concentration increases. As has been proven, this phenomenon fits perfectly with the caloric range of the total sugars present in fresh fruits, which have been the basis of human nutrition for millions of years. Evolutionary adaptation suggests that our gastrointestinal system is designed to effectively manage the wide caloric range of fruits, thus helping to maintain stable blood glucose.
Impact of large quantities of fresh fruits. Within the range of 0.2 to 1.0 kcal/ml, it has been observed that doubling the volume of a glucose meal does not significantly alter the emptying rate. This implies that the ingestion of large quantities of fresh fruits did not affect the homeostasis – the balance and internal stability – of glucose in our ancestors, and that human gastrointestinal physiology is adapted to efficiently handle even large quantities of fresh fruits, without affecting negatively regulates glucose.
The unknown free sugars. As the caloric concentration exceeds 1.0 kcal/ml, a more rapid delivery of calories to the small intestine is observed. This change occurs just above the highest caloric concentration in fresh fruits, suggesting that free sugars can be considered genetically unknown foods. The introduction of agriculture, about 10,000 years ago, is too recent at an evolutionary level for the human genome to have fully adapted to this change.
We must also take into account the role played by salt, the use of which was unknown to our ancestors until about 5,000 years ago. It was only from then on that humans began to use it in large quantities to preserve food. However, our physiological systems have not had enough time to adapt to this increase in consumption.
Today, we know that excess salt is harmful to health. But not only is it a risk factor for hypertension, it also accelerates the absorption of sugars in the intestine, which could explain the connection between sugary drinks and type 2 diabetes.
This relationship is due to the fact that the consumption of sugary soft drinks tends to go hand in hand with a decrease in the intake of vegetables and milk, foods naturally low in salt, and a greater consumption of fast food and ultra-processed foods, rich in this condiment. .
The amount of salt present in ultra-processed foods contributes to a small portion inevitably passing through the consumption of sugary drinks, unhealthily accelerating the absorption of sugars and promoting obesity.
In fact, some studies have shown that this association is mediated by salt in the diet, but they omitted to mention the detrimental effect of that ingredient on the absorption of sugars. Such links provide us with valuable insights into how our food choices can holistically affect our health.
We need a study to be conducted that takes both sugar and salt into account, which would be in line with evolutionary physiology, and confirm what many already believe: that intrinsic sugar is harmless and free sugar is harmful. As we said, Riccardo Baschetti has already set the tone for how to carry out this study. The only thing missing is that someone, with a project without a conflict of interest, can carry it out.
This article was originally published on The Conversation. Jose Miguel Soriano del Castillo is Professor of Nutrition and Bromatology at the Department of Preventive Medicine and Public Health of the University of Valencia.
