Why Nutritional Science Is Complex and Rapidly Changing

The science of nutrition, compared to other fields, is relatively young. Medicine dates back 3000 years to ancient Egypt. In the 5th century BCE, anatomical studies were conducted on pigs in ancient Greece, and experiments were performed on chicken embryos. In 1796, a vaccine for true measles was successfully used for the first time. In 1853, DNA was first described. In 1747, Scottish physician James Lind conducted the first clinical trial, proving that citrus fruits can cure tuberculosis. It was not until 1932 that vitamin C was isolated, and it was demonstrated that its deficiency is the cause of the disease. In 1902, Wilbur Atwater estimated the energy content of carbohydrates, fats, and proteins. The link between low HDL levels and heart disease was observed in the 1970s. Scientific discoveries require time, numerous trials, and often errors. Compared to medicine, chemistry, or physics, nutrition science is still in its early stages, so we will have to wait for further groundbreaking discoveries.

When evaluating study results, it is essential to consider who participated – healthy young individuals, men, women, elderly people, or those with specific conditions. Some studies are conducted on animals, which does not diminish their value, but the findings cannot be directly applied to humans. Differences may arise from genetic factors, gut microbiota, or lifestyle. Thus, no universal rule exists. BMI is an example, as it does not distinguish between children and adults or muscle mass and fat. Therefore, diets should be personalized.

It is essential to recognize that the calorie count listed on food packaging represents only an approximation. The information that 1 g of protein provides 4 kcal, 1 g of carbohydrates 4 kcal, and 1 g of fat 9 kcal is derived from experimental studies conducted outside the human body, with results adjusted to account for physiological processes within the body. By examining nutritional value tables, we can determine the energy content of foods, such as the amount of carbohydrates. These tables also provide details regarding fiber, vitamin, and mineral content. However, how confident can we be that a carrot grown in our garden has the same nutritional profile as one purchased at a market or supermarket? Unfortunately, the likelihood of this is low. There are multiple databases containing nutritional information for foods, with values varying significantly depending on the country and institution that compiled them. When using calorie-counting apps, it is advisable to verify which database the app utilizes. Many nutrition studies rely on observational methods. Participants in such studies must complete questionnaires detailing the foods and quantities they consumed. As is easily apparent, the results of these studies are imprecise because researchers cannot be certain of the actual composition of the consumed foods. Participants often omit information or forget important details. The highest scientific value is attributed to experimental studies, where researchers administer identical portions of foods under controlled conditions. However, such studies in nutrition research are rare due to the high costs and logistical challenges. Most research funding is allocated to studies focused on treating specific diseases rather than prevention. Additionally, ethical considerations play a role. It is not possible to conduct studies, for example, examining the harmful effects of red meat on the cardiovascular system by providing participants with daily servings of beef, as this could negatively impact their health.

Research on a drug designed to provide pain relief within 20 minutes of ingestion differs significantly from studies examining the impact of dairy consumption on bone health. It is evident that bone health will not improve immediately after consuming a serving of quark, but consistent intake of low-fat dairy over an extended period can help prevent osteoporosis. Consequently, studies on the effects of food on health take a very long time—several or even multiple decades. Throughout this duration, various factors can arise, such as participants dropping out or altering their lifestyle, which can affect the outcomes. This complexity makes the analysis and interpretation of such studies particularly challenging.

When evaluating scientific research, it is crucial to identify any potential conflicts of interest. Such information must always be clearly disclosed in the publication. The purpose is to assess whether financial ties exist between institutions that could benefit from the dissemination of specific findings. Of course, a conflict of interest does not necessarily imply that the research was conducted poorly. However, if we encounter a study that, for instance, highlights the beneficial properties of white sugar and it transpires that it was funded by a sugar manufacturer, we should approach its results with caution. It is essential not to accept the conclusions uncritically but to compare them with findings from other studies on the same subject.

Evaluating scientific literature requires a solid understanding of research methodologies. Key considerations include: the type of study conducted – experimental and large observational studies are the most reliable; the study population – whether the research involved animals, humans, or specific groups such as women, athletes, or elderly individuals; sample size – larger groups yield more credible results; the publishing journal – the impact factor (IF) indicates citation frequency and journal prestige; and potential conflicts of interest. When relying on publicly available sources, extra caution is necessary. Sensational claims often circulate online, bearing little resemblance to actual research findings. Misinformation spreads rapidly. Always verify sources when reading online articles to ensure the information is not published solely for sensationalism. Articles lacking source references are untrustworthy. Nutrition science is a complex and evolving field. Avoid falling for misleading claims or quick fixes. There is no guarantee that removing a single dietary component or taking a supplement will resolve all health issues.