In the Technical University’s Sustainability Months, the focus in January is on heat and light. In addition to clothing and heating systems, it’s worth thinking about your winter diet to stay healthy and keep warm. Global food and health magazines publish lists every winter of foods to prioritize in cold weather for warming the body and gaining energy. These lists feature familiar ingredients, spices, and herbs that help during colds but also fit into daily meals. Almost every list in the media or recommendations from health professionals includes ginger, turmeric, cinnamon, garlic, chili, oats, nuts, seeds, and dark leafy greens. It's especially good to make soups or teas from these beneficial ingredients (highlighted examples include pumpkin soup, bean soup, oatmeal porridge, and ginger tea). Everyone has probably seen a foreign movie or series where someone brings chicken soup to a sick main character. The health portal Health even shares dietary tips for every moment and health condition.

Tradition versus science

In traditional Chinese food culture, foods are classified as cold, cool, warm, or hot based on their effect on the body, according to a scientific article published by Chinese researchers in the Journal of Agriculture and Food Research. Warm or hot foods help increase internal body heat, improve circulation, and “nourish” body energy, while cold or cool foods soothe, detoxify, and reduce heat. In the East, these properties have been used for thousands of years as the basis for healthy food choices.

Modern people, however, are interested in how these cold/hot properties relate to a food’s nutritional value. Should we trust folk wisdom and tradition? Traditional Chinese medicine holds that a food’s cold or hot properties stem from its components.

In the aforementioned Chinese study, 179 foods were analyzed based on the categories of cold, neutral, and hot. Compared to previous similar studies, the variety of foods was significantly greater. Nutritional composition data were sourced from the USDA and Chinese databases. Using ANOVA and multivariate statistical analysis, researchers examined the factors and component interactions that influence a food’s warming or cooling properties.

What did the results show?

The study confirmed that the cold and hot nature of foods largely depends on their composition. Specifically, energy-yielding substances – proteins, carbohydrates, and lipids – significantly contribute to a food’s “hot” character because they supply the body with energy to maintain its functions.

The study found that 18 food components have a statistically significant impact on a food’s cold or hot (warming) properties. These included vitamin B6, folate, water, vitamin B12, manganese, energy content, carbohydrates, proteins, vitamin E, phosphorus, potassium, niacin, vitamin C, fiber, calcium, lipids, vitamin A, and caffeine.

Since seven of these are vitamins, vitamins can be considered important influencing factors (B6, A, C, folate). Caffeine was found to make food “warming,” suggesting that functional components also play a key role. Statistically significant interaction effects were also identified for some components.

It’s also important to note that a food’s effect on body warmth doesn't come only from its physical temperature but also from how it is metabolized and which macronutrients it contains (protein, fat, carbs), which increase heat production during digestion. The study showed that traditional “hot” and “cold” foods are partly consistent with scientific findings: energy-dense foods and certain spices (e.g., chili, ginger) stimulate heat and circulation.

A detailed overview of the Chinese researchers’ study and its findings can be found in the Journal of Agriculture and Food Research.