Léo Ramos Chaves / Revista Pesquisa FAPESPThe method for preparing expresso is not effective in keeping cafestol from the cupLéo Ramos Chaves / Revista Pesquisa FAPESP
Studies into coffee have produced three practical recommendations — the first: don’t drink coffee right after meals, but rather one or two hours later. The caffeine and tannins combine with minerals and reduce the absorption of iron, as demonstrated by researchers from the University of Kansas, US, in a piece published in the American Journal of Clinical Nutrition in March 1983. In a more recent study, published in Nutrients in September 2021, researchers at Wroclaw Medical University in Poland concluded that in addition to iron, drinking coffee after eating also impairs the absorption of calcium, zinc, magnesium, and phosphorus.
Indications suggest that the habit of taking a cup of coffee after meals instead of liquor or port wine was brought to Brazil in 1829 by the Empress Amélia de Leuchtenberg (1812-1873), the second wife of Dom Pedro I (1798–1834), adopted by frequenters of the Court, and then spreading among the plebeians. This effect, however, is not exclusive to coffee, given that more than 60 plants contain caffeine, such as guarana, cacao, black, green, and yerba mate teas, along with chewing gums, medications, and energy drinks.
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Conversely, foods rich in vitamin C, such as dark leafy greens and citrus fruits, increase iron absorption: a single orange can multiply the rate between three and six times. “More vulnerable people tend to develop anemia, primarily when they ingest large quantities of coffee right after meals,” says nutritionist Denise Tavares Giannini of Rio de Janeiro State University (UERJ). “It’s important to choose the right moment to consume coffee.” One of her group’s studies, published in Nutrition in February, demonstrated that drinking coffee in the morning and the afternoon does not adversely affect sleep duration in teenagers.
Léo Ramos Chaves / Revista Pesquisa FAPESPThe paper filter retains cafestol, which can increase cholesterol levelsLéo Ramos Chaves / Revista Pesquisa FAPESP
The second recommendation: to reduce (or not to increase) blood cholesterol levels, it is best to drink filtered or instant coffee. One component of coffee is a lipid known as cafestol, which can increase cholesterol levels, but much of it is retained by the paper filter, as shown in June 1995 by a group from Holland’s Leiden University, in the American Journal of Clinical Nutrition. Preparation methods for espresso, Turkish, and boiled coffee are less effective in keeping cafestol from the cup.
The third: do not add sugar, or reduce it to the minimum possible. This is advice from the Guia alimentar para a população brasileira (Dietary guide for the Brazilian population) published by the Ministry of Health in 2021, and is a way of reducing the amount of calories consumed over the course of the day, and optimizing the beneficial effects of coffee, which are many.
“A cup of coffee may be doing much more for your brain than just helping you to feel more awake in the morning,” observes American physician Michael Greger in his book How not to die (Intrínseca, 2018), in which he details the effects of coffee on the organism, based on scientific studies.
To increase energy expenditure, caffeine and other coffee compounds, such as diterpenes, can reduce the risk of obesity and loss of muscle mass. But not always. Researchers from UERJ and the Federal University of Rio de Janeiro (UFRJ) spent two years monitoring 163 people who had undergone kidney transplants, and found that coffee consumption in this group was associated to gains in body fat and the loss of muscle strength, as detailed in a study published in October 2023 in Clinical Nutrition.
The effects of coffee on the organism are not all positive. Among other undesirable effects, it may increase anxiety, cause the hydrochloric acid produced in the stomach to rise to the esophagus in people with gastroesophageal reflux, or bring about more epileptic fits in those who suffer with the condition. Nutritionist Helen Hermsdorff, of the Federal University of Viçosa (UFV) in Minas Gerais, recommends moderate consumption — between one and three cups per day.
Her team verified a well-known effect of caffeine — its capacity to interfere with sleep — through questionnaires answered by 6,356 professionals with an average age of 32.7 years, having graduated with degrees from seven universities across the state of Minas Gerais. Almost a third (31.9%) of the participants slept less than the minimum recommended seven hours, as detailed in a December 2023 article in the International Journal of Food Sciences and Nutrition. “One of our hypotheses is that professionals working part-time or full days use coffee to keep them more alert,” she says.
Scientific articles
COSTA, M. S. da et al. Association of habitual coffee consumption with obesity, sarcopenia, bone mineral density and cardiovascular risk factors: A two-year follow-up study in kidney transplant recipients. Clinical Nutrition. vol. 42, no. 10, pp. 1889-1900. oct. 2023.
MORCK, T. A. et al. Inhibition of food iron absorption by coffee. The American Journal of Clinical Nutrition. vol. 37, no. 3, pp. 416–20. mar. 1983.
RODAK, K. et al. Caffeine as a factor influencing the functioning of the human body ‒Friend or foe? Nutrients. vol. 13, no. 9, 3088. sept. 2, 2021.
ROOIJ, J. van et al. A placebo-controlled parallel study of the effect of two types of coffee oil on serum lipids and transaminases: Identification of chemical substances involved in the cholesterol-raising effect of coffee. The American Journal of Clinical Nutrition. vol. 61, no. 6, pp. 1277–83. june 1873.
TEIXEIRA, C. M. et al. Higher caffeine consumption is associated with insufficient sleep time in Brazilian adults (Cume study). International Journal of Food Sciences and Nutrition. vol. 74, no. 8. dec. 12, 2023.
VIZENTIN, N. P. et al. Caffeine consumption and association with sleep duration and screen time in Brazilian adolescents (Erica Study). Nutrition. vol. 118, 112233. feb. 2024.
Books
GREGER, M. Comer para não morrer: Conheça o poder dos alimentos capazes de prevenir e até reverter doenças. Rio de Janeiro: Intrínseca, 2018.
Guia alimentar para a população brasileira. Brasília: Ministério da Saúde. 2021.
