Until recently, information on coffee depleting magnesium could be found in various online publications. Where did the belief that coffee can flush out magnesium?
Where did the idea come from – the basics
The content of magnesium in the human body is physiologically regulated through three main mechanisms. The first mechanism is intestinal absorption. The second is absorption and excretion by the kidneys [1]. In the kidneys, as much as 90% of magnesium is reabsorbed in the renal tubules, mainly in the thick segment of the arm in the loop of Henle [2]. The third mechanism is the storage of magnesium in the bones [1].
So, the information that has been repeated about the leaching of magnesium by coffee came from combining two facts. First, that magnesium is flushed out in the urine. Secondly, that caffeine, which is a component of coffee, has a diuretic effect.
And what does it really look like? Indeed, large amounts of caffeine have a diuretic effect. On the other hand, high consumption means consumption of 300-360 mg of caffeine at a time. This amount of caffeine is equivalent to about four cups of coffee drunk at once [3].
How is it really with magnesium and coffee?
Researchers have estimated that magnesium losses due to caffeine consumption, when its source is coffee, are small. This is because coffee itself is a source of magnesium [3]. As a result, larger amounts of this element are supplied to the body than its losses. It is estimated that the effect of consuming one cup of coffee may cover 7.5% of the daily magnesium requirement for women and 6.4% for men [4]. It follows that the effect of coffee consumption has a positive effect on the daily coverage of magnesium requirements. And it is known that this element is important for our body.
In conclusion, it is essential to remember that high doses of caffeine have a diuretic effect. In contrast, single doses of caffeine at the level found in commonly consumed beverages have little diuretic effect. In addition, people who regularly consume caffeine get used to its effects [5]. In practice, this means that the diuretic effect is neutralized. Thus, even less magnesium is lost.
Coffee – a source of micro and macro elements
Coffee contains over a thousand bioactive ingredients. These include carbohydrates, lipids, proteins, chlorogenic acids, diterpenes, alkaloids, caffeine. The content of minerals varies in different varieties and infusions. For example, the infusion has less bioactive ingredients than coffee beans [4]. Therefore, preparing coffee from coarsely ground beans may have more health benefits for us. Green coffee beans typically contain 3.0–5.4% minerals by dry weight. However, coffee made from green beans is not the tastiest choice. On the other hand, roasting does not change the concentration of minerals. The main component of coffee beans is potassium – it constitutes as much as 40% of ash [4]. Potassium is an essential element of the human diet, so it is worth remembering that it is also present in coffee beans.
The Polish edition of food composition and nutritional value tables gives the following nutritional values for coffee infusion. The coffee brew, however, has not been defined as to type or species.
| Coffee, infusion | in 100 ml |
| Energy | 2 kcal |
| Water | 99,4 g |
| Protein | 0,2 g |
| Ash | 0,1 g |
| Carbohydrates | 0,3 g |
| Starch | 0,3 g |
| Calcium | 9 mg |
| Iron | 0,2 mg |
| Magnesium | 12 mg |
| Phosphorus | 11 mg |
| Potassium | 126 mg |
| Sodium | 14 mg |
| Zinc | 0,07 mg |
| Copper | 0,05 mg |
| Manganese | 0,05 mg |
| Iodine | 1 µg |
| Riboflavin | 0,010 mg |
| Niacin | 0,70 mg |
Source: Tabele składu i wartości odżywczej żywności, H. Kunachowicz, B. Przygoda, I. Nadolna, K. Iwanow, PZWL, Warszawa 2020 [6].
Coffee as a source of magnesium
Coffee provides some magnesium due to its widespread consumption. However, its content in coffee varies depending on its type. The method and time of its brewing also affect the content of this element. An important element is also the geographical area from which the coffee comes. The way it is grown and the type of soil it grows in all affect its magnesium content.
The type of water from which we prepare coffee also affects the magnesium content. Interestingly, brewing coffee using tap water can increase the magnesium content in the infusion by about 30%. On the other hand, coffees brewed with mineral, distilled or filtered water show a lower content of this element [4].
Depending on the study, how it was conducted, the water used and many other factors, researchers obtain different values of magnesium in the coffee infusion. For example, in the case of ground coffee, the highest content of magnesium was recorded in the infusion of arabica coffee (10.7 mg per 100 ml) [4]. On the other hand, in the infusion of Turkish coffee, the level of magnesium was measured in the amount of 14.92 mg in 100 ml [4].
Differences in magnesium content in relation to different types of coffee and the method of its brewing.
As I mentioned above, there are many factors that affect the final magnesium content in a cup of coffee prepared by us. We can influence some of them, e.g., the method and time of brewing, the degree of grinding, the type, and temperature of the water used. And some of them are beyond our control, such as the origin of coffee, the type of soil it grew on or the methods of its cultivation.
Summarizing the measurements carried out by scientists, I will give the extreme values of the amount of magnesium for a cup of coffee with a volume of 150 ml. In the infusion of ground coffee, the magnesium content ranged from 3.22 mg to 22.38 mg. Among beverages prepared from ground coffee, these values oscillated between 3.22 mg and 16.05 mg of magnesium. Espresso coffee had 2.55 mg of magnesium per 30 ml of drink[3].
The role of magnesium in the human body
Magnesium plays a role as a cofactor in more than 300 enzyme systems. It participates in the regulation of blood pressure, muscle contraction, myocardial excitability, DNA and RNA protein synthesis, as well as in neuromuscular conduction and insulin metabolism [4].
Magnesium, next to potassium, is the most important intracellular cation. It is the fourth most common element in the human body [1].
Magnesium is involved in virtually all major metabolic and biochemical processes in a single cell. These include bone development, neuromuscular function, signaling pathways. In addition, it is responsible for the storage and transfer of energy, glucose, lipid and protein metabolism. And it is also responsible for the stability of DNA and RNA and cell proliferation [1].
Magnesium deficiency – symptoms and risks
Magnesium deficiency is becoming more and more common in modern society [4]. This is due to a diet low in this element, stress, and high alcohol consumption. It is also affected by certain diseases such as diabetes and metabolic syndrome. Magnesium deficiency is also associated with the use of certain medications, including proton pump inhibitors, cardiac glycosides and diuretics. Magnesium deficiency also occurs in congenital disorders of its transport [4].
To avoid deficiencies of this element, it is worth remembering where it occurs. Sources of magnesium are: green vegetables (thanks to chlorophyll), nuts, seeds, unprocessed cereal products. As well as legumes, fruits, meat, and fish [4]. In addition, rennet cheeses, cocoa, dark chocolate [7]. Mineralized water and coffee are also a valuable source of it.
Low magnesium intake and general deficiency of this micronutrient cause changes in biochemical pathways. These changes may increase the risk of disease, especially chronic degenerative diseases [1].
Magnesium deficiency has been shown to increase inflammation. This increases the risk of cardiovascular disease, metabolic syndrome and diabetes. A meta-analysis from 2013 showed that magnesium intake in the diet and its concentration in blood serum are inversely proportional to the risk of cardiovascular events [4].
Magnesium deficiencies may be a risk factor for postmenopausal osteoporosis. They can also cause insulin resistance and impair secretion of this hormone [7].
Early symptoms of magnesium deficiency include weakness, loss of appetite, fatigue, nausea, and vomiting. Then, as magnesium deficiency worsens, muscle spasms and spasms, numbness, tingling, personality changes, coronary spasms, cardiac arrhythmias, and seizures can occur. Finally, severe magnesium deficiency can result in hypocalcemia or hypokalemia. This is due to the disturbed mineral homeostasis [1].
Conclusions
Magnesium is a critical element for the proper functioning of the human body. Due to its increasingly frequent deficiencies in modern society, people without health contraindications should take care of a magnesium-rich diet. You should not be afraid that by consuming coffee, we will expose ourselves to magnesium deficiency. However, let’s not forget about a varied diet and other food ingredients in which this element is present.
Bibliography:
- Fiorentini D, Cappadone C, Farruggia G, Prata C. Magnesium: Biochemistry, Nutrition, Detection, and Social Impact of Diseases Linked to Its Deficiency. Nutrients. 2021 Mar 30;13(4):1136. doi: 10.3390/nu13041136. PMID: 33808247; PMCID: PMC8065437.
- Gajewski P. (Red. Prow.) (2020). Interna Szczeklika 2020., wyd. Medycyna Praktyczna, 2020, Polski Instytut Evidence Based Medicine.
- Barghouthy, Y., Corrales, M., Doizi, S. et al. Tea and coffee consumption and pathophysiology related to kidney stone formation: a systematic review. World J Urol 39, 2417–2426 (2021).
- Olechno E, Puścion-Jakubik A, Socha K, Zujko ME. Coffee Brews: Are They a Source of Macroelements in Human Nutrition Foods. 2021; 10(6):1328.
- Maughan RJ, Griffin J. Caffeine ingestion and fluid balance: a review. J Hum Nutr Diet. 2003 Dec;16(6):411-20. doi: 10.1046/j.1365-277x.2003.00477.x. PMID: 19774754.
- Kunachowicz H., Przygoda B., Nadolna I., Iwanow K. (2020). Tabele składu i wartości odżywczej żywności. PZWL Wydawnictwo Lekarskie.
- Jarosz M. (Red.) (2020). Normy żywienia dla populacji polskiej – nowelizacja. Instytut Żywności i Żywienia.