Another example is vitamin B3, also called niacin, which is reported to possibly become hepatotoxic, if taken for prolonged periods of time in higher amounts than those recommended [9]. Still, vitamin B3 has a number of functions in our body, it is needed for the health of our nervous system as well as for maintaining the integrity of our skin [9,10]. Like vitamin C, also niacin is an essential component of our diet, as we are not able to independently synthesize it [10]. It is primarily contained in meat, fish, eggs and wheat flour. 100 g of tuna fish, for example, contains roughly 10 mg of it [11, 10] and the recommended daily intake is 16.5 mg for men and 13.2 mg for women [9].

Concerning minerals, potassium is an example of an essential mineral (among many) that we need to introduce with our diet. The recommended daily intake is around 3-3.5 g [12, 13]: one baked potato of medium size contains around 600 mg of it, one cup of cooked lentils around 700 mg, and half a cup of raisins again around 600 mg [13]. Potassium overdose from dietary intake is considered unlikely, especially in healthy individuals [14]. However, hyperkalemia (the condition linked to higher potassium blood levels than the normal ones) can occur especially in individuals with impaired kidney function and it can in some cases cause severe symptoms like palpitations, arrhythmia, muscle pain, muscle weakness, or numbness [15, 16].

Dietary supplements of vitamins and minerals can play an important role in some specific situations. For example, vitamin D supplements can be useful or even necessary during the winter season (especially for inhabitants of northern countries) when the exposure to sunlight is substantially reduced. In fact, the chemical reaction leading to vitamin D synthesis is dependent on the UVB rays that reach our skin while being exposed to sun [17, 18, 19]. Vitamin D is required for enhancing the intestinal absorption of some minerals (e.g. calcium, magnesium, phosphate) and its deficiency, especially if occurring in young children, can lead to serious consequences, such as bone deformities [18]. At the same time, its prolonged excessive intake can cause damage to kidneys, heart and, again, bones [17]. Further examples of this kind could be listed and individual recommendations should be left to expert professionals.

To conclude, the “the more the better” rule does not apply even for (apparently) harmless substances like vitamins and minerals. Provided that dietary supplements of some of these nutrients can be required in specific cases and periods of our life (following competent recommendations), we often already get the required amounts from a healthy, balanced diet and, in the best-case scenario, we just eliminate the excess intake through urine.