# Spirulina Supplements as a Source of Mineral Nutrients in the Daily Diet
## 4 Discussion
we have not found any studies that would address the effect of supplement form or cultivation method on the mineral content of spirulina supplements. The only paper of this type was authored by our team and described the fluoride content of spirulina supplements. In this study, we found that the fluoride content in supplements in tablet form was significantly higher. No statistically significant differences in the fluoride content were observed depending on the method of cultivation [14]. Publications on various plant raw materials confirm that the method of their cultivation is one of the factors affecting the content of elements [36; 37]. Our findings show that both supplement form and cultivation method affect the mineral content of spirulina. Supplements in powder form had a significantly higher content of important elements, such as Fe, Mg and K, while at the same time containing significantly less Na. This is an important observation, given that the consumption of Na, whose main dietary source is table salt, is often alarmingly high. Consequently, supplements in powder form appear to be a far better choice. In terms of the cultivation method, organic spirulina supplements turned out to be a richer dietary source of Fe and K. In turn, conventionally grown supplements had higher contents of Ca, P and Sr. It should also be noted that organic spirulina supplements were only available in tablet form. Thus, in the comparison of the mineral content of spirulina tablets originating from organic vs. conventional cultivation, it was found that organic spirulina tablets contained more Fe, Mg and K.  
Manufacturers differ in their recommendations regarding the intake of spirulina supplements. The recommended daily dosage of spirulina usually ranges from 2 to 3 g (4-6 servings per day of 500 mg each), and can go up to 10 g, with a maximum daily limit for consumption of 30 g [38]. When writing about spirulina as a source of minerals, it is worth highlighting their importance in the diet. In the Discussion, the authors will refer to the recommended intake of 2-3 g, as these values are the most common in the literature. Therefore, when referring to the percentage of the daily requirement for a given mineral, the first value refers to the intake of 2 g of spirulina and the second value to the intake of 3 g of spirulina per day. Ca serves as a building block of not only bones and teeth, but also connective tissue. It is also involved in blood coagulation, conduction of nerve impulses and regulation of certain hormones [39]. Its recommended daily intake is between 1.0 and 1.20 mg/day for men and women. Spirulina supplements cover approximately 2% of the requirement for this mineral. P is one of the most important elements in the human body. It is responsible for the normal structure of bones, forming compounds with Ca, and is a component of ATP, nucleic acids and phospholipids [40]. The recommended daily intake of P is 700 mg/day for both men and women. The studied supplements cover on average from 4% to 6% of the daily requirement for this mineral. Mg is very important for the normal functioning of the human body. It is involved in the biochemical processes that regulate the functioning of the circulatory, endocrine, digestive and bone and joint systems. It also plays a role in nerve conduction [41]. The requirement for Mg is 420 mg/day for men and 320 mg/day for women. The studied supplements cover between 1.8% and 2.7% of the requirement for men and 2.3-3.5% for women (when taking 2 g or 3 g of spirulina per day, respectively). A diet containing the optimal amounts of K can have a positive effect on lowering blood pressure [42]. Excess K is excreted by the kidneys, and hence its high levels in people with kidney disease are dangerous [43]. The studied supplements cover a small percentage of the K requirement, as little as 0.2-0.3%. Table salt is the primary source of sodium in the human diet. According to the WHO, one should consume no more than 2 g of Na per day, which is the equivalent of 5 g of salt (one teaspoon) [44].