Deficiency of vitamins and minerals has been associated to countless clinical conditions, including chronic pain and FM [2, 5]. In this study, it has been found that dietary intake of magnesium and calcium remained below recommended levels for both groups, which reflects inadequate dietary consumption of said minerals by the Brazilian population . This may be due to the increased consumption of processed food and fast food . In parallel, there is also low intake of foods that are rich in magnesium such as dark-green vegetables, vegetables in general, fish, nuts and seeds, and wholegrain cereals , and low intake of foods that are rich in calcium such as milk and dairy, dark-green vegetables, seafood and fish .
In spite of the fact that the general population has low dietary intake of foods that are rich in Mg and Ca, the women with FM who participated in this study had substantially lower dietary intakes than the control group. That has been related to worsening of pain for women with FM. Such assumption was confirmed by the results of this research work, in which dietary intake of Mg and Ca correlated positively with the pain threshold and negatively with TP count. This means that the lower the intake of said minerals, the lower the pain threshold and higher TP count. That being said, it is necessary to make dietary assessments to adjust the intake of these minerals in order to ensure a healthy, balanced diet that helps reduce pain and painful points in women with FM.
In parallel, although the studied groups had lower dietary intake of magnesium and calcium, that did not reduced these minerals levels in blood samples. Moreover, even though some studies have shown reduced intracellular contents and levels of serum Mg and high levels of serum Ca in patients with FM [7, 8, 25, 26], in this study there was no differences in levels of serum Mg and Ca between the FM group and the control group. Nevertheless, such fact needs to be further investigated given that studies have adopted different methodologies for analysis of minerals, and present varying levels of serum, erythrocytes, leucocytes, urinary, muscular and hair.
Various authors have stated that plasma concentration of Mg may not reflect the entire body content of Mg since the body has mechanisms that maintain constant serum levels within a narrow range of normality [7, 16]. Additionally, several studies have shown that in spite of concentrations of Mg in plasma being within normal ranges, the concentration of erythrocyte Mg was below normal [9, 27]. Magaldi et al.  presented in their study that patients with FM had normal levels of serum Mg and reduced levels in leucocytes. This confirms the assumption that serum Mg is a poor predictor of the Mg status in the body as a whole, and that intracellular analyses are more representative [11, 16, 29,30,31,32].
Lower levels of serum calcium (Ca) have not been noticed in women with FM participating in this research work. Although some studies have already found low serum Ca levels in patients with FM, others present normal serum levels but with reduced intracellular concentrations of Ca, such as in leucocytes  and hair . This demonstrates that, similarly to what occurs with Mg, Ca concentration may be normal in blood but different in the intracellular level .
Levels of serum Mg of women with FM participating in this study have not shown correlation with pain parameters, quality of life and depression risk. Similar results have been found by Sakarya et al. . Sendur et al.  found solely correlation of serum Mg with fatigue severity.
On the other hand, Bagis et al.  presented correlation between levels of serum Mg with VAS (visual analogue scale of pain), TP count, TP index, FIQ, anxiety and depression score, and somatic symptoms in women with FM. Erythrocyte levels of Mg in this study correlated with the same variables, as well as with the pain threshold, fatigue, headache and numbness.
As to levels of serum Mg and Ca, only the control group presented positive correlation of said minerals with the pain threshold. It is important to notice the role of Mg in cognitive-affective functions, and studies have shown an improvement in pain and depression parameters after supplementation of Mg . The Hagenston and Simonetti review study (2014) showed the involvement of neuronal calcium signaling in the processes that mediated chronic pain .
Although the minerals analyzed in this study did not correlate with quality of life and depression risk for women with FM, additional research is required to investigate the role of minerals in the symptoms of this disease in order to improve the impact of dietary therapies in the quality of life of patients.
The present study has limitations related to serum mineral dosage, which does not seem to be a good predictor of intracellular reserves. In addition, serum Ca values were not corrected by albumin, and it was not possible to measure complementary tests such as ionic Ca, Vitamin D, and PTH (parathyroid hormone), which would help to better analyze the metabolism of these minerals.
Additionally, the three-day food register is a method with intrinsic limitations to its use: it is subjective, requires a high level of motivation and collaboration, requires time, there may be difficulty in estimating portions, and the individual must know the home measures. In parallel, consumption may be altered as the individual knows that it will be assessed, and therefore there may be underreporting of consumption. There may also be regional variations and errors in the software used for data tabulation.
Finally, it is noteworthy that this was a cross-sectional study, which has a number of limitations inherent to its methodology. Therefore, it is very important to conduct clinical trials randomized, with food intervention to lead to a conclusion related to the specific intake of these evaluated nutrients.