Free radical attack has been linked to numerous pathological conditions such as inflammation and infections in all organs of the body. Reactive oxygen species are generated endogenously during inflammation and lipid peroxidation. Low antioxidant level affects the immune system. Oxidative stress is an important factor involved in the pathogenesis of MS, including speeding up the production of reactive oxygen species [
11‐
13]. Both demyelination and inflammation are linked with the generation of reactive oxygen species. Factor facilitating the activation of oxidative process induced by reactive oxygen species is an increased demand for oxygen by neurons in the central nervous system and decreased concentrations of endogenous antioxidants and other compounds that can inactivate free radicals [
12]. Se is an active component of various enzymes involved in redox reactions which protect membranes from oxidative damage. Deficit of selenium is one of the risk factors that may predispose to inflammatory diseases [
14]. Dietary Se, mainly through its incorporation into selenoproteins, plays an important role in inflammation and immunity processes so, appropriate concentration of Se is important for immunity but it also helps in regulation of excessive immune responses and chronic inflammation [
15].
The reference level of Se in the serum is 70 – 140 μg/L [
16] and the reference range of GSH-Px is 4171 – 10881 U/L [
17]. We observed decreased Se concentration in the serum of the examined patients with MS, whereas the average level of Se was within the reference range in the control group. Serum concentration of TAS in patients with MS was also below the references ranges for European population (1.30 – 1.77 mmol/L) [
17].
So far, the concentration of Se, GSH-Px activity and TAS in the serum of patients with MS have not been estimated in the north-eastern region of Poland. Similar results for the decreased Se concentration in Mongolian patients with MS obtained Komatsu et al. [
18]. Also similar to our research, studies of Mai et al. [
19] showed lower level of GSH-Px in MS patients than in healthy volunteers. Miller et al. [
20] evaluated the TAS in patients with MS living in the central Poland and also found its significant reduction in comparison to the control group.
The content of Se in a diet depends on Se availability in the environment. It has been well documented that Se levels in subjects from different regions of Poland are rather low [
21,
22]. Our previous investigations showed that a degree ratio of realization of the recommended daily allowance for Se (60 and 70 μg/day for women and men, respectively) was about 50% [
23]. A stepwise multiple linear regression analysis showed that dietary habits influence on concentration of Se in the serum both in patients with MS and the control group, but other products have an impact on that status, which may result from differences in the diet of the study groups. An analysis of the frequency distribution of consumption in individual food groups, indicated that diet differs between the patients with MS and the healthy subjects. People with MS more often consumed processed products such as canned meat and canned fish, margarine, sweetened beverages, jam and sugar, while those in the control group frequently consumed products such as fish, fruits, vegetables, legumes. According to the food pyramid, cereals which form the basis were consumed with similar frequency in both groups. Certain cereal products and vegetables are also known to deliver a significant amount of Se to the organism. Among Spanish population levels of Se were positively correlated with the consumption of fruit and vegetables [
24]. Among the food stuffs high content of Se is in Brasil nuts, fish, kidney, liver, chicken, eggs and bean [
24,
25]. Wholegrain cereals, despite the high mineral content, have a lower bioavailability due to a competition between mineral elements in the stage of absorption in the gastrointestinal tract. Additionally, the presence of dietary fiber has a negative impact on bioavailability [
26]. In our region, meat products can be a main source of Se in diets. Our earlier study of food products from the Podlasie region showed that meat, especially poultry and offal, are the best source of Se in diets [
24,
27]. Our earlier research showed that meat products can provide on average about 24% general content of Se in diet [
28]. Milk products are rather poor source of Se in our region, but it is considered that Se derived from high protein products has a good bioavailability [
29,
30]. Our research showed that consumption of sugar and sweet beverages may decrease the serum level of Se. Refined sugar is devoid of minerals, and it is considered that sugar can leach minerals from the body [
31]. That explains in a part the results of our work on the influence of dietary habits on serum Se concentration of the patients with MS.