## 1 Introduction  
Inflammatory bowel diseases (IBDs), such as ulcerative colitis and Crohn's disease, are associated with inflammation in the digestive system, without a specific cause. IBDs are promoted by an abnormal innate immune response from the intestinal microbiota [1,2]. Frequent bloody stool, diarrhea, weight loss, abdominal pain, anemia, and nutrient loss are major clinical symptoms in IBD patients [3,4]. Inflammatory and immune cytokines seem to play a major role in controlling complications such as intestinal inflammation, diarrhea, rectal bleeding, and furnucle formation [5,6]. Autoimmune diseases can also develop from a leaky gut, which is caused by dysregulation of tight junctions (TJ) in the intestinal epithelial barrier [7,8].  
Mineral deficiency is associated with various diseases. In the absence of extracellular calcium, myosin light chain kinase is activated to increase the intestinal monolayer TJ permeability. TJ protein complexes in the intestinal monolayer are the main structures controlling intercellular tightness [9; 10]. Increased TJ permeability can result from invading harmful molecules and causes systemic disorders of the intestine, leading to dysregulation of the mucosal immune system and inflammation [11]. Magnesium deficiency causes asymptomatic inflammation in the small intestine, rendering the cells sensitive to oxidative stress [12; 13].  
In modern times, numerous mineral supplements are available in pill form. However, previous studies have shown that minerals have a higher absorption rate when consumed in the ionized form, especially the water-soluble form [14; 15; 16; 17]. Ingested water is the most efficiently absorbed in the intestine. Hence, if drinking water contains a large amount of harmful substances, it can cause a variety of problems, including abdominal pain and diarrhea. The mineral types and contents in drinking water have an important effect on IBD. A study of the correlation between water intake and IBD in Norway suggested that iron in drinking water is an important cause of IBD. A high iron content in drinking water acts as a catalyst for oxidative stress, causing inadequate immune responses that provoke inflammation and stimulate bacterial growth [18]. Among various sources of drinking water, deep-sea water (DSW) is usually pumped from a depth of more than 200 m, and desalted. DSW has numerous minerals, including magnesium (Mg), calcium (Ca), potassium (K), selenium (Se), zinc (Zn), and vanadium (V) [19; 20]. Although the health benefits of DSW has been examined in numerous studies, they have focused primarily on the hardness of DSW [19]. In fact, a study showed that, when the effects of the main minerals in DSW (calcium and magnesium), at the same hardness as that of DSW, were examined, the effect was lower than that of DSW [20]. We, therefore, sought to generate water samples that would allow us to determine if the health benefits of DSW were derived from the amount of calcium and magnesium, or that of other trace minerals, or alternatively, by the calcium:magnesium composition ratio.  
Numerous studies have demonstrated that DSW is effective in treating metabolic diseases such as obesity and diabetes, and in improving atopy [20; 21; 22; 23; 24; 25]. Although several studies have investigated the effects of DSW in minimizing immune and metabolic diseases, no studies focused on the effects of DSW on intestinal health [26; 27; 28; 29]. Therefore, this study aimed to evaluate the effect of mineral controlled DSW on intestinal health in enteritis models. DSW is generally richer in magnesium than in calcium. Therefore, to determine the optimal ratio of minerals included in mineral water, DSW was desalted and different ions were added. The effect of the mineral waters on gut health was evaluated using an in vitro coculture system of Caco-2 and Raw264.7 cells, and a dextran sulfate sodium (DSS)-induced enteritis mouse model.