## 4 Discussion  
Dietary non-organic nitrates have a bad reputation mostly due to their supposed connection with creating nitrosamines and possible cancer risk [28; 29]. In this study, we found that life-long supplementation of dietary nitrates had no evident adverse effects in mice. The treatment groups that were fed with 2-3% KNO\({}_{3}\) solution showed somewhat longer life span and developed significantly fewer structural pathologies than the mice from 0-1% KNO\({}_{3}\) treatment groups. Similarly, the treatment groups (those fed with 1-3% KNO\({}_{3}\)) had significantly fewer pathological changes in comparison to the control group. These results are in line with previous studies [30; 31] as well as recent long-term studies on male mice diet supplementation with NaNO\({}_{3}\) by [PERSON] et al. [32] and rats by [PERSON] et al. [33], adding to growing evidence considering the safety and possible beneficial effects of dietary nitrates. However, the effects on both sexes still need to be addressed. As for the possible mechanisms resulting in longer lifespan of mice, we suggest a viewpoint to nitrate-related compounds that has been applied in recent research where lower levels of the oxidation (using hydrogen peroxide) stimulated a scavenging enzyme that helped slow down the aging of the yeast cells [34]. As shown by our previous experiment with fruit flies [22], this could be explained by the previously hypothesized inverted \"U shape\" curve effect for this given compound, assuming that too small a concentration has very little or no effect and too high a concentration is/could be harmful. This hypothesis is supported by other studies showing the importance of quantity, where the low doses of nitrite, but not higher ones, had protective effects in in vivo and in vitro models of vascular dysfunction [35; 36], myocardial ischemic injury, and liver ischemia-reperfusion injury [37; 38]. The newest research has shown that usual nitrate and nitric oxide production in the bodies can prevent cardiovascular and metabolic diseases that shorten the lifespan [39; 40; 41; 42; 43], as well as help to maintain the capacity of mitochondria and, in unison, the whole organism [15; 44; 45]. Scientists suggest that by the mid-21 st century 20-25% of the population in developed countries will consist of people over 65 years old [46; 47; 48]. Hence, the number of concomitant conditions that accompany aging (e.g., sarcopenia, cardiovascular, neurodegenerative diseases, type II diabetes, and cancer) will increase together with increasing lifespan [49]. There is a demand for innovative and reliable methods that would increase longevity and prevent chronic conditions [50]. This is why it is important to find natural components that would allow for improving body functioning even while aging. Nitric oxide holds an important position among all health-enhancing supplements. Our results suggest that nitric oxide, along with nitrate supplementation, may delay pathological changes within the body and prolong life with no chronic conditions. Due to a lack of a standardized approach in rodent aging and toxicological studies, we examined the organs most likely to be affected: lungs, liver, kidneys, and spleen, but excluded endocrine and reproductive as well as cardiovascular systems, because they tend