Diet has long been considered a risk factor related to an increased risk of cancer. This challenges us to understand the relationship between the immune system and diet when abnormal cells appear in a tissue. In this paper, we propose and analyze a model from the point of view of a person who follows a healthy diet, i.e., one correlated to the food pyramid, and a person who follows an unhealthy diet. Normal cells and immune cells are used in the design of the model, which aims to describe how the immune system functions when abnormal cells appear in a tissue. The results show that the immune system is able to inhibit and eliminate abnormal cells through the three following stages: the response stage, the interaction stage, and the recovery stage. Specifically, the failure of the immune system to accomplish the interaction stage occurs when a person follows an unhealthy diet. According to the analysis and simulation of our model, we can deduce that dietary pattern has a significant impact on the functioning of the immune system.

Changes in diet are heavily associated with high mortality rates in several types of cancer. In this paper, a new mathematical model of tumor cells growth is established to dynamically demonstrate the effects of abnormal cell progression on the cells affected by the tumor in terms of the immune system’s functionality and normal cells’ dynamic growth. This model is called the normal-tumor-immune-unhealthy diet model (NTIUNHDM) and governed by a system of ordinary differential equations. In the NTIUNHDM, there are three main populations normal cells, tumor cell and immune cells. The model is discussed analytically and numerically by utilizing a fourth-order Runge–Kutta method. The dynamic behavior of the NTIUNHDM is discussed by analyzing the stability of the system at various equilibrium points and the Mathematica software is used to simulate the model. From analysis and simulation of the NTIUNHDM, it can be deduced that instability of the response stage, due to a weak immune system, is classified as one of the main reasons for the coexistence of abnormal cells and normal cells. Additionally, it is obvious that the NTIUNHDM has only one stable case when abnormal cells begin progressing into early stages of tumor cells such that the immune cells are generated once. Thus, early boosting of the immune system might contribute to reducing the risk of cancer.

The natural sources of the vitamins, which come from a balanced diet (as recommended by the World Cancer Research Fund and the American Institute for Cancer Research) contribute to protecting the body from advancing progressive of cancer stages. Thus, in this study, we analyze the effect of the intervention of vitamins on delaying the growth of cancer cells based on the dynamics of a normal cell cycle when the tumor cells appear in a tissue as a resulting for progressing abnormal cells due to the weak response of the immune system. We developed a mathematical model, called tumor-normal-vitamins model (TNVM), which is governed by a system of ordinary differential equations and refers to two main populations normal cells and tumor cells. This model considers the intervention of vitamins as a moderating factor within thirty days. The models are discussed analytically and numerically by utilizing the Runge-Kutta method to simulate them. The results of the analysis and simulation of free model illustrate that the model will be stable if the tumor cells succeed in eliminating normal cells in the tissue. Whereas, the analysis and simulation of the TNVM showed a case of coexistence between normal cells and tumor cells occur if an individual consumes a regular rate of vitamins that have been simulated to be 87% per day from a natural food source. Even though the response of the immune system is weak, the daily consumption of enough vitamins can play an essential role in delaying the development of an early stage of cancer. This study contributes to the increasing awareness regarding a healthy diet to reduce the risk of some deadly diseases, especially cancer. INDEX TERMS Dynamic system, numerical simulation, tumor-normal model, healthy diet. I. INTRODUCTIONCancer is classified as a civilization disease nowadays, where GLOBOCAN 2018 database estimated that 9.6 million cases of death have occurred owing to cancer. The number of new cases of cancer is predicted to be about 18.1 million [1]. Lung cancer is common for both sexes. A previously conducted study indicated that the mortality rate of lung cancer is about 18.4% of the total mortality rate of cancer, and the percentage of new cases of cancer is about 11.6% of the total cancer cases. This is followed by breast cancer among females, with a mortality rate of about 11.6% compared to 7.1% of prostate cancer among males. In 2018, Australia and New Zealand recorded the highest mortality rate of 94.2% due to cancer, which comprised 571.2 per 100000 male and 362 per 100000 female deaths compared to 95.6 per 100000 males in Western Africa. Among females,The associate editor coordinating the review of this manuscript and approving it for publication was Aniruddha Datta.

Background Psychological disorders are common among individuals who experienced COVID-19. Previous studies have shown that females report higher depression and anxiety than males. The present study aims to test the differences in depression and anxiety between males and females who have experienced COVID-19. This a descriptive, observational, comparative study, among Saudi Arabian population. A total of 686 participants have been recruited. Participants completed an online questionnaire that contains questions about sociodemographic, COVID-19, Generalized Anxiety Disorder (GAD-7) questionnaire, and Patient Health Questionnaire (PHQ-9) to measure anxiety and depression, respectively. Results Twenty-six percent of the participants were excluded and our final sample consisted of 507 participants (median age 23; 65% females). Of the final sample, 23% (118) have been previously diagnosed with COVID-19. There is no significant difference in GAD-7 and PHQ-9 scores between COVID-19- positive and COVID-19-negative populations. However, females who have experienced COVID-19 reported significantly higher GAD-7 and PHQ-9 scores compared to males. Conclusion The results of our study show that females are significantly at a higher risk for depression and anxiety as a result of COVID-19 infection compared to males. Further epidemiological studies are required for a better understanding of this correlation.

Introduction Waterpipe smoking (WPS), which is otherwise called shisha, narghile, and Gozaor hookah, has been one of the most common strategies for tobacco use in developing nations for approximately 400 years [1-4]. Its device consists of a head, body, water bowl, and hose [5]. WPS contains tobacco-specific nitrosamines and glycerol nicotine, which are derived from raw materials, and it produces chemical substances (such as carbon monoxide (CO)), which are synthesised during smoking, and produces 34 polyaromatic hydrocarbons, which are synthesised and transmitted when smoking [6]. WPS has been used for around 400 years [1]; the Arabian Peninsula, Turkey, India and Pakistan are among the countries where WPS has become increasingly popular [7]. WPS has considerable effects, both short and long term, on human health. Its short-term health effects include headache, nausea, lethargy, and fainting. Waterpipe smoking also impairs baroreflex control, which helps control blood pressure. Various long-term health effects may be caused including pulmonary diseases (e.g. chronic obstructive pulmonary disease) and coronary heart disease. WPS appears to increase the risk of several cancers such as lung, oral, oesophageal, and gastric cancer [3, 8, 9]. WPS also leads to numerous communicable diseases and respiratory diseases such as influenza, hepatitis and TB [10, 11]. Mahfouz et al. studied the prevalence of tobacco use and its associated factors in 4100 students, both male and female, at Jazan University, and states that (according to the World Health Organization) around four million people die annually due to tobacco use worldwide [12]. The percentage of males who used WPS was 12.1% (95% Confidence Interval [CI]: 10.6-13.8), whereas that of females was 2.5% (95% CI: 1.8-3.4). Hassan et al. conducted a study in Riyadh, Saudi Arabia in 2014, with 156 students from Al-Ghad International College, to assess the prevalence of tobacco smoking [13]. The study showed of those surveyed: 42.3% were current smokers, 17.9% were past smokers, 34.8% were cigarette smokers and 21.2% were WPS users. In 2010, Taha et al. conducted a cross-sectional study at Lord Faisal College in Dammam City, Saudi Arabia, to investigate the prevalence of WPS among male understudies from three medical colleges [14]. The general prevalence of WPS was found to be 12.6% (n = 47). The worldwide prevalence of WPS has also been studied. In Aleppo, Syria (2014), WPS prevalence was 25.5% and 4.9% among male and female university students,