Can an anti-inflammatory diet be effective in preventing or treating viral respiratory diseases? A systematic narrative review

Respiratory Viruses infections (RVI) such as rhinovirus, coronavirus, influenza virus, and adenovirus affect the respiratory and the immune systems. The role of nutrition in the respiratory and immune systems has been studied in some studies, and its importance is undeniable. In addition, one of the key findings in this disease is high inflammation that affects almost all patients. This systematic narrative review aims to answer the question, "Can an anti-inflammatory diet be effective in preventing or treating viral respiratory diseases?" A systematic review search was used for the articles extraction. All studies published in English from 1999 to 2020 investigating dietary inflammatory conditions and RVI were included. Food items with anti-inflammatory properties were selected based on the definition of the dietary inflammatory index (DII). We used Google Scholar, Pub Med, Scopus, Web of Science, Springer, Science Direct, Directory of Open Access Journals, Elsevier, Taylor and Francis, ProQuest, EBSCO, MEDLINE, and SciELO databases for extracting articles. Keywords were restricted by DII. Based on DII, food items/nutrients are involved in inflammation, some of which have anti-inflammatory and some inflammatory properties. Some foods/nutrients, in addition to their anti-inflammatory properties, have antioxidant, antiviral, and immune-enhancing properties. Considering the immune system's involvement, increased inflammation, and involvement of the pulmonary system in RVI and the remarkable role of the anti-inflammatory foods for counteracting them, it is recommended to use a predominantly anti-inflammatory diet along with prevention/control and treatment protocols. An anti-inflammatory diet (based on DII) includes turmeric, ginger, garlic, onions, saffron, dietary vitamin C, vitamin D, zinc, and omega-3 are recommended to reduce infection symptoms and duration.

The Association Among Maternal Index of Nutritional Quality, Dietary Antioxidant Index, and Odds of Miscarriage Incidence: Case-Control Study

OBJECTIVE

Miscarriage is a pregnancy condition in which the fetus or embryo naturally dies before being able to survive independently. According to studies, diet and dietary factors are associated with the risk of miscarriage (pregnancies <20 weeks). A 168-item semi-quantitative feed frequency questionnaire was used to estimate the Dietary Antioxidant Index (DAI) and the Index of Nutritional Quality (INQ). We aimed to assess the relationship between INQ and DAI with odds of miscarriage.

METHOD

In summary, 135 Iranian women with a history of three or more miscarriages were included. We calculated the INQ using the following formula: INQ = consumed amount of a nutrient per 1,000 kcal/Recommended Dietary Allowance of that nutrient per 1,000 kcal. We standardized each dietary vitamins/minerals by subtracting the global mean and dividing the result by the universal standard deviation to compute DAI. We computed the DAI by summing up the standardized intakes of these vitamins and minerals and equal weight.

RESULTS

Regression models were used to extract the odds ratios (ORs) and 95% confidence intervals (CIs) in crude and multivariate adjustments. Controls significantly had higher INQ of vitamin B12, niacin, vitamin D, vitamin E, vitamin C, and zinc. Modeling INQs of vitamin D (OR: 0.004, 95% CI, 0.00-0.025) and B12 (OR: 0.04, 95% CI, 0.005-0.41) as a continuous variable showed a significant and protective effect in multivariate adjustment. Modeling DAI as a categorical variable showed a significant protective effect (OR_{DAI<0.054vs.DAI ≥0.054} = 0.43, 95% CI, 0.20-0.91).

CONCLUSIONS

Recommending a diet rich in antioxidants such as vitamin E, C, zinc, and selenium and a quality diet containing vitamins B12 and D can be considered an effective strategy to reduce the odds of miscarriage in women with a history of recurrent miscarriage.

The association between dietary antioxidant index (DAI) and nonalcoholic fatty liver disease (NAFLD) onset; new findings from an incident case-control study

BACKGROUND

Evidence suggests an increasing global trend in non-alcoholic fatty liver disease (NAFLD) prevalence. Researchers have noted the importance of the role of dietary antioxidants in reducing the incidence of NAFLD. The dietary antioxidant index (DAI) is a valid indicator that considers the -diet's total antioxidant properties. The present study was designed and conducted to investigate the relationship between DAI and NAFLD. We hypothesized that there is a link between the DAI and the NAFLD.

METHODS

This case-control study included 295 patients with NAFLD and 704 controls. The patients' dietary intake was assessed through a valid and reliable semi-quantitative food frequency questionnaire. We standardized each of vitamin A, C, E, and selenium, manganese, and zinc by subtracting the global mean and dividing by the global SD to calculate the DAI.

RESULTS

Subjects with DAI score -0.46 < were at higher odds of having NAFLD compared to subjects with DAI -0.46 ≥ (OR_{DAI<-0.46/≥-0.46} = 0.55; 95% CI = 0.41-0.73). After adjustment for age, gender, and total energy intake (model B) a reverse and significant association was seen (OR_{DAI<-0.46/≥-0.46} = 0.57; 95% CI = 0.39-0.82).

CONCLUSION

The role of antioxidants in reducing the odds of NAFLD is fundamental. Taking antioxidants such as vitamins A, E, C, zinc, selenium, and manganese through food can effectively reduce NAFLD odds. On the other hand, studies should examine DAI's sensitivity and specificity in various settings and outcomes to use it in clinical work.

Validation of Dietary Antioxidant Index (DAI) and investigating the relationship between DAI and the odds of gastric cancer

BACKGROUND

Gastric cancer (GC) incidence and mortality are rapidly growing worldwide. It is estimated that more than 1,000,000 new cases are diagnosed each year, and more than 78,000 people lose their lives due to GC. The association between dietary antioxidants and GC has been shown in some studies. However, because of the discrepancy between the findings and the lack of a valid indicator, it seems necessary to design and validate the Dietary Antioxidant Index (DAI) to examine the diet's total antioxidant content. The present study aimed to survey the validity of DAI and its association with the odds of GC.

METHODS

In this hospital-based case-control study, 82 patients with GC and 95 healthy controls were examined. We used a 168-item food frequency questioner to assess dietary intakes. The DAI was calculated based on the intake of vitamin A, C, E, and selenium, manganese, and zinc. We standardized each of the six vitamins and minerals by subtracting the global mean and dividing by the global standard deviation to calculate DAI. We then calculated the DAI by summing up the standardized intakes of these vitamins and minerals of the individuals with equal weight.

RESULTS

We observed a significant correlation between DAI and total antioxidant capacity (TAC) after controlling for age, body mass index (BMI), energy intake, smoking and fasting blood sugar, education, total fat intake, helicobacter pylori infection, total cholesterol, and saturated fatty acid (SFA) intakes. Results obtained from modeling DAI as a continuous variable in relation to GC showed a negative association after adjustment for age and in the multivariable analysis (OR = 0.64, CI = 0.43-0.95).

CONCLUSION

DAI is a valid indicator of dietary antioxidants assessments, and it can be used as a predictor of antioxidant status due to its correlation with serum antioxidant levels. The results showed that dietary antioxidants have a significant relationship with GC, which indicates the importance of antioxidants in this cancer's etiology.

Persistence of an endemic (toxigenic) isolate of Clostridium difficile in the environment of a general medicine ward

The epidemiology of Clostridium difficile-associated diarrhea (CDAD) in an endemic setting was investigated by use of DNA typing methods to determine the strain identity of C. difficile isolates. Two predominant toxigenic clones were found in the environment and accounted for 29.8% (type 1) and 15.5% (type 2) of CDAD cases, respectively. In endemic settings, the environment and cross-transmission may play a role in acquisition of CDAD.

Detection of Bacteroides fragilis enterotoxin gene by PCR

Bacteroides fragilis constitutes about 1% of the bacterial flora in intestines of normal humans. Enterotoxigenic strains of B. fragilis have been associated with diarrheal diseases in humans and animals. The enterotoxin produced by these isolates induces fluid changes in ligated intestinal loops and an in vitro cytotoxic response in HT-29 cells. We developed a nested PCR to detect the enterotoxin gene of B. fragilis in stool specimens. After DNA extraction, a 367-bp fragment was amplified with two outer primers. The amplicon from this reaction was subjected to a second round of amplification with a set of internal primers. With these inner primers, a 290-bp DNA fragment was obtained which was confirmed as part of the B. fragilis enterotoxin gene by Southern blotting with a nonradioactive internal probe and a chemiluminescence system. By this approach, B. fragilis enterotoxin gene sequences were detected in eight known enterotoxigenic human isolates and nine enterotoxigenic horse isolates. No amplification products were obtained from DNA extracted from 28 nonenterotoxigenic B. fragilis isolates or B. distasonis, B. thetaiotaomicron, B. uniformis, B. ovatus, Escherichia coli, or Clostridium difficile. The sensitivity of this assay allowed us to detect as little as 1 pg of enterotoxin DNA sequences or 100 to 1,000 cells of enterotoxigenic B. fragilis/g of stool. Enterotoxin production of all isolates was confirmed in vitro in HT-29 cells. A 100% correlation was obtained between enterotoxin detection by cytotoxin assay and the nested PCR assay. This rapid and sensitive assay can be used to identify enterotoxigenic B. fragilis and may be used clinically to determine the role of B. fragilis in diarrheal diseases.