Dietary Fiber and Cancer Prevention

Properties and physiological effects of dietary fiber-enriched meat products: a review

Meat is a rich source of high biological proteins, vitamins, and minerals, but it is devoid of dietary fiber, an essential non-digestible carbohydrate component such as cellulose, hemicellulose, pectin, lignin, polysaccharides, and oligosaccharides. Dietary fibers are basically obtained from various cereals, legumes, fruits, vegetables, and their by-products and have numerous nutritional, functional, and health-benefiting properties. So, these fibers can be added to meat products to enhance their physicochemical properties, chemical composition, textural properties, and organoleptic qualities, as well as biological activities in controlling various lifestyle ailments such as obesity, certain cancers, type-II diabetes, cardiovascular diseases, and bowel disorders. These dietary fibers can also be used in meat products as an efficient extender/binder/filler to reduce the cost of production by increasing the cooking yield as well as by reducing the lean meat content and also as a fat replacer to minimize unhealthy fat content in the developed meat products. So, growing interest has been observed among meat processors, researchers, and scientists in exploring various new sources of dietary fibers for developing dietary fiber-enriched meat products in recent years. In the present review, various novel sources of dietary fibers, their physiological effects, their use in meat products, and their impact on various physicochemical, functional, and sensory attributes have been focused.

Anticancer potential of Phoenix dactylifera L. seed extract in human cancer cells and pro-apoptotic effects mediated through caspase-3 dependent pathway in human breast cancer MDA-MB-231 cells: an in vitro and in silico investigation

Background

Phoenix dactylifera L. has a diverse set of pharmacological properties due to its distinct phytochemical profile. The purpose of this study was to investigate the anticancer potential of Phoenix dactylifera seed extract (PDSE) in human breast cancer MDA-MB-231 and MCF-7 cells, as well as liver cancer HepG2 cells, and to investigate the anticancer efficacy in triple-negative MDA-MB-231 cells, followed by in silico validation of the molecular interaction between active components of PDSE and caspase-3, an apoptosis executioner protein .

Methods

In this study, human cancer cell lines were cultured and subsequently treated with 10 to 100 μg/mL of PDSE. MTT test was performed to determine the cell viability, MMP was measured using fluorescent probe JC-1, nuclear condensation was determined by Hoechst 33258 dye, Annexin V-FITC & PI staining and cell cycle analysis were evaluated through flow cytometer, and apoptotic markers were detected using western blotting. The bioactive agents in PDSE were identified using high-performance liquid chromatography (HPLC) analysis. The binding affinity was validated using molecular docking tools AutoDock Vina and iGEMDOCK v2.1.

Results

Cell viability data indicated that PDSE inhibited cell proliferation in both breast cancer cells and liver cancer cells. MDA-MB-231 cells showed maximum growth inhibition with an IC₅₀ value of 85.86 μg/mL for PDSE. However, PDSE did not show any significant toxicity against the normal Vero cell line. PDSE induced MMP loss and formation of apoptotic bodies, enhanced late apoptosis at high doses and arrested cells in the S phase of cell cycle. PDSE activated the enzymatic activity of cleaved caspase-3 and caused the cleavage of poly-ADB ribose polymerase (PARP) protein. PDSE upregulated pro-apoptotic Bax protein markedly but  no significant effect on tumor suppressor protein p53, while it downregulated the anti-apoptotic Bcl-2 protein expression. HPLC analysis showed the presence of rutin and quercetin bioactive flavonols in ethanolic extract of PDS. Interestingly, both active components revealed a strong binding interaction with amino acid residues of caspase-3 (PDB ID: 2XYP; Hetero 4-mer - A2B2) protein.

Conclusion

PDS could serve as a potential medicinal source for apoptotic cell death in human breast cancer cells and, thus, could be used as a promising and crucial candidate in anticancer drug development. This study warrants further in vivo research, followed by clinical investigation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-022-03533-0.

Short-chain free-fatty acid G protein-coupled receptors in colon cancer

The dietary role of macronutrients and their metabolites in cancer has been evident for many decades. Dietary ingestion of fat, carbohydrates, protein, and fiber, as well as probiotics that influence gut microbiota, have all been linked to gastrointestinal (GI) tract health and disease, particularly in the colon, where it has long been known that fat and fiber can regulate inflammation and carcinogenesis. Short-chained fatty acids (SCFA), including acetate, propionate, and butyrate, which are biosynthesized by microbiota-mediated metabolism of dietary fiber, have previously been shown to play important roles in colorectal health, including decreasing inflammation and oxidative stress. Since the 1980s, a growing number of studies have also demonstrated a link between SCFA and colon epithelial cell carcinogenesis and prevention of colorectal cancers (CRC). While the effects of SCFA have historically been associated with their intracellular metabolism and function, the discovery of a family of G protein-coupled free-fatty acid receptors in the early 2000s suggests that many effects of SCFA are cell-surface receptor mediated. Indeed, the SCFA GPCRs FFA2 (previously termed GPR43), FFA3 (previously termed GPR41), and GPR109A are now well established to be expressed within the GI tract, where they modulate a variety of functions in response to luminal SCFA. While the role of SCFA in cancers, including CRC, has been reviewed in detail elsewhere, the goal of this report is to provide a review on the current body of evidence in regard to the effects of SCFA on FFA2, FFA3, and GPR109A in colon cancers.

Nutrition and pharyngeal cancer: results from a case-control study in Spain

BACKGROUND

Oropharyngeal and hypopharyngeal cancer is increasing all over the world, frequently affecting more and more women and younger individuals and not only the typical 50- to 60-year-old heavy smoker and drinking man. In addition, 5-year overall survival rate remains poor (30% to 40% in most series), despite advances in treatment. Therefore, it is crucial to understand as accurately as possible the risk factors for these malignancies to improve primary prevention.

METHODS

We report the results from a case-control study of pharyngeal cancer risk factors conducted in Spain involving 232 consecutive patients who were gender- and age-matched with 232 controls. Data were collected by interviewer-administered personal interview.

RESULTS

Our results show that low intake of fruit, fruit juice, uncooked vegetables, dietary fiber-containing foods (legume and cereals), fish, milk, and dairy products is an independent risk factor for pharyngeal cancer and that high consumption of meat and fried foods also increases the risk once data are adjusted for tobacco smoking and alcohol drinking.

CONCLUSIONS

Although findings for fruit, juice, and uncooked vegetables are in accordance with those from other authors and can be explained on a biologic basis, the relationship between pharyngeal cancer and dietary excess of saturated fatty acids needs experimental investigation. Findings for milk, dairy products, and fish also warrant more detailed epidemiologic research because of conflicting data reported in the literature and because of the reportedly ambiguous role of retinol in human cancers. No conclusive explanations for the protective effect of dietary fiber-containing foods can be put forward today. Our results are uniquely attributable to oropharyngeal and hypopharyngeal cancers because of the small size of our nasopharyngeal cancer subsample.

Phytochemicals for the prevention of breast and endometrial cancer

Although there is evidence that phytochemicals decrease the incidence of breast and endometrial cancer, many observations are only phenomenologic, and much work needs to be done to explore basic mechanisms and the strategic exploitation of their interactions. The multiplicity of phytochemical actions at different sites in the process of tumorigenesis may eventually lead to the development of a multiagent strategy designed to maximize the complementary effects of different agents. A number of effects with possible relevance to cancer chemoprevention have been excluded from this review, including effects of phytochemicals on the immune response; the question of dietary restriction, which has a profound effect on tumorigenesis; the relatively low methionine levels in some phytochemicals such as soy, which may limit the synthesis of polyamines necessary for tumor growth [151]; and the fact that diets higher in plant products are usually lower in fat and result in leaner individuals with less potential for the synthesis of estradiol in adipose tissue. Also, many studies dealing solely with in vitro mutagenesis were excluded.

Vegetarian diet: panacea for modern lifestyle diseases?

We review the beneficial and adverse effects of vegetarian diets in various medical conditions. Soybean-protein diet, legumes, nuts and soluble fibre significantly decrease total cholesterol, low-density lipoprotein cholesterol and triglycerides. Diets rich in fibre and complex carbohydrate, and restricted in fat, improve control of blood glucose concentration, lower insulin requirement and aid in weight control in diabetic patients. An inverse association has been reported between nut, fruit, vegetable and fibre consumption, and the risk of coronary heart disease. Patients eating a vegetarian diet, with comprehensive lifestyle changes, have had reduced frequency, duration and severity of angina as well as regression of coronary atherosclerosis and improved coronary perfusion. An inverse association between fruit and vegetable consumption and stroke has been suggested. Consumption of fruits and vegetables, especially spinach and collard green, was associated with a lower risk of age-related ocular macular degeneration. There is an inverse association between dietary fibre intake and incidence of colon and breast cancer as well as prevalence of colonic diverticula and gallstones. A decreased breast cancer risk has been associated with high intake of soy bean products. The beneficial effects could be due to the diet (monounsaturated and polyunsaturated fatty acids, minerals, fibre, complex carbohydrate, antioxidant vitamins, flavanoids, folic acid and phytoestrogens) as well as the associated healthy lifestyle in vegetarians. There are few adverse effects, mainly increased intestinal gas production and a small risk of vitamin B12 deficiency.

Influence of gender and socio-economic status on dietary patterns and nutrient intakes in 18-year-old Australians

This study used two-day diet records to examine dietary behaviours in 504 Australian 18 year-olds in relation to gender, socio-economic status (SES) and national dietary guidelines. Fat intake exceeded 30% of energy in about 80% of subjects and was greater than 40% in about one-quarter. Saturated fat provided more than 10% of dietary energy in more than 90% of participants; less than 1% achieved a polyunsaturated to saturated fat ratio of at least one. The major food groups contributing to fat intake were convenience foods (32% in men, 28% in women) and meat (27% in men, 25% in women). Fibre intake was less than 30 g/day in 93% of women and 77% of men. Intakes of calcium, magnesium, potassium, and vitamins C and A, as a ratio of energy consumption, were greater in women than men, while sodium intake was significantly higher in men. Convenience foods were the greatest contributors to sodium intake (27% in men, 22% in women) followed by meat, bread, and soups and sauces. Greater consumption of cereals, fruit, vegetables and low-fat foods in young women of higher SES was reflected in their nutrient profile with higher intake of fibre and vitamin C and lower intake of fat. Men ate more cereals, meat and sugary foods and less fruit, vegetables and low-fat foods. Only 2.5% of men and 4.1% of women conformed with the health promotion message, widely publicised locally, to eat two fruits and five vegetables daily. Not eating breakfast was associated with lower calcium intake in men and women, and lower iron and fibre in take in women. Achieving behavioural changes in young adults must take into account differences in dietary behaviour related to gender and SES.

Dietary fiber: nutritional lessons for macronutrient substitutes

The wide array of low-fat foods containing soluble fibers have the potential for helping in weight loss or weight control. Consumption of soluble fibers in sufficient quantities has been shown to lower serum lipid concentrations and to improve glycemic response. Some individuals could, eventually, consume a significant portion of their soluble dietary fiber from processed foods containing soluble-fiber fat substitutes. Changes in dietary fiber and starch sources increase the amount of fermentable material reaching the colon. Short-chain fatty acids thus produced are used as an energy source by colonocytes and may inhibit hepatic cholesterol synthesis. However, colonic fermentation can also result in flatulence or diarrhea. In addition, some diets high in soluble fiber have been shown to change intestinal cell morphology in rats. The possible benefits from consumption of a diet high in soluble fiber fat substitutes in serum lipid reduction, glycemic response improvement, and/or weight reduction as well as potential problems in flatulence, mineral absorption, and colonic cell hyperproliferation should be investigated.

Comparison of pure inositol hexaphosphate and high-bran diet in the prevention of DMBA-induced rat mammary carcinogenesis

Inositol hexaphosphate (IP6), abundant in cereals and legumes, has been demonstrated to be a promising anticancer agent in different in vivo and in vitro models. Because IP6 is particularly abundant in the bran part of certain mature seeds such as wheat, we investigated whether a high-fiber bran diet containing high IP6 shows a dose-response inhibition of 7,12-dimethylbenz[a]anthracene (DMBA)-induced rat mammary carcinogenesis. Starting at two weeks before DMBA intubation, rats were divided into five groups and fed AIN-76A diet only or AIN-76A diet containing 5%, 10%, or 20% Kelloggs' All Bran; the fifth group received 0.4% IP6 given in drinking water, an amount equivalent to the IP6 content in 20% bran. After carcinogen administration, the rats remained on these regimens for 29 weeks. Compared with the carcinogen control, at 29th week, tumor incidence was reduced by 16.7%, 14.6%, and 11.4% in rats fed 5%, 10%, and 20% bran, respectively (not statistically significant). However, rats given 0.4% IP6 in drinking water, equivalent to that in 20% bran, had a 33.5% reduction in tumor incidence (p < 0.02) and 48.8% fewer tumors (p < 0.03). These data show that supplemental dietary fiber in the form of bran exhibited a very modest, statistically nonsignificant inhibitory effect, which was also not dose dependent. In contrast, animals given IP6 showed significant reduction in tumor number, incidence, and multiplicity. Thus IP6 an active substance responsible for cereal's beneficial anticancer effect, is clearly more effective than 20% bran in the diet. In practical terms, intake of IP6 may be a more pragmatic approach than gorging enormous quantities of fiber for cancer prophylaxis.

Experience from clinical trials in cancer prevention

Conduct of randomized, controlled, large-scale prevention trials is fundamental to the full assessment of the efficacy of interventions to prevent cancer. Clinical trials in cancer prevention, which include dietary modification and chemoprevention, are based on leads from epidemiological and laboratory studies. Dietary intervention trials involve the modification of overall eating patterns, whereas chemoprevention trials involve the administration of natural or synthetic substances reported to have anticarcinogenic properties, e.g. vitamins, minerals, and pharmaceuticals. Clinical/metabolic studies can help advance knowledge of the role of diet in the etiology and prevention of cancer by investigating the metabolism of factors thought to influence cancer risk; thus, these studies have the potential to provide a stronger scientific base for progression to randomized, controlled clinical trials. Cancer prevention trials supported by the National Cancer Institute include the Polyp Prevention Trial, which is testing a low-fat, high-fibre, and vegetable- and fruit-enriched eating pattern on the prevention of polyp recurrence, and the Nutrition Intervention Trials of Oesophageal Cancer in Linxian, China, which are testing the efficacy of vitamin-mineral supplements in the prevention of oesophageal cancer in high-risk populations. Results from clinical cancer prevention trials will enable investigators to establish more firmly the relationships between diet and cancer and to translate the information effectively into significant reductions in cancer incidence and mortality.

Diet as risk and therapy for cancer

This article provides a brief overview of the scientific rationale for dietary guidelines that may reduce the risk of some types of cancers--breast, colon, and prostate in particular. Dietary modification clinical trials currently sponsored by the National Cancer Institute are described. Other topics include the role of total parenteral nutrition in cancer therapy and low-fat dietary interventions as an adjunct to breast cancer treatment.

Protective mechanisms of dietary fibers in nutritional carcinogenesis

Fibers in foods are complex carbohydrates. There are several types of fiber, but, for the purpose of mechanistic insight into their mode of protective action in carcinogenesis, classification into two broad types, soluble and insoluble fibers, is warranted. Soluble fibers are present in fruits, vegetables, and certain grains like oats. This type of fiber undergoes metabolism in the small intestine and especially in the large intestine through bacterial enzymes, converting it to products that increase stool size only moderately. But, they have appreciable effects in modifying the metabolism of colon carcinogens like azoxymethane to yield detoxified products and, thus, reducing colon carcinogenesis. In contrast, insoluble fibers present in sizeable amounts in bran cereals, like wheat or rice, are not significantly metabolized by enzymes in the intestinal flora. Such fibers increase stool size substantially through several mechanisms, including higher water retention. The larger bulk dilutes carcinogens, especially tumor promoters such as secondary bile acids, resulting in lower risk of colon cancer in animals and in humans. Evidence in animal models and in humans also indicates that fiber may lower the risk of breast cancer, possibly via an endocrine mechanism. Based on these concepts, increased intake of total fiber, but especially of wheat bran cereal fiber, to yield a daily stool in adults of about 200 grams can significantly reduce the risk of colon cancer and, to a lesser but definite extent, of breast cancer. Thus, adequate fiber intake from cereals, fruits, and vegetables can help prevent important types of human cancer.