Dietary approach to stop hypertension (DASH): diet components may be related to lower prevalence of different kinds of cancer: A review on the related documents.

BACKGROUND: Dietary approaches to stop hypertension (DASH) eating plan is a healthy dietary pattern. Our object is to review surveys in the field of major components of DASH diet and different kinds of cancers.
MATERIALS AND METHODS: Our search result from PubMed search engine recruited to find related articles.
RESULTS: Adherence to the DASH diet components was significantly related to lower prevalence of various cancers due to their high content of fiber, nutrients, vitamins, mineral, and antioxidant capacity.
CONCLUSION: In this review, positive association of DASH diet components and different cancers were observed. However, the exact association of DASH with cancers should be clarified in future longitudinal studies due to potential interaction among foods and nutrients.

INTRODUCTION

The most previous studies have been conducted on the relationship between single nutrients, foods, food groups, and cancer risk. Researches in this field are valuable but according to consumption of various dietary groups together and their synergistic and antagonistic effects, evaluation of diet as a healthy dietary pattern can provide a more comprehensive dataset.[123] Several studies have been demonstrated advantageous influence of dietary approaches to stop hypertension (DASH) diet on cardiovascular disease, metabolic syndrome, diabetes, and mortality.[45678] Beneficial influence of DASH diet through emphasis on reduction in salt intake and monitoring dietary fat intake on some cancers has been observed. Researchers are mainly focused on the association between DASH diet and colorectal and breast cancer.[9101112] More surveys require indicating the favorable effect of DASH diet in various cancers. Nevertheless, numerous studies have assessed the effect of DASH component in cancer prevention. In this review, we are going to assess the association between components of DASH diet and different kinds of cancers.

MATERIALS AND METHODS

In order to investigate the association between DASH eating plan component and cancers, PubMed search engine was searched. Our keyword was DASH diet without any limitations.

RESULT

Articles included in our study are demonstrated in Figure 1 and Table 1.

Figure 1

Flowchart of conducted studies in the field of dietary approaches to stop hypertension components

Table 1

Studies examined association of DASH diet component and various cancers

Dairy

Moderate intake of low-fat dairy is suggested by DASH diet. Several studies have assessed the effects of dairy products consumption on various cancers. Meta-analyses could not find supportive independent relationship between the intake of milk or dairy products and the risk of bladder and gastric cancers.[1314]

Findings of the meta-analysis indicate that increased consumption of total dairy food, but not milk, may be associated with a reduced risk of breast cancer.[15] Meta-analyses carried out on prostate cancer did not strongly support increasing effect of various kinds of dairy products.[1617] The effects of milk and total dairy products have been indicated in reduction of colorectal cancer risk.[1819]

Salt

Salt intake is limited in DASH diet. In this regard, meta-analysis on salt intake and risk of various cancers has approved its rising effect significantly.[2021]

Whole grain

Whole grains that replaced with refined grains in DASH diet recommended increasing in this dietary pattern. An expanded review and meta-analyses on various cancers and whole grain consumption supported the hypothesis of its preventive effect.[222324]

Red meat

Many epidemiological and clinical trials have investigated the relationship between red meat and processed products and different cancers, but their findings are so inconsistent. Findings of a meta-analysis demonstrated high intake of processed meat may related to augmentation of bladder cancer risk (1.22; 95% CI: 1.04-1.43).[25] Increasing association of red and processed meat and lung cancer has been supported by meta-analysis of epidemiological studies.[26] Dose-response analysis indicated every increment of 100 g red meat per day increase stomach cancer risk 17%.[27] Also, esophageal cancer risk has been increased by high consumption of red and processed meat.[28] Meta-analysis suggested that every 50 g increase in processed meat consumption augments risk of pancreatic cancer 19%.[29]

Findings show every 100 g/day increase in red meat consumption, enhance risk of colorectal cancer by 14%.[30] On the other hand, other meta-analyses could not observe significant association between red meat intake and colorectal, ovarian, breast, and prostate cancers.[31333435] However, frequency of red meat consumption is mostly linked to colorectal cancer risk.[32]

Fruit and vegetable

Increase in fruits and vegetables consumption is recommended in DASH diet due to their fiber, antioxidants, vitamins, and minerals content. This hypothesis has been assessed in meta-analysis on bladder cancer that total fruit and vegetable indicate 17% reduction in cancer risk significantly.[36]

Meta-analysis has been demonstrated significant gastric cancer risk reduction only for fruits, but not vegetables.[37] Moreover, no significant protective effect observed for prostate cancer and fruit and vegetable consumption (vegetable: 0.97; 95% CI: 0.93, 1.01, and fruit: 1.02; 95% CI: 0.98, 1.07).[38] Meta-analysis on nasopharyngeal cancer and fruits and vegetables intake support positively risk reduction.[39]

Nuts

High consumption of nuts and seeds appears to be appropriate for cancer prevention. Epidemiologic studies observed a protective association between the increment in nut consumption and decrement in colorectal cancer, especially in women.[404142] In addition, a large body of data presented that higher consumption of nuts and seeds decrease risk of prostate cancer and mortality.[4344]

Regards to debates that breast cancer prevention should be started in adolescence, epidemiologic surveys shown that fiber and nuts intake during adolescence might protect against breast cancer in older ages.[45]

DISCUSSION

The evidence from studies approved protective effect of DASH diet components in most of the various cancers. All studies regarding dairy products were meta-analyses that summarized results of papers in that field. The effect of dairy products on cancer prevention refers to its ingredients such as calcium, lactoferrin, fat component, and its bacterial effect. Conjugated linoleic acid is one of the positive health effective parameters of dairy products.[46] Lactic acid bacteria in fermented dairy products can inhibit from Helicobacter pylori growth and its invasion and inflammation thus prevent from gastric cancer.[4748] Another important component especially in colorectal cancer prevention is calcium with several hypothetical mechanisms.[495051] Salt intake is a component of DASH diet which considered greatly in this healthy dietary pattern.

The potential mechanism could be alteration in mucus viscosity of stomach[52] and increment in H. pylori colonization.[53] Therefore, it causes mucosal injury that result in augmentation of cell proliferation in stomach mucosa.[5455]

High consumption of whole grains is usually suggested due to beneficial effect of several components such as dietary fibers, antioxidants, vitamins, trace minerals, phytate, phenolic acids, lignans, and phytoestrogens.[425657] Dietary fiber is one of the most important ingredients in colorectal cancer prevention because it can enhance stool bulk, attenuating fecal carcinogens, and decline transit time so decrease contact between carcinogens and colorectal cells.[58] Moreover, bacterial activation in colon results in fiber fermentation and short chain fatty acid output that is effective in cancer inhibition.[56]

High red meat consumers are at risk of different cancers more than low consumers. Modification of dietary pattern and lifestyle should be a priory to prevent of cancers and reduce burden of disease. The effect of red and processed meat in incidence of cancers connected to preservation, cooking or processing that could produce mutagens and carcinogens including N-Nitroso compounds (NOCs), heterocyclic amines, and polycyclic aromatic hydrocarbons.[596061626364] Furthermore, high heme iron content of meat, especially red meat, could provide free radicals[65] such as stimulation of endogenous NOC production,[66] and also iron is crucial growth factor for H. pylori.[67] Saturated fatty acids (SFAs) are another component that may be related to cause of cancer.[6568]

Beneficial effects of fruit and vegetables have been investigated in some cancers. Multiple components of fruits and vegetables such as beta-carotene, fiber, vitamins, alpha-tocopherol, retinoids, phytoestrogens and folate can cause their protective effect against cancers[69] through potent mechanism such as prohibition of cell growth, normalize DNA synthesis and methylation, and protection against DNA damage and oxidative stress.

Sulforaphane is an isothiocyanate component found in vegetables such as cruciferous vegetables which its protective effect is considered greatly in new epidemiological studies.[7071727374]

Nuts are extremely valuable nutritionally due to wide range of nutrients such as proteins, unsaturated fatty acids, vitamins (B6, niacin, folic acid, tocopherol), dietary fiber, copper, magnesium, potassium, zinc, antioxidants (i.e., resveratrol, ellagic acid, and several flavonoids), phytoestrogens, and many phytochemicals (i.e., anacardic acid). Most of these components play important role in cancer prevention through prohibition of cancer cell proliferation, decrease metastasis, inducing cancer cell death and intervention in some other pathways related to cancer cell growth.

This review create new ideas and attract researchers to conduct more surveys in the field of DASH diet because its superior effect to other patterns including emphasis on the amount of salt intake, and restriction in intake of total fat. A limitation was lack of discussion about quality of articles due to different cancer categories of articles. Nevertheless, efforts in our review with covering the major component of DASH diet were to assess their relationship with cancers comprehensively.

CONCLUSION

There are limited investigations regarding the association of DASH eating plan and the risk of different cancers. Although many studies have assessed the association of its component with different cancers, due to potential interaction among foods and nutrients, the exact association of DASH with cancers should be clarified in future longitudinal studies.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

AUTHOR'S CONTRIBUTION

SHO contributed in the conception of the work, drafting the manuscript, FH contributed in the conception of the work, conducting the study, drafting and revising the draft, LA contributed in the conception of the work, conducting the study, revising the draft, approval of the final version of the manuscript, and agreed for all aspects of the work.