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Can Whole Grains Consumption reduce Cancer Risk?

Aug 3, 2020

Highlights

To stay healthy and reap a variety of nutritional benefits, in our daily diet/nutrition, we should replace breads and tortilla made of refined grain flour with those made of whole grains such as corn and wheat, that are good sources of dietary fiber, B vitamins, minerals, proteins and carbs. Several observational cohort studies suggest that unlike refined grain intake, whole grain intake may be associated with a reduced risk of different cancer types including colorectal, gastric, esophageal, breast, prostate (in African Americans and European Americans), liver and pancreatic cancers. However, there may be no significant association between intake of whole grains and the risk of endometrial and prostate cancers in Danish population.



Grains are referred to as small, hard, dry seeds from grass-like plants which may or may not be attached to the hull or fruit layer. Harvested grains have been a part of the human diet since thousands of years. These are an important source of a variety of nutrients including fiber, B vitamins such as thiamin, riboflavin, niacin and folate and minerals such as iron, magnesium and selenium.

whole grain and cancer risk;  whole grain rich in dietary fibers, B vitamins, minerals, proteins and carbs;  rye or corn tortillas are more healthy compared to refined flour tortillas

Different Types of Grains

There are different types of grains in many shapes and sizes. 

Whole grains

Whole grains are unrefined grains which simply means that their bran and germ are not removed by milling and the nutrients are not lost via processing. Whole grains contain all parts of the grains including bran, germ, and endosperm. Some examples of whole grains include barley, brown rice, wild rice, triticale, sorghum, buckwheat, bulgur (cracked wheat), millet, quinoa and oatmeal. These are a better source of dietary fibers, proteins, carbs, nutrients including minerals such as selenium, potassium, magnesium, and B vitamins and more healthy, and are used for making foods such as popcorn, bread from whole grain flour, tortilla (corn tortillas), pasta, crackers and different types of snacks.

Refined grains

Unlike whole grains, refined grains are processed or milled removing both the bran and germ giving them a polished texture with greater shelf life. The refining process removes different nutrients along with dietary fibers. Some examples of refined grains include white rice, white bread and white flour. Refined grain flours are also used for making a variety of foods including breads, tortilla, pasta, crackers, snacks and desserts. 

Health Benefits of Whole Grain Foods

Whole grains have been a part of research for a while and scientists have identified many health benefits of whole grains and whole grain products. Unlike refined grains, whole grains are high in dietary fibers and nutrients including dietary fibers, B vitamins, including niacin, thiamine, and folate, minerals such as zinc, iron, magnesium, and manganese, proteins, carbohydrates and  antioxidants including phytic acid, lignans, ferulic acid, and sulfur compounds.

General health benefits of whole grains include:

  • Reduced risk of heart diseases
  • Reduced risk of stroke 
  • Reduced risk of type 2 diabetes
  • Better weight control
  • Reduced inflammation

There are many questions that are usually being searched over the internet these days such as: “Corn / whole grain or refined flour tortilla – which is more healthy – which one has more nutritional value – carbs content in tortilla” and so on.

The answer is clear. To stay healthy, in our daily diet/nutrition, we should start replacing tortilla made of refined grain flour with corn / whole grain which are known to be more nutritious and contain dietary fiber, B vitamins, minerals, proteins and carbs.

Whole Grain Consumption and Cancer Risk

Being an excellent source of dietary fibers along with high nutritional value, whole grains have been of great interest for researchers across the world. Many of them also evaluated the association between whole grain consumption and the risk of different cancers. Some of the cohort and observational studies related to this topic are elaborated below.

Whole Grain Consumption and Cancers of the Digestive Tract

Study evaluating the association with Colorectal, Gastric cancer and Esophageal cancers.

In a study published in 2020, the researchers from Henan, China evaluated the association between whole grains intake and digestive tract cancer risk. For this they obtained data through literature search  in different databases till March 2020 and used 34 articles reporting 35 studies. Out of these, 18 studies were of colorectal cancer, 11 studies of gastric cancer and 6 studies of esophagus cancer and included 2,663,278 participants and 28,921 cases. (Xiao-Feng Zhang et al, Nutr J., 2020)

The study found that when compared to those with the lowest whole grain intake, the highest-intake participants may have a significant reduction in colorectal cancer, gastric cancer  and esophageal cancer. They also found that American population didn’t show a significant reduction in gastric cancer with high whole grain intake.

Study evaluating the association with Colorectal Cancer

In a study published in 2009, the researchers, mainly from Brazil,  identified 11 cohort studies with a total of 1,719,590 participants between 25 and 76 years of age, from various databases till 31 December 2006, to evaluate the effectiveness of whole grains in the prevention of colorectal cancer based on data from food frequency questionnaires. The studies that reported the consumption of whole grains, fibers of whole grains, or whole cereals were included for the analysis. During a follow-up period of 6 to 16 years, 7,745 persons developed colorectal cancer. (P Haas et al, Int J Food Sci Nutr., 2009)

The study found that the high consumption of whole grains may be associated with a reduced risk of developing colorectal cancer.

Study evaluating the association with Gastric Cancer 

  1. In a study published in 2020, the researchers from Jinan University, China, evaluated the association between whole grain consumption and gastric cancer risk based on data obtained from 19 studies identified through literature search  in databases such as PubMed, Embase, Web of Science, the Cochrane Library and Chinese databases. The study found that a very high intake of whole grains may be protective against gastric cancer. However, they found that the  consumption of refined cereals may elevate the risk of gastric cancer, with the risk increasing with the increase of refined grain intake. (Tonghua Wang et al, Int J Food Sci Nutr., 2020)
  2. In a study published in 2018, the researchers from Sichuan University, Chengdu, China obtained data through literature search in databases such as PubMed, EMBASE, Web of Science, MEDLINE, and the Cochrane Library till October 2017 which included 530,176 participants, to evaluate the association between cereal, whole, or refined grain and the risk of gastric cancer. The study found that a higher whole grain and lower refined grain intake, but not cereal consumption may reduce gastric cancer risk. (Yujie Xu et al, Food Sci Nutr., 2018)

Study evaluating the association with Esophageal Cancer 

In a study published in 2015, the researchers from Norway, Denmark and Sweden evaluated the association between whole grain consumption and risk of esophageal cancer.The analysis used food frequency data from the HELGA cohort study, a prospective cohort study consisting of 3 sub cohorts in Norway, Sweden and Denmark with 113,993 members, including 112 cases, and a median follow-up period of 11 years. The study found that compared to those with the lowest whole grain intake, the highest-intake participants had a 45% reduction in esophageal cancer. (Guri Skeie et al, Eur J Epidemiol., 2016)

The study concluded that whole-grain consumption, particularly whole-grain wheat, may reduce the risk of esophageal cancer.

Whole Grain Consumption and Pancreatic Cancer Risk

In a study published in 2016, the researchers from China obtained data through literature search in databases such as PubMed, Embase, Scopus and Cochrane library databases for the period from January 1980 to July 2015 which included 8 studies, to evaluate the association between whole grain consumption and pancreatic cancer risk. The study found that a high intake of whole grains may be associated with a reduced risk of pancreatic cancer. However, the researchers suggested  more studies to be conducted to ensure that these findings are more robust. (Qiucheng Lei et al, Medicine (Baltimore)., 2016)

Whole Grain Consumption and Breast Cancer Risk

In a study published in 2018, the researchers from China and U.S. obtained data through literature search in databases such as PubMed, Embase, Cochrane library databases, and Google Scholar till April 2017 which included 11 studies with 4 cohort and 7 case-control studies involving 1,31,151 participants and 11,589 breast cancer cases, to evaluate the association between whole grain intake and the risk of breast cancer. (Yunjun Xiao et al, Nutr J., 2018)

The study found that a high intake of whole grains may reduce the risk of breast cancer. However, since this association was only observed in case-control studies but not cohort studies, the researchers suggested more large-scale cohort studies to confirm these findings.

Whole Grain Consumption and Endometrial Cancer Risk

In a study published in 2012, the researchers evaluated the association between whole grains and dietary fiber intake and endometrial cancer risk using questionnaire based data obtained from the Danish Diet, Cancer and Health cohort study including 24,418 women aged 50–64 years who were enrolled between 1993 and 1997 of which 217 had a diagnosis of endometrial cancer. (Julie Aarestrup et al, Nutr Cancer., 2012)

The study did not find any association between intake of whole grains or dietary fiber and the incidence of endometrial cancer.

Whole Grain Consumption and Prostate Cancer Risk

  1. In a study published in 2011, the researchers evaluated the association between whole grain intake and prostate cancer risk using questionnaire based data obtained from the Danish Diet, Cancer and Health cohort study which included 26,691 men aged between 50 and 64 years. During a median follow-up of 12.4 years, a total of 1,081 prostate cancer cases were reported. The study found that higher intakes of total or specific whole-grain products may not be associated with a risk of prostate cancer in a population of Danish middle-aged men. (Rikke Egeberg et al, Cancer Causes Control., 2011)
  2. In a study published in 2012, the researchers evaluated the association between whole grain intake and prostate cancer risk in 930 African Americans and 993 European Americans in a population-based, case study named the North Carolina-Louisiana Prostate Cancer Project or PCaP Study. The study found that whole grain intake may be associated with a reduced risk of prostate cancer in both African Americans and European Americans.(Fred Tabung et al, Prostate Cancer., 2012)

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Whole Grain Consumption and Liver Cancer Risk

In a study published in 2019, the researchers evaluated the association between whole grain intake and liver cancer risk using questionnaire based data obtained from 1,25455 participants including 77241 women and 48214 men with a mean age of 63.4 in 2 cohorts of the Nurses’ Health Study and the Health Professionals Follow-up Study in US Adults. During a mean follow up of 24.2 years, 141 liver cancer cases were identified. (Wanshui Yang et al, JAMA Oncol., 2019)

The study found that an increased intake of whole grains and possibly cereal fiber and bran may be associated with a reduced risk of liver cancer among adults in the United States.

Conclusion 

Findings from most of the observational studies suggest that, unlike refined grain intake, whole grain intake may be associated with a reduced risk of cancers including colorectal, gastric, esophageal, breast, prostate (in African Americans and European Americans), liver and pancreatic cancers.  However, a study published in 2012 did not find any association between intake of whole grains and the risk of endometrial and prostate cancers in Danish population. 

To stay healthy, one should start replacing breads and tortilla made of refined grain flour in our daily diet/nutrition with those made of whole grains such as wheat, rye, barley and corn, that are rich in dietary fiber, B vitamins, minerals, proteins and carbs. However, keep in mind that, while whole grains are considered to be healthy and a staple source of fibers, b-vitamins, proteins and carbs, foods made of whole grain flour or corn tortilla might not be appropriate for people with gluten sensitivity and irritable bowel syndrome (IBS).


Cancer patients often have to deal with different chemotherapy side effects which affect their quality of life and look out for alternative therapies for cancer.Taking the right nutrition and supplements based on scientific considerations (avoiding guesswork and random selection) is the best natural remedy for cancer and treatment related side-effects.


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