Highlights
Potatoes are high in glycemic index/load – a relative ranking of carbohydrates in foods based on their effect on blood glucose levels. However, there aren’t many well-defined studies which clearly suggest whether potatoes are good or bad for cancer patients and cancer prevention. While few studies found that potatoes may be linked to an increased risk of cancers such as colorectal cancer, many studies found null or insignificant associations with cancers such as pancreatic or breast cancer. Furthermore, these findings need to be further confirmed in more well-defined studies. Also, regular intake of fried potatoes is not healthy and should be avoided by healthy individuals and cancer patients.
Nutrient Contents in Potatoes
Potatoes are starchy tubers which have been a staple food in many countries across the world for thousands of years. Potatoes are rich in carbohydrates, fiber, potassium and manganese and a variety of other nutrients including :
- beta-Sitosterol
- Vitamin C
- Caffeic acid
- Chlorogenic acid
- Citric acid
- Vitamin B6
- Linoleic acid
- Linolenic acid
- Myristic acid
- Oleic acid
- Palmitic acid
- Solasodine
- Stigmasterol
- TryptophanIsoquercitrin
- Gallic acid
Depending on the cooking method and the type of potato, the nutrient contents may vary. Mostly, these are rich in carbohydrates, antioxidants, vitamins, minerals, and fiber and have great nutritional benefits. Additionally, β-Sitosterol-d-glucoside (β-SDG), a phytosterol isolated from sweet potato, also has potent anticancer activity.
“Are potatoes good or bad for you?”
“Can cancer patients eat potatoes?”
These very common queries that are searched over the internet when it comes to diet and nutrition.
As we all know, potatoes have a very high concentration of carbohydrates and may affect blood sugar levels. Hence, potatoes are tagged under the foods with high glycemic index/load- a relative ranking of carbohydrates in foods based on their effect on blood glucose levels. Many foods with a high glycemic index/load have been associated with several diseases including diabetes and cancer. It is also known that a high consumption of potatoes and processed potato chips may contribute significantly to weight gain.
This may raise many questions as to whether potatoes high in glycemic index/load are good or bad for you, whether they increase the cancer risk, whether cancer patients can eat potatoes, and finally what does the scientific evidence say.
In this blog, we have collated different analyses which evaluated the association between potato consumption and cancer risk. Let us find out whether there are enough well-defined studies to conclude whether potatoes high in glycemic index/load are good or bad for you!
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Potato Consumption and Colorectal Cancer Risk
In a study published in 2017, the researchers of the University of Tromsø-The Arctic University of Norway and Danish Cancer Society Research Center in Denmark, evaluated the association between potato consumption and the risk of colorectal cancer. The study used questionnaire based data from 79,778 women aged between 41 and 70 years, in the Norwegian Women and Cancer study. (Lene A Åsli et al, Nutr Cancer., May-Jun 2017)
The study found that high potato consumption may be associated with a higher risk of colorectal cancer. The researchers found similar association in both rectal as well as colon cancer.
Study on the association between a Diet including Meat and Potatoes and Breast Cancer Risk
In a study published by the researchers of different Universities in New York, Canada and Australia, they evaluated the association between different dietary patterns and breast cancer risk. Dietary pattern analysis was done based on data from 1097 breast cancer cases and an age-matched group of 3320 women from 39,532 female participants in the Canadian Study of Diet, Lifestyle and Health (CSDLH). They also confirmed the findings of the analysis in 49,410 participants in the National Breast Screening Study (NBSS) in which 3659 cases of breast cancer incidence were reported. Three dietary patterns were identified in the CSLDH study including “healthy pattern” which consisted of vegetable and legume food groups; “ethnic pattern” which consisted of groups who took rice, spinach, fish, tofu, liver, eggs, and salted and dried meat; and “meat and potatoes pattern” which included red meat groups and potatoes. (Chelsea Catsburg et al, Am J Clin Nutr., 2015)
The researchers found that while a “healthy” dietary pattern was associated with a reduced risk of breast cancer, the “meat and potatoes” dietary pattern was associated with an increased risk of breast cancer in postmenopausal women. The findings on the association between “meat and potatoes” dietary pattern with increased breast cancer risk was further confirmed in the NBSS study. However, they didn’t find any association between “healthy” dietary pattern and breast cancer risk.
Though the researchers found that “meat and potatoes” dietary pattern showed an increased risk of breast cancer, the study cannot be used to conclude that intake of potatoes may increase breast cancer. The risk of breast cancer could be due to red meat consumption which has been established in various other studies. More studies are needed to evaluate whether potatoes are good or bad for breast cancer prevention.
Potato Consumption and Pancreatic Cancer Risk
A recent study published in the British Journal of Nutrition by the researchers from Norway, Denmark and Sweden in 2018, evaluated the association between consumption of potatoes and the risk of pancreatic cancer among 1,14,240 men and women in the HELGA cohort study, which included participants in the Norwegian Women and Cancer Study, the Danish Diet, Cancer and Health Study and the Northern Sweden Health and Disease Study Cohort. A questionnaire based dietary information data was obtained from the participants of the study. During a mean follow-up period of 11.4 years, a total of 221 pancreatic cancer cases were identified. (Lene A Åsli et al, Br J Nutr., 2018)
The study found that, compared to those with the lowest intake of potatoes, people with the highest consumption of potatoes showed a higher risk of pancreatic cancer,although this risk was not significant. When analyzed based on gender, the study found that this association was significant in females, but not for males.
Hence the study concluded that though there may be an association between potato consumption and pancreatic cancer risk, the associations were not consistent among all. Based on these results, there is not enough evidence to conclude that potatoes may increase the risk of pancreatic cancer and may be bad for pancreatic cancer patients. The researchers suggested further studies with larger populations to explore the differential associations in the two genders.
Potato Consumption and Kidney Cancer Risk
A previous study done by the researchers of Sapporo Medical University School of Medicine, Hokkaido in Japan, evaluated the risk factors for kidney cancer death using the database of the Japan Collaborative Cohort (JACC) Study. The analysis included 47,997 males and 66,520 females who were aged 40 years and older. (Masakazu Washio et al, J Epidemiol., 2005)
During a mean follow-up period of approximately 9 years, deaths of 36 males and 12 females from kidney cancer were reported. The study found that a medical history of high blood pressure, a fondness for fatty food, and consumption of black tea were associated with an increased risk of kidney cancer death. It was also found that intake of taro, sweet potato and potato was associated with a decreased risk of kidney cancer death.
However, since the number of kidney cancer deaths in the present study was small, the researchers pointed out that more studies may be needed to evaluate the risk factors for kidney cancer death in Japan.
Reports on Potato Consumption and Stomach Cancer
In 2015, there were plenty of media reports which hyped about consuming potatoes as a way to decrease the risk of stomach cancer, based on a study published by the researchers of Zhejiang University in China. In fact, the study had not found any specific link between eating potatoes and a decreased risk of stomach cancer.
This was a meta-analysis of 76 studies identified through literature search in Medline, Embase, and Web of Science databases up to June 30, 2015, to evaluate the association between diet and stomach cancer. During a follow-up period of 3.3 to 30 years, 32,758 gastric cancer cases were identified out of 6,316,385 participants in relation to intake of 67 dietary factors, covering a wide range of vegetables, fruit, meat, fish, salt, alcohol, tea, coffee, and nutrients.(Xuexian Fang et al, ur J Cancer., 2015)
The study found that while a high intake of fruits and white vegetables was associated with a 7% and 33% reduction in stomach cancer respectively, a diet including processed meats, salted foods, pickled vegetables and alcohol was associated with an increased risk. The study also found that vitamin C was also associated with a reduced risk of stomach cancer.
The inverse association with stomach cancer risk was observed in white vegetables in general, and not for potatoes specifically. However, the media created a hype on potatoes since different vegetables including onions, cabbages, potatoes and cauliflower fall under white vegetables.
Hence, based on the results of this study, one cannot draw any firm conclusions whether eating potatoes high in glycemic index/load are good for stomach cancer prevention and cancer patients.
Fried Potatoes and Cancer
Dietary Intake of Acrylamide and Risk of Breast, Endometrial, and Ovarian Cancers
Acrylamide is a probable cancer causing chemical which is also produced by starchy foods such as potatoes that are fried, roasted or baked at a high temperature, over 120oC. In a recent meta-analysis, the researchers evaluated the association between estimated dietary intake of acrylamide and risk of female breast, endometrial, and ovarian cancers in 16 cohort and 2 case-control studies published through February 25, 2020. (Giorgia Adani et al, Cancer Epidemiol Biomarkers Prev., 2020)
The study found that high acrylamide intake was associated with increased risks of ovarian and endometrial cancers, especially among those who never smoked. However, except for premenopausal women, no significant association was observed between acrylamide intake and breast cancer risk.
Though this study does not directly evaluate the impact of fried potato consumption on the risk of these cancers, it is better to avoid or minimize taking fried potatoes regularly as it may have adverse effects.
Potato Consumption and Risk of Cancer Deaths
- In a recent study published in 2020, the researchers evaluated the long-term impact of potato consumption on deaths due to heart diseases, cerebrovascular disease and cancer and also on deaths due to all causes. For the study, they used data from the National Health and Nutrition Examination Surveys (NHANES) 1999–2010. The study did not find any significant association between potato consumption and cancer deaths. (Mohsen Mazidi et al, Arch Med Sci., 2020)
- In another study published in the Critical Reviews in Food Science and Nutrition Journal, the researchers from Tehran University of Medical Sciences and Isfahan University of Medical Sciences in Iran examined the association of potato consumption and risk of cancer and cardiovascular deaths and all-cause deaths in adults. Data for the analysis was obtained through literature search in PubMed, Scopus databases up to September 2018. 20 studies were included with 25,208 cases reported for all-cause deaths, 4877 for cancer deaths and 2366 for cardiovascular deaths. The study didn’t find any significant association between potato consumption and risk of all-cause and cancer deaths. (Manije Darooghegi Mofrad et al, Crit Rev Food Sci Nutr., 2020)
Conclusion
Potatoes are known to be high in glycemic index/load. While few studies found that potatoes may be linked to an increased risk of cancers such as colorectal cancer, some studies found null or insignificant associations with cancers such as pancreatic or breast cancer. Few studies also tried to hint a protective effect. However, all these findings need to be further confirmed through more well-defined studies. So far, no firm conclusions could be drawn from these studies on whether potatoes are good or bad for cancer patients and cancer prevention.
It is known that a very high intake of potatoes (high in glycemic index/load) and fried potato chips/crisps significantly contributes to weight gain and associated health issues. However, taking moderate quantities of cooked potatoes and avoiding or minimizing fried potato intake should not cause any harm.
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