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is a very common question. Personalized Nutrition Plans are foods and supplements which are personalized to a cancer indication, genes, any treatments and lifestyle conditions.

Natural Foods/Supplements that may cause/harm Cancer

May 1, 2020

Estimated reading time: 12 minutes
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After being diagnosed with cancer, patients tend to look out for alternative options and natural remedies and make changes in diet/nutrition by including natural foods and dietary supplements. However, many natural foods and supplements may not favor reducing the cancer risk or may even interfere with the treatments intended to cure cancer and have to be avoided. This blog provides information on some of the foods and supplements to avoid that may cause cancer and the need for dietary restrictions for cancer patients, as anything natural is not always safe!

Finding out that you or somebody you care about has cancer is a life-changing or devastating moment. People always try out one or more strategies to reduce the chances of getting cancer, which is why they often reach out for natural remedies including natural foods and over-the-counter dietary supplements. However, they often end up taking anything natural assuming that all natural foods and supplements are safe and may help to prevent or cure cancer, or if nothing, may still do no harm. But this is not always true! Many natural foods or supplements can cause or increase the risk of specific cancers, interfere with certain cancer treatments and worsen the side-effects and one should have the information of these foods and supplements before deciding on their diet. 

Taking the right natural foods and dietary supplements to reduce the risk of cancer is as important as it is during and after cancer treatment post a diagnosis. Just as there are foods and dietary supplements that can help to reduce the risk of cancer, there are foods and dietary supplements that can increase the risk too. Hence one needs to be very careful and take care of dietary/food restrictions to reduce the risk of cancer and avoid adverse interactions with treatments in cancer patients.

Natural Foods and Dietary Supplements that may cause Cancer or worsen Treatments


Foods to avoid that may cause Cancer

There are many foods that are well-known to cause or increase the risk of cancer and definitely do not fall under the “foods that can cure cancer” category. Some of these foods are those that we have daily (based on lifestyle) and can end up leading to cancer. Few of these foods which need to be avoided/restricted to reduce the risk of cancer are :

  • Red meat, Charred meat and Processed Meat
  • Refined Sugar, Sugary Foods and Sweetened Beverages
  • Alcohol
  • Processed Foods
  • Hydrogenated Oils

These details would be generally highlighted in the foods/dietary restrictions designed by the health care providers/nutritionists. Many studies also suggest various other natural foods and supplements which may cause or increase the risk of a specific cancer.

Information on Few Food/Dietary Supplements to Avoid that may cause Specific Cancers

1. High intake of Retinol may cause Prostate Cancer

The National Cancer Institute (NCI), National Institute of Health (NIH), USA driven alpha-tocopherol, beta-carotene cancer prevention study of over 29,000 participants between 1985-1993 with a follow-up to 2012, found that higher serum retinol concentration is associated with an increased risk of prostate cancer.  The study also found that higher serum retinol was not associated with overall cancer risk and was observed to lower risk of liver and lung cancer. However, across multiple studies there has been a positive correlation seen between serum Retinol (Vitamin A) levels and elevated risk of prostate cancer (Hada M et al, Am J Epidemiol, 2019).

Findings suggest that a high intake of dietary Retinol/Vitamin A supplements may increase the risk of prostate cancer and should be avoided. Information on dietary supplements to be avoided becomes crucial to reduce the risk of prostate cancer.

2. High intake of Vitamin B12 may cause Colorectal Cancer and Lung Cancer

A clinical trial study, named the B-PROOF (B Vitamins for the Prevention of Osteoporotic Fractures) trial, conducted in the Netherlands evaluated data from 2524 participants. The study found that long term folic acid and vitamin-B12 supplementation may be associated with a high risk of overall cancer and a significantly higher risk of colorectal cancer. (Oliai Araghi S et al, Cancer Epidemiol Biomarkers Prev., 2019).

In a different study, the researchers analyzed the results from 20 population based studies and data from 5,183 lung cancer cases and their matched 5,183 controls, to evaluate the impact of high intake of vitamin B12 concentration on cancer risk by directly measuring the circulating vitamin B12 in pre-diagnostic blood samples. The study concluded that a higher vitamin B12 concentration may be associated with an increased risk of lung cancer and for every doubling levels of Vitamin B12, the risk increased by ~15% (Fanidi A et al, Int J Cancer., 2019).

Findings suggest that a high intake of Vitamin B12 supplements may increase the risk of colorectal cancer and lung cancer and should be avoided. Information on dietary supplements to be avoided becomes crucial to reduce the risk of colorectal and lung cancer.

3. High intake of Vitamin E may cause Brain Cancers

A study based in different neuro oncology and neurosurgery departments across the United States hospitals analyzed structured interview data from 470 patients that was conducted following diagnosis of brain cancer glioblastoma multiforme (GBM).  The study found that a significantly large number of these patients (77%) reported randomly using some form of complementary therapies like vitamins or natural supplements.  It was also found that Vitamin E users had a higher mortality rate as compared to those who did not use Vitamin E. (Mulphur BH et al, Neurooncol Pract., 2015)

In another study from Umea University, Sweden and Cancer Registry of Norway, the researchers took serum samples up to 22 years prior to glioblastoma diagnosis and compared the metabolite concentrations of serum samples of those who developed the cancer from those who did not. The study found significantly higher serum concentration of Vitamin E isoform alpha-tocopherol and gamma-tocopherol in cases that developed glioblastoma. (Bjorkblom B et al, Oncotarget, 2016)

Findings suggest that a high intake of dietary Vitamin E supplements may increase the risk of brain cancers and should be avoided. Information on dietary supplements to be avoided becomes crucial to reduce the risk of brain cancer.

4. High intake of Beta-Carotene may increase the risk of Lung Cancer in Smokers

Studies have highlighted that natural dietary supplements like beta carotene may increase the risk of lung cancer in current smokers and people who have a significant smoking history.  In one such study, the researchers from the Thoracic Oncology Program at Moffitt Cancer Center in Florida evaluated data from 109,394 subjects and concluded that among current smokers, beta-carotene supplementation was found to be significantly associated with an increased risk of lung cancer (Tanvetyanon T et al, Cancer. 2008). 

Findings suggest that a high intake of natural dietary beta carotene supplements may increase the risk of lung cancers in Smokers. Information on dietary supplements to be avoided becomes crucial to reduce the risk of lung cancer.

Foods to Eat After Cancer Diagnosis!

No two cancers are the same. Go beyond the common nutrition guidelines for everyone and make personalized decisions about food and supplements with confidence.

Examples of Foods/Supplements to avoid by Cancer Patients 

A cancer diagnosis brings about major lifestyle changes in patients including a trend towards the use of natural foods and supplements with anti-cancer properties, boost immunity and general well-being. However, many of these natural foods and dietary supplements can cause adverse interactions with the treatments and worsen the cancer. Cancer patients need to be advised on their dietary/food restrictions to ensure that with an intention to cure cancer or improve quality of life, they do not take any random foods or supplements which can harm their cancer.

Some of the studies which highlighted certain foods or dietary supplements which may not support ongoing treatments to cure cancer, instead, may cause harm to specific treatments or specific cancers and have to be added to the information on patients’ dietary restrictions are summarized below.

1. Reduce the intake of Linoleic Acid rich Chia Seeds and Flax Seeds if diagnosed with Gastric Cancer

Chia seeds and Flaxseeds contain fatty acids called Linoleic acid which, according to a recent study, may worsen Gastric Cancer.  The study was done by the National Institute of Environmental Health Sciences (NIEHS) and found that excessive dietary linoleic acid enhanced angiogenesis (the sprouting of new blood vessels) and enhanced tumor growth in animal models (Nishioka N et al, Br J Cancer. 2011). Angiogenesis refers to the development of new blood vessels to supply nutrients and oxygen which are necessary for the normal growth and healing. However, tumors have a greater need of oxygen and nutrients supplied by the blood vessels for their rapid growth and spread, which is why increased angiogenesis is not favorable in cancer therapy.

Findings from this study indicate that linoleic acid supplements as well as chia seeds and flax seeds should added to the information on gastric patients’ dietary restrictions and avoided. Information on natural foods or dietary supplements to be avoided becomes crucial to reduce any unwanted interactions while treating prostate cancer.

2. Avoid Curcumin Supplement while on Tamoxifen treatment for Breast Cancer

India to New York for Cancer Treatment | Need for Personalized Nutrition-specific to Cancer

Patients diagnosed with hormone positive breast cancers are usually treated with endocrine therapy such as Tamoxifen for breast cancer prevention and recurrence. Tamoxifen acts as a selective estrogen receptor modulator, which inhibits the hormone receptors in breast cancer tissue to reduce the survival of the cancer cells and reduce risk of relapse.  Curcumin, the key active ingredient of turmeric, is a natural supplement that is popular among cancer patients and survivors due to its anti-cancer and anti-inflammatory properties. Therefore, the likelihood of breast cancer patients taking Curcumin while on Tamoxifen treatment is quite high.  

The oral drug Tamoxifen is metabolized in our body into its pharmacologically active metabolites through the cytochrome P450 enzymes in the liver.  Endoxifen is the clinically active metabolite of Tamoxifen and the key mediator of efficacy of tamoxifen therapy (Del Re M et al, Pharmacol Res., 2016). A recently clinical study (EudraCT 2016-004008-71/NTR6149) from the Erasmus MC Cancer Institute in the Netherlands, found adverse interactions between Curcumin and Tamoxifen in breast cancer patients (Hussaarts KGAM et al, Cancers (Basel), 2019).  The findings indicated that the concentration of the active metabolite Endoxifen significantly decreased when Tamoxifen was taken along with Curcumin supplement.  

Breast cancer patients should be cautioned to avoid Curcumin supplements when treated with Tamoxifen. However, using turmeric in curries in small quantities should not have a negative effect.

3. Avoid DIM (Diindolylmethane) Supplement while on Tamoxifen treatment for Breast Cancer

DIM (diindolylmethane) is a common dietary supplement which is the metabolite of I3C (Indole-3-carbinol) commonly found in cruciferous vegetables such as broccoli, cauliflower, kale, and cabbage.  DIM has probably gained its popularity based on findings from clinical studies which showed that a very high consumption of cruciferous vegetables in the diet was significantly associated with a 15% reduced risk of breast cancer (Liu X et al, Breast, 2013).  However, a clinical study that tested the use of DIM supplement along with Tamoxifen in breast cancer patients found that DIM supplementation significantly reduced the active metabolite of Tamoxifen (endoxifen), thereby reducing the effectiveness of Tamoxifen.(NCT01391689; Thomson CA, Breast Cancer Res. Treat., 2017).

Hence, breast cancer patients should avoid taking DIM supplements when treated with Tamoxifen. Taking a normal healthy diet including cruciferous vegetables should not be harmful.

4. Avoid Caffeine if receiving Cisplatin Chemotherapy

Cisplatin is a commonly used chemotherapy for solid tumors. One of the well known  side-effects of Cisplatin is hearing loss in patients that can be permanent.  In a recent study done by the researchers from Southern Illinois University in the United States, the researchers found that a single dose of caffeine worsened cisplatin-induced hearing loss without damaging the outer hair cells but increased inner ear inflammation. The study also found that multiple doses of caffeine could also cause damage to the hair cells in the cochlea besides causing inflammation. Cochlea is a part of the ear responsible for breaking down all of the different pitches that make up sound. (Sheth S et al,  Sci Rep. 2019). 

The findings of the study suggest that cancer patients receiving Cisplatin treatment should avoid caffeine from the diet and the patients should strictly follow these dietary restrictions.

5. Avoid High Consumption of Dietary Supplements along with Chemotherapy in Breast Cancer Patients

Cancer patients often tend to use high amounts of dietary antioxidant and non-antioxidant supplements along with their chemotherapy treatments with the intention to help cure cancer or improve their quality of life. As part of a large co-operative group therapeutic clinical trial to assess dosing regimens of doxorubicin, cyclophosphamide and paclitaxel, for treatment of high-risk breast cancer, a prospective ancillary trial was done to evaluate the association between dietary supplement use and breast cancer outcomes.  The clinical study evaluated questionnaire-based data from around 1,134 breast cancer patients. 

The study found that use of antioxidant supplements such as Vitamins A, C and E, carotenoids and coenzyme Q10 or non-oxidant supplements such as Vitamin B12 and iron before and during treatment was associated with a negative impact on the cancer treatment and recurrence and also reduced the overall survival.  (Ambrosone CB et al, J Clin. Oncol, 2019)  

The findings suggest that dietary supplements including vitamins and antioxidants, used by cancer patients post their diagnosis, before and during their chemotherapy treatments could have a potential of having a negative impact on treatment outcomes when used along with their chemo treatments.  Patients should avoid such supplements and strictly follow the dietary restrictions.


Healthy people who are tested positive for certain genetic mutations associated with a specific cancer may end up selecting random natural foods or supplements that may cause/increase the risk of the cancer. Cancer patients also often reach out for natural remedies including foods and supplements to cure cancer or aid the cancer treatments or alleviate the treatment side-effects. However, taking random foods and supplements may not help ongoing treatments to cure cancer. When it comes to cancer, taking a  healthy diet with scientifically selected foods and supplements is crucial. Equally important is to follow a personalized diet instructions designed by health care providers/nutritionists which should also elaborate the dietary/food restrictions for the cancer patient. Information on natural foods or dietary supplements to be avoided (for specific chemo and cancers) becomes crucial to reduce any unwanted interactions with the ongoing treatments which are intended to treat or cure the cancer. Healthy individuals who are at a higher risk of cancer based on their genetics and lifestyle conditions such as alcohol consumption, smoking, weight, age, gender and ethnicity should also get a personalized nutrition with scientific relevance designed by nutritionists, which can help them reduce the risk of specific cancers.

What food you eat and which supplements you take is a decision you make. Your decision should include consideration of the cancer gene mutations, which cancer, ongoing treatments and supplements, any allergies, lifestyle information, weight, height and habits.

The nutrition planning for cancer from addon is not based on internet searches. It automates the decision making for you based on molecular science implemented by our scientists and software engineers. Irrespective of whether you care to understand the underlying biochemical molecular pathways or not - for nutrition planning for cancer that understanding is needed.

Get started NOW with your nutrition planning by answering questions on the name of cancer, genetic mutations, ongoing treatments and supplements, any allergies, habits, lifestyle, age group and gender.


Personalized Nutrition for Cancer!

Cancer changes with time. Customize and modify your nutrition based on cancer indication, treatments, lifestyle, food preferences, allergies and other factors.

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.

Scientifically Reviewed by: Dr. Cogle

Christopher R. Cogle, M.D. is a tenured professor at the University of Florida, Chief Medical Officer of Florida Medicaid, and Director of the Florida Health Policy Leadership Academy at the Bob Graham Center for Public Service.

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