Dietary Supplements and Cancer

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Dietary supplements for mesothelioma include vitamins, minerals, herbs, antioxidants and natural substances. However, some dietary supplements have side effects that may interfere with mesothelioma treatment and increase cancer risk. Always consult a doctor before taking these.

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Why Are Dietary Supplements Important for Cancer Patients?

Dietary supplements for cancer are important to mesothelioma patients who may come up short on important vitamins or minerals because of dietary restrictions or side effects of treatment.

Patients can consume these missing nutrients in the form of dietary supplements to fill those gaps.

Herbs, antioxidants and natural substances are promoted for cancer prevention, too. Some of these products may be safe to use during mesothelioma treatment.

While some symptoms suggest you may not be getting enough of a particular nutrient, only blood tests will indicate a vitamin or mineral deficiency with certainty.

If your doctor orders blood tests to check your nutrition status and the results indicate you are low or deficient in a particular nutrient, your doctor will prescribe a specific dietary supplement.

Vitamins for Cancer Patients

Some vitamins protect cells from damage linked to cancer development. Researchers are studying other vitamins for their important role in cancer treatment.

Benefits and Risks of Vitamin Supplements

  • Vitamin A: Cancer patients should consume vitamin A in carotene-rich foods. However, supplements of vitamin A. Clinical trials show this supplement can increase rates of lung cancer and deaths among smokers and people exposed to asbestos.
  • Vitamin D: Lung cancer patients with higher vitamin D intakes and higher blood levels of the nutrient showed reduced lung cancer risk and better outcomes, according to a 2017 analysis that combined results from several high-quality studies.
  • Vitamin K: Studies show vitamin K2, one type of this nutrient, is linked with decreased inflammation and reduced cancer risk. Reports show no vitamin K2 dietary supplement side effects in humans. However, vitamin K may interfere with blood thinners.

Cancer-Fighting Minerals

Researchers are studying several minerals for their role in cancer prevention and treatment. Minerals form structure in tissues, such as calcium and phosphorus in bone, and enable cell activities necessary for life and good health.

Magnesium, Potassium and Calcium

These minerals are critical dietary supplements for mesothelioma patients, especially if they are receiving cisplatin, a drug in the standard chemotherapy cocktail used to treat this cancer.

Key Facts About Magnesium, Potassium and Calcium

  • Cisplatin can decrease blood levels of magnesium, potassium and calcium to dangerously low levels.
  • Your doctor will check your blood to track these and other important minerals during treatment.
  • Some people need to supplement them during chemotherapy.
  • Magnesium has strong laxative effects and may cause loose stools.
  • To minimize the risk of loose stools, take the recommended dietary allowance for magnesium — 420 mg per day for men and 320 mg for women — in several smaller doses throughout the day.
  • Powdered magnesium or supplements that require four or five pills to reach the RDA work well for this.
  • A combination magnesium-calcium supplement also can decrease the laxative effects of magnesium.


Selenium bolsters the body’s own antioxidant systems. For this reason, it has been promoted to reduce cancer risk. However, the research doesn’t support this approach.

Key Facts About Selenium and Cancer

  • Multiple studies show selenium supplements are beneficial only to people who are deficient in the mineral.
  • Supplemental selenium may increase cancer and heart disease risk in people who are not deficient.
  • In some cell and animal studies, mesothelioma tumors grow more aggressively when extra selenium is supplied.
  • Selenium in dietary supplements is inorganic, which is different from the organic form of the nutrient found naturally in food.
  • If you want a safer way to get more selenium, try one Brazil nut per day. A single nut provides 110% of the recommended dietary allowance in a natural, easily absorbable form.

Based on available evidence, people at risk for developing mesothelioma or who are currently undergoing treatment for this asbestos-related cancer should avoid selenium supplements.

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Role of Herbs and Spices in Cancer Care

People often recommend herbs and other plant substances as dietary supplements for cancer. Some of these products are safe during mesothelioma treatment, but others should be avoided.

Moringa Tree

Moringa tree leaves are used in cooking in India. They can be powdered and taken as a dietary supplement, and moringa extracts are used to supplement diet, too.

Studies in cancer cells and animal models suggest moringa has anticancer activity. There are no studies on whether moringa is a good or bad dietary supplement for mesothelioma, so talk to your doctor before you use moringa supplements.

Essiac Tea

Essiac tea was first promoted as a cancer therapy in Canada in the early 20th century. The product also is marketed under the name Flor-Essence.

According to a 2018 report from the National Institutes of Health, Essiac tea contains substances with antioxidant, anti-inflammatory and anticancer activities, but there is no controlled data from human studies to suggests the product is effective in the treatment of people with cancer.


Animal studies suggest flaxseeds and lignans, which are substances found in seeds, protect against asbestos-related inflammation and cell damage.

Flax is an important food in the Budwig diet, which is promoted as an anticancer eating plan.

Ground flaxseeds are considered food and are safe for most people to consume. A daily intake of one to two tablespoons is a common recommendation.

Flax can have strong laxative effects so avoid them if you have loose stools or diarrhea due to your cancer treatment.

Do not take flaxseeds if you have an intestinal blockage or have been told to follow a low-residue or low-fiber diet.

Cancer-Fighting Antioxidants and Natural Substances

Some dietary supplements for cancer patients aren’t vitamins, minerals or herbs. Instead, they are simply natural substances found in plants or animals.

Beta glucan

Beta glucans are a type of soluble fiber in whole grains such as oats, barley, wheat and rye. Reishi, shiitake and maitake mushrooms also contain this healthy substance.

Researchers are studying beta glucans for their ability to bolster immune function, protect against bacterial infections and support the function of immune cells called natural killer cells. This component of immunity plays an important role in fighting cancer.

Beta glucan-rich foods are safe for mesothelioma patients, but check with your doctor before trying beta glucan supplements.

Beta carotene

Beta carotene is the natural, orange pigment in sweet potatoes, carrots, mangos and other fruits and vegetables.

Consuming beta carotene from food is associated with reduced risk of cancer among smokers and people with a history of asbestos exposure. However, beta carotene supplements are proven to increase the risk of lung cancer and death in these same high-risk groups.

People with a history of smoking or asbestos exposure should avoid high-dose beta carotene supplements.

Coenzyme Q10

This antioxidant is produced by the body and obtained from foods such as beef, chicken, pork, trout, herring, sardines, soybeans, lentils and peanuts.

Animal studies and small, uncontrolled human trials suggest this substance may protect the heart against damage due to some chemotherapy drugs.

Coenzyme Q10 is a potent antioxidant and some oncologists feel antioxidants may interfere with cancer treatments. It is important to tell your doctor if you plan to try this or any other dietary supplements.

Mushrooms and Mushroom Extracts

Mushrooms have a long history of use in traditional Chinese and Japanese medicine. They are promoted as a way to improve immune function and lessen side effects in patients receiving cancer therapy.

One of the most popular cancer-fighting mushrooms is coriolus versicolor, commonly called turkey tail. Researchers have studied turkey tail mushroom and its extract PSK in gastric, breast, colorectal and lung cancers. They have not been studied in mesothelioma patients.

A systematic review published in Integrative Cancer Therapies concluded, “PSK may improve immune function, reduce tumor-associated symptoms, and extend survival in lung cancer patients.”

A 2019 NCI Cancer Information Summary indicates PSK has been used as adjuvant therapy in thousands of cancer patients since the mid-1970s. It has been safely used in people for a long time in Japan with few side effects have been reported.

Still, as with all over-the-counter products, ask your doctor before trying it for yourself.

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Dietary Supplements and Side Effects

While many of these are safe for mesothelioma patients, some dietary supplements have side effects or interfere with your cancer treatment.

  • Grapefruit: Eating grapefruit or drinking grapefruit juice can block an enzyme in the intestine that helps metabolize certain mesothelioma chemotherapy drugs, including vincristine and paclitaxel.
  • Vitamin C: This vitamin may protect cells from chemotherapy and radiation therapy in ways that reduce the efficacy of treatment. Studies suggest oral vitamin C may be more problematic than IV vitamin C, because delivering the vitamin right into the blood stream makes it act more like a drug than an antioxidant.
  • Probiotics: Probiotics may lead to infections in cancer patients with poor immunity due to treatment. These supplements also may reduce efficacy of immunotherapy.

If you decide to try dietary supplements for mesothelioma, discuss each one with your mesothelioma doctor or another member of your health care team.

They can consider all of the drugs you are taking, other medical conditions you have and planned mesothelioma treatments to make a thorough assessment of whether a dietary supplement is safe for you.

Risks and Side Effects of Dietary Supplements

The U.S. Food and Drug Administration (FDA) offers an online, nonmandatory reporting system to track dietary supplement side effects. Their data shows people are increasingly reporting cases of illness and injury associated with using supplements.

Between 2010 and 2012, reports of dietary supplement-related adverse events more than doubled from 1,009 to 2,844. A 2015 New England Journal of Medicine study attributed approximately 23,000 emergency room visits per year to adverse reactions to dietary supplements.

A 2018 JAMA Forum Commentary noted dietary supplements are a $30 billion a year business and calls for more research on safety, benefits and harms of dietary supplements.

Risks and side effects of taking dietary supplements may include:

  • Exposure to supplements contaminated with toxic chemicals
  • Consuming supplements containing none of the listed ingredients
  • Reduced effectiveness of chemotherapy, radiation therapy and other anti-cancer drugs
  • Increased effectiveness of chemotherapy to the point of toxicity
  • Increased skin sensitivity, which may harm radiation therapy patients
  • Liver damage from certain herbs such as kava root and comfrey

Excessive amounts of vitamin A causes headaches, reduced bone strength and bone fractures, liver damage and birth defects. Excess iron may lead to nausea and vomiting and can damage the heart, liver, lungs, kidneys and other organs. Vitamin K interferes with the blood thinner warfarin (Coumadin).

Common Misconceptions of Supplements

There are some common misconceptions around supplements and natural products.

Natural Is Better, Safer

The term “all natural” has become a buzzword in the health industry. Because some people have had adverse reactions to lab- or factory-made chemicals, “all natural” can feel safer.

While this feeling is totally understandable, it should be weighed with the knowledge that many natural substances can be harmful, too. For example, arsenic and asbestos are naturally occurring and toxic. Plants are natural, yet many are poisonous including oleander and tobacco.

Natural is not always better or safer.

Taking a Megadose of Vitamins Is Safe

In the 1990s it became popular to megadose, or take large amounts of certain supplements, such as vitamins C and E.

Some people believed large doses of vitamin C could cure the common cold or treat cancer. Research does not indicate it can cure any cancer. In fact, too much vitamin C can block your body’s ability to absorb copper, an essential trace mineral involved in making red blood cells.

It Can’t Hurt to Take Supplements with My Medicine

Unfortunately, some supplements have negative interactions with prescription medication and cancer treatment. It isn’t safe to assume any herb, vitamin or mineral won’t interact with your medication or cancer treatment just because it is natural or seems harmless.

Additionally, few drug companies or supplement producers research potential interactions, and this fact leads to consumers becoming the guinea pigs.

The FDA Won’t Allow It on the Market if It Isn’t Safe

Dietary supplements are regulated differently than prescription drugs and cancer treatments. Unlike pharmaceuticals and anti-cancer treatments, supplements do not undergo years of testing before reaching the market.

Consult Your Doctor

If you are considering dietary supplements, gather information about these natural products from a trustworthy source such as the NIH Office of Dietary Supplements. Share this information with your doctor, so they can give you the best advice possible.

Tell your doctor if you took any supplements before your diagnosis, too.

Once you have completed cancer treatment and begun recovery, your oncologist may give you approval to take certain supplements. Don’t start supplements without talking to them first.

Your doctor will know how long it may take for your body to process cancer treatment, such as chemotherapy, and this can help you avoid a potential nutrient-drug interaction

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Joining the team in February 2008 as a writer and editor, Michelle Whitmer has translated medical jargon into patient-friendly information at for more than eight years. Michelle is a registered yoga teacher, a member of the Academy of Integrative Health & Medicine, and was quoted by The New York Times on the risks of asbestos exposure.

Walter Pacheco, Managing Editor at
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Last Modified July 24, 2019

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