Cancer isn't Caused by What You Eat — Or Don't Eat

There’s plenty of noise out there about what to eat to prevent or ‘cure’ cancer. But what does the science actually say? It’s not as fraught as some people suggest.

Not long after I received my breast cancer diagnosis, a well-meaning relative reached out to me on social media with advice.

She suggested I mostly eat fruits and vegetables and limit foods that “carry cancer cells,” such as meat, eggs, and cheese. My relative was not alone in offering unsolicited advice about how my diet could impact my cancer prognosis, though she was wildly incorrect.

Then there were claims about “Anti-Cancer Diets” on the internet and social media, and “alternative” cancer centers offering oxygen therapy, alkaline protocols, and juicing as treatments.

Sorting through all these conflicting messages made an incredibly overwhelming and frightening situation worse. Though I knew my genetics were behind my cancer, I felt less certain about how my diet might impact my treatment, not to mention the prospect of recurrence or metastasis.

The truth about diet and cancer is nuanced. While it may be tempting to take advice from wellness influencers or nutrition “experts” on TV and online, seeking vetted, science-based information sources can save you a lot of anxiety.

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Food and cancer: Sorting fact from fiction

Among the myths surrounding cancer, food-based inaccuracies seem especially persistent. Some of the most common claims about diet and cancer include:

• Eliminating sugar will “starve” cancer away.
• Eating meat, particularly red meat, causes cancer.
• Eating soy causes cancer.
• Genetically modified (GMO) foods cause cancer.
• Dairy and eggs cause cancer.
• Eating burnt food causes cancer.
• Artificial sweeteners cause cancer.

Food-related cancer myths don’t just cover items people shouldn’t eat. A number of wellness trends and fads claiming to treat or prevent cancer also have cropped up over the years, particularly on social media. These include:

• Eating “superfoods” prevents cancer.
• Eating an alkaline diet kills cancer cells.
• Drinking chlorophyll water prevents cancer.
• Juicing prevents cancer.

The truth? Little to no scientific evidence exists to back these claims.

A 2014 editorial reviewed Dr. Oz’s claims on TV that eating endive and sea bass could reduce cancer risk by up to 75%. The authors’ review of the evidence didn’t support those claims. They also pointed to the public’s fear-driven need to find ways to decrease their risk of cancer, which fuels the fire of celebrity doctors and experts like Dr. Oz.

According to the National Cancer Institute, evidence has not shown a connection between any single food and cancer, with few exceptions, like alcohol.

While some studies using animals or cancer cells in a laboratory indicate that isolated compounds may have carcinogenic or anticancer properties, that research has not been applied to humans.

In addition, cancer and cancer treatments can lead to malnutrition. When you’re facing potential muscle mass loss and are challenged to have an appetite or simply keep food down, some food is better than no food.

When possible, eating a diet of fresh fruits and vegetables, plant-based proteins, and lean proteins can benefit people during and after cancer treatment.

What the science says about food and cancer

A number of studies have been conducted over the years examining the connection between diet and cancer.

In 2019, a review of a decade’s worth of studies on nutrition and breast cancer examined the role-specific foods and drinks, as well as overall diet, play in the disease.

The researchers found that an overall healthy diet was far more beneficial than focusing on specific foods to eat or avoid. They defined a “healthy” diet as one rich in fruits, vegetables, nuts, olive oil, and unrefined cereals with a low to moderate intake of red meat and saturated fatty acids.

Another review conducted in 2021 of studies examining nutrition and 11 primary cancers — including breast, colon, and esophageal cancers — only found a few foods with cancer associations supported by strong evidence.

Alcohol

The researchers found an association between alcohol consumption and the risk of breast, colon, rectal, esophageal, head and neck, and liver cancers. According to the National Cancer Institute, the risk of breast cancer increases in accordance with the amount of alcohol consumption.

Dairy

The review found an inverse association with dairy, coffee, and whole grains. This may come as a surprise because dairy is often demonized for containing saturated fat.

Other studies have similarly pointed to a correlation between dairy products and a reduced risk of breast cancer. A systematic review published in 2023 found a link between dairy consumption and a reduced risk of breast cancer.

Another analysis of studies found that dairy was associated with an overall risk reduction for breast cancer, but results varied based on specific breast cancer subtypes and whether or not the patient had gone through menopause.

Meat

Studies have shown several things about the role of meat in cancer risk.

A 2021 systematic review and meta-analysis of prospective studies identified an increased risk of seven types of cancer — including a 6% increase for breast cancer — with high consumption of red and processed meat.

When it comes to how meat is cooked, the evidence connecting charring or burning with an uptick in cancer is inconclusive. While studies in animals suggest a connection between chemicals formed when meat is cooked at high temperatures and cancer, this has yet to be shown in humans.

Sugar

Eating sugar doesn’t cause cancer, and avoiding sugar doesn’t “starve” cancer.

However, a 2022 review of multiple studies identified a link between high sugar diets and cancer. Researchers found that high-sugar diets, even without obesity, may have a connection to the development and progression of cancer.

With artificial sweeteners, the data is murkier.

According to the National Cancer Institute, some studies have shown a link between sugar substitutes in beverages and cancer while others found no such connection.

Soy

Soybeans and foods made with them often get accused of increasing breast cancer risk, but the science does not back up that belief.

A 2020 meta-analysis of 18 separate studies found that diets high in soy were associated with a lower risk of breast cancer, particularly among premenopausal women.

A 2022 meta-analysis of studies of soy isoflavones and breast cancer found a reduction in risk for both premenopausal and postmenopausal participants.

GMO foods

Genetically modified organism (GMO) foods may get a bad rap, but according to Breastcancer.org, they don’t present any greater risk of breast cancer than any other food.

GMO crops are bioengineered to be resistant to disease and pests, among other growing benefits.

These crops and the foods made from them are regulated by the Environmental Protection Agency (EPA), the Food and Drug Administration (FDA) and the U.S. Department of Agriculture (USDA). These agencies require extensive scientific data to prove their safety to humans before they enter the marketplace.

To date, no research shows that GMO foods increase cancer risk or cause long-term health problems.

Ultimately, finding significant ties between food and cancer is tricky because most people consume a variety of foods that change often. According to the American Association for Cancer Research, that makes it difficult to pinpoint one specific food or beverage as causing cancer.

Finding peace with my food choices

During my first appointment at the cancer center, my oncologist brought in a nutritionist who specializes in cancer care.

I breathed a sigh of relief as she debunked myths I’d seen online and offered science-based advice on what to eat during and after treatment. She gave me the confidence to make food choices that would nourish my body as I endured the rigors of chemotherapy and surgery.

Once treatment ended, understanding the science behind food and cancer helped me find greater balance in my diet while continuing to enjoy foods and beverages I loved.

Takeaway

While general dietary guidelines exist, each person’s nutritional needs vary. That means consulting your oncologist, nutritionist, and others on your care team can help you find the foods your body needs to stay strong and healthy — during treatment and beyond.

Taking a science and medicine-based approach to diet allows you to cut through the noise and provide your body with the nourishment it needs to heal and thrive.

Though you’ll likely continue to receive unsolicited diet advice or stumble across food fads on social media, arming yourself with research can give you confidence in your eating choices.