About 40% of us will be diagnosed with cancer at some point in our lifetime, and so much of it comes down to genetics and bad luck. But here's the good news: up to 40% of all cancers are preventable. You can't change your genetics, but you can absolutely influence how your genes behave, and one of the most powerful ways to do that is through the food you eat every day.
.jpg "How Certain Foods Feed Cancer Cells (And How to Avoid Them)")
Many cancers aren't purely a genetic disease; they're also a metabolic disease and an immune function disease. And the wrong foods, even ones we consider normal or healthy, can quietly foster the exact conditions cancer needs to grow and proliferate.
In this article, I want to break down the science of how certain foods feed cancer cells and give you a simple framework for avoiding them.
I'm Dr. Leonid Kim. I'm board-certified in Internal Medicine and Obesity Medicine, and I provide the most up-to-date, evidence-based information on weight loss, metabolic health, and longevity. Let's get into it.
How Cancer Grows: The Foundation
Cancer starts when a normal cell becomes abnormal, often from just a single mutation, something that happens constantly in the body. If that mutation goes unrepaired or unchecked, it can lead to uncontrolled cell growth. But for a mutated cell to actually survive and spread, several conditions need to fall into place:
- Glucose as fuel. Cancer cells rely on glucose as their primary energy source.
- Growth hormones. Hormones like insulin and IGF-1 act as signals that activate growth pathways.
- Inflammation. Inflammation breaks down protective barriers and suppresses the immune system, our first line of defense against cancer.
- Blood supply. Cancers need a blood supply, which they secure through a process called angiogenesis, forming new blood vessels that act as a lifeline delivering nutrients for growth.
Unfortunately, many foods in our modern diet directly support every one of these steps. The good news is that we can use this understanding to our advantage by choosing foods that either feed cancer or help fight it.
Aflatoxins
Let's start with one of the most potent naturally occurring carcinogens known: aflatoxins, toxins produced by certain molds found on grains, nuts, or corn. Foods to be especially careful with include peanuts and tree nuts like almonds, walnuts, and pistachios.
To be clear, there's nothing wrong with nuts themselves, and there's no need to avoid them altogether. The key is being cautious about sourcing, avoiding nuts or grains from warm, humid climates prone to mold contamination, and being mindful of indirect exposure through products like peanut butter or almond butter, which may be made from less thoroughly inspected nuts.
To minimize aflatoxin exposure:
- Look for brands that don't source nuts from humid regions.
- Inspect nuts carefully and avoid those that look discolored or shriveled, which are potential signs of mold contamination.
- Eat nuts within a month of purchase and pay attention to expiration dates.
- Roast peanuts and pistachios, which can reduce (though not eliminate) aflatoxin content.
Aflatoxins can also enter the food supply indirectly through milk and dairy. Animals fed aflatoxin-contaminated feed, like corn, can pass a related toxin called aflatoxin M1 into their milk. Being cautious with milk from cows fed untested grain, or with unregulated raw milk and dairy products, can help reduce this exposure.
Sugar and Processed Carbohydrates
Foods high in sugar or processed carbohydrates have been linked to increased cancer risk, particularly for breast, colon, and possibly pancreatic cancer, largely because cancer cells thrive on sugar.
Picture the body as made up of trillions of tiny engines, our cells. Normally, these engines burn fuel efficiently using oxygen, extracting a lot of energy from each bite of food.
Cancer cells, however, behave more like broken engines: inefficient, but burning through fuel, especially glucose, extremely fast. This is partly explained by the Warburg effect, a process called aerobic glycolysis, where cancer cells preferentially burn sugar rapidly even when oxygen is abundant. Cancer cells don't care about efficiency; they want to grow fast.
When you eat foods that spike blood sugar, the body releases hormones like insulin and IGF-1. Normally, this is a healthy response, but in excess, these hormones send growth signals that tell cells to divide and proliferate.
This creates a double effect: you're feeding cancer cells their preferred fuel while simultaneously amplifying the signals that tell them to grow and divide faster. This is especially notable in breast cancer, where some studies show cancerous cells can have up to six times more insulin receptors than healthy cells.
On top of that, excess sugar contributes to chronic inflammation, which can cause further DNA damage, making it easier for cancer to develop, while also weakening the immune system, our first line of defense against cancer.
The takeaway is that cancer cells are sugar-hungry. We can use that to our advantage by limiting sugar intake, especially processed or high-glycemic carbohydrates, and prioritizing low-glycemic, high-fiber carbohydrates like beans, whole grains, vegetables, and berries. If you drink regular soda, switching to tea, water, or even diet soda is a simple, immediate change. (There's ongoing debate about diet drinks, sweeteners, and their potential association with cancer, but that's a nuanced topic deserving its own deeper discussion.)
Processed Meat and Red Meat
Another food category to approach carefully is processed and red meat, though the science here is more nuanced than headlines often suggest.
Numerous studies and meta-analyses are showing an association between high intake of processed meat (ham, bacon, sausages, hot dogs) or red meat (pork, beef, lamb) and cancer risk, especially colorectal cancer. Importantly, though, these are observational studies showing association, not necessarily causation. Researchers track what people eat and which groups develop cancer.
Still, it's difficult to separate other factors, like whether people who ate more processed or red meat also smoked more or exercised less, or whether people who ate less of these meats had better access to fresh food or healthcare overall. This is sometimes called "healthy user bias," in which other lifestyle factors, rather than the food itself, may explain the observed differences.
That said, there are plausible mechanistic explanations for why red or processed meat could contribute to cancer risk. Many processed meats contain nitrites, preservatives used for curing and flavor. Once in the stomach, stomach acid can convert nitrites into nitrosamines, specifically N-nitrosodimethylamine (NDMA), a known carcinogen linked to increased stomach cancer risk.
Cooking method matters too: grilling, frying, or barbecuing meat at high temperatures can produce compounds called heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs), both of which have been shown in animal studies to damage DNA and promote cancer cell development.
Taking the full picture into account, the correlation between red or processed meat and cancer is real, but I'm not entirely convinced the meat itself is the primary driver.
It's more likely that eating more red or processed meat means eating less of something protective, particularly fiber-rich foods like fruits, vegetables, beans, and whole grains. Numerous studies and meta-analyses show that higher dietary fiber intake is associated with a lower risk of several cancers and a 13% reduction in cancer mortality.
So there's likely no need to eliminate red meat or grilled meat, but it's probably wise not to overdo it, and to make sure to load up on fiber with every meal.
Alcohol
There's pretty strong scientific evidence that alcohol causes cancer. The International Agency for Research on Cancer classified alcohol as a Group 1 carcinogen back in 1987, based on sufficient evidence linking it to cancers of the oral cavity, pharynx, esophagus, and liver, along with associations with breast cancer in women and colorectal cancer.
Alcohol contributes to cancer risk through several mechanisms:
- The liver metabolizes alcohol into acetaldehyde, a toxic compound that directly damages DNA and interferes with DNA repair.
- Alcohol causes vitamin deficiencies, including lower levels of vitamin B1 (thiamine), which is critical for healthy mitochondrial function and energy metabolism.
- Alcohol impairs the body's ability to absorb folate, and folate deficiency can lead to further errors in DNA synthesis.
- Alcohol acts as a solvent, enhancing the absorption of other carcinogens, like those from tobacco or NDMA, into tissues.
Conclusion
While cancer risk is shaped heavily by genetics and factors outside our control, diet remains one of the most powerful and accessible tools we have to influence how our cells behave. Limiting exposure to aflatoxins, reducing intake of sugar and processed carbohydrates, being thoughtful (without being fearful) about red and processed meat, prioritizing fiber-rich whole foods, and minimizing alcohol intake can all meaningfully reduce the metabolic and inflammatory conditions that allow cancer cells to thrive. None of these changes require perfection; small, consistent shifts toward whole, fiber-rich foods and away from the biggest offenders can meaningfully shift the odds in your favor over a lifetime.
FAQ
Can diet really help prevent cancer?
Yes, to a meaningful degree. While genetics plays a role, up to 40% of cancers are considered preventable, and diet influences several of the underlying mechanisms, glucose availability, growth hormone signaling, inflammation, and blood vessel formation, which allow cancer cells to grow and spread.
What are aflatoxins, and why are they concerning?
Aflatoxins are potent carcinogens produced by mold that can contaminate grains, nuts, and corn, as well as milk from animals fed contaminated feed. Choosing well-sourced nuts, avoiding discolored or shriveled nuts, and being mindful of freshness can help reduce exposure.
Does sugar really "feed" cancer cells?
Cancer cells preferentially use glucose for energy through a process called the Warburg effect, and high blood sugar also triggers insulin and IGF-1 signaling that can promote cell growth and division. This is why limiting high-glycemic, processed carbohydrates is often recommended as part of a cancer-conscious diet.
Does eating red or processed meat cause cancer?
The evidence shows an association, particularly with colorectal cancer, but it's largely based on observational studies that can't fully separate the effects of meat itself from other lifestyle factors. Processed meat's nitrites and high-temperature cooking methods do have plausible carcinogenic mechanisms, but the displacement of fiber-rich foods may also play a significant role.
How does alcohol increase cancer risk?
Alcohol is classified as a Group 1 carcinogen. It's metabolized into acetaldehyde, a DNA-damaging compound, impairs DNA repair, causes deficiencies in thiamine and folate, and enhances the absorption of other carcinogens into tissue.
What's the single most impactful dietary change for reducing cancer risk?
There isn't a single change that outweighs all others, but consistently prioritizing fiber-rich whole foods, fruits, vegetables, beans, and whole grains, while limiting processed sugar, ultra-processed carbohydrates, and excessive alcohol intake, addresses several cancer-promoting mechanisms at once.