Cancer: Does a Vegetarian Diet Help?

If you had a magic pill that would reduce your risk for cancer between 30% or more, the threat from dying from heart disease by 32%, reduce your risk for type 2 diabetes by 47-78 %, and taste good—wouldn’t you take it? In this article we will show how a vegetarian diet can improve the quality of your life by reducing your cancer risks. After all, nearly 1/2 of Americans will develop some form of cancer during their lifetime.

Many Advantages

Plant-based diets improve the quality of our lives. Vegetarian diets are often linked to health advantages including lower blood cholesterol levels, lower risk of heart disease, lower blood pressure levels, lower risk of hypertension, and type 2 diabetes. Vegetarians tend to have a lower body mass index and lower overall cancer rates. According to the Academy of Nutrition and Dietetics, appropriately planned vegetarian and vegan diets are healthful, nutritionally adequate, and may provide health benefits for the prevention and treatment of certain diseases as long as vitamin B-12 is included in sufficient amounts.¹

Benefits of whole food, well-balanced vegetarian diets:

• They are high in fiber, are nutrient dense, and contain no cholesterol.
• Magnesium and potassium in plant foods protect from diabetes and hypertension.
• Phytochemicals are available as plant compounds, in addition to the basic nutrients that protect health.
• Inflammation fuels chronic and acute diseases. Whole fruits, vegetables, and nuts provide a large arsenal of anti-inflammatory compounds.

Slash Your Cancer Risk!

Dietary factors account for at least 30% of all cancers in Western countries. Researchers from Loma Linda University reported that vegans have lower rates of cancer than both meat-eaters and vegetarians. Vegan women, for example, had 34 percent lower rates of female-specific cancers such as breast, cervical, and ovarian cancer when compared to a group of healthy omnivores who ate substantially less meat than the general population (two servings a week or more). This study controlled for non-dietary factors such as smoking, alcohol, and a family history of cancer.²

Consumption of detrimental foods (meat, fried foods, and saturated fats) does more harm than the help that regular consumption of healthful foods provides. The World Health Organization considers processed meat (hot dogs or frankfurters, ham, sausages, corned beef, and biltong, or beef jerky, as well as canned meat and meat-based preparations and sauces) as a class 1 carcinogen. In other words, there is compelling evidence that it produces cancer. Research from epidemiological studies shows positive links between eating red meat and developing colorectal cancer, and gives strong mechanistic evidence (direct evidence that links a factor or an intervention to a specific outcome). Red meat consumption is considered as probably carcinogenic.³

A systematic review and a meta-analysis of 148 studies found that meat consumption was significantly associated with a greater risk of breast cancer, endometrial cancer, colorectal cancer, colon cancer, rectal cancer, lung cancer, and hepatocellular carcinoma. Processed meat consumption was significantly associated with a 6% greater breast cancer risk, an 18% greater colorectal cancer risk, a 21% greater colon cancer risk, a 22% greater rectal cancer risk, and a 12% greater lung cancer risk.⁴

Meat, Inflammation, and Cancer

Inflammation fuels chronic diseases like cancer. Red meat consumption encourages inflammation and cancer promotion.⁵ A sugar called Neu5Gc, is naturally found in most mammals but not in humans. Neu5Gs is prevalent in beef, pork, and lamb. As a foreign molecule, Neu5Gc promotes a chronic inflammatory response that promotes inflammation and tumor formation. ⁶

The eating of both red and white meat increases the risk of kidney cancer.⁷

More Trouble-Makers from Meat

Meat also contains heme iron, which can facilitate the production of cancer-producing compounds.⁸ Cooking meat– especially high-temperature cooking including cooking meats over a flame (e.g., pan-frying, grilling, barbecuing)– can also produce carcinogenic chemicals.⁹ The carcinogen PhiP found in fried chicken spells danger for prostate cancer.¹⁰

Breast milk of mothers who eat meat contains this carcinogen. PhiP is not present in the milk of vegetarian mothers.¹¹

Refined Carbs Increase Cancer Risk

However, going vegetarian may not help reduce cancer risks that much if one eats largely refined carbohydrates or fails to get adequate nutrients like vitamin B-12 and vitamin D. One study in over 47,000 adults found that those who consumed a diet high in refined carbohydrates were almost twice as likely to die from colon cancer than those who ate a diet low in refined carbs. ((Sieri S. Dietary glycemic index and glycemic load and risk of colorectal cancer: results from the EPIC-Italy study. Int J Cancer. 2015 Jun 15;136(12): 2923-31.) 

The Real Villain of Chronic Disease

Inflammation encourages the development of cancer and plays a major factor in the actual pathology of cancer and all chronic diseases. No preventive measures or treatment plan can be successful without successfully quelling inflammation.

We know that the typical Western diet—high in sugar, fat, and refined products, and low in high fiber plant foods—encourages the growing populations of unfriendly gut bacteria. This unfriendly bacteria produces pro-inflammatory compounds that contribute and reinforce chronic disease. Indeed, a single meal of meat, dairy, and eggs triggers an inflammatory reaction inside the body within hours of consumption.¹²

In contrast, friendly gut bacteria produce anti-inflammatory compounds which discourage inflammation and could reduce the risk for certain cancers and delay the development of cancer.¹³

Whole, nutrient-dense plant foods contain myriads of anti-inflammatory compounds. Additionally, they are rich in fiber which promotes the production of friendly gut bacteria which release even more anti-inflammatory compounds and decrease the population of unfriendly gut bacteria.¹⁴

Why Do Vegetarians Have Much Lower Cancer Risk?

Besides elimination of inflammatory and carcinogenic compounds in meat, vegetarian diets help in other ways.

1. They can slow down the growth of cancer. In an in vitro study, women ate different diets. Their blood was then dripped on human cancer cells growing in a petri dish. Women who ate plant-based diets for just two weeks were found to suppress the growth of three different types of breast cancer.¹⁵ A vegetarian diet, when coupled with other healthful lifestyle changes, can slow down the progression of low-grade prostate cancer.¹⁶

Please do not misunderstand. We are not saying vegetarian diets always slow down the progression of cancer nor take the place of appropriate medical treatment. Healthful vegetarian diets provide a boost to the immune system if one does have cancer. In all fairness, it is not just diet or avoidance of animal protein that may help cancer to develop and spread. Eating a high sugar diet, or a high-fat diet, alcohol consumption, obesity, excessive calorie intake, specific nutrient deficiencies, and disturbed circadian rhythms increase inflammation.

2. Prognosis may improve on a vegetarian diet. Even while being treated with chemotherapy, the type of protein consumed can make a big difference. In one experiment, mice with ovarian cancer were divided into two groups. One group ate 20% of their calories from soy protein. The other group received their protein calories from casein. The prognosis of the 20% plant protein group was better than that of the 20% animal protein group with or without chemotherapy.¹⁷

3. Cancer-protective compounds found in whole fruits, whole grains, nuts, and non-starchy vegetables help to quell inflammation and offer an entire arsenal of cancer-fighting compounds. What foods possess cancer preventive and therapeutic properties? Purple grapes and blue berries contain cancer-fighting resveratrol (grapes). Cruciferous green veggies contain another powerful cancer-fighter, sulforaphane. In order to get the most sulforophane, crush your broccoli and let it sit for a few minutes before steaming them.  Anthocyanins  in red, blue, and purple fruits and vegetables, curcumin in turmeric, lycopene in tomatoes all help in the cancer fight.¹⁸

4. Hormones: IGF-1 (insulin-like growth factor) is a growth hormone essential for normal growth during childhood. Excessive amounts in adult years can promote abnormal growth and the proliferation and spread of cancer cells. Vegetarians have less IGF-1 than meat-eaters.¹⁹

5. A healthy vegetarian diet that emphasizes whole foods helps weight control. Obesity causes serious inflammation that substantially increases the risk for cancer.  Obesity and a high-fat diet allow cancer cells to outcompete immune cells for fuel, impairing immune function and accelerating tumor growth. Cancer cells reprogram their metabolism in response to increased fat availability to better gobble up energy-rich fat molecules. This action deprives certain immune T cells of needed fuel, accelerating tumor growth.²⁰

Vegetarians have less prevalence of obesity. However, even for consumers of vegetarian cuisine, obesity still increases the risk of cancer. Comparing low-calorie diets: the vegetarian diet was found to be almost twice as effective as a conventional anti-diabetic diet in helping weight loss. One problem with diabetes is that fat builds up inside the muscle.  In this study, the intramuscular fat was more significantly reduced by the vegetarian diet.²¹ This fact suggests that a vegetarian diet helps to reduce the risk for diabetes which is a risk factor in itself for several cancers.

4. Soluble fibers exert anti-inflammatory effects in the colon. Dietary fibers can be fermented or metabolized by microbes in the gut, generating anti-inflammatory and cancer-fighting compound such as butyrate. This compound helps to inhibit the proliferation of colon cells.²²

Vegetarian Diet and the Immune System

Dietary habits significantly impact the immune system. Your gut plays an essential part in your immune responses. Vegetarian diets decrease activity of pro-inflammatory genes in the gut. A vegetarian diet increases natural killer cell activity by a factor of 2.34 compared to an omnivorous diet.²³

Good Carbs Reduce Cancer Risks!

Substituting legume-based dishes for meat is an excellent idea for most people. One study in over 3,500 people found that those eating the most legumes had up to a 50% lower risk of certain types of cancer.²⁴

Epidemiologic studies find that whole grains are protective against cancer, especially gastrointestinal cancers such as gastric and colonic, and hormonally-dependent cancers including breast and prostate. ²⁵ Fiber-rich whole grains are high in antioxidants, including trace minerals and phenolic compounds. These active antioxidants exert anti-inflammatory activity. Like legumes, whole grains contain considerable amounts of resistant starches. Resistant starches (RS) are not digested in the small intestine. RS reduce the risk for breast and colon cancer.^26,27,28 Resistant starch helps the body resist colorectal cancer through mechanisms including killing pre-cancerous cells and reducing inflammation that can otherwise promote colon cancer. The fermentation of resistant starch in the gut increases the amounts of beneficial short-chain fatty acids, produces positive change in the microbiota, and increases gene activity. This gene activity is involved in normal healthy proliferation and apoptosis of potential cancer cells in colon cancer. Moreover, resistant starch helps to prevent post-meal surges in blood sugar and improves the cells’ ability to respond to insulin.²⁹ Although none of the studies cited in this article referred to organically grown foods, one would be wise to use organically grown grains and produce when possible.

Cancer-Fighters in Foods

Liberal and regular consumption of fruits and vegetables not only decreases the risk for certain cancers, but also reduces the risk of dying from cancer. Their phytochemicals may also help to prevent and even fight cancer. Although lab experimentation involves isolated identifiable phytochemicals, in reality, they work in synergy with other phytochemicals and nutrients found in plant food to preserve health. Smoking, obesity, alcohol, and consumption of red meats substantially increase the risk of cancer more strongly than fruits and vegetables protect from it.

Green Vegetables

Green vegetables and cruciferous (broccoli, kale, turnips, collards, cabbage, bok choy, Brussels sprouts) offer many cancer-fighting compounds. Chlorophyll from green vegetables reduces toxin absorption from the gut, thereby reducing the toxin load that the liver has to handle. When consumed five times a week, cruciferous vegetables substantially lower the risk for breast, prostate, colon, and bladder cancer.  Sulforaphane in green cruciferous vegetables is a potent cancer fighter. It protects DNA from attacks of certain carcinogens and stimulates the proteins that suppress tumor growth and development.

The phytochemical I3C (indole-3-carbinol) in cabbage increases the activity of anti-cancer genes and liver detoxification.³⁰ Studies suggest that the phytochemical apigenin from parsley, celery, and artichoke has the potential to stop breast cancer cells from inhibiting their own death.³¹ Dried parsley and oregano are especially high in apigenin. Apigenin is better absorbed if taken with a meal that contains healthful fats. Apigenin may also be useful in fighting liver cancer and prostate cancer cells.

Green Drinks Aren’t For Everyone!

Green drink for cancer? May be helpful in some cases, but there are a few important caveats for habitual use. Individuals with some cancers have increased risk for clotting. Since green leafy vegetables have vitamin K which helps clotting, it is advisable to limit the intake of greens if you have cancer already. Have your doctors evaluate your clotting factors first. Raw kale and other cruciferous vegetables have anti-thyroid factor which cooking deactivates. This author does not recommend frequent or regular consumption of raw kale. Cooked kale is excellent for the carotenoids. The carotenoids in green leafy vegetables are better absorbed when they are eaten raw. If mixing with fruits, it is better to make a smoothie than juicing. A smoothie will contain some fiber whereas juice has no appreciable amount of fiber.

Red (Strawberries, Raspberries, Cherries, Pomegranates, Apples, Tomatoes)

Strawberries, raspberries, cherries, and pomegranates contain ellagic acid. This important phytochemical helps to protect from cancers of the breast, esophagus, skin, colon, prostate, and pancreas. It also blocks specific enzymes that are necessary for the cancer cells to operate.

Orange Foods

Carotenoids in orange fruits and vegetables help to protect DNA from free radical damage, improve DNA repair, and inhibit inflammation. Beta-carotene helps to protect from lung, mouth, throat, stomach, intestine, bladder, prostate, and breast cancers. Carotenoids are better absorbed from cooked vegetables than from raw foods.

Legumes

How do legumes help? They are high in fiber, do not spike the blood sugar, and have phytic acid. In test tube studies, phytates have been shown to inhibit the growth of human leukemia cells, colon cancer cells, both estrogen receptor-positive and negative breast cancer cells, voice box cancer, cervical cancer, prostate cancer, liver tumors, pancreatic, melanoma, and muscle cancers while they do not affect normal cells. Additionally, phytates help to reverse cells slipping into abnormal cells back to normal.³² Isoflavones found in soybeans and black beans exert antioxidant, antimicrobial, and anti-inflammatory properties. A meta-analysis of six studies showed that consuming 60 milligrams of soy isoflavones is linked to a 26% reduction in breast cancer.³³

A meta-analysis of 14 cohort studies of 1,903,459 participants and 12,261 cases who contributed 11,628,960 person-years, found that higher legume consumption was associated with a decreased risk of colorectal cancer. This held true for soybeans.³⁴

Conclusions:

How about a vegetarian diet as a cancer treatment regimen? There is early evidence that it might help. There is accumulating physiologic evidence that it can help as an adjunct treatment. As a cure for cancer by itself? No conclusive studies presently exist. If you have cancer, please get the medical counsel of qualified physicians. If you choose a vegetarian diet, please consult with a dietician as to the variety, the number of calories, and any supplementation you might require.

So does a vegetarian diet help reduce the risk of cancer? Many, but not all epidemiological studies, point that way. There is substantial evidence about the benefits of cancer-fighting compounds in plant food.  Substantial evidence exists for the hazards of eating processed meat. And there is accumulating evidence for the dangers associated with red meat consumption. Vegetarian-based dietary patterns have been linked to reduce inflammatory markers: lowered serum C-reactive protein, fibrinogen, and total leukocyte concentrations.³⁵.

Dietary factors only account for 40% of the risk of cancer. We would add that only a whole-food vegetarian diet (with vitamin B-12 and vitamin D) may physiologically offer substantial benefits as an adjunct treatment. In the treatment of cancer, all known contributory and aggravating factors must be addressed. As previously mentioned a high non-resistant starch (white bread, white rice), high-fat, refined food, vegetarian diet is not protective and could enhance one’s risk for developing cancer.

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