By Dr. Mercola
Colorectal cancer, which includes both cancers of the colon and rectum, is the third most common cancer diagnosed in the US (not including skin cancers). In 2015, it’s estimated there will be more than 93,000 new cases of colon cancer (and nearly 40,000 cases of rectal cancer) diagnosed.1
As with most cancers, diet is thought to play a role in your risk of colon cancer. It’s known, for instance, that a diet high in processed meats like hot dogs and certain luncheon meats, increases your risk, while a diet high in whole foods, such as vegetables and fruits, lowers it.
New research by Texas A&M researchers, presented at the 2015 Experimental Biology conference in Boston, MA, even found consuming dried plums regularly might play a role in reducing colon cancer risk.
In case you’re wondering, dried plums are also known as prunes. According to the California Dried Plum Board (99 percent of the US supply of dried plums is grown in California), their target audience (women aged 25 to 54) responded more favorably to the name “dried plums” instead of “prunes,” so the name was changed. Elsewhere in the world, however, most people still call dried plums prunes.2
Another interesting fact is that while all prunes are plums, all plums cannot be made into prunes. Plum varieties used to make prunes have very high sugar content, which, according to the California Dried Plum Board, allows them “to be dried without fermenting while still containing the pits.”3
Dried Plums May Lower Your Risk of Colon Cancer By Building Gut Bacteria
Dried plums are rich in potassium, fiber, and phytochemicals, including antioxidants, all of which may help lower your risk of chronic disease. However, it’s dried plums’ influence on the bacteria in your colon that may be most impressive of all.
In an animal study, researchers fed rats either a diet containing dried plums or a control diet (the same as the first diet but without the plums). Those fed the dried plums had significant increases in the number of bacteria in the gut known as Bacteroidetes and Firmicutes.
Rats on the dried-plum diet also had reduced numbers of aberrant crypts, which are signs of precancerous lesions that may be an indicator for future cancer development. Study author Dr. Nancy Turner explained:4
“From this study we were able to conclude that dried plums did, in fact, appear to promote retention of beneficial microbiota and microbial metabolism throughout the colon, which was associated with a reduced incidence of precancerous lesions.”
A 2005 study similarly revealed that dried plums “favorably altered… colon cancer risk factors” in rats, possibly due to their high content of dietary fiber and polyphenolics.5
There Are Many Reasons to Eat Dried Plums… In Moderation
Dried plums are perhaps most well known for their role as a digestive aid (including having a mild laxative effect). They’re useful for this not only because they contain both soluble and insoluble fiber but also due to their high sorbitol content.
Sorbitol, an unfermentable sugar sometimes described as a prebiotic, is said to act as “a good medium for the production of desirable intestinal microorganisms”6 and has been suggested as the reason for dried plums’ laxative effect.7
Further, despite being high in sugar, dried plums do not lead to a rapid rise in blood sugar concentration, possibly due to their high fiber and sorbitol content.8 A review published in Critical Reviews in Food Science and Nutrition in 2001 cited dried plums as the “epitome of functional foods” and continued:9
“Dried prunes contain approximately 6.1 g of dietary fiber per 100 g, while prune juice is devoid of fiber due to filtration before bottling…
Prunes contain large amounts of phenolic compounds (184 mg/100 g), mainly as neochlorogenic and chlorogenic acids, which may aid in the laxative action and delay glucose absorption.
Phenolic compounds in prunes had been found to inhibit human LDL oxidation in vitro, and thus might serve as preventive agents against chronic diseases, such as heart disease and cancer.
Additionally, high potassium content of prunes (745 mg/100 g) might be beneficial for cardiovascular health.
Dried prunes are an important source of boron, which is postulated to play a role in prevention of osteoporosis. A serving of prunes (100 g) fulfills the daily requirement for boron (2 to 3 mg).”
Dried Plums May Be Beneficial for Obesity, Diabetes, Heart Disease, and More
Again in 2013, research published in Critical Reviews in Food Science and Nutrition touted dried plums’ beneficial role in health. This review included mentions of dried plums’ potential role in reducing not only colon cancer but also other chronic disease currently plaguing the developed world:10
“Dried plums contain significant amounts of sorbitol, quinic acid, chlorogenic acids, vitamin K1, boron, copper, and potassium. Synergistic action of these and other compounds, which are also present in dried plums in less conspicuous amounts, may have beneficial health effects when dried plums are regularly consumed.
Snacking on dried plums may increase satiety and reduce the subsequent intake of food, helping to control obesity, diabetes, and related cardiovascular diseases. Despite their sweet taste, dried plums do not cause large postprandial rise in blood glucose and insulin.
Direct effects in the gastrointestinal tract include prevention of constipation and possibly colon cancer. The characteristic phenolic compounds and their metabolites may also act as antibacterial agents in both gastrointestinal and urinary tracts.
The indirect salutary effects on bone turnover are supported by numerous laboratory studies with animals and cell cultures.”
Despite these impressive benefits, it’s important to eat prunes in moderation due to their high fructose content. One medium prune contains 1.2 grams of fructose. If you're insulin- or leptin resistant (are overweight, diabetic, hypertensive, or have high cholesterol), then it would be especially advisable for you to limit your fruit intake.
As a general rule, I recommend limiting your fructose intake to a maximum of 15 grams of fructose per day from ALL sources, including whole fruit.
If you are not insulin/leptin resistant, (are of normal weight without diabetes, hypertension, or high cholesterol) I suggest limiting your fructose intake to 25 grams per day (or less) from all sources.
As far as preservatives and sulfating agents, which are a concern if you consume many types of dried fruit, this isn’t a major concern when consuming most dried plums.
According to the California Dried Plum Board, only potassium sorbate, which is considered a natural preservative, is used in processing dried plums. And since they’re already dark in color, there is no need to use sulfating agents (which are typically used to prevent darkening).11
Eat Real Food to Prevent Colon Cancer
The foods you eat can play a major role in your risk of cancer, and this includes colon cancer. As mentioned, processed meats – those preserved by smoking, curing, salting, or the addition of chemical preservatives – are known to be a major risk factor.
This includes bacon, ham, pastrami, salami, pepperoni, hot dogs, some sausages, and hamburgers (if they have been preserved with salt or chemical additives), and more. Particularly problematic are the nitrates that are added to these meats as a preservative, coloring, and flavoring.
The nitrates found in processed meats are frequently converted into nitrosamines, which are clearly associated with an increased risk of certain cancers. Real food, like that described in my nutrition plan, on the other hand, may help you lower your cancer risk.
Vegetables, for instance, contain an array of antioxidants and other disease-fighting compounds that are very difficult to get anywhere else – such as magnesium. Results from one meta-analysis indicated that for every 100-milligram increase in magnesium intake, the risk of colorectal tumor decreased by 13 percent, while the risk of colorectal cancer was lowered by 12 percent.12
The researchers noted magnesium’s anti-cancer effects may be related to its ability to reduce insulin resistance, which may positively affect the development of tumors. They noted: “The consumption of magnesium-rich foods may be a new avenue to explore further in the search for cancer-prevention strategies.”
Green leafy vegetables such as spinach and Swiss chard are excellent sources of magnesium, as are some beans, nuts, and seeds, such as almonds, pumpkin seeds, sunflower seeds, and sesame seeds. Avocados are also a good source. Beyond magnesium, plant chemicals called phytochemicals can reduce inflammation and eliminate carcinogens, while others regulate the rate at which your cells reproduce, get rid of old cells, and maintain DNA. Vegetables are also one of the best forms of dietary fiber. Studies have repeatedly shown that people with higher vegetable intake have lower rates of cancer.
One study found people who ate seven or more portions of vegetables and fruit a day had a 42 percent lower risk of dying from any cause compared to those who ate less than one portion. They also enjoyed a 31 percent lower risk of heart disease and a 25 percent lower risk of cancer.13
Eating Right Nourishes Your Gut Microbes
Nearly 100 trillion bacteria, fungi, viruses, and other microorganisms compose your body's microflora, and advancing science has made it quite clear that these organisms play a major role in your health, both mental and physical. For instance, the featured study showed that one way dried plums may lower colon cancer risk is by encouraging the growth of beneficial microbes in your gut. When you eat too many grains, sugars, and processed foods, these foods serve as “fertilizer” for pathogenic microorganisms and yeast, causing them to rapidly multiply.
While today 80 percent of processed foods are made up of genetically modified (GM) corn and soy, wheat, and meat, 15,000 years ago people ate about 150 different ingredients each week, according to Tim Spector, professor of Genetic Epidemiology at King’s College London and author of The Diet Myth.14
Spector wanted to find out what happens to your gut if you eat only fast food, specifically McDonald’s, for 10 solid days. His son, Tom, became the willing guinea pig and reported his symptoms, as well as sent stool samples to different labs, throughout the 10-day trial.
After 10 days of fast food about 40 percent of his bacteria species were lost, which amounted to about 1,400 different types. As you continue to subsist on junk food, your gut microbes respond and “bad” bacteria may proliferate, furthering your cravings for more unhealthy foods, and allowing diseases like cancer to flourish. For example, microbes can affect cancer susceptibility by modulating your immune system and inflammation. They can also influence gene expression, and appear to have the ability to alter the stability of your genes. Dr. Eva Sirinathsinghji of the Institute of Science for Society also noted:15
"A failure of the intestinal barrier to limit host-microbiota interactions is also thought to be important. Anatomical separation between the host and microbes is a crucial first line of defense and is maintained through an intact epithelial lining and mucosal layer, as well as a sensing system that detects and eliminates bacteria. Consistently, ulcerative colitis, a condition that disrupts the barrier, increases the risk of colon cancers. Studies that have induced barrier failure in lab animals have also shown that carcinogens are more likely to pass through a disrupted gut lining, leading to increased tumor formation in local and distant organs."
Gut Bacteria May Reveal Colon Cancer
Your microbiome may even reveal your risk for, or presence of, colon cancer. A total of 90 people participated in a study published in Cancer Prevention Research.16 Thirty of the participants were healthy, 30 had precancerous intestinal polyps, and 30 had been diagnosed with advanced colon or rectal cancer. After assessing the composition of each person’s microbiome, it became apparent that microbiome analysis (using a fecal test) might be a viable way to screen for precancerous polyps and colorectal cancer.
According to the findings, adding microbiome analysis to other known risk factors for precancerous polyps resulted in a 4.5-fold improved prediction for the condition. Adding microbiome analysis to risk factors for invasive colorectal cancer resulted in a five-fold improvement in their ability to predict cancer.
The best way to optimize your microbiome is through your diet. A good place to start is by drastically reducing grains and sugar, and avoiding genetically engineered ingredients, processed foods, and chlorinated tap water. A gut-healthy diet is one rich in whole, unprocessed, and unsweetened foods, along with traditionally fermented or cultured foods.
Top Cancer Prevention Tips
I believe you can virtually eliminate your risk of cancer and chronic disease, and radically improve your chances of recovering from cancer if you currently have it, by adhering to the following strategies.
- Buy whole organic foods and cook from scratch. This will automatically reduce your sugar consumption. The evidence is also quite clear that if you want to avoid cancer, or you currently have cancer and insulin resistance, you MUST avoid all forms of sugar, especially fructose, which feeds cancer cells and promotes their growth. Make sure your total fructose intake is less than 25 grams per day, or 15 grams if you’re struggling with insulin resistance or have symptoms of insulin resistance (diabetes, high blood pressure, obesity, or heart disease).
If you buy organic produce, you’ll also cut your exposure to pesticides and genetically engineered ingredients, and in ditching processed foods, you’ll automatically avoid artificial sweeteners, cut down on sugar, and avoid harmful processed fats. Speaking of fats, most people need upward of 50 to 85 percent healthy fats in their diet for optimal health.
Sources of healthy fats to add to your diet include avocados, butter made from raw grass-fed organic milk, raw organic dairy, coconuts and coconut oil, unheated organic nut oils, raw nuts and seeds, organic pastured egg yolks, and grass-fed meats. For more detailed dietary advice, please see my free Optimized Nutrition Plan.
- Opt for organic grass-fed meats to avoid genetically engineered ingredients, pesticides, hormones, antibiotics, and other growth-promoting drugs. You may also want to consider reducing your protein consumption to one gram per kilogram of lean body weight, as excess protein (especially from hormone- and antibiotic-treated meat) may promote tumor growth.
- Opt for glass packaging and storage containers to avoid endocrine-disrupting chemicals.
- Reconsider how you prepare and cook your food: I recommend eating at least one-third of your food raw. Avoid frying or charbroiling; boil, poach, or steam your foods instead. Consider adding cancer-fighting whole foods, herbs, spices, and supplements to your diet, such as broccoli, curcumin, and resveratrol.
- Intermittent fasting is an excellent strategy if you’re insulin/leptin resistant, have diabetes, high blood pressure, heart disease, or struggle with your weight. Intermittent fasting is not a permanent eating program; once your insulin resistance improves and you are normal weight, you can start eating more food, more frequently again, as you will have reestablished your body’s ability to burn fat for fuel.
- Normalize your ratio of omega-3 to omega-6 fats by taking a high-quality krill oil and reducing your intake of processed vegetable oils, such as corn, soy, and canola.
- Optimize your gut flora to reduce inflammation and strengthen your immune response. Researchers have found a microbe-dependent mechanism through which some cancers mount an inflammatory response that fuels their development and growth. They suggest that inhibiting inflammatory cytokines might slow cancer progression and improve the response to chemotherapy. Adding naturally fermented food to your daily diet is an easy way to help prevent cancer or speed recovery. You can always add a high-quality probiotic supplement as well, but naturally fermented foods are the best.
- Exercise: Exercise lowers your insulin levels, thereby promoting weight loss, and discouraging the growth and spread of cancer cells. In one three-month study, exercise was found to alter immune cells into a more potent disease-fighting form in cancer survivors who had just completed chemotherapy. Researchers and cancer organizations increasingly recommend making regular exercise a priority in order to reduce your risk of cancer and help improve cancer outcomes.
Research has also found evidence suggesting exercise can help trigger apoptosis (programmed cell death) in cancer cells. Ideally, your exercise program should include balance, strength, flexibility, and high-intensity interval training (HIIT). For help getting started, refer to my Peak Fitness Program.
- Vitamin D: There is scientific evidence you can decrease your risk of cancer by more than half simply by optimizing your vitamin D levels with appropriate sun exposure. Your serum level should hold steady at 50 to 70 ng/ml, but if you are being treated for cancer it may be advisable to be closer to 80 to 90 ng/ml for optimal benefit. If you take oral vitamin D and have cancer, it would be very prudent to monitor your vitamin D blood levels regularly, as well as supplementing your vitamin K2 and magnesium, as these nutrients work in tandem.
- Sleep: Make sure you are getting enough restorative sleep. Most of us need eight hours so strive for that by getting to bed early enough. Poor sleep can interfere with your melatonin production, which is associated with an increased risk of insulin resistance and weight gain, both of which raise your risk of cancer. Melatonin in and of itself is also a potent antioxidant with known anti-cancer properties, which is another reason why sleeping well is so important for cancer prevention.
- Avoid toxins: Reduce your exposure to environmental toxins like pesticides, herbicides, household chemical cleaners, synthetic air fresheners, and toxic cosmetics.
- Avoid radiation exposure: Limit your exposure and protect yourself from radiation produced by cell phones, towers, base stations, and Wi-Fi stations, as well as minimizing your exposure from radiation-based medical scans, including dental x-rays, CT scans, and mammograms.
- Manage your stress: Stress from all causes is a major contributor to disease. It is likely that stress and unresolved emotional issues may be more important than the physical ones, so make sure this is addressed. My favorite tool for resolving emotional challenges is the Emotional Freedom Techniques (EFT).