Does Rye Bread Protect Against Cancer?

Previously, I’ve explored the beneficial effects of flaxseeds on prostate cancer (Flaxseeds vs. Prostate Cancer), as well as breast cancer prevention and survival (Flaxseeds & Breast Cancer Prevention and Breast Cancer Survival & Lignan Intake). The cancer-fighting effect of flaxseeds is thought to be because of the lignans, which are cancer-fighting plant compounds found in red wine, whole grains, greens (cruciferous vegetables), and especially sesame seeds and flaxseeds, the most concentrated source on Earth. But this is based on per unit weight. People eat a lot more grains than seeds. Of the grains people eat, the highest concentration of lignans is found in rye. So, can rye intake decrease the risk of cancer? Theoretically yes, but unlike flaxseeds, it’s never been directly put to the test… until now.

In my video Does Rye Bread Protect Against Cancer?, I discuss the evidence that does exist. If you measure the levels of lignans in the bloodstream of women living in a region where they eat lots of rye, the odds of breast cancer in women with the highest levels do seem to be just half that of women with the lowest levels. But lignans are also found in tea and berries, so we couldn’t be sure where the protection is coming from. To get around this, researchers decided to measure alkylresorcinol metabolites, a class of phytonutrients relatively unique to whole grains.

Researchers collected urine from women with breast cancer and women without, and the women with breast cancer had significantly lower levels compared to those without. This suggests that women at risk for breast cancer consume significantly lower amounts of whole grains like rye. But if we follow older women in their 50s through 60s, the intake of whole grain products was not associated with risk of breast cancer. A similar result was found in older men for prostate cancer. Is it just too late at that point?

We know from data on dairy that diet in our early life may be important in the development of prostate cancer, particularly around puberty when the prostate grows and matures. If you look at what men were drinking in adolescence, daily milk consumption appeared to triple their risk of advanced prostate cancer later in life. (Learn more about milk and prostate cancer in my video Prostate Cancer and Organic Milk vs. Almond Milk.) So, researchers looked at daily rye bread consumption during adolescence.

Those who consumed rye bread daily as kids did appear to only have half the odds of advanced prostate cancer. This is consistent with immigrant studies suggesting that the first two decades of life may be most important for setting the pattern for cancer development in later life. These findings are certainly important for how we should feed our kids, but if we’re already middle-aged, is it too late to change course? To answer this question, researchers in Sweden put it to the test.

Researchers took men with prostate cancer and split them into two groups. One group got lots of rye bread, while the other got lots of high-fiber, but low-lignan, wheat bread. There’s been some indirect evidence that rye may be active against prostate cancer—like lower cancer rates in regions with high rye consumption—but it had never been directly investigated… until this study. Biopsies were taken from the subjects’ tumors before and after three weeks of bread eating, and the number of cancer cells that were dying off were counted. Though there was no change in the cancer cell clearance of the control bread group, there was a 180% increase in the number of cancer cells being killed off in the rye group. A follow-up study lasting 6 weeks found a 14% decrease in PSA levels, a cancer marker suggesting a shrinkage of the tumor.

The researchers note they used very high rye bread intakes, and it remains to be tested if more normal intake levels would have effects that are of clinical importance. As a sadly typical American, my lack of intimate familiarity of the metric system did not flag the “485 grams” of rye bread a day as far out of the ordinary, but that translates to 15 slices! Rather than eating a loaf a day, the same amount of lignans can be found in a single teaspoon of ground flaxseeds.


I’ve created several videos on flaxseeds for both breast cancer prevention and treatment, including Flaxseeds & Breast Cancer Prevention, Breast Cancer Survival and Lignan Intake, Flaxseeds & Breast Cancer Survival Epidemiological Evidence, and Flaxseeds & Breast Cancer Survival: Clinical Evidence.

What’s more, flaxseeds may help with cyclical breast pain (Flaxseeds for Breast Pain), prostate cancer (Flaxseed vs. Prostate Cancer), diabetes (Flaxseeds vs. Diabetes), and hypertension (Flaxseeds for Hypertension).

And if you’re wondering Which Are Better: Chia Seeds or Flaxseeds?, get the answer in the video!

The wonders of whole grains are also discussed in Whole Grains May Work as Well as Drugs, Can Oatmeal Reverse Heart Disease?, and Can Oatmeal Help Fatty Liver Disease?.

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

The Best Diet for Rheumatoid Arthritis

Rheumatoid arthritis is a chronic systemic autoimmune disease affecting millions. It is characterized by persistent pain, stiffness, and progressive joint destruction leading to crippling deformities, particularly in the hands and feet. What can we do to prevent and treat it?

In my video Why Do Plant-Based Diets Help Rheumatoid Arthritis?, I show a famous 13-month randomized controlled trial of plant-based diets for rheumatoid arthritis where patients were put on a vegan diet for three and a half months and then switched to an egg-free lactovegetarian diet for the remainder of the study. Compared to the control group (who didn’t change their diet at all), the plant-based group experienced significant improvements starting within weeks. Their morning stiffness improved within the first month, cutting the number of hours they suffered from joint stiffness in half. Their pain level dropped from 5 out of 10 down to less than 3 out of 10. Disability levels dropped, and subjects reported feeling better; they had greater grip strength, fewer tender joints, less tenderness per joint, and less swelling. They also had a drop in inflammatory markers in their blood, such as sedimentation rate, C-reactive protein, and white blood cell count. As a bonus, they lost about 13 pounds and kept most of that weight off throughout the year.

What does diet have to do with joint disease?

Rheumatoid arthritis is an autoimmune disease, in which our own body attacks the lining of our joints. There’s also a different autoimmune disease called rheumatic fever, in which our body attacks our heart. Why would it do that? It appears to be a matter of friendly fire.

Rheumatic fever is caused by strep throat, which is itself caused by a bacterium that has a protein that looks an awful lot like a protein in our heart. When our immune system attacks the strep bacteria, it also attacks our heart valves, triggering an autoimmune attack by “molecular mimicry.” The protein on the strep bacteria is mimicking a protein in our heart; so, our body gets confused and attacks both. That’s why it’s critical to treat strep throat early to prevent our heart from getting caught in the crossfire.

Researchers figured that rheumatoid arthritis might be triggered by an infection as well. A clue to where to start looking was the fact that women seem to get it three times more frequently than men. What type of infection do women get more than men? Urinary tract infections (UTIs). So, researchers started testing the urine of rheumatoid arthritis sufferers and, lo and behold, found a bacterium called Proteus mirabilis. Not enough to cause symptoms of a UTI, but enough to trigger an immune response. And indeed, there’s a molecule in the bacterium that looks an awful lot like one of the molecules in our joints.

The theory is that anti-Proteus antibodies against the bacterial molecule may inadvertently damage our own joint tissues, leading eventually to joint destruction. Therefore, interventions to remove this bacterium from the bodies of patients, with consequent reduction of antibodies against the organism, should lead to a decrease in inflammation.

As we saw in my video Avoiding Chicken to Avoid Bladder Infections, urinary tract infections originate from the fecal flora. The bacteria crawl up from the rectum into the bladder. How might we change the bugs in our colons? By changing our diet.

Some of the first studies published more than 20 years ago to fundamentally shift people’s gut flora were done using raw vegan diets, figuring that’s about as fundamental a shift from the standard Western diet as possible. Indeed, within days researchers could significantly change subjects’ gut flora. When researchers put rheumatoid arthritis sufferers on that kind of diet, they experienced relief, and the greatest improvements were linked to greatest changes in gut flora. The diet was considered so intolerable, though, that half the patients couldn’t take it and dropped out, perhaps because they were trying to feed people things like “buckwheat-beetroot cutlets” buttered with a spread made out of almonds and fermented cucumber juice.

Thankfully, regular vegetarian and vegan diets work too, changing the intestinal flora and improving rheumatoid arthritis. However, we didn’t specifically have confirmation that plant-based diets brought down anti-Proteus antibodies until 2014. Subjects that responded to the plant-based diet showed a significant drop in anti-Proteus mirabilis antibodies compared to the control group. Maybe it just dropped immune responses across the board? No, antibody levels against other bugs remained the same; so, the assumption is that the plant-based diet reduced urinary or gut levels of the bacteria.

A shift from an omnivorous to a vegetarian diet has a profound influence on the composition of urine as well. For example, those eating plant-based had higher levels of lignans in their urine. Up until now, it was thought that they only protected people from getting cancer, but we now know lignans can also have antimicrobial properties. Perhaps, they help clear Proteus mirabilis from the system. Either way, these data suggest a new type of therapy for the management of rheumatoid arthritis: anti-Proteus measures including plant-based diets.


I have to admit I had never even heard of Proteus mirabilis. That’s why I love doing work—I learn as much as you do!

I explored another unconventional theory as to why plant-based diets are so successful in treating inflammatory arthritis in Potassium and Autoimmune Disease.

There’s another foodborne bacteria implicated in human disease, the EXPEC in chicken leading to urinary tract infections—another game-changer: Avoiding Chicken To Avoid Bladder Infections.

I have a bunch of videos on gut flora—the microbiome. They include: 

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Image Credit: Sally Plank / Flickr. This image has been modified.