Fruits And Vegetables: Cancer Benefits

 

Tomatoes and watermelon may ward off kidney cancer in older women

A higher intake by postmenopausal women of the natural antioxidant lycopene, found in foods like tomatoes, watermelon and papaya, may lower the risk of renal cell carcinoma, a type of kidney cancer.

A team led by Cathryn Bock, Ph.D., M.P.H., associate professor of Oncology at Wayne State University's School of Medicine, made the conclusion after analyzing data from 96,196 women nationwide and in Detroit who enrolled in the Women's Health Initiative from 1993 to 1998 and were followed through July 2013 by participating initiative sites, including Wayne State University.

"We were surprised to observe a protective effect of lycopene, as several previous studies in other populations did not detect a similar relationship," Bock said.

The results are explained in "Antioxidant micronutrients and the risk of renal cell carcinoma in the Women's Health Initiative cohort," featured in the Feb. 15 issue of Cancer.

The investigators analyzed the risks for kidney cancer associated with intake of lycopene and other micronutrients that have antioxidant properties, including lutein and vitamins C and E. During follow-up, 240 women were diagnosed with kidney cancer. Compared with women who reported a lower intake of lycopene, those who ingested more had a 39 percent lower risk. No other micronutrient was significantly associated with the same risk.

The 63,920 estimated new cases of kidney and renal pelvis cancer in 2014 made up 3.8 percent of all new cancer cases, according to the National Cancer Institute's Surveillance, Epidemiology, and End Results Program. In 2011, there were an estimated 358,603 people living with the cancer in the United States.

It is the eighth-leading cancer among women and is commonly diagnosed at a more advance stage.

"Kidney cancer is a relatively rare cancer, and so focusing only on reducing risk of this disease would be short-sighted," Bock said. "Rather, a diet focused on one's own personal risk factors, such as family history, would be more beneficial."

A low-salt diet is recommended for women with a risk of hypertension, a major risk factor for kidney cancer. There are other steps women can take now for their health, including eating more foods and fruits with naturally-occurring lycopene.

"Lycopene from food sources has also been associated with decreased risk of breast and prostate cancers, and a diet high in vegetables and fruits are generally well-accepted for promoting good health," she said.

Good sources of lycopene include tomatoes and tomato-based products, watermelon, pink grapefruit, guava and papaya. Dr. Bock suggests consulting a doctor before taking a lycopene supplement.

The team is now examining whether there is a relationship between antioxidant nutrient intake and kidney cancer risk in a National Cancer Institute-funded case-control study primarily conducted with participants from the metropolitan Detroit area.

"This study included a broader population, including both men and women, and with greater representation of African-Americans, and therefore may help describe the associations in populations beyond post-menopausal women who are primarily of European descent," Dr. Bock said.

Flavonoids found in fruits and vegetables could play a role in preventing cancer or heart disease.

Flavonoids, a group of compounds found in fruits and vegetables that had been thought to be nutritionally important for their antioxidant activity, actually have little or no value in that role, according to an analysis by scientists in the Linus Pauling Institute at Oregon State University.

However, these same compounds may indeed benefit human health, but for reasons that are quite different – the body sees them as foreign compounds, researchers say, and through different mechanisms, they could play a role in preventing cancer or heart disease.

Based on this new view of how flavonoids work, a relatively modest intake of them – the amount you might find in a healthy diet with five to nine servings of fruits and vegetables – is sufficient. Large doses taken via dietary supplements might do no additional good; an apple a day may still be the best bet.

A research survey, and updated analysis of how flavonoids work and function in the human body, were recently published in Free Radical Biology and Medicine, a professional journal.

“What we now know is that flavonoids are highly metabolized, which alters their chemical structure and diminishes their ability to function as an antioxidant,” said Balz Frei, professor and director of the Linus Pauling Institute. “The body sees them as foreign compounds and modifies them for rapid excretion in the urine and bile.”

Flavonoids are polyphenolic compounds with some common characteristics that are widely found in fruits and vegetables and often give them their color – they make lemons yellow and certain apples red. They are also found in some other foods, such as coffee, tea, wine, beer and chocolate, and studies in recent years had indicated that they had strong antioxidant activity – and because of that, they might be important to biological function and health.

“If you measure the activity of flavonoids in a test tube, they are indeed strong antioxidants,” Frei said. “Based on laboratory tests of their ability to scavenge free radicals, it appears they have 3-5 times more antioxidant capacity than vitamins C or E. But with flavonoids in particular, what goes on in a test tube is not what’s happening in the human body.”

Research has now proven that flavonoids are poorly absorbed by the body, usually less than five percent, and most of what does get absorbed into the blood stream is rapidly metabolized in the intestines and liver and excreted from the body. By contrast, vitamin C is absorbed 100 percent by the body up to a certain level. And vitamin C accumulates in cells where it is 1,000 to 3,000 times more active as an antioxidant than flavonoids.

The large increase in total antioxidant capacity of blood observed after the consumption of flavonoid-rich foods is not caused by the flavonoids themselves, Frei said, but most likely is the result of increased uric acid levels.

But just because flavonoids have been found to be ineffectual as antioxidants in the human body does not mean they are without value, Frei said. They appear to strongly influence cell signaling pathways and gene expression, with relevance to both cancer and heart disease.

“We can now follow the activity of flavonoids in the body, and one thing that is clear is that the body sees them as foreign compounds and is trying to get rid of them,” Frei said. “But this process of gearing up to get rid of unwanted compounds is inducing so-called Phase II enzymes that also help eliminate mutagens and carcinogens, and therefore may be of value in cancer prevention.

“Flavonoids could also induce mechanisms that help kill cancer cells and inhibit tumor invasion,” Frei added.

It also appears that flavonoids increase the activation of existing nitric oxide synthase, which has the effect of keeping blood vessels healthy and relaxed, preventing inflammation, and lowering blood pressure – all key goals in prevention of heart disease.

Both of these protective mechanisms could be long-lasting compared to antioxidants, which are more readily used up during their free radical scavenging activity and require constant replenishment through diet, scientists say.

However, Frei said, it’s also true that such mechanisms require only relatively small amounts of flavonoids to trigger them – conceptually, it’s a little like a vaccine in which only a very small amount of an offending substance is required to trigger a much larger metabolic response. Because of this, there would be no benefit – and possibly some risk – to taking dietary supplements that might inject large amounts of substances the body essentially sees as undesirable foreign compounds.

Numerous studies in the United States and Europe have documented a relationship between adequate dietary intake of flavonoid-rich foods, mostly fruits and vegetables, and protection against heart disease, cancer and neurodegenerative disease, Frei said.

Higher Intake of Fruits and Vegetables = Lower Risk of Bladder Cancer

University of Hawaii Cancer Center Researcher Song-Yi Park, PhD, along with her colleagues, recently discovered that a greater consumption of fruits and vegetables may lower the risk of invasive bladder cancer in women.

The investigation was conducted as part of the Multiethnic Cohort (MEC) Study, established in 1993 to assess the relationships among dietary, lifestyle, genetic factors, and cancer risk. Park and her fellow researcher's analyzed data collected from 185,885 older adults over a period of 12.5 years, of which 581 invasive bladder cancer cases were diagnosed (152 women and 429 men).

After adjusting for variables related to cancer risk (age, etc.) the researchers found that women who consumed the most fruits and vegetables had the lowest bladder cancer risk. For instance, women consuming the most yellow-orange vegetables were 52% less likely to have bladder cancer than women consuming the least yellow-orange vegetables. The data also suggested that women with the highest intake of vitamins A, C, and E had the lowest risk of bladder cancer. No associations between fruit and vegetable intake and invasive bladder cancer were found in men.

"Our study supports the fruit and vegetable recommendation for cancer prevention, said Park. "However, further investigation is needed to understand and explain why the reduced cancer risk with higher consumption of fruits and vegetables was confined to only women."

Plant Flavonoid Luteolin Blocks Cell Signaling Pathways in Colon Cancer Cells

Luteolin is a flavonoid commonly found in fruit and vegetables. Dietary sources include celery, green pepper, thyme, perilla, chamomile tea, carrots, olive oil, peppermint, rosemary, navel oranges, and oregano. This compound has been shown in laboratory conditions to have anti-inflammatory, anti-oxidant and anti-cancer properties but results from epidemiological studies have been less certain.

Research published January, 2012 in BioMed Central's open access journal BMC Gastroenterology shows that luteolin is able to inhibit the activity of cell signaling pathways (IGF and PI3K) important for the growth of cancer in colon cancer cells.

Colon cancer is the second most frequent cause of cancer-related death in the Western World. Colon cancer cells have elevated levels of IGF-II compared to normal colon tissues. It is thought that this is part of the mechanism driving uncontrolled cell division and cancer growth. Researchers from Korea showed that luteolin was able to block the secretion of IGF-II by colon cancer cells and within two hours decreased the amount of receptor (IGF-IR) precursor protein. Luteolin also reduced the amount of active receptor (measured by IGF-I dependent phosphorylation).

Luteolin inhibited the growth stimulatory effect of IGF-I and the team led by Prof Jung Han Yoon Park found that luteolin affected cell signaling pathways which are activated by IGF-I in cancer. Prof Jung Han Yoon Park explained, "Luteolin reduced IGF-I-dependent activation of the cell signaling pathways PI3K, Akt, and ERK1/2 and CDC25c. Blocking these pathways stops cancer cells from dividing and leads to cell death."

Prof Jung Park continued, "Our study, showing that luteolin interferes with cell signaling in colon cancer cells, is a step forward in understanding how this flavonoid works. A fuller understanding of the in vivo results is essential to determine how it might be developed into an effective chemopreventive agent."

Flavonoids in Fruit, and Veggies Might Fight Prostate Cancer

Prostate cancer patients who, before their diagnosis, routinely consumed hefty helpings of the flavonoid compounds found in plant-based foods and drinks may be at lower risk for the most aggressive form of the disease, new research suggests.

But the research has significant limitations, the study authors noted, so it's too soon to say that a plant-based diet protects against prostate cancer.

Flavonoids are found in vegetables and fruits, as well as in tea, wine, juices and cocoa. Researchers have long theorized that these particular antioxidants may help reduce cancer risk by fighting inflammation, oxidation, cell death and tumor cell growth.

The new study did not assess the ability of flavonoids to prevent the onset of cancer as a whole. But the investigation, involving about 1,900 patients newly diagnosed with prostate cancer, found that those whose diets included the highest amount of flavonoids were 25 percent less likely to have been diagnosed with the fastest-moving and harshest form of the disease compared to those who had been taking in the fewest flavonoids.

"We compared men with low-aggressive disease to high aggressive," said study lead author Susan Steck, associate professor at the University of South Carolina's Arnold School of Public Health. "We did not have a healthy comparison group. So while we think that consuming more fruits and vegetables will improve the odds of not getting prostate cancer altogether, we can't say that based on our study results."

"But what we are seeing here is the impact of flavonoids on reducing the risk for aggressive prostate cancer," she added. "They may not affect your risk for getting the cancer, but it may mitigate against the kind of cancer you would get."

The authors looked at self-reported dietary habits already in place at the time of diagnosis among their patient pool, which included 920 black men and 977 white men. No dietary intervention was imposed after diagnosis.

All the men had been enrolled in the North Carolina-Louisiana Prostate Cancer Project.

The new study found that smokers and men younger than 65 appeared to receive the most protective benefit from fruit and vegetable consumption.

The authors identified green and black tea, as well as orange and grapefruit juice, as the prime sources of flavonoids consumed by study participants. Strawberries, onions, cooked greens, kale and broccoli also were popular flavonoid-rich foods.

No single class of plant-based food was linked on its own to the observed protective effect, leading the team to conclude that the benefit was rooted in a dietary mix of flavonoids.

Dr. Lionel Banez, assistant professor of urologic surgery at Duke University Medical Center in Durham, N.C., said the study design makes it hard to read much into the findings.

It is "difficult to be confident about the conclusions," he said, given that the current study was a backward look at patients' recollections of their pre-diagnosis diets.

Banez suggested that the findings of a flavonoid benefit would be more reliable if they had stemmed from a highly controlled study of risk levels among patients who were proactively placed on a specific dietary plan, and then tracked for the future onset of cancer.

"These results are not enough to warrant recommending plant-based diets as regimens to treat prostate cancer or prevent aggressive prostate cancer," he said.

Although the study found an association between flavonoids and risk for a form of prostate cancer, it did not prove a cause-and-effect relationship. Because the study was presented at a medical meeting, the data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.

Eating Meat Promotes Colon Cancer, Eating Plants Fights It

A team of Children’s Hospital and Research Center Oakland (CHORI) researchers has found that a category of lipids known as sphingolipids may be an important link in the relationship between diet, inflammation and cancer.   In a paper published online October, 2014 in the Journal of Clinical Investigation, Dr. Julie Saba, MD, PhD and her team provide evidence that a sphingolipid metabolite called sphingosine-1-phosphate (S1P) found in both mammalian food products and generated by normal human cells can contribute to inflammation of the colon, inflammatory bowel disease (IBD) and inflammation-associated colon cancer, whereas soy and plant-type sphingolipids called sphingadienes may protect against these conditions.

A connection between inflammation and cancer has been recognized for over a hundred years. This connection is particularly evident in colon carcinogenesis, because patients with IBD have a higher incidence of colon cancer than the general population. There is increasing evidence that inflammation contributes to the earliest stages of carcinogenesis, namely in the process of cell transformation, where the cell acquires many aspects of cancer characteristics. The observation that IBD and colon cancer incidence rise as nations industrialize suggests that changes in diet and nutrition contribute to colitis and colitis-associated colon cancer. 

Bioactive sphingolipids play fundamental roles in carcinogenesis via their ability to regulate programmed cell death pathways, stress responses, immunity, and inflammation. The impact of sphingolipid metabolism is particularly germane in colon cancer, as gut epithelial cells are exposed to sphingolipid metabolites generated by the breakdown of dietary sphingolipids. S1P, the final breakdown product of mammalian sphingolipids, is a pro-inflammatory signaling lipid that promotes cell growth and carcinogenesis. During malignant transformation and colon cancer progression, genetic changes occur in the gut tissues, including an increase in the enzyme that generates S1P and a decrease in S1P lyase (SPL), the enzyme that catalyzes S1P degradation. These changes lead to accumulation of S1P in the gut mucosa.

To explore the impact of S1P accumulation on inflammation and carcinogenesis, the researchers produced a mouse lacking SPL in the gut tissues. They then characterized its responses using a chemical-induced model of colitis-associated colon cancer. Compared to control mice, the mutated mice exhibited more inflammation and a higher incidence of tumors on this regimen. Using a combination of mouse and cell culture experiments, the scientists identified a cascade of steps downstream of S1P that lead eventually to the silencing of two tumor suppressing proteins whose functions are to protect against the formation of cancer. 

In contrast to the cancer-promoting effects of S1P, the researchers showed that soy or plant-type sphingolipids called sphingadienes cannot be metabolized to S1P and instead enhance the metabolism of S1P by increasing SPL levels in gut tissues when fed to mice. Further, sphingadiene treatment of mice reduced inflammation, signs of IBD, and the incidence of tumors. Finally, the researchers showed an increase in S1P-related gene expression in the colons of patients with IBD compared to controls. 

The research suggests that while mammalian sphingolipids may promote inflammation and carcinogenesis, plant/soy sphingolipids cannot be converted into S1P, are anti-inflammatory and reduce the activity of several cancer signaling pathways. The data suggests that dietary sphingolipids may enhance or inhibit colon carcinogenesis, depending on their ability to be metabolized to S1P.  The findings reveal a mechanistic link between diet, inflammation and cancer and provide evidence supporting the further investigation of sphingadienes as colon cancer chemopreventive agents in patients at risk, such as children and adults with IBD.

Vegetables Fight Prostate Cancer

Prostate cancer patients who, before their diagnosis, routinely consumed hefty helpings of the flavonoid compounds found in plant-based foods and drinks may be at lower risk for the most aggressive form of the disease, new research suggests.

But the research has significant limitations, the study authors noted, so it's too soon to say that a plant-based diet protects against prostate cancer.

Flavonoids are found in vegetables and fruits, as well as in tea, wine, juices and cocoa. Researchers have long theorized that these particular antioxidants may help reduce cancer risk by fighting inflammation, oxidation, cell death and tumor cell growth.

The new study did not assess the ability of flavonoids to prevent the onset of cancer as a whole. But the investigation, involving about 1,900 patients newly diagnosed with prostate cancer, found that those whose diets included the highest amount of flavonoids were 25 percent less likely to have been diagnosed with the fastest-moving and harshest form of the disease compared to those who had been taking in the fewest flavonoids.

"We compared men with low-aggressive disease to high aggressive," said study lead author Susan Steck, associate professor at the University of South Carolina's Arnold School of Public Health. "We did not have a healthy comparison group. So while we think that consuming more fruits and vegetables will improve the odds of not getting prostate cancer altogether, we can't say that based on our study results."

"But what we are seeing here is the impact of flavonoids on reducing the risk for aggressive prostate cancer," she added. "They may not affect your risk for getting the cancer, but it may mitigate against the kind of cancer you would get."

Steck and her colleagues discussed their findings at the annual (2012) cancer prevention meeting of the American Association for Cancer Research, in Anaheim, Calif.

The authors looked at self-reported dietary habits already in place at the time of diagnosis among their patient pool, which included 920 black men and 977 white men. No dietary intervention was imposed after diagnosis.

All the men had been enrolled in the North Carolina-Louisiana Prostate Cancer Project.

The new study found that smokers and men younger than 65 appeared to receive the most protective benefit from fruit and vegetable consumption.

The authors identified green and black tea, as well as orange and grapefruit juice, as the prime sources of flavonoids consumed by study participants. Strawberries, onions, cooked greens, kale and broccoli also were popular flavonoid-rich foods.

No single class of plant-based food was linked on its own to the observed protective effect, leading the team to conclude that the benefit was rooted in a dietary mix of flavonoids.

Dr. Lionel Banez, assistant professor of urologic surgery at Duke University Medical Center in Durham, N.C., said the study design makes it hard to read much into the findings.

It is "difficult to be confident about the conclusions," he said, given that the current study was a backward look at patients' recollections of their pre-diagnosis diets.

Banez suggested that the findings of a flavonoid benefit would be more reliable if they had stemmed from a highly controlled study of risk levels among patients who were proactively placed on a specific dietary plan, and then tracked for the future onset of cancer.

"These results are not enough to warrant recommending plant-based diets as regimens to treat prostate cancer or prevent aggressive prostate cancer," he said.

Fruit and vegetable intake and head and neck cancer

A new study among AARP members shows that just one additional serving of fruit and vegetables per day may lower your risk of head and neck cancer, but the data suggest that you may not want to stop at just one, according to researchers from the National Cancer Institute.

A large prospective study of 500,000 men and women aged 50 and older has found that those who ate more fruit and vegetables had a reduced risk of head and neck cancer. Head and neck cancer is the sixth leading cause of cancer-related mortality worldwide, resulting in more than 350,000 deaths annually.

"Identifying protective factors for head and neck cancer is particularly important as it has a high mortality rate," said Neal Freedman, Ph.D., cancer prevention fellow at the National Cancer Institute.

At the beginning of the study, participants reported their typical dietary habits on a food frequency questionnaire. Freedman and his colleagues followed participants for five years and recorded all diagnoses of head and neck cancer cases during this time.

In their findings, the researchers report that participants who ate six servings of fruit and vegetables per day per 1000 calories had 29 percent less risk for head and neck cancer than did participants who consumed one and a half servings per 1000 calories per day. Typically, adults consume approximately 2000 calories per day. One serving equals approximately one medium sized fresh fruit, one half cup of cut fruit, six ounces fruit juice, one cup leafy vegetables, or one half cup of other vegetables.

"Increasing consumption by just one serving of fruit or vegetables per 1000 calories per day was associated with a six percent reduction in head and neck cancer risk," Freedman said.

According to Freedman, people who ate a lot of fruit also tended to eat a lot of vegetables, and vice versa. To measure these two types of foods independently, the researchers included both fruit and vegetable intake in the statistical models, a common statistical approach. This allowed them to compare participants with different levels of fruit consumption while holding constant the level of vegetable intake and vice versa. When examining fruit and vegetable intake simultaneously, the protective association with vegetables seemed to be stronger than the association with fruits.

"Although we cannot absolutely rule out a cancer preventive role for other lifestyle factors that go along with eating more fruits and vegetables, our results are consistent with those from previous studies," Freedman said. "Our study suggests that fruit and vegetable consumption may protect against head and neck cancer and adds support to current dietary recommendations to increase fruit and vegetable consumption."

Flavonols and pancreatic cancer risk

A study of food consumption in 183,518 residents of California and Hawaii has found that a diet high in flavonols might help reduce pancreatic cancer risk, especially in smokers. These compounds are generally ubiquitous in plant-based foods, but are found in highest concentrations in onions, apples, berries, kale and broccoli.

People who ate the largest amounts of flavonols had a 23 percent reduced risk of developing pancreatic cancer compared to those who ate the least, according to a research team led by Laurence Kolonel, M.D., Ph.D., at the Cancer Research Center of Hawaii.

Smokers gained the most benefit. Those who ate the most flavonols reduced their risk of developing pancreatic cancer by 59 percent, compared to those who ate the least, says the study’s lead author, Ute Nöthlings, DrPH, who conducted the study as a postdoctoral fellow in Hawaii and is now a researcher at the German Institute of Human Nutrition Potsdam-Rehbruecke.

‘The effect was largest in smokers, presumably because they are at increased pancreatic cancer risk already," said Nöthlings. Smoking is the only established risk factor for pancreatic cancer, and "short of stopping tobacco use, it has been difficult to consistently show lifestyle factors that might help protect against this deadly cancer," she says.

As part of a larger research project known as The Multiethnic Cohort Study, Kolonel and Nöthlings followed the participants for an average of eight years after they filled out a comprehensive food questionnaire.

Although Nöthlings says the study has a large statistical power because of the large number of pancreatic cancer cases (529) that occurred in the study population, she says that this one study cannot firmly answer the question of whether flavonols can prevent development of pancreatic cancer. "Further epidemiological studies in other populations and geographic regions are needed to confirm our findings," she said.

The study also is the first to examine prospectively specific classes of flavonols and pancreatic cancer risk.

The researchers looked at consumption of three flavonols: quercetin, which is most abundant in onions and apples; kaempferol, found in spinach and some cabbages; and myricetin, found mostly in red onions and berries.

Of the three individual flavonols, kaempferol was associated with the largest risk reduction (22 percent) across all participants. When the researchers divided intake into quartiles, and then compared highest intake to lowest, all the three classes of flavonols were associated with a significant trend toward reduced pancreatic cancer risk in current smokers, but not in never or former smokers. The interaction with smoking status was statistically significant for total flavonols, quercetin and kaempferol.

The researchers say their study did not examine the biological mechanisms by which these flavonols could exert a protective effect against pancreatic cancer. "But anti-carcinogenic effects of flavonoids in general have been attributed to the ability of these constituents to inhibit cell cycle, cell proliferation and oxidative stress, and to induce detoxification enzymes and apoptosis," Nöthlings said.

Fruit and vegetable intake is associated with lower risk of breast cancer

There is no association between total fruit and vegetable intake and risk of overall breast cancer, but vegetable consumption is associated with a lower risk of estrogen receptor-negative (ER-) breast cancer, according to a study published January 24, 2013 in the Journal of the National Cancer Institute.

The intake of fruits and vegetables has been hypothesized to lower breast cancer risk, however the existing evidence is inconclusive. There are many subtypes of breast cancer including ER- and ER positive (ER+) tumors and each may have distinct etiologies. Since ER- tumors, which have lower survival rates and are less dependent on estrogen levels than ER+ tumors, account for only 15-20% of breast cancers, large pooled analyses are needed to determine the suspected link to lower ER- breast cancer risk and the consumption of fruits and vegetables.

In order to determine if there is a link between the lowered risk of ER- breast cancers and the intake of fruits and vegetables, Seungyoun Jung, Sc.D., formerly from the Department of Nutrition, Harvard School of Public Health, and currently at the Channing Division of Network Medicine, Brigham and Women's Hospital, and colleagues analyzed data from 20 cohort studies of women who were followed for a maximum of 11-20 years. They investigated the association of high compared to low intake of fruit and vegetables and risk of developing breast cancer in each study and then combined the study-specific estimates to generate summary estimates for all studies combined.

The researchers found that total fruit and vegetable intake was statistically significantly linked to a lower risk of ER- breast cancer, but not with risk of overall breast cancer or risk of ER+ breast tumors. The results showed that the lower risk was mostly associated with higher vegetable consumption. "These findings support the value of examining etiologic factors in relation to breast cancer characterized by hormone receptor status in large pooled analyses because modest associations with less common breast cancer subtypes may have been missed in smaller studies," the authors write.

In an accompanying editorial, Cynthia A. Thomson, Ph.D., and Patricia A. Thompson, Ph.D., both of the University of Arizona Cancer Center, write that the findings of the study support the emphasis on greater intake for vegetables (and to a lesser extent fruit) to lower the risk of ER- breast cancer. However, they also write that, "interpretation of these findings may also be challenged by the known effects of other potential confounders, including the aggregation of health behaviors."

More fruits and vegetables = lower risk of breast cancer

Women with higher circulating carotenoid levels are at a reduced risk of breast cancer according to a study published December 6, 2012 in the Journal of the National Cancer Institute.

Carotenoids, which are micronutrients found in fruits and vegetables, have been found to have anticarcinogenic properties. Previous experimental studies have shown that carotenoids inhibit the tumor progression and reduce proliferation of estrogen receptor–positive (ER+) and estrogen receptor–negative (ER-) breast cancers. Despite the inverse association between carotenoids and breast cancer in prior studies, the specific carotenoid has differed across multiple studies.

In order to determine the associations that specific carotenoids have with breast cancer, A. Heather Eliassen, Channing Division of Network Medicine, Department of Medicine, Brigham & Women's Hospital and Harvard Medical School, and colleagues, conducted a pooled analysis of eight cohort studies, which gathered over 80% of the world's published prospective data on plasma or serum carotenoids and breast cancer. The analysis included 3,055 case subjects and 3,956 matched control subjects. Participant carotenoid levels were recalibrated to a common standard to explain laboratory differences as well as to examine the differences across populations.

The researchers found that in over 3,000 case subjects, there were statistically significantly inverse associations between circulating levels of individual and total carotenoids and breast cancer risk, with a stronger finding in ER- breast cancers. "The inverse associations we observed among ER tumors highlight carotenoids as one of the first modifiable risk factors for this poor prognosis tumor type," the authors write, adding that while some evidence has shown that carotenoids inhibit the growth of ER+ breast cancers as well, it's possible that its effect is hidden by hormone related associations which overpower other risk factors. Still, the researchers feel that, "A diet high in carotenoid-rich fruits and vegetables offers many health benefits, including a possible reduced risk of breast cancer." 

Consuming vegetables linked to decreased breast cancer risk in African-American women

Investigators from the Slone Epidemiology Center at Boston University School of Medicine (BUSM) have reported that African American women who consume more vegetables are less likely to develop estrogen receptor-negative breast cancer than women with low vegetable intake.

\The study results, published October, 2010 in the American Journal of Epidemiology, were based on data from the Black Women's Health Study (BWHS), a large follow-up study of 59,000 African American women from across the U.S. conducted by investigators at the Slone Epidemiology Center since 1995.

The investigators followed 51,928 participants in the BWHS for 12 years, during which time 1,268 cases of breast cancer developed. Among cases on which hormone receptor status was obtained, 35 percent were estrogen receptor-negative/progesterone receptor-negative (ER-/PR-) breast cancers. The incidence of ER-/PR- breast cancer was 43 percent lower among women consuming at least two vegetables per day compared with women who ate fewer than four vegetables per week. African American women are more likely than white women to be diagnosed with estrogen receptor-negative tumors, which have a poorer prognosis than estrogen receptor-positive tumors.

According to the BUSM researchers, specific types of vegetables may play a greater role in reducing breast cancer risk. The investigators reported that high intake of cruciferous vegetables in particular may be associated with reduced risk of breast cancer overall. Cruciferous vegetables, which include broccoli, mustard and collard greens, and cabbage, are sources of glucosinolates, which may play a role in preventing the development of breast cancer through their effects on both estrogen metabolism and detoxification enzymes. The researchers also observed evidence suggesting that increased carrot consumption may be associated with lower risk of breast cancer. Carrots are rich sources of carotenoids, which may reduce cancer risk through their antioxidant properties.

Tea and citrus products could lower ovarian cancer risk

Research published October 28, 2014  reveals that women who consume foods containing flavonols and flavanones (both subclasses of dietary flavonoids) significantly decrease their risk of developing epithelial ovarian cancer, the fifth-leading cause of cancer death among women.

The research team studied the dietary habits of 171,940 women aged between 25 and 55 for more than three decades.

The team found that those who consumed food and drinks high in flavonols (found in tea, red wine, apples and grapes) and flavanones (found in citrus fruit and juices) were less likely to develop the disease.

Ovarian cancer affects more than 6,500 women in the UK each year. In the United States, about 20,000 women are diagnosed with ovarian cancer each year.

Prof Aedin Cassidy, from the Department of Nutrition at UEA’s Norwich Medical School, led the study. She said: “This is the first large-scale study looking into whether habitual intake of different flavonoids can reduce the risk of epithelial ovarian cancer.

“We found that women who consume foods high in two sub-groups of powerful substances called flavonoids – flavonols and flavanones – had a significantly lower risk of developing epithelial ovarian cancer.

“The main sources of these compounds include tea and citrus fruits and juices, which are readily incorporated into the diet, suggesting that simple changes in food intake could have an impact on reducing ovarian cancer risk.

“In particular, just a couple of cups of black tea every day was associated with a 31 per cent reduction in risk.”

The research was the first to comprehensively examine the six major flavonoid subclasses present in the normal diet with ovarian cancer risk, and the first to investigate the impact of polymers and anthocyanins.

The study was led by Prof Cassidy and Prof Shelley Tworoger, from the Brigham and Women’s Hospital and Harvard Medical School. Data was derived from the Nurses’ Health Study.

‘Intake of dietary flavonoids and risk of epithelial ovarian cancer’ is published in the American Journal of Clinical Nutrition on Nov. 1, 2014. BD.

Diverse diet of veggies may decrease lung cancer risk

Adding a variety of vegetables to one's diet may help decrease the chance of getting lung cancer, and adding a variety of fruits and vegetables may decrease the risk of squamous cell lung cancer, especially among smokers.

Study results were published, August 2010 in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.

"Although quitting smoking is the most important preventive action in reducing lung cancer risk, consuming a mix of different types of fruit and vegetables may also reduce risk, independent of the amount, especially among smokers," said H. Bas Bueno-de-Mesquita, M.D., M.P.H., Ph.D., senior scientist and project director of cancer epidemiology at The National Institute for Public Health and the Environment, The Netherlands.

Using information from the ongoing, multi-centered European Prospective Investigation into Cancer and Nutrition (EPIC) study, Bueno-de-Mesquita and colleagues evaluated 452,187 participants with complete information, 1,613 of whom were diagnosed with lung cancer.

Information was obtained on 14 commonly eaten fruits and 26 commonly eaten vegetables. The fruits and vegetables evaluated in the EPIC study consisted of a wide variety of fresh, canned or dried products.

Previous results from the EPIC study showed that the quantity of vegetables and fruits may decrease risk of lung cancer; in particular the risk of one specific type of lung cancer, squamous cell carcinoma, decreased in current smokers.

Regardless of the amount, the researchers on the current study found that risk of lung cancer also decreased when a variety of vegetables were consumed. In addition, the risk of squamous cell carcinoma decreased substantially when a variety of fruits and vegetables were eaten. However, Bueno-de-Mesquita said that they "cannot exclude that these results can still be explained by smoking."

"Fruits and vegetables contain many different bioactive compounds, and it makes sense to assume that it is important that you not only eat the recommended amounts, but also consume a rich mix of these bioactive compounds by consuming a large variety," he said.

While previous research has shown the influence of the quantity of fruits and vegetables on cancer development, Stephen Hecht, Ph.D., editorial board member for Cancer Epidemiology, Biomarkers & Prevention, believes this study is one of the first to evaluate diversity of fruit and vegetable consumption, rather than quantity.

"The results are very interesting and demonstrate a protective effect in smokers. There are still over a billion smokers in the world, and many are addicted to nicotine and cannot stop in spite of their best efforts," added Hecht, who is the Wallin Land Grant Professor of Cancer Prevention at the Masonic Cancer Center, University of Minnesota.

Tobacco smoke contains a complex mixture of cancer causing agents. Therefore, a mixture of protective agents is needed to have any beneficial effect in reducing one's chance of lung cancer, Hecht said.

"Nevertheless, the public should be made aware and be reminded that the only proven way to reduce your risk for lung cancer is to avoid tobacco in all its forms," he said.

Cooked green vegetables, dried fruit, legumes, and brown rice associated with fewer colon polyps

Eating legumes (beans, peas, soybeans, chickpeas) at least three times a week and brown rice at least once a week was linked to a reduced risk of colon polyps by 33 percent and 40 percent respectively, according to Loma Linda University research recently published (August, 2011) in Nutrition and Cancer. High consumption of cooked green vegetables and dried fruit was also associated with greater protection, the study shows.

"Eating these foods is likely to decrease your risk for colon polyps, which would in turn decrease your risk for colorectal cancer," says lead author Yessenia Tantamango, MD, a post-doctoral research fellow with Adventist Health Study-2 at Loma Linda University. "While a majority of past research has focused on broad food groups, such as fruits and vegetables, in relation to colon cancer, our study focused on specific foods, as well as more narrowed food groups, in relation to colon polyps, a precursor to colon cancer.

Our study confirms the results of past studies that have been done in different populations analyzing risks for colon cancer."

Colon cancer is the second leading cause of cancer death in the United States and the third most common cancer in both men and women, according to the American Cancer Society.

Results also show that consuming cooked green vegetables once a day or more, as compared to less than five times a week, was associated with a 24 percent reduction in the risk of rectal/colon polyps. Consuming dried fruit three times a week or more, versus less than once a week, was associated with a 26 percent reduced risk.

The protective effects of these foods could be due in part to their cancer-fighting agents, the study reported.

"Legumes, dried fruits, and brown rice all have a high content of fiber, known to dilute potential carcinogens," Dr. Tantamango says. "Additionally, cruciferous vegetables, such as broccoli, contain detoxifying compounds, which would improve their protective function."

Past studies examining the effect of meat intake and legumes on colon cancer have shown that people eating meat, associated with an increased risk of colon cancer, may receive some protection when they also consume legumes. Dr. Tantamango says this suggests that besides fiber content, there may be something else present in legumes that provides a protective effect.

Researchers analyzed data from 2,818 subjects who participated in Adventist Health Study-1 (administered from 1976-77) and who answered a follow-up survey 26 years later from Adventist Health Study-2. The first survey asked respondents to indicate how often, on average, they consumed specific foods.

The follow-up survey asked respondents who had undergone colonoscopies to indicate physician-diagnosed colorectal polyps. During the 26-year follow-up, 441 cases of rectal/colon polyps were identified.

The study assessed several possible confounding factors, including a family history of colorectal cancer, education, physical activity level, alcohol intake, smoking, constipation, intake of sweets, pain medication, and multivitamins, as well as different food variables. The study then adjusted for those factors that were shown to distort the effect of the foods and food groups under study. About 25 foods and food groups in total were examined.

Dr. Tantamango says there is a need for future studies to examine foods shown to reduce the risk of colon polyps, since it is possible that interactions between various nutrients with anti-cancerous properties will be better able to explain these findings.

Vegetables Work in Cancer-Fighting Diet

Your vegetables are good for you, says a research review published March, 2011 by scientists from the University of Alabama at Birmingham in the journal Clinical Epigenetics.

In particular, vegetables such as broccoli and cabbage are filled with compounds that could help reverse or prevent cancers and other aging-related diseases as part of the “epigenetics diet,” a new lifestyle concept coined after the article’s publication.

“Your mother always told you to eat your vegetables, and she was right,” says co-author Trygve Tollefsbol, Ph.D., D.O., a biology professor in the UAB College of Arts and Sciences. “But now we better understand why she was right — compounds in many of these foods suppress gene aberrations that over time cause fatal diseases.”

Epigenetics is the study of the changes in human gene expressions with time, changes that can cause cancer and Alzheimer’s, among other diseases. In recent years, epigenetics research worldwide, including numerous studies conducted at UAB, have identified specific food compounds that inhibit negative epigenetic effects.

Those foods include soybeans, cauliflower, broccoli and cabbage. Green tea, fava beans, kale, grapes and the spice turmeric round out the diet.

“The epigenetics diet can be adopted easily, because the concentrations of the compounds needed for a positive effect are readily achievable,” says lead author Syed Meeran, Ph.D., a research assistant professor in Tollefsbol’s UAB Department of Biology laboratory.

For example, Meeran says sipping tea compounds called polyphenols in daily amounts that are equivalent to approximately three cups of green tea has been shown to reverse breast cancer in laboratory mice by suppressing the gene that triggers the disease. Similarly, a daily cup of broccoli sprouts, which has sulforaphane as an active compound, has been shown to reduce the risk of developing many cancers.

“Our review article has drawn everything together from global studies, and the common theme is that compounds in the epigenetics diet foods can, at the very least, help us lead healthier lives and help our bodies prevent potentially debilitating diseases like breast cancer and Alzheimer’s,” Tollefsbol says.