Health for life

A high-fiber diet may have the clinical potential to control the progression of prostate cancer in patients diagnosed in early stages of the disease.

The rate of prostate cancer occurrence in Asian cultures is similar to the rate in Western cultures, but in the West, prostate cancer tends to progress, whereas in Asian cultures it does not. Why? A University of Colorado Cancer Center study published in the January 2013 issue of the journal Cancer Prevention Research shows that the answer may be a high-fiber diet.

The study compared mice fed with of inositol hexaphosphate (IP6), a major component of high-fiber diets, to control mice that were not. Then the study used MRI to monitor the progression of prostate cancer in these models.

"The studys results were really rather profound. We saw dramatically reduced tumor volumes, primarily due to the anti-angiogenic effects of IP6," says Komal Raina, PhD, research instructor at the Skaggs School of Pharmacy and Pharmaceutical Sciences, working in the lab of CU Cancer Center investigator and School of Pharmacy faculty member, Rajesh Agarwal, PhD.

Basically, feeding with the active ingredient of a high-fiber diet kept prostate tumors from making the new blood vessels they needed to supply themselves with energy. Without this energy, prostate cancer couldnt grow. Likewise, treatment with IP6 slowed the rate at which prostate cancers metabolized glucose.

Possible mechanisms for the effect of IP6 against metabolism include a reduction in a protein called GLUT-4, which is instrumental in transporting glucose.

"Researchers have long been looking for genetic variations between Asian and Western peoples that could explain the difference in prostate cancer progression rates, but now it seems as if the difference may not be genetic but dietary. Asian cultures get IP6 whereas Western cultures generally do not," Raina says.

Coffee consumption is associated with a lower risk of prostate cancer recurrence and progression, according to a new study by Fred Hutchinson Cancer Research Center scientists that is online ahead of print in Cancer Causes & Control.

Corresponding author Janet L. Stanford, Ph.D., co-director of the Program in Prostate Cancer Research in the Fred Hutch Public Health Sciences Division, conducted the study to determine whether the bioactive compounds in coffee and tea may prevent prostate cancer recurrence and delay progression of the disease.

Stanford and colleagues found that men who drank four or more cups of coffee per day experienced a 59 percent reduced risk of prostate cancer recurrence and/or progression as compared to those who drank only one or fewer cups per week.

They did not, however, find an association between coffee drinking and reduced mortality from prostate cancer, although the study included too few men who died of prostate cancer to address that issue separately.

First study to assess the link between tea and prostate cancer outcomes

Regarding tea consumption, the researchers did not find an associated reduction of prostate cancer recurrence and/or progression. The study also did not draw any conclusions regarding the impact of tea drinking on prostate-specific death.

“To our knowledge, our study is the first to investigate the potential association between tea consumption and prostate cancer outcomes,” the authors wrote. “It is important to note, however, that few patients in our cohort were regular tea drinkers and the highest category of tea consumption was one or more cups per day. The association should be investigated in future studies that have access to larger populations with higher levels of tea consumption.”

The population-based study involved 1,001 prostate cancer survivors, aged 35-74 years old at the time of diagnosis between 2002-2005, who were residents of King County, Wash. Participants answered questions regarding their diet and beverage consumption two years prior to prostate cancer diagnosis using a validated food frequency questionnaire, and were interviewed about demographic and lifestyle information, family history of cancer, medication use and prostate cancer screening history.

The researchers followed up with patients more than five years after diagnosis to ascertain whether the prostate cancer had recurred and/or progressed. Those who were still living, willing to be contacted and had been diagnosed with non-metastatic cancer were included in the follow-up effort.

Of the original 1,001 patients in the cohort, 630 answered questions regarding coffee intake, fit the follow-up criteria and were included in the final analysis. Of those, 61 percent of the men consumed at least one cup of coffee per day and 12 percent consumed the highest amount: four or more cups per day.

The study also evaluated daily coffee consumption in relation to prostate cancer-specific death in 894 patients using data from the initial food frequency questionnaire. After the median follow-up period of eight-and-a-half years, 125 of the men had died, including 38 specifically from prostate cancer. Daily coffee consumption was not associated with prostate cancer-specific mortality or other-cause mortality, but with few deaths these analyses were limited.

“Our study differs from previous ones because we used a composite definition of prostate cancer recurrence/progression,” said first author Milan Geybels, a doctoral student at Maastricht University in the Netherlands who was a graduate student in Stanford’s Prostate Studies group at Fred Hutch when the study was conducted. “We used detailed information on follow-up prostate-specific antigen levels, use of secondary treatment for prostate cancer and data from scans and biopsies to assess occurrence of metastases and cause-specific mortality during follow up. Using these detailed data, we could determine whether a patient had evidence of prostate cancer recurrence or progression.”

The results are consistent with findings from Harvard’s Health Professionals Follow-up Study, which found that men who drank six or more cups of coffee per day had a 60 percent decreased risk of metastatic/lethal prostate cancer as compared to coffee abstainers.

Phytochemicals in coffee have anti-inflammatory and antioxidant effects

Further research is required to understand the mechanisms underlying the results of the study, but biological activities associated with consumption of phytochemical compounds found in coffee include anti-inflammatory and antioxidant effects and modulation of glucose metabolism. These naturally occurring compounds include:

Caffeine, which has properties that inhibit cell growth and encourage apoptosis, or programmed cell death. Previous studies have found that caffeine consumption may reduce the risk of several cancer types, including basal-cell carcinoma, glioma (a cancer of the brain and central nervous system) and ovarian cancer.
Diterpenes cafestol and kahweol, which may inhibit cancer growth.
Chlorogenic acid, which, along with caffeic acid, can inhibit DNA methylation, a biochemical process involved in the development and progression of many cancer types.
Additional studies needed to confirm whether coffee can prevent cancer recurrence

The researchers emphasize that coffee or specific coffee components cannot be recommended for secondary prevention of prostate cancer before the preventive effect has been demonstrated in a randomized clinical trial. Further, there’s ongoing debate about which components in coffee are anti-carcinogenic, and additional large, prospective studies are needed to confirm whether coffee intake is beneficial for secondary prevention.

Coffee drinking may even be problematic for some men, Geybels said.

“Although coffee is a commonly consumed beverage, we have to point out that increasing one’s coffee intake may be harmful for some men. For instance, men with hypertension may be vulnerable to the adverse effects of caffeine in coffee. Or, specific components in coffee may raise serum cholesterol levels, posing a possible threat to coronary health. Patients who have questions or concerns about their coffee intake should discuss them with their general practitioner,” he said.

The investigators also noted limits to their study, which included a lack of data on how coffee consumption might have changed following diagnosis, whether the coffee that participants consumed was caffeinated or decaffeinated, and how the coffee was prepared (espresso, boiled or filtered), a factor that may affect the bioactive properties of the brew.

Decades worth of research shows that tea—the second most consumed beverage in the world—may help prevent chronic illnesses, including heart disease, certain types of cancer and type 2 diabetes. New research shows tea has been found to help promote weight loss and maintain a healthy weight, improve bone health and activate areas of the brain that bolster attention, problem solving and mood.

The December 2013 issue of the American Journal of Clinical Nutrition features 12 new articles about the relationship between tea and human health. Each paper is based on presentations from world-renowned scientists who participated in the Fifth International Scientific Symposium on Tea and Human Health, held at USDA in September 2012. Highlights of some of the compelling reports published through the AJCN include the following five papers:

Tea Leaf Polyphenols May Promote Weight Loss

Tea polyphenols and the caffeine content in tea increase energy expenditure and fat oxidation, providing benefits for achieving and maintaining an ideal body weight. The results of one meta-analysis suggests the increase in caloric expenditure is equal to about 100 calories over a 24-hour period, or 0.13 calories per mg catechins. In a related review, researchers concluded that subjects consuming green tea and caffeine lost an average of 2.9 pounds within 12 weeks while adhering to their regular diet. Population-based studies also show that habitual tea drinkers have lower Body Mass Indexes (BMIs) and waist-to-hip ratios and less body fat than non-tea drinkers. In addition, green tea and caffeine also appear to boost fat oxidation over 24 hours by an average of 16% or 0.02 grams per mg catechins.

Tea May Reduce Risk for Some Cancers

Green tea polyphenols may play a role in arresting the progression of certain cancers. For example, in a double-blind, placebo-controlled study, supplementation with 600 mg/d green tea catechins reduced the progression of prostate cancer. The researchers reported that after a year, 9% of men in the green tea supplemented group had progressed to prostate cancer whereas 30% of men in the placebo group had progressed.

Hundreds—if not thousands—of laboratory, epidemiological and human intervention studies have found anti-cancer properties in compounds present in tea. The types of cancer that have shown benefits of tea include cancers of the gastrointestinal tract, lung, prostate, breast, and skin. The proposed mechanisms of action for providing protection against cancer include antioxidant effects, inhibition of growth factor signaling, as well as improving the efficacy of chemotherapy agents.

Tea Catechins are Cardioprotective

Numerous studies suggest tea supports heart health and healthy blood pressure, and appears to be associated with a reduced risk of cardiovascular disease, including stroke and heart attack. New research, published in the AJCN provides further support. Study results published by Claudio Ferri, MD, University LAquila, Italy, found that black tea reduced blood pressure, and among hypertensive subjects, it helped counteract the negative effects of a high-fat meal on blood pressure and arterial blood flow. Hypertensive subjects were instructed to drink a cup of tea after a meal that contained 0.45 grams fat/lb. body weight. The results suggest that tea prevented the reduction in flow-mediated dilation (FMD), the ability to increase arterial blood flow that occurs after a high-fat meal. In a previous study conducted by Ferri, tea improved FMD from 7.8 to 10.3%, and reduced both systolic and diastolic blood pressure by -2.6 and -2.2 mmHg, respectively, in study participants.

"Our studies build on previous work to clearly show that drinking as little as one cup of tea per day supports healthy arterial function and blood pressure. These results suggest that on a population scale, drinking tea could help reduce significantly the incidence of stroke, heart attack and other cardiovascular diseases," concluded Dr. Ferri.

Tea Flavonoids Improve Bone Strength and Quality

Osteoporosis is a major public health concern but new research suggests that polyphenols in green tea may help improve bone quality and strength through many proposed mechanisms. In fact, one study found that tea drinking was associated with a 30% reduced risk in hip fractures among men and women over 50 years old. In a study of 150 postmenopausal women, researchers reported that 500 mg green tea extract (equivalent to 4-6 cups of green tea daily), alone or in combination with Tai Chi, improved markers for bone formation, reduced markers of inflammation and increased muscle strength in study participants. Numerous other studies have found that green tea flavanols provide a restorative effect to bone remodeling to help maintain bone density and slow bone loss.

Tea Improves Mood, Alertness and Problem Solving

Results from new research published in the American Journal of Clinical Nutrition found that drinking tea improved attention and allowed individuals to be more focused on the task at hand. In this placebo-controlled study, subjects who drank tea produced more accurate results during an attention task and also felt more alert than subjects drinking a placebo. These effects were found for 2-3 cups of tea consumed within a time period of up to 90 minutes. Several studies have evaluated the role of tea in strengthening attention, mood and performance, and the results have been promising. It is thought that the amino acid theanine and caffeine, both present in tea, contribute to many of teas psychological benefits.

Twelve internationally renowned researchers contributed to the AJCN supplement, including experts from USDA, National Institutes of Health, UCLA, University of Glasgow and University of LAquila, among others. "The scientists who contributed their original research and insights are among the best in the world, and together, this body of research has significantly advanced the science of tea and human health," said compendium editor Jeffrey Blumberg, PhD, Professor, Friedman School of Nutrition Science and Policy and Director, Antioxidants Research Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston.

"These new peer-reviewed papers add to the previously-published body of evidence that shows that tea can improve human health—both physically and psychologically," added Blumberg. "Humans have been drinking tea for some 5,000 years, dating back to the Paleolithic period. Modern research is providing the proof that there are real health benefits to gain from enjoying this ancient beverage."

AJCN published 12 new articles on the relationship between tea and human health including:

• Tea consumption and cardiovascular disease risk
  
• Human studies on the absorption, distribution, metabolism, and excretion of tea polyphenols
  
• Tea, flavonoids, and cardiovascular health: endothelial protection
  
• Acute effects of tea consumption on attention and mood
  
• Cancer prevention by green tea: evidence from epidemiologic studies
  
• Catechin- and caffeine-rich teas for control of body weight in humans
  
• Tea and flavonoids: where we are, where to go next
  
• Cellular targets for the beneficial actions of tea polyphenols
  
• Does tea prevent cancer? Evidence from laboratory and human intervention studies
  
• Tea and bone health: steps forward in translational nutrition
  
• Interactions of black tea polyphenols with human gut microbiota: implications for gut and cardiovascular health