Grapes reduce heart failure associated with hypertension

A study appearing in the Journal of Nutritional Biochemistry¹ demonstrates that grapes are able to reduce heart failure associated with chronic high blood pressure (hypertension) by increasing the activity of several genes responsible for antioxidant defense in the heart tissue. Grapes are a known natural source of antioxidants and other polyphenols, which researchers believe to be responsible for the beneficial effects observed with grape consumption. This study, funded by a grant from the National Institutes of Health (NIH), and conducted at the University of Michigan Health System, uncovered a novel way that grapes exert beneficial effects in the heart: influencing gene activities and metabolic pathways that improve the levels of glutathione, the most abundant cellular antioxidant in the heart.

An estimated 1 billion people worldwide have hypertension, which increases the risk of heart failure by 2 to 3-fold. Heart failure resulting from chronic hypertension can result in an enlarged heart muscle that becomes thick and rigid (fibrosis), and unable to fill with blood properly (diastolic dysfunction) or pump blood effectively. Oxidative stress is strongly correlated with heart failure, and deficiency of glutathione is regularly observed in both human and animal models of heart failure. Antioxidant-rich diets, containing lots of fruits and vegetables, consistently correlate with reduced hypertension.

In this study, conducted at the University of Michigan Health System, hypertensive, heart failure-prone rats were fed a grape-enriched diet for 18 weeks. The results reproduced earlier findings that grape consumption reduced the occurrence of heart muscle enlargement and fibrosis, and improved the diastolic function of the heart. Furthermore, the mechanism of action was uncovered: grape intake "turned on" antioxidant defense pathways, increasing the activity of related genes that boost production of glutathione.

"Our earlier studies showed that grapes could protect against the downward spiral of hypertensive heart failure, but just how that was accomplished – the mechanism – was not yet known," said lead investigator E. Mitchell Seymour, Ph.D. "The insights gained from our NIH study, including the ability of grapes to influence several genetic pathways related to antioxidant defense, provide further evidence that grapes work on multiple levels to deliver their beneficial effects."

Seymour noted that the next phase of the NIH study, which will continue into 2014, will allow his team to further define the mechanisms of grape action, and also look at the impact of whole grape intake compared to individual grape phytonutrients on hypertension-associated heart failure.

"Our hypothesis is that whole grapes will be superior to any individual grape component, in each of the areas being investigated," said Dr. Seymour. "The whole fruit contains hundreds of individual components, which we suspect likely work together to provide a synergistic beneficial effect."

The insights gained from this research will further the knowledge on grapes and heart health, but will also provide translational information on the value of dietary (whole foods) and dietary supplement approaches for prevention of heart disease stemming from chronic hypertension.

"The NIH grant is allowing the team at the University of Michigan Medical System to expand its work in this important area and further highlight the multi-faceted role of grapes in supporting heart health," said Kathleen Nave, president of the California Table Grape Commission. "This work will also provide key insights into the role of whole fruit versus individual components of a fruit, using grapes as the benchmark."

Eating more red meat associated with increased risk of Type 2 diabetes

Eating more red meat over time is associated with an increased risk of type-2 diabetes mellitus (T2DM) in a follow-up of three studies of about 149,000 U.S. men and women, according to a report published Online First by JAMA Internal Medicine, a JAMA Network publication.

Red meat consumption has been consistently related to an increased risk of T2DM, but previous studies measured red meat consumption at a baseline with limited follow-up information. However, a persons eating behavior changes over time and measurement of consumption at a single point in time does not capture the variability of intake during follow-up, the authors note in the study background.

An Pan, Ph.D., of the National University of Singapore, and colleagues analyzed data from three Harvard group studies and followed up 26,357 men in the Health Professionals Follow-up Study; 48,709 women in the Nurses Health Study; and 74,077 women in the Nurses Health Study II. Diets were assessed using food frequency questionnaires.

During more than 1.9 million person-years of follow-up, researchers documented 7,540 incident cases of T2DM.

"Increasing red meat intake during a four-year interval was associated with an elevated risk of T2DM during the subsequent four years in each cohort," according to the study.

The results indicate that compared with a group with no change in red meat intake, increasing red meat intake of more than 0.50 servings per day was associated with a 48 percent elevated risk in the subsequent four-year period. Reducing red meat consumption by more than 0.50 servings per day from baseline to the first four years of follow-up was associated with a 14 percent lower risk during the subsequent entire follow-up.

The authors note the study is observational so causality cannot be inferred.

"Our results confirm the robustness of the association between red meat and T2DM and add further evidence that limiting red meat consumption over time confers benefits for T2DM prevention," the authors conclude.

(JAMA Intern Med. Published online June 17, 2013. doi:10.1001/jamainternmed.2013.6633. Available pre-embargo to the media at http://media.jamanetwork.com.)

Editors Note: This work was supported by grants from the National Institutes of Health. An author also made a funding disclosure. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.

Commentary: Oxygen-Carrying Proteins in Meat and Risk of Diabetes Mellitus

In an invited commentary, William J. Evans, Ph.D., of GlaxoSmithKline and Duke University, Durham, N.C., writes: "The article by Pan et al confirms previous observations that the consumption of so-called red meat is associated with an increased risk of type 2 diabetes mellitus (T2DM)."

"Perhaps a better description of the characteristics of the meat consumed with the greatest effect on risk is the saturated fatty acid (SFA) content rather than the amount of oxygen-carrying proteins," Evans continues.

"A recommendation to consume less red meat may help to reduce the epidemic of T2DM. However, the overwhelming preponderance of molecular, cellular, clinical and epidemiological evidence suggests that public health messages should be directed toward the consumption of high-quality protein that is low in total and saturated fat. … These public health recommendations should include cuts of red meat that are also low in fat, along with fish, poultry and low-fat dairy products. It is not the type of protein (or meat) that is the problem: it is the type of fat," Evans concludes.