Whole grains have several positive impacts on health.

Porvoo, Finland was the site last month of an international symposium, "Whole Grain and Human Health," organized by scientists at the VTT Technical Research Center (VTT Biotechnology, PO Box 1500, 02044 VTT, Finland). About 150 scientists and industry experts gathered to hear the latest on the health impact of whole grain foods. About 70 scientific contributions described effects on the metabolism of bioactive grain compounds and their influence on the risk of getting diabetes, cardiovascular disease and cancer.

The outer layers of the grain, often removed in milling processes and used as animal feed, contain a large part of the cereal dietary fiber. Current research has revealed the importance of the bioactive substances associated with this dietary fiber complex. Lignans, phenolic acids, phytate, sterols, tocotrienols and folate are examples of such compounds that are expected to play a role in maintaining human health.

Many recent epidemiological studies described at the symposium point out the significance of whole grains in decreasing the risk of coronary heart disease, diabetes and breast cancer. Studies in human subjects show improved regulation of blood glucose and insulin levels, reduction of cholesterol levels, increased levels of bioactive compounds in blood and improved gut function. Results are encouraging regarding the grain's ability to retard adenoma growth in animal models for cancer.

The roots of the symposium lie in the Nordic collaborative project "Rye and Health," coordinated by Kaisa Poutanen at VTT. The project focused on rye lignans, their uptake and conversion in humans, and their significance in reducing the risk of prostate and breast cancer. Lignans are diphenolic phytoestrogens located in the outer bran layers of rye grain. In addition to the commonly known plant lignans matairesinol and secolariciresinol, completely new lignan structures were identified in rye.

Rye lignans are efficiently converted to the mammalian lignan enterolactone in the fermentation by intestinal bacteria in the colon. The mechanism of absorption was studied in detail by the group of researchers at the Danish Institute of Animal Sciences. In animal and human experiments whole grain rye bread produced significantly higher levels of blood enterolactone than white wheat bread. Higher enterolactone levels are associated with reduced risk of coronary heart disease and breast cancer. The quick enterolactone analysis methods developed by Herman Adlercreutz at University of Helsinki have made these studies possible.

Rye contains alkylresorcinols, which also mainly locate in the aleurone fraction of the kernel. Endosperm, as well as white wheat flour, did not contain any detectable amounts of alkysresorcinols. In animal and human studies researchers found that 60% to 70% of these compounds are converted or absorbed in the upper parts of the gastrointestinal tract, indicating that they could be good biomarkers for the intake of whole grain rye. Scientists at the Swedish University of Agricultural Sciences are continuing the work by developing methods to analyze alkylresorcinols from urine and plasma samples.

Experiments show that adding fat to a rye diet abolishes the beneficial effects on tumor take, tumor cell apoptosis and tumor growth. Fat also decreases the urinary excretion of enterolactone. This shows that fat interacts with the formation of enterolactone in the gut, possibly by a reduced rate of fermentation.

At present the aggregated results from studies in humans are insufficient to permit conclusions indicating that rye or phytoestrogens are cancer-protective. There are, however, some studies pointing in that direction. A delay in clinical cancer may be very important from a public health perspective. Dietary intervention studies in humans are therefore needed.

Further information. Kaisa Poutanen; phone: [phone]; fax: [phone]; URL: www.vtt.fi/bel.