Lignans

In addition to much healthy fibre rye contains phytochemicals of great value for our health. One important group is the lignans, which of all grains consumed, are most abundant in rye. Most known lignans in rye are converted in the large bowel to enterolactone (ENL) that is the end product circulating in blood. Both plant lignans and ENL are excreted in urine in the conjugated form and in faeces mainly in the free form. Lignans are also abundant in some vegetables, fruits and seeds. ENL in plasma serves as a biomarker of lignan intake and microbial metabolism in the gut. Antibiotic intake reduces ENL formation and two of four studies have shown that antibiotics increase BC risk. Obesity and smoking are also associated with low ENL levels. In experimental studies rye bran, flaxseed, or lignans seem to protect against formation of aberrant colonic crypt foci and formation of polyps and cancer. Also prostate cancer risk may be influenced by whole-grain intake.

In case-control studies high plasma ENL values have been associated with low BC risk, but rarely in prospective studies. High lignan intake during adolescence is protective. The source of the lignans seems important. High intake of whole-grain e.g. rye bread intake is associated with high plasma ENL values and low risk of BC. Some researchers have found that only women with certain polymorphisms benefit from diets with much lignans. Several researchers have found that lignans protect against estrogen receptor negative BC. Women using hormone replacement therapy (HRT) and consuming much lignans have lower BC risk than those having low intake. Many experimental studies in APCmin mice have produced negative results.  Negative results have also been found in human studies but in those cases when food intake has been controlled, the values in plasma have derived from wine, juices or coffee and to lesser degree from whole-grain products. It is likely that whole-grain contains other phytochemicals that act synergistically with lignans and other compounds, like Vitamin E and alkylresorcinols.