Antibiotics Found to Counteract Benefits of Whole Grain Foods


Whole grains are a staple of the traditional, healthy diet. Rich in fiber and full of nutrients, whole grains are recommended by nutritionists and doctors to create a balanced diet and healthy body. However, the use of antibiotics may neutralize the benefits of whole grains, rendering them useless in terms of health.

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Whole grains, specifically unrefined grains such as oatmeal and rye, carry a high content of lignans. One they enter the system, lignans are metabolized by gut bacteria into enterolignans. Enterolignans are associated with reduced risk of heart disease and improved cardiovascular health, and can possibly reduce the risk of certain types of cancers, especially in women. The effect of antibiotics on lignans is more noticeable in women as well.

The Aarhus University and The Danish Cancer Society collaborated on this study, which details the effect of high antibiotic use on lignans through whole grain consumption. It is part of a larger report entitled, “Diets, Cancer, and Health.” This report follows approximately 57,000 Danish people from the year 1993 through 1997.

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For the purpose of the study, the researchers gathered biological tissue such as blood and adipose tissue. The participants also provided detailed survey information on their diets and lifestyle health habits. In particular, the group of participants who developed cancer during this time were brought under observation. Over 2,200 people were in this group.

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They found that in almost all cases among women, those who used antibiotics within three months of testing their blood showed significantly lower levels of enterolignans. They showed levels up to 40 percent lower than those who had not used antibiotics during this time. This shows the long-term effect of antibiotics on enterolignan levels, even after several months.

“The results confirm our hypothesis, and also point towards the importance of maintaining a restrictive use of antibiotics. You will not achieve the full beneficial effects of whole grain, when the intestinal bacteria are negatively affected by antibiotics. Most likely, it also applies to a number of other compounds present in the diet and which require microbial conversion in order to have a positive effect on health,” said Knud Erik Bach Knudsen. Knudsen is part of the Department of Animal Science at Aarhus University.

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The researchers confirmed their findings through further experimentation, using pigs as the subjects in a separate study. They had two groups of pigs, both of which were supplied with a similar diet of whole grains; one group was given higher doses of antibiotics. In the antibiotic group, the pigs showed 37 percent less lignans in their blood samples than the control group. This is an almost direct reflection of the “Diets, Cancer, and Health” study.

Knudsen stated that “this is the first time that an animal experiment confirms a direct relationship between enterolignan concentrations and antibiotic treatments.” He urges researchers to take up further study on the effect of antibiotics on lignan levels, as these findings could possibly relate to other medications as well.