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The latest research findings and discoveries from U of T faculty and students

Folic’s Effects

The synthetic version of a micronutrient found in broccoli may have role in breast cancer, study finds

January 31, 2011

While it may seem like nothing more than broccoli in a pill, folic acid is not entirely benign. New research suggests that at levels consumed by the average Canadian woman, it may increase the risk of breast cancer in offspring.

Pregnant women are advised to take 400 micrograms of folic acid a day, and since 1998, North American flour-based products have been fortified with it. As a consequence, the incidence of neural tube defects in the general population has been cut in half. But folic acid also plays a role in cancer, and while it’s often protective, it’s sometimes not.

Folic acid is a synthetic version of the micronutrient folate, which is found in foods like nuts, leafy green vegetables and orange juice. Consumption of micronutrients is known to affect whether our genes are switched on or off — so-called epigenetics — even if we consume them via our mothers’ diet, while we are developing in utero.

Young-in Kim and his colleagues at the University of Toronto wanted to know how consumption of folic acid both during gestation and after birth would affect breast tumour development. They fed pregnant rats either a normal diet or one supplemented with folic acid. Then, after they were weaned, the rat pups were randomised to be fed either a normal diet or a diet fortified with folic acid. Folic acid levels were the rat equivalent of a human intake of one milligram per day.

At puberty, or seven weeks of age, 70 pups from each group were injected with DMBA, an agent used in animal studies to induce breast tumour formation. Twenty-one weeks later, the animals were killed and their tumours were examined.

The researchers found that both rats that had been supplemented with folic acid in utero and rats that had been fed extra folic acid early in life had increased risk of breast cancer tumour formation. There was a higher incidence of tumours and they grew faster and earlier, the researchers report in the journal Cancer Research.

“There are a lot of benefits to maternal supplementation,” he says, “but there may be adverse effects too.” He suggests people try to get more of their folate through foods that contain it naturally, and that they avoid extra supplementation through nutritional drinks and bars.


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