A study that has just been published in Japan reveals that post-menopausal women who consume seaweed regularly have a higher rate of developing some forms of cancer.
The 14-year national survey collected responses from nearly 53,000 Japanese women. The women were between the ages of 40 and 69.
The study found that for the group there was a reported 134 thyroid cancer cases which including 113 cases of papillary carcinoma, a common type of the cancer.
The figures from the study show that women who consumed seaweed daily were 1.7 times more likely to develop cancer than those who ate it only two times a week, according to the study.
But the study also found that the risk of developing these cancers more than doubled among post-menopausal women who were about 3.8 times more likely to develop that type of cancer.
"Seaweed consumption was clearly associated with an increased risk of papillary carcinoma," according to the study, which was conducted by the National Cancer Center and National Institute for Environmental Studies.
Researchers were not sure why post-menopausal women had an increased risk of developing cancer, but they are guessing it might have to do with iodine found in seaweed, according to research published in the European Journal of Cancer Prevention.
Researchers explained that Japanese women were at a higher risk given that seaweed is a widely consumed food in Japan.
The survey did not say precisely how much seaweed participants consumed during 1993 and 2007- the period focused on by the study.
"It is believed that the increased risk of developing thyroid cancer from seaweed consumption after menopause is related to changes in female hormone concentrations," according to Takehiro Michikawa, a member of the research team.
"We'd like to conduct further research. Post-menopausal women should take care not to eat too much seaweed," she continued.