Soy isoflavones may aid with sleep, says study

By Adi Menayang

- Last updated on GMT

Related tags Soybean

Photo: Christopher Bauer/Wikimedia Commons
Photo: Christopher Bauer/Wikimedia Commons
Can isoflavones found in soybeans help insomniacs get some sleep? Researchers in Japan, who studied more than a thousand participants from various walks of life, think so.

Recent data show a growing demand for sleep aid supplements, and consumers are looking for natural alternatives​. Researchers at Tohoku University in Japan found that isoflavones, found in soybeans, may have positive benefits for sleep-seekers.

The chemical structure isoflavone comprises a class of phytoestrogens, resembling human estrogen, which modulates sleep duration and quality​ in some populations, with weak estrogenic effects.

“Higher daily isoflavone intake was positively associated with optimal sleep duration and quality in a Japanese population,” ​wrote the authors in the Nutrition Journal​. “This finding suggests that daily isoflavone intake may have a potentially beneficial effect on sleep status.”

Naturally occurring ingredient in popular food

The researchers analysed 1,076 Japanese adults aged 20-78 years using self-administered diet history and sleep evaluation questionnaires. “To our knowledge, only two studies have examined the relationship between isoflavones and sleep​,” the researchers wrote. “No studies, however, have investigated the relationship between daily intake of isoflavone from food and sleep status in the general population,” ​they noted, adding that existing studies only analysed sleep disorders in postmenopausal women.

The typical isoflavone intake among subjects was measured using three soy foods common to the Japanese diet: natto, tofu, and fried tofu. Participants then were asked to indicate the mean frequency of consumption of these foods over the past month by checking one of seven frequency categories. 

Natto © yumehana
Natto.Image: © iStockPhoto / yumehana

Then, participants are asked to fill a questionnaire that included sleep-related questions, such as “how many hours do you usually sleep per day?” and “Do you usually feel refreshed after sleep?”

Causality clarification still needed

“Our results suggest that high daily isoflavone intake from food is significantly related to optimal sleep duration (7-8h) and better sleep quality,” ​the report said. A discovery not noted in past studies involving isoflavones and sleep is that the chemical structure can potentially be a sleep aid to various demographics.

“This relationship was not changed when adjusted for a number of potentially confounding variables, such as age, sex, BMI, total energy intake, coffee or vitamin consumption, smoking and drinking habits, level of education, occupation, depression, or hypnotic drug use,” ​the report said.

But more research is still needed to find out how exactly isoflavones aid with sleeping, if at all. “Prospective or intervention studies are required to clarify the causality,” ​the researchers wrote.

Source: Nutrition Journal
2015, 14​:127, doi: 10.1186/s12937-015-0117-x
"Relationship between daily isoflavone intake and sleep in Japanese adults: a cross-sectional study"
Authors: Y. Cui, et al. 

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