Plant proteins and tofu linked to lower heart disease risk

23 Mar 2020 --- Consuming tofu and foods rich in isoflavones – such as plant proteins – has been linked to lower risk of heart disease, especially for younger women and postmenopausal women not taking hormones. This is according to observational research, published in Circulation, the flagship journal of the American Heart Association (AHA). However, the researchers flag that the study should be interpreted with caution because their observations found a relationship, but did not prove causality. 

The research comes amid a boom in plant-based diets, which are increasingly popular among health-conscious consumers. “The Plant-Based Revolution” is pegged by Innova Market Insights as a pivotal trend set to shape the F&B landscape this year and onward. According to the market researcher, 2019 saw a 59 percent increase in plant-based claims in new product launches globally.

Plant-based for better heart health?
Researchers at Harvard Medical School and Brigham and Women’s Hospital in the US, analyzed data from more than 200,000 people who participated in three prospective health and nutrition studies. All participants were free of cancer and heart disease when the studies began. 

After eliminating a number of other factors known to increase heart risk, investigators found that consuming tofu, which is high in isoflavones, more than once a week was associated with a 18 percent lower risk of heart disease, compared to those who ate tofu less than once a month. Moreover, the favorable association with eating tofu regularly was found primarily in young women before menopause or postmenopausal women who were not taking hormones.

“Despite these findings, I don’t think tofu is by any means a magic bullet,” says lead author Qi Sun of Harvard’s T.H. Chan School of Public Health. “Overall diet quality is still critical to consider, and tofu can be a very healthy component.”

Qi Sun, M.D., Sc.D., Researcher, Harvard’s T.H. Chan School of Public Health, Boston, US.Sun underscores that populations that traditionally consume isoflavone-rich diets including tofu, such as in China and Japan, have lower heart disease risk compared to populations that follow a largely meat-rich and vegetable-poor diet. However, the potential benefits of tofu and isoflavones as they relate to heart disease needs more research.

In line with Sun’s observation, a recent study from Greece noted that plant-based diets have been widely promoted for cardiovascular disease (CVD) risk reduction, but not all kinds of plant-based diets are healthy. The research concluded that the health benefits of plant-based dietary patterns are not a given and differences may exist between men and women.

Tofu, which is soybean curd, and whole soybeans such as edamame are rich sources of isoflavones. Chickpeas, fava beans, pistachios, peanuts and other fruits and nuts are also high in isoflavones. Soymilk, on the other hand, tends to be highly processed and is often sweetened with sugar, Sun says. This study also found no significant association between soymilk consumption and lower heart disease risk.

“Other human trials and animal studies of isoflavones, tofu and cardiovascular risk markers have also indicated positive effects, so people with an elevated risk of developing heart disease should evaluate their diets,” Sun notes. “If their diet is packed with unhealthy foods, such as red meat, sugary beverages and refined carbohydrates, they should switch to healthier alternatives. Tofu and other isoflavone-rich, plant-based foods are excellent protein sources and alternatives to animal proteins.”

A large scale study
In the study, researchers analyzed health data of more than 74,000 women from the Nurses’ Health Study (NHS) from 1984 to 2012; around 94,000 women in the NHSII study between 1991 and 2013; and more than 42,000 men who participated in the Health Professionals Follow-Up Study from 1986 to 2012. 

Dietary data was updated using patient surveys, conducted every two to four years. Data on heart disease was collected from medical records and other documents, while heart disease fatalities were identified from death certificates.

A total of 8,359 cases of heart disease were identified during 4,826,122 person-years of follow-up, which is the total number of years that study participants were free of heart disease and helps to measure how fast it occurs in a population.

Sun flags that the findings cannot prove causality and that there are many other factors that can influence the development of heart disease, including physical exercise, family history and a person’s lifestyle habits. 

“For example, younger women who are more physically active and get more exercise tend to follow healthier, plant-based diets that may include more isoflavone-rich foods like tofu. Although we have controlled for these factors, caution is recommended when interpreting these results,” he warns.

In 2000, the US Food and Drug Administration (FDA) approved health claims that soy edibles protect against CVD. However, since then, clinical trials and epidemiological studies have been inconclusive, and the agency is reconsidering its now twenty-year-old decision. AHA’s 2006 Diet and Lifestyle Recommendations and a 2006 science advisory on soy protein, isoflavones and cardiovascular health found minimal evidence that isoflavones convey any cardiovascular benefits and any protections provided by higher soy intake was likely due to higher levels of polyunsaturated fats, fiber, vitamins and minerals, and lower levels of saturated fat.

Previously a US study also found that adhering to a plant-based diet over animal products may counteract unfavorable microbes known to increase risk of heart disease, especially in women.

 Edited by Kristiana Lalou