The US Food and Drug Administration (FDA) might soon revoke soy's longstanding claim to boost cardiovascular health.
But now comes long-term research that appears to bolster the notion that soy does indeed do a heart good.
No major benefit
Canadian researchers pored over the results of 46 separate trials. Their conclusion: "These data strongly support the rationale behind the original FDA heart health claim for soy," said study lead author David Jenkins, a professor of nutritional sciences and of medicine at the University of Toronto.
Co-author John Sievenpiper, also a professor of nutritional sciences at the university, stressed that the overall benefit of soy for heart health wasn't major – just an average 5% reduction in cholesterol levels.
However, "if you put that together with other plant-based foods in a portfolio you get a much stronger effect," he said in a university news release.
The team's findings come as the FDA mulls possibly removing the right to a labelling claim that soy "may reduce the risk of heart disease", first approved by the agency in 1999.
In an announcement issued in October 2017, the agency said it was considering revoking the claim, "based on our review of the totality of publicly available scientific evidence currently available".
The FDA said that evidence "does not support our previous determination that there is significant scientific agreement among qualified experts for a health claim regarding the relationship between soy protein and reduced risk of coronary heart disease".
Consistency is important
It's thought that the FDA will make a decision on the issue this summer.
But the Toronto researchers say their review shows a consistent and long-term cardiovascular benefit.
They looked at the same 46 trials the FDA cited in its 2017 announcement, and found reductions in LDL ("bad") cholesterol and total cholesterol among people who ate lots of soy. The benefit appeared steady across all 46 trials, they added.
That consistency is important, Sievenpiper said.
In some data reviews, "analyses with small studies produce big effects that diminish over time as sample sizes increase and results get more precise. We saw that with fish oil, for example," he said. "But in this case, nothing has changed."
In Jenkins' view, "these data strongly support the rationale behind the original [supportive] FDA heart health claim for soy".
The new analysis received no direct funding from the soy industry. However, a university news release states that "Jenkins and Sievenpiper have received support from government, nonprofit and industry funding sources, some of which include companies and industry groups that produce or promote soy and other plant-based foods".
Two nutrition experts had varying views on the new data.
Michelle Milgrim is a registered dietitian who directs employee wellness at Northwell Health in Lake Success, New York. Reading over the findings, she said soy probably has a "modest" benefit to heart health.
"The bottom line: soy protein can still be enjoyed as part of an overall healthy diet, but you may want to consider additional actions to help reduce your risk for heart disease – exercise, smoking cessation, stress reduction, maintaining a healthy weight, and routine visits with your doctor," Milgrim said.
Nutritionist Katrina Hartog said the new review has some flaws, however.
An age of plant-based protein
In fact, the "limitations of this study would be similar to limitations associated with the proposed FDA soy health claim reversal," she said. These limitations include "the fact that some studies included in the analysis compared soy with a variety of alternative foods, and other studies used soy flour, added to high-temperature foods, which can possible damage the soy protein structure and thus reduce the effectiveness of soy protein".
In Hartog's opinion, "With or without the health claim, soy foods are generally good for the heart and blood vessels if they replace less healthful choices such as red meat or high-fat protein foods."
Jenkins agreed with that notion.
"We're moving into an age of plant-based protein, and it would be a shame to see that shift undermined" by the FDA rescinding soy's heart-healthy label, he said.
The findings were published in the Journal of the American Heart Association.
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