Eat More Plants, Suffer Less Heart Disease? Not Exactly

Taking dietary advice from headlines is an iffy proposition. Today many headlines are telling us to eat more foods from plants and we’ll have less heart disease. The basis for this claim is two new studies in JAHA. The American Heart Association is pretty clear about the message it wants to send. Its press release says:

Eating More Plant Foods May Lower Heart Disease Risk in Young Adults, Older Women

But is this what the studies really show? Not exactly. These are good studies, but they are observational. So they don’t prove cause and effect as this headline suggests. Then there’s the issue of simply eating more plant foods to gain health. That’s not what these studies examined. Rather, they examined the benefits of following a high quality diet that emphasizes plant-based foods.

The difference may seem subtle, but it matters.

In Younger Adults

The first study followed 4,946 adults for 32 years, starting when they were between 18 and 30 years old. Researchers used a dietary score called APDQS as a measure of how much these young adults followed a high-quality plant-based diet. In short, they found a correlation between following a high-quality, plant-centered diet with less risk of heart disease in middle age. The risk reduction was 52 percent when comparing the top 20 percent of subjects to the bottom 20 percent by the quality of their diets. Risk also went down for people who shifted toward a higher quality diet during the study.

Two things are important to bear in mind. First, this finding is all about an association – not cause and effect. Second, this study focuses on diet quality and plant-based foods. Less healthful plant-based foods (e.g., veggie chips) don’t count for diet quality.

In Postmenopausal Women

The second study followed 123,330 women after menopause. In this study, the point of reference for a high-quality plant-based diet was the Portfolio Diet. For the women who followed it, researchers found fewer incidents of heart disease, heart attacks, stroke, heart failure, and atrial fibrillation. Again, this is an observational study, so it documents a correlation, not a cause and effect relationship.

And just as in the study of younger people, it’s a study of a high-quality, plant-based diet. Not just eating more plant-based foods of any kind.

Many Ways to Have a Healthful Diet

There are many healthful patterns for what to eat. Following a high-quality plant-based diet is one way to do it. It has added advantages for sustainability over diets that lean more on animal products. This is why so many thought leaders are emphasizing plant-based diets.

But simply eating more plants will not lead you to better dietary health if you don’t pay attention to the quality of the plant-based foods you eat. That means getting plenty of fiber, high-quality protein, and fresh, whole fruits and vegetables.

So headlines advising us to eat more plants to get less heart disease are slightly misleading.

Click here for the study in young adults, here for the study of postmenopausal women. For further reporting, click here and here.

Tata with Vegetables, painting by Zinaida Serebriakova / WikiArt

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August 5, 2021