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Eating a plant-based diet has been shown to be very good for your heart and your overall health, as well as that of the planet. In fact, a recent study found a young person could live an additional 13 years by eating more vegetables and legumes, as well as whole grains, fruit and nuts.
Which makes the findings of a new analysis of the diets of nearly 400,000 UK adults published Monday in the journal Frontiers in Nutrition rather startling: Eating veggies, especially cooked ones, doesn’t reduce your risk of heart disease over time.
“Our large study did not find evidence for a protective effect of vegetable intake on the occurrence of CVD (cardiovascular disease),” said Qi Feng, an epidemiologist at the Nuffield Department of Population Health at the University of Oxford, in a statement.
While the study found eating raw veggies could protect against heart disease, cooked vegetables did not. Any benefit went away when researchers factored in lifestyle factors such as physical activity, educational level, smoking, drinking, fruit intake, red and processed meat consumption, and use of mineral and vitamin supplements.
“Instead, our analyses show that the seemingly protective effect of vegetable intake against CVD risk is very likely to be accounted for by bias … related to differences in socioeconomic situation and lifestyle,” Feng said.
Not so fast, critics say
Don’t start celebrating yet, veggie haters. Experts in the UK and United States quickly took exception to the study’s conclusion.
“Although this study found that eating more vegetables wasn’t associated with a lower risk of heart and circulatory diseases once other lifestyle and other factors were taken into account, that doesn’t mean we should stop eating vegetables,” said Victoria Taylor, a senior dietitian at the British Heart Foundation, in a statement.
“There is good trial evidence that eating foods rich in fibre such as vegetables, can help lower weight, and improve levels of risk factors known to cause heart disease. The present observational study cannot overcome such evidence and its conclusions can be debated since the authors may have over adjusted for factors that account for lower intake of vegetables,” said Naveed Sattar, a professor of cardiovascular and metabolic medicine at the University of Glasgow in Scotland, in a statement.
“The results are not surprising. Picking out one single component and assuming just adding it to the diet, e.g., vegetables, is not likely to result in the desired effect,” Alice Lichtenstein, director and senior scientist at Tufts University’s Cardiovascular Nutrition Laboratory, told CNN in an email.
“One thing that has become clear over the past decade is we should not be looking at single foods or nutrients, rather the whole dietary pattern,” said Lichtenstein, who is also a Gershoff Professor of Nutrition Science and Policy at Tufts University.
Only 5 tablespoons of vegetables
The study used data from the UK Biobank, a longitudinal study of nearly a half a million UK adults designed to investigate how genetics and environment contribute to many common diseases.
People were asked at the beginning of the study how many raw and cooked vegetables they ate, and then followed for over 10 years to see if they developed heart disease.
On average, people in the UK study reported eating an average of 5 tablespoons of vegetables each day – that’s only 71 grams or one-third of a cup. About 2.5 tablespoons were raw vegetables, the other three were cooked.
“That’s so little,” said Dr. Andrew Freeman, co-chair of the American College of Cardiology’s Nutrition and Lifestyle Work Group.
Dietary guidelines in the UK call for five portions of fruits and veggies a day, with each portion being about 80 grams (1 cup), for a total of 5 cups a day.
In the US, dietary guidelines are more specific, recommending most adults eat at least 1.5 to 2 cups of fruit and 2 to 3 cups of vegetables each day as part of a healthy diet. Translating cups into tablespoons, a healthy intake of vegetables would include up to 48 tablespoons of veggies each day.
“That’s a ton of tablespoons,” Freeman said. “So the question is: If these people in the study were eating such a very small amount of vegetables, what else are they eating and how much did that confound these results?”
Gunter Kuhnle, a professor of nutrition at the University of Reading in the UK, also pointed to the impact of alternate food choices.
“People who don’t eat vegetables need to eat something else – and when estimating the health effect of eating vegetables it is important to consider what they replace,” Kuhnle said in a statement.
“Replacing a sugary snack with carrot sticks is likely to improve health – and have a beneficial effect on CVD risk. That wouldn’t be the case when replacing a whole-grain snack with carrots,” he said.
What’s the takeway for the vegetable eating (and hating) public?
“This is a very interesting study – but not one that should be used as a justification to stop eating vegetables,” Kuhnle said.
“The best advice we can give people is to focus on their whole diet, what foods to emphasize as well as what to minimize,” Lichtenstein said. “In general, I think the data still supports beneficial effects of a dietary pattern rich in fruits, vegetables, whole grains, legumes, fish, fat-free and low fat dairy and relatively low in added sugar and salt.”