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Eating sufficient amounts of vegetables might be good for overall health, but surprising results from a study suggested that their inclusion in the diet might have little or no effect on the risk of developing cardiovascular disease (CVD).
An investigation, led by the Nuffield department of population health at the University of Oxford, found that They said their findings, published in the journal Frontiers in Nutrition might mean that advice on vegetable intake and heart disease in high-income countries should be reappraised.
However, leading experts commented that the findings confirmed that higher overall vegetable consumption did lower the risk of cardiovascular disease.
UK Biobank data
Boosting health through a diet rich in vegetables has been backed by a large body of evidence, with guidelines consistently recommending them as a valuable source of macronutrients and micronutrients, such as dietary fiber, vitamins, and phytochemicals. However, the research team, which included the Chinese University of Hong Kong and the University of Bristol, set out to probe the independent effects of cooked and raw vegetables on health outcomes. Previous epidemiological studies had demonstrated inconsistent findings, they said.
They based their research on 399,586 people with no history of angina, stroke, and myocardial infarction, who enrolled in the UK Biobank. Of those, 55.4% were women, and 90.9% were of White ethnicity. The average body mass index was 27.3.
Raw and cooked vegetables
From their enrollment questionnaire, the mean intake of vegetables was found to be 2.3 heaped tablespoons per day of raw vegetables, and 2.8 of cooked vegetables. During an average follow-up of 12.1 years, 4.5% of the participants went on to develop CVD.
There was an inverse association between incident CVD and total and raw vegetable intake, but not cooked vegetable intake. Those who ate the most vegetables – both cooked and raw – had a 10% lower incidence of CVD, compared with those who ate the least. However, whereas raw vegetable intake was associated with an 11% reduction in CVD for those who ate the most, compared with the least, no reduction was seen for cooked vegetables.
Consuming two or more heaped tablespoons each day of cooked and raw vegetables was associated with a lower risk of dying from CVD, but little evidence was seen that a higher intake increased protection further. Similarly, there was evidence of an inverse association of CVD mortality with raw vegetable intake.
Researcher Qi Feng, from the Nuffield department of population health, said: “Our large study did not find evidence for a protective effect of vegetable intake on the occurrence of CVD. Instead, our analyses show that the seemingly protective effect of vegetable intake against CVD risk is very likely to be accounted for by bias from residual confounding factors, related to differences in socioeconomic situation and lifestyle.”
Expert opinions
Some clinical specialists took issue with the interpretation of the findings.
Dr. Dipender Gill, BMBCh, PhD, National Institute for Health Research clinical lecturer at St George’s, University of London, told the Science Media Centre that: “Many of the considered confounders that were adjusted for may actually represent mediating mechanisms. For example, vegetable consumption may reduce cardiovascular risk by lowering blood pressure and bodyweight, and improving glycaemic control.
“By adjusting for such traits, the authors may inadvertently be negating some of the mechanisms by which vegetable consumption is exerting beneficial effects.”
Tom Sanders, DSc, PhD, professor emeritus of nutrition and dietetics at King’s College London, said: “The conclusion that cooked vegetables may not be effective in reducing risk of cardiovascular disease may not be justified, especially as the group consuming the highest levels of vegetables were more likely to be receiving medication for high blood cholesterol and high blood pressure (i.e. this group was at higher risk of CVD), compared with those consuming the lowest intake.” He added: “These findings should not be taken to indicate that eating more vegetables has no benefit to health, especially cardiovascular health.”
Naveed Sattar, FMedSci, FRCPath, FRCPGlas, professor of metabolic medicine at the University of Glasgow, agreed. “In short, this paper should in no way change advice to eat at least five portions of fruit and vegetables a day,” he said. “Many living in the U.K. fall well short of this, sadly, and more needs to be done to encourage better intake of vegetables.
“In fact, I suspect we may have underestimated the importance of a healthy diet on health and disease in general.”
A version of this article first appeared on Medscape.com.
Eating sufficient amounts of vegetables might be good for overall health, but surprising results from a study suggested that their inclusion in the diet might have little or no effect on the risk of developing cardiovascular disease (CVD).
An investigation, led by the Nuffield department of population health at the University of Oxford, found that They said their findings, published in the journal Frontiers in Nutrition might mean that advice on vegetable intake and heart disease in high-income countries should be reappraised.
However, leading experts commented that the findings confirmed that higher overall vegetable consumption did lower the risk of cardiovascular disease.
UK Biobank data
Boosting health through a diet rich in vegetables has been backed by a large body of evidence, with guidelines consistently recommending them as a valuable source of macronutrients and micronutrients, such as dietary fiber, vitamins, and phytochemicals. However, the research team, which included the Chinese University of Hong Kong and the University of Bristol, set out to probe the independent effects of cooked and raw vegetables on health outcomes. Previous epidemiological studies had demonstrated inconsistent findings, they said.
They based their research on 399,586 people with no history of angina, stroke, and myocardial infarction, who enrolled in the UK Biobank. Of those, 55.4% were women, and 90.9% were of White ethnicity. The average body mass index was 27.3.
Raw and cooked vegetables
From their enrollment questionnaire, the mean intake of vegetables was found to be 2.3 heaped tablespoons per day of raw vegetables, and 2.8 of cooked vegetables. During an average follow-up of 12.1 years, 4.5% of the participants went on to develop CVD.
There was an inverse association between incident CVD and total and raw vegetable intake, but not cooked vegetable intake. Those who ate the most vegetables – both cooked and raw – had a 10% lower incidence of CVD, compared with those who ate the least. However, whereas raw vegetable intake was associated with an 11% reduction in CVD for those who ate the most, compared with the least, no reduction was seen for cooked vegetables.
Consuming two or more heaped tablespoons each day of cooked and raw vegetables was associated with a lower risk of dying from CVD, but little evidence was seen that a higher intake increased protection further. Similarly, there was evidence of an inverse association of CVD mortality with raw vegetable intake.
Researcher Qi Feng, from the Nuffield department of population health, said: “Our large study did not find evidence for a protective effect of vegetable intake on the occurrence of CVD. Instead, our analyses show that the seemingly protective effect of vegetable intake against CVD risk is very likely to be accounted for by bias from residual confounding factors, related to differences in socioeconomic situation and lifestyle.”
Expert opinions
Some clinical specialists took issue with the interpretation of the findings.
Dr. Dipender Gill, BMBCh, PhD, National Institute for Health Research clinical lecturer at St George’s, University of London, told the Science Media Centre that: “Many of the considered confounders that were adjusted for may actually represent mediating mechanisms. For example, vegetable consumption may reduce cardiovascular risk by lowering blood pressure and bodyweight, and improving glycaemic control.
“By adjusting for such traits, the authors may inadvertently be negating some of the mechanisms by which vegetable consumption is exerting beneficial effects.”
Tom Sanders, DSc, PhD, professor emeritus of nutrition and dietetics at King’s College London, said: “The conclusion that cooked vegetables may not be effective in reducing risk of cardiovascular disease may not be justified, especially as the group consuming the highest levels of vegetables were more likely to be receiving medication for high blood cholesterol and high blood pressure (i.e. this group was at higher risk of CVD), compared with those consuming the lowest intake.” He added: “These findings should not be taken to indicate that eating more vegetables has no benefit to health, especially cardiovascular health.”
Naveed Sattar, FMedSci, FRCPath, FRCPGlas, professor of metabolic medicine at the University of Glasgow, agreed. “In short, this paper should in no way change advice to eat at least five portions of fruit and vegetables a day,” he said. “Many living in the U.K. fall well short of this, sadly, and more needs to be done to encourage better intake of vegetables.
“In fact, I suspect we may have underestimated the importance of a healthy diet on health and disease in general.”
A version of this article first appeared on Medscape.com.
Eating sufficient amounts of vegetables might be good for overall health, but surprising results from a study suggested that their inclusion in the diet might have little or no effect on the risk of developing cardiovascular disease (CVD).
An investigation, led by the Nuffield department of population health at the University of Oxford, found that They said their findings, published in the journal Frontiers in Nutrition might mean that advice on vegetable intake and heart disease in high-income countries should be reappraised.
However, leading experts commented that the findings confirmed that higher overall vegetable consumption did lower the risk of cardiovascular disease.
UK Biobank data
Boosting health through a diet rich in vegetables has been backed by a large body of evidence, with guidelines consistently recommending them as a valuable source of macronutrients and micronutrients, such as dietary fiber, vitamins, and phytochemicals. However, the research team, which included the Chinese University of Hong Kong and the University of Bristol, set out to probe the independent effects of cooked and raw vegetables on health outcomes. Previous epidemiological studies had demonstrated inconsistent findings, they said.
They based their research on 399,586 people with no history of angina, stroke, and myocardial infarction, who enrolled in the UK Biobank. Of those, 55.4% were women, and 90.9% were of White ethnicity. The average body mass index was 27.3.
Raw and cooked vegetables
From their enrollment questionnaire, the mean intake of vegetables was found to be 2.3 heaped tablespoons per day of raw vegetables, and 2.8 of cooked vegetables. During an average follow-up of 12.1 years, 4.5% of the participants went on to develop CVD.
There was an inverse association between incident CVD and total and raw vegetable intake, but not cooked vegetable intake. Those who ate the most vegetables – both cooked and raw – had a 10% lower incidence of CVD, compared with those who ate the least. However, whereas raw vegetable intake was associated with an 11% reduction in CVD for those who ate the most, compared with the least, no reduction was seen for cooked vegetables.
Consuming two or more heaped tablespoons each day of cooked and raw vegetables was associated with a lower risk of dying from CVD, but little evidence was seen that a higher intake increased protection further. Similarly, there was evidence of an inverse association of CVD mortality with raw vegetable intake.
Researcher Qi Feng, from the Nuffield department of population health, said: “Our large study did not find evidence for a protective effect of vegetable intake on the occurrence of CVD. Instead, our analyses show that the seemingly protective effect of vegetable intake against CVD risk is very likely to be accounted for by bias from residual confounding factors, related to differences in socioeconomic situation and lifestyle.”
Expert opinions
Some clinical specialists took issue with the interpretation of the findings.
Dr. Dipender Gill, BMBCh, PhD, National Institute for Health Research clinical lecturer at St George’s, University of London, told the Science Media Centre that: “Many of the considered confounders that were adjusted for may actually represent mediating mechanisms. For example, vegetable consumption may reduce cardiovascular risk by lowering blood pressure and bodyweight, and improving glycaemic control.
“By adjusting for such traits, the authors may inadvertently be negating some of the mechanisms by which vegetable consumption is exerting beneficial effects.”
Tom Sanders, DSc, PhD, professor emeritus of nutrition and dietetics at King’s College London, said: “The conclusion that cooked vegetables may not be effective in reducing risk of cardiovascular disease may not be justified, especially as the group consuming the highest levels of vegetables were more likely to be receiving medication for high blood cholesterol and high blood pressure (i.e. this group was at higher risk of CVD), compared with those consuming the lowest intake.” He added: “These findings should not be taken to indicate that eating more vegetables has no benefit to health, especially cardiovascular health.”
Naveed Sattar, FMedSci, FRCPath, FRCPGlas, professor of metabolic medicine at the University of Glasgow, agreed. “In short, this paper should in no way change advice to eat at least five portions of fruit and vegetables a day,” he said. “Many living in the U.K. fall well short of this, sadly, and more needs to be done to encourage better intake of vegetables.
“In fact, I suspect we may have underestimated the importance of a healthy diet on health and disease in general.”
A version of this article first appeared on Medscape.com.
FROM FRONTIERS IN NUTRITION