"Mediterranean Diet Reverses Metabolic Syndrome"
Eating a Mediterranean diet supplemented with either nuts or extra-virgin olive oil as opposed to eating a low-fat diet was more likely to reverse metabolic syndrome 5 years later, in a new study. This was largely due to a greater likelihood of having a smaller waist by following Mediterranean diet or having decreased blood glucose levels by eating the diet that was supplemented with nuts.
However, the onset of metabolic syndrome in participants who did not have it at baseline was similar in all three diet groups.
These findings, from the PREDIMED study, were published October 14, 2014 in CMAJ.
"Our study provides evidence that long-term adherence to an energy-unrestricted Mediterranean diet supplemented with extra-virgin olive oil or nuts—which is high in monounsaturated fat and bioactive antioxidants—could be an useful tool in the management of metabolic syndrome among individuals at high cardiovascular risk, especially in those with central obesity and hyperglycemia or frank diabetes," Dr Jordi Salas-Salvadó (Universitat Rovira i Virgili, Reus, Spain) told heartwire .
The Mediterranean diet as a whole, rather than any individual component of it, appears to be responsible for improving a person's metabolic profile, he stressed.
PREDIMED highlighted that healthy fat can be beneficial, while consuming too many carbohydrates can be harmful. "During the past decades, a low-fat diet was promoted worldwide, and as a consequence people consume too many refined carbohydrates," Salas-Salvadó noted.
Effect of Diet on Cardiovascular Risk Factors
Previously, as described by heartwire , the authors reported that that 1-year data from 1224 participants in PREDIMED showed that adhering to a Mediterranean diet supplemented with nuts was more likely to reverse metabolic syndrome than following a low-fat diet.
The current study looked at data from the final PREDIMED cohort after a median of 4.8 years (range 2 to 8 years) to determine the long-term effects of a Mediterranean diet on metabolic syndrome.
Participants were classed as having metabolic syndrome if they met three criteria related to fasting glucose, blood pressure, triglycerides, HDL cholesterol, and waist circumference.
From 2003 to 2009, PREDIMED randomized men aged 55 to 80 and women aged 60 to 80 who had either diabetes or at least three risk factors for cardiovascular disease to one of three nutrition interventions.
Two groups received a Mediterranean diet—one supplemented with about 1 L of extra-virgin olive oil a week, and one supplemented with 30 g/day of walnuts, hazelnuts, and almonds. The control group was instructed to reduce their fat intake from all sources.
The current study analyzed data from 5801 participants in PREDIMED.
At baseline, 3707 participants (63.9%) had metabolic syndrome. During follow-up, half of the participants without metabolic syndrome developed it; the risk was similar in all three diet groups.
Of 3392 participants who had metabolic syndrome at baseline and had follow-up data available, 28.2% experienced reversal of this syndrome.
Compared with participants who followed a low-fat diet, the hazard ratio for reversal of metabolic syndrome was 1.35 among those who followed a Mediterranean diet supplemented with extra-virgin olive oil and 1.28 in those who followed a Mediterranean diet supplemented with nuts.
Changes in body weight and physical activity were small and similar in the three groups.
"In fact, the novelty of our findings is that the higher reversion rate of metabolic syndrome that was . . . observed in those individuals allocated to the Mediterranean diet . . . must be attributed to differences in diet, as no differences in weight loss or energy expenditure from physical activity occurred between interventions,"Salas-Salvadó said.
Possible Explanation for Dietary Impact on Metabolic Syndrome
"Many Mediterranean-diet constituents are likely to be beneficial on metabolic-syndrome reversion by ameliorating several metabolic-syndrome components," Salas-Salvadó noted.
For example, olive oil is very rich in monounsaturated fatty acid (MUFA), and replacing saturated fatty acid with MUFA improves lipid profile and insulin sensitivity, he observed. Olive-oil consumption is associated with lower risk of developing hypertension. Nuts are also rich in MUFAs, except walnuts, which are higher in polyunsaturated fatty acids. Nuts also contain substantial amounts of dietary fiber, magnesium, potassium, and antioxidant vitamins (ie, folate, vitamin E).
The Mediterranean diet emphasizes eating fruits, vegetables, and seeds, many of which contain minerals, polyphenols, and other phytochemicals that combat oxidative stress, inflammation, and insulin resistance, Salas-Salvadó noted. For example, legumes are associated with a better lipid profile and with improved glucose and inflammatory responses.
Salas-Salvadó serves on the board of and has received grant support from the International Nut and Dried Fruit Council; he has received consulting fees from Danone and grant support from Eroski and Nestlé. Disclosures for the coauthors are listed in the article.