Effects of superfoods on risk factors of metabolic syndrome: a systematic review of human intervention trials.

Key points

Metabolic syndrome consists of a cluster of risk markers predisposing to the onset of type II diabetes mellitus and cardiovascular diseases (CVDs). The term “superfoods” has been introduced to describe foods with particular health benefits. The aim of the present systematic review is to provide an overview of foods described as superfoods including flaxseed, focusing on the results of controlled human intervention studies examining parameters related to metabolic syndrome. Twenty-two studies were identified. Twelve studies measured waist circumference, BMI or both. One study found a decrease in both waist circumference and BMI, five studies found a decrease in BMI, and one study found a decrease in waist circumference. In contrast, no changes in BMI were observed in six other studies. Systolic and diastolic blood pressure decreased in PAD patients and dyslipidemic subjects. In contrast, systolic and diastolic blood pressure did not change in healthy subjects. overweight adolescents and subjects with metabolic syndrome. Results on triacylglycerol concentrations are also conflicting.  Triacylglycerol concentrations were lowered in seven studies, but remained unchanged in the other ten studies. In one study, HDL cholesterol concentrations decreased, while in three other studies HDL cholesterol concentrations increased, and did not change in thirteen other studies. Finally, glucose concentrations were lowered in two studies, but not in the other five studies measuring glucose concentrations. It should be noted that this review focused on the effects of foods labelled as superfoods on markers related to metabolic syndrome and not on other potential health benefits. Conclusions may be different if other potential health benefits are considered.

ABSTRACT

Functional foods can be effective in the prevention of metabolic syndrome and subsequently the onset of cardiovascular diseases and type II diabetes mellitus. More recently, however, another term was introduced to describe foods with additional health benefits: “superfoods”, for which, to date, no generally accepted definition exists. Nonetheless, their consumption might contribute to the prevention of metabolic syndrome, for example due to the presence of potentially bioactive compounds. This review provides an overview of controlled human intervention studies with foods described as “superfoods” and their effects on metabolic syndrome parameters. First, an Internet search was performed to identify foods described as superfoods. For these superfoods, controlled human intervention trials were identified until April 2017 investigating the effects of superfood consumption on metabolic syndrome parameters: waist circumference or BMI, blood pressure, or concentrations of HDL cholesterol, triacylglycerol or glucose. Seventeen superfoods were identified, including a total of 113 intervention trials: blueberries (8 studies), cranberries (8), goji berries (3), strawberries (7), chili peppers (3), garlic (21), ginger (10), chia seed (5), flaxseed (22), quinoa (1), cocoa (16), maca (1), spirulina (7), wheatgrass (1), acai berries (0), hemp seed (0) and bee pollen (0). Overall, only limited evidence was found for the effects of the foods described as superfoods on metabolic syndrome parameters, since results were not consistent or the number of controlled intervention trials was limited. The inconsistencies might have been related to intervention-related factors, such as duration or dose. Furthermore, conclusions may be different if other health benefits are considered.