[Efectiveness of long-term consumption of nuts, seeds and seeds' oil on glucose and lipid levels; systematic review].

OBJECTIVE

The aim of this study was to determine the effectiveness of long-term consumption of nuts, seeds and vegetable oil (NSO) on weight, glucose, and lipid levels.

METHODS

We searched English articles published in Pubmed and Ebsco up to May 2011. Studies were included if they were randomized clinical trials, and had an intervention period of 24 or more weeks. Search terms include: "diabetes mellitus", "Nuts", "Diet Mediterranean", "Seeds", "Oils", "Canola oil", "Olive oil","Walnut", "Almond", "Pistachio", "Paleolithic diet", "High monounsaturated diet", "High polyunsaturated diet", "Soya" and "Sunflower".

RESULTS

Thirteen studies met the inclusion criteria; eight studies had a 24 weeks intervention period, one had 42 weeks, one had 48 weeks, and for the other three the intervention lasted 52 or more weeks. At 24 weeks a consistent increase of HDL levels and inconsistent improvement of weight, BMI, waist to hip index, A1C, total cholesterol, LDL: HDL, LDL, triglycerides, and diastolic blood pressure was observed. Four studies with an intervention ≥ 48 weeks showed no statistical difference, and in one study a reduction of weight, BMI, waist hip index, glucose, insulin, total cholesterol, HDL: cholesterol, triglycerides, and blood pressure was observed.

CONCLUSIONS

No evidence of long-term improvement of NSO on weight, glucose or lipids in the adult population was found.