Background: Nuts have been an indispensable component of the human diet for hundreds because of
their unique nutrient composition and are thought to play a beneficial part in the prevention of cardiovascular
Objective: To evaluate the extent, validity and presence of evidence for studies investigating the impact of nuts
intake on biomarkers of cardiovascular disease and cardiovascular events, we performed an umbrella review of all
published meta-analyses synthesizing data from both observational studies and randomized controlled trials.
Method: PubMed (between 1966 and April 2016) was searched for systematic reviews and meta-analyses.
Methodological quality was assessed by applying the AMSTAR score (0-11 points), and the meta-evidence by
applying NutriGrade, our recently developed scoring system (0-10 points).
Results: In total, 14 meta-analyses were included in the umbrella review. Only 4 out of 14 reported an AMSTAR
score ≥8 (high methodological quality), whereas NutriGrade meta-evidence score varied between 2 (very low
meta-evidence) and 7.9 (moderate meta-evidence). There is consistent evidence from intervention trials, reporting
significant reductions for total cholesterol, and from observational studies that higher intakes of nuts were
associated with reduced risk of cardiovascular disease and hypertension. On the other side no effect could be
observed for stroke, HDL-cholesterol, and blood pressure in the normal range.
Conclusion: In summary, the present umbrella review showed that nuts intake was associated with reduced risk
of cardiovascular disease and hypertension, and lower levels of total cholesterol. The observed evidence is limited
by the moderate methodological quality and very low to moderate quality of evidence.