"Given walnuts are a high-energy food, a prevailing concern has been that their long term consumption might be associated with weight gain," said Emilio Ros from Hospital Clinic of Barcelona in Spain.
"The preliminary results of the Walnuts and Healthy Ageing (WAHA) study demonstrates that daily consumption of walnuts for one year by a sizable cohort of ageing free-living persons has no adverse effects on body weight," said Ros.
"They also show that the well-known cholesterol-lowering effect of walnut diets works equally well in the elderly and is maintained in the long term," he added.
Participants were not given advice on total calorie and macronutrient intake or food substitution for walnuts. After one year, the study found that both diets had minimal effect on body weight, triglycerides, and high-density lipoprotein (HDL, or 'good') cholesterol.
However, the walnut-diet resulted in significant low-density lipoprotein (LDL, or 'bad') cholesterol reductions compared to the control, nut-free diet.
"As we continue the WAHA study, we will assess how walnut consumption may affect, among other outcomes, cognitive decline and age-related macular degeneration, conditions that were major public health concerns," said Ros.