Table 1.

The various low-protein diets offered in our Unit and included in this study

Type of diet	Protein restriction (g/Kg of body weight per day)	Main features	Notes
“Traditional”	0.6–0.8 g/Kg/day; mixed protein (animal and plant derived)	Modulated upon quantity of usual food; mainly based on the traditional Italian regional cuisines.	Often corresponds to what elderly patients already follow, in particular if they cook their own food from raw ingredients.
Vegan	0.6–0.8 g/Kg/day; vegetable protein	Protein intake in unrestricted vegan diets is on the average 0.7–0.9 g/Kg/day; due to the different bioavailability, a 0.7 diet roughly corresponds to a 0.6 mixed protein diet	This diet is based upon the integration of cereals and legumes at each meal, thus ensuring complementarity in amino acids. The 1–3 unrestricted meals per week are also crucial for this goal.
Vegan supplemented (moderate restriction)	0.6 g/Kg/day; vegetable protein, supplemented with amino- and keto-acids (Alfa-kappa or Ketosteril)	Based upon forbidden (animal origin) and allowed (all other) food. Animal-derived food is allowed in unrestricted meals. Supplementation with Alfa-kappa or Ketosteril pills is tailored upon nutritional status and clinical situation (1:8–1:10 Kg BW)	The supplements of amino- and ketoacids ensure protein complementarity without need to choose among plant derived food.
Protein-free food	0.6 g/Kg/day; mixed protein	Protein-free pasta, bread and other carbohydrates substituting for the usual bread, pasta or rice.	Since carbohydrates are the basis of the Mediterranean cuisine, their substitution allows subjects to easily reach a 0.6 g/Kg/BW diet
Very low-protein supplemented vegan diet	0.3 g/Kg/day; vegetable protein only, supplemented with Alfa-kappa or Ketosteril, with protein-free food	This diet is also based upon forbidden (animal origin) and allowed (all other) food. Animal-derived food is allowed only in “free meals” (usually no more than 1 per week) Supplementation with Alfa-kappa or Ketosteril pills is higher (1:5 Kg BW). Carbohydrates are mainly protein-free.	This diet merges the concepts of vegan supplemented and protein-free food. It is demanding and requires compliance to the high number of pills employed in supplementation. It is not prescribed as a “first line” diet.
Tailored solutions	Usually 0.6 g/Kg/day, vegetable or mixed	These solutions employ different combinations of protein-free food, vegan diets and supplementation.	The main reason for prescribing these diets is to take into account patients’ needs or preferences: an example: alternating vegan-supplemented meal and protein-free food.

BW body weight