On Fri, 1 Jul 2005 17:20:31 +0200, Enrico C wrote in
<news:email@example.com> on it.salute.alimentazione :
Post by Enrico C Post by Filippo
30-40 gr di carboidrati.
In questa settimana devi fare molta attenzione ai cibi che assumi.
Dovresti aumentare un po' le proteine nei primi giorni (rispetto al tuo
fabbisogno standard) per contrastare un po' di catabolismo indotto dal
cambio di regime.
I carboidrati prendili esclusivamente da vegetali crudi (insalata verde,
radicchio rosso,zucchine,finocchi,ravanelli per esempio) questo per
contrastare/bilanciare l'acidità indotta da proteine e chetoni.
Sul contrasto dell'acidità da proteine, capisco, visto che il tutto passa
comunque per il PRAL renale, almeno secondo quanto afferma
quest'articolo che afferma l'importanza del PRAL nell'osteoporosi...
[su questo argomento dell'equilibrio acido-base, e sulla reale importanza
della dieta, dovrei ancora chiarirmi bene le idee...]
Mi pare che gli effetti, o meno, dell'acidità indotta dalla dieta siano
ancora oggetto di valutazione e discussione, insomma siamo al livello di
ipotesi, non si tratta di dati certi. Vedo che ci sono studi che confermano
l'ipotesi ma anche altri con risultatati contrastanti... Per esempio
(sul sito c'è il testo integrale, riporto solo l'Abstract)
American Journal of Clinical Nutrition, Vol. 77, No. 6, 1517-1525, June
© 2003 American Society for Clinical Nutrition
ORIGINAL RESEARCH COMMUNICATION
Protein intake: effects on bone mineral density and the rate of bone loss
in elderly women1,2,3,4
Prema B Rapuri, J Christopher Gallagher and Vera Haynatzka
1 From the Bone Metabolism Unit (PBR and JCG), Creighton University, School
of Medicine (VH), Omaha.
2 Presented at the 23rd Annual Meeting of the American Society for Bone and
Mineral Research, Phoenix, AZ, October 12-16, 2001.
3 Supported by research grants UO1-AG10373 and RO1-AG10358 from the
National Institutes of Health.
4 Address reprint requests to PB Rapuri, Bone Metabolism Unit, Creighton
University, School of Medicine, 601 North 30th Street, Room 6718, Omaha, NE
68131. E-mail: ***@creighton.edu.
Background: The role of dietary protein in bone metabolism is
Objective: We investigated the associations of dietary protein intake with
baseline bone mineral density (BMD) and the rate of bone loss over 3 y in
postmenopausal elderly women.
Design: Women aged 65-77 y (n = 489) were enrolled in an osteoporosis
intervention trial. We studied the associations of protein intake as a
percentage of energy with baseline BMD and the rate of bone loss in 96
women in the placebo group (n = 96). We also examined the effect of the
interaction of dietary calcium intake with protein intake on BMD.
Results: In the cross-sectional study, a higher intake of protein was
associated with higher BMD. BMD was significantly higher (P < 0.05) in the
spine (7%), midradius (6%), and total body (5%) in subjects in the highest
quartile of protein intake than in those in the lower 2 quartiles. This
positive association was seen in women with calcium intakes > 408 mg/d.
There was no significant effect of protein intake on hip BMD. In the
longitudinal study of the placebo group, there was no association between
protein intake and the rate of bone loss.
Conclusions: The highest quartile of protein intake (: 72 g/d) was
associated with higher BMD in elderly women at baseline only when the
calcium intake exceeded 408 mg/d. In the longitudinal study, no association
was seen between protein intake and the rate of bone loss, perhaps because
the sample size was too small or the follow-up period of 3 y was not long
enough to detect changes.
Key Words: WORDS Protein * bone mineral density * bone loss * calcium
intake * bone markers * calciotropic hormones * elderly * parathyroid
The relation between dietary protein intake and bone metabolism is
controversial, and questions about this relation are unresolved. Excess
dietary protein was shown to cause urinary calcium loss, negative calcium
balance, and bone loss in young and elderly men and women, and these
effects are mainly attributable to high acid load from metabolism of animal
protein (1-11). It has been proposed that bone buffers the excess acid
load, which results in urinary calcium loss that leads to reduced bone
mineral content and bone mass (12). The type of dietary protein has also
been suggested to play a role, but the results of studies on this aspect
remain unclear (13-19). At the other end of the spectrum, protein
undernutrition is suspected to be a risk factor for bone loss and
osteoporosis. There is convincing evidence from the literature that
indicates that low protein intake is associated with low bone mineral
density (BMD) (20-23) and greater fracture risk (24, 25). Studies of
protein supplementation after hip fracture in the elderly further
substantiate the importance of adequate protein intake in bone biology
The relations of dietary protein intake with BMD and bone loss in
postmenopausal women and the elderly, who have the highest risk of
developing osteoporosis, are not very clear. Among cross-sectional studies,
some showed a positive association between protein intake and BMD (20-22,
29, 30), whereas others did not find any such association (23, 31-34).
There are few longitudinal studies that examined the relation between
dietary protein intake and bone loss in postmenopausal women and the
elderly, and the results of these studies are conflicting. Freudenhiem et
al (32) and Hannan et al (18) reported that higher protein intake is
associated with lower rates of bone loss, whereas Nordin and Polley (35)
and, more recently, Sellmeyer et al (15) reported contrasting results.
Studies examining the association between dietary protein intake and
fracture risk also reported conflicting observations (14-16, 19, 26, 27).
Dietary calcium was shown to influence the association between dietary
protein and BMD by some researchers (17, 19, 36-39) but not by others (21).
Promislow et al (17) reported that under conditions of low calcium intake,
increasing protein intake increased BMD. On the other hand, Dawson-Hughes
and Harris (38) reported that in elderly subjects supplemented with calcium
and vitamin D, dietary protein was inversely associated with the rate of
bone loss. Feskanich et al (19) and Meyer et al (39) observed a positive
association between protein intake and fracture risk when calcium intake
was < 540 mg/d. In contrast, Kerstetter et al (21) reported that the
association between dietary protein intake and BMD is not related to
In the present study, we examined the association at baseline between
different dietary protein intakes and bone metabolism in postmenopausal
elderly women. Furthermore, in women receiving the placebo treatment, we
prospectively studied whether different baseline protein intakes influence
the rate of bone loss and changes in biochemical markers. In addition, we
examined whether dietary calcium intake influences the associations of
protein intake with BMD, biochemical variables, and the rate of bone loss
in both the population studied cross-sectionally and the population studied