Μιας και έχουν αναφερθεί τα γαλακτοκομικά στο παρών νήμα, παραθέτω μια αξιόλογη έρευνα (έχω χάσει κάμποσες σελίδες του νήματος και δεν γνωρίζω αν την έχετε βάλει ήδη), η οποία αναφέρει ότι η λήψη πρωτεΐνης & ασβεστίου από τα γαλακτοκομικά προϊόντα συνδέεται με τον καρκίνο του προστάτη (ή καλύτερα με το ρίσκο της εμφάνισης του καρκίνου και στην ουσία είναι ένα μέρος μιας "φήμης" που αναφέρεται καιρό και απλά δεν υπάρχουν αξιόλογα αποτελέσματα) και παρακάτω παραθέτω μόνο ένα μέρος της έρευνας:
Animal foods, protein, calcium and prostate cancer risk: the European Prospective Investigation into Cancer and Nutrition
In this prospective study of 2727 cases of prostate cancer,
the consumption of protein and calcium derived from dairy foods were significantly positively associated with risk.
Strengths of the EPIC study are its prospective design, the large number of prostate cancer cases and the wide range of animal food intakes.
We were also able to consider other possible risk factors such as education, marital status, alcohol intake, height, weight, energy intake, smoking and physical activity.
Our results are compatible with the hypothesis that a high intake of dairy protein is associated with increased prostate cancer risk (Gao et al, 2005).
Although we found no association with milk intake per se,
protein and calcium intake derived from dairy foods, and also yoghurt intake, were significantly associated with increased risk.
This apparent discrepancy may, in part, be because dairy protein and calcium are derived from a combination of dairy products, which on their own only exhibit a weak association with risk.
It has been hypothesised that the high protein content of dairy products may increase risk by increasing circulating levels of IGF-I, as shown in several cross-sectional studies and some intervention trials (Heaney et al, 1999; Hoppe et al, 2004).
Vegan men and women (who consume no dairy or other animal products) have significantly lower serum IGF-I levels than both lacto-ovo vegetarians and meat eaters, which may be due to their lower intake of essential amino acids.
Intervention studies have also shown that protein restriction can lower IGF-I levels in both animals and humans, and that the increases in IGF-I levels following re-feeding are strongly related to the essential amino-acid component of the diet.
The effects of protein and especially dairy protein on IGF-I could be important, because high serum IGF-I levels have been associated with a moderately increased risk of prostate cancer in several large-scale prospective studies.
However, few studies have reported on protein intake in relation to risk and, to our knowledge,
this is the first study to examine specifically the association of dairy protein in risk.
An alternative hypothesis is that dairy products may increase prostate cancer risk via their high calcium content, and our finding of a positive association with calcium intake is consistent with some, but not all, prospective studies.
It has been suggested that a high calcium intake may increase risk by suppressing the synthesis of 1,25-dihydroxyvitamin D, which has an antitumour effect on human prostatic cells in vitro.
However, a randomised controlled trial showed that, although long-term calcium supplementation (1.2 g calcium per day) slightly reduced serum 1,25-dihydroxyvitamin D concentrations, it was not associated with increased risk, although this trial was too small to exclude a moderate effect.
In addition, the evidence that circulating levels of either 1,25-dihydroxyvitamin D or its precursor 25-dihydroxyvitamin D are inversely related to risk is inconsistent.
Overall, the evidence that a high calcium intake affects risk through mechanisms related to vitamin D production appears limited.
It is possible that the association seen with dairy calcium intake may be due to its high correlation with other aspects of dairy foods, particularly protein, although it is difficult to separate out their independent effects.
Further, although the intake of nondairy calcium was low, the finding that it was not associated with risk suggests that another component of dairy foods may be of greater aetiological relevance.
Some studies have suggested that the associations with dairy foods and calcium intake are stronger for aggressive disease.
In the current study, although these associations were slightly stronger for high-grade disease and for men recruited before the age of 60 years, the differences between the groups were not significant, and there were no comparable differences between localised and advanced-stage disease.
Several previous studies have found that risk is particularly elevated in men with a total calcium intake (i.e., diet plus supplement intake) above 2 g day−1.
However, we had no information on supplement use and although the present study found a significantly elevated risk in the top fifth of dietary intake, the mean intake of this category, based on 24-h recall data, was 1.3 g day−1; less than 1% of the cohort had a dietary calcium intake of 2 g day−1 or more.
As such, we had limited power to assess whether very high calcium intake is associated with increased risk.
Our finding that total meat or red meat intake is not associated with prostate cancer risk is consistent with most previous prospective studies, although some found positive associations with red meat, hamburgers, beef or cooked processed meat for either total or advanced prostate cancer.
For fish, our results, which are based on a wide range of intake, provide no evidence that intake is associated with risk, and is consistent with most previous studies, although some have reported a negative or positive association.
Our study has some limitations. As in other large epidemiological studies, dietary intake is estimated using relatively simple dietary questionnaires that are subject to measurement errors leading to attenuated risk estimates. Nonetheless, the questionnaires in all EPIC centres were validated, and dietary intakes were calibrated with measures from a standardised 24-h diet recall method.
In conclusion,
the results from this large prospective study are consistent with the hypothesis that a high intake of protein or calcium from dairy products may increase prostate cancer risk.
