This Review paper available on Google Scholar is not about PCa but I found it interesting. The Abstract and a couple of sections from the paper are reproduced below. The main things I take from the study are that it is ok to have a high protein diet if you are an older person (66+) but go easy on the protein from animal sources.
Review
The impact of dietary protein intake on longevity and metabolic health
Author links open overlay panelMunehiroKitadaabYoshioOguraaItaruMonnoaDaisukeKoyaab
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doi.org/10.1016/j.ebiom.201... rights and content
Under a Creative Commons licenseopen access
Abstract
Lifespan and metabolic health are influenced by dietary nutrients. Recent studies show that a reduced protein intake or low-protein/high-carbohydrate diet plays a critical role in longevity/metabolic health. Additionally, specific amino acids (AAs), including methionine or branched-chain AAs (BCAAs), are associated with the regulation of lifespan/ageing and metabolism through multiple mechanisms. Therefore, methionine or BCAAs restriction may lead to the benefits on longevity/metabolic health. Moreover, epidemiological studies show that a high intake of animal protein, particularly red meat, which contains high levels of methionine and BCAAs, may be related to the promotion of age-related diseases. Therefore, a low animal protein diet, particularly a diet low in red meat, may provide health benefits. However, malnutrition, including sarcopenia/frailty due to inadequate protein intake, is harmful to longevity/metabolic health. Therefore, further study is necessary to elucidate the specific restriction levels of individual AAs that are most effective for longevity/metabolic health in humans.
3.2. Human studies
Levine et al. investigated the relationship between the level of protein intake and all-cause, cancer- and diabetes-related mortality in a major nationally representative study of nutrition involving a United States population (6381 individuals aged 50 years and over) [6]. The results were analysed using Cox proportional hazard models and revealed that both the moderate protein (MP;10–19% of calories from protein) and high protein (HP; ≥20% of calories from protein) intake groups had higher risks of diabetes-related mortality than the participants in the low protein(LP; <10% of calories from protein) group (Table 1). Among those aged 50–65 years, higher protein levels were linked to significantly increased risks of all-cause and cancer-related mortality (Table 1). In this age range, the HP intake group exhibited a 74% increase in their relative risk of all-cause mortality and were >4-fold likely to die of cancer than those in the LP group. Additionally, the higher risks of all-cause and cancer-related mortality in the HP intake group compared to those in the LP intake group were further increased among those who also had high levels of IGF-1 [6] (Table 1). However, among those aged 66 years and older, the HP diet was associated with the opposite effect on all-cause and cancer-related mortality (Table 1). Compared to those in the LP group, the participants in the HP and MP groups exhibited a 28% and 21% reduction in all-cause mortality, respectively. Additionally, compared to those in the LP group, HP consumption resulted in a 60% reduction in cancer mortality. Thus, LP intake during middle age may be beneficial for the prevention of cancer and improvement of overall mortality. However, among elderly people, avoiding LP intake or consuming adequate dietary protein may be important to prevent sarcopenia and frailty, thus potentially preventing an increase in all-cause mortality.
Interestingly, on the Japanese island of Okinawa, many people exhibit increased longevity, and the centenarian population is five times larger than that in other developed nations [69]. The CVD and cancer death rates in Okinawa were found to be only 60–70% of those in other regions of Japan on average, and the all-cause mortality rate among 60- to 64-year-olds was only half that of other Japanese populations. Based on the 1972 Japan National Nutrition Survey, Kagawa et al. reported that the Okinawan adult population had a low caloric intake (83% of the Japanese average) and documented that the anthropometric and morbidity data of older Okinawans were consistent with CR [70]. Therefore, CR may be associated with the longevity observed in Okinawa [71]. In addition to CR, many factors, including food, genes and physical activity, contribute to longevity. The types of foods included in the traditional Okinawan diet, which includes a high intake of green leafy and yellow root vegetables, sweet potatoes (as a dietary staple), and soy (as the principle protein) supplemented with small amounts of fish and meat, are adequate in most nutrients [72,73]. The energy obtained from the Okinawan diet is derived from 9%protein and 85%carbohydrates [74]. Interestingly, the Okinawan values of dietary protein and the protein to carbohydrate ratio (1:10) are very low and are remarkably similar to those found to optimize the lifespan in recent animal studies investigating ageing.
4. Relationships among protein sources, longevity and metabolic health
The protein source, including animal or plant protein, may be more important for mortality risk than the level of protein intake. The associations between animal and plant protein intake and the risk of mortality were examined by a prospective US cohort study involving 131,342 participants and 32 follow-up years [7]. Animal protein intake was related to a higher risk of mortality, particularly CVD mortality. In contrast, higher plant protein intake was associated with lower all-cause mortality. The substitution of animal protein from a variety of food sources, particularly processed red meat, with plant protein was associated with a lower risk of mortality, indicating that the protein source is important for long-term health.
As described above, compared to LP intake in middle-aged humans, HP intake is associated with increased all-cause mortality and cancer- and diabetes-related mortality [6]. However, after controlling for the percent of calories from animal protein, the association between the level of protein intake and all-cause and cancer-related mortality was eliminated or significantly reduced, suggesting that animal protein mediates a significant portion of those relationships. In contrast, after controlling for the effect of plant protein, there was no change in the association between protein intake and mortality, indicating not only that high levels of animal proteins promote mortality but also that plant proteins have a protective effect.
Among animal proteins, the consumption of red meat and processed meat is associated with the risk of developing chronic diseases, including CVD, CKD, cancer and diabetes [8,9]. A meta-analysis indicated that a high consumption of red meat tends to increase the risk of CVD mortality and cancer and that a high consumption of processed meat significantly increases the risk of cancer and CVD mortality and diabetes [8]. Red meat is an important dietary source of EAAs and micronutrients, including vitamins, iron and zinc, that perform many beneficial functions. However, a high intake of red meat and processed meat results in an increased intake of saturated fat, cholesterol, iron, salt, and phosphate; oxidative stress/inflammation; elevation of by-products of protein or AA digestion by the gut microbiota, such as trimethylamine n-oxide or indoxyl sulfate; acid load; and protein/AA load, which are possibly associated with increased risks of CVD mortality and CKD.
BCAAs - Tyrosine, phenylalanine - protein powders
