From http://sportsnutritioninsider.insidefitnessmag.com/2100/sni-interviews-sports-nutrition-expert-lonnie-lowery-phd-rd
SNI: Which protein is best (if any) for promoting gains in skeletal muscle mass? Or are all proteins created equal?
Dr. Lowery: Well, there are plenty of very good protein sources, from meats to eggs to dairy. If I had to pick, I’d suggest whey or casein. Research varies somewhat as to which is superior for different age groups or times of the day but the dairy proteins seem to have real partitioning effects (preferentially helping one build muscle mass.) For me, it’s whey or a whey-casein blend pre- and post-workout, then casein like cottage cheese or a whey-casein supplement at bed time. I like whey-casein blends because of their versatility; the whey remains fast acting, raising circulating amino acids and protein synthesis while the casein portion clots in the gut for a more steady, ‘anti-catabolic’ effect. I do think eggs and moderately lean meats are a close second, though, due to other nutrients they provide.
There are several ways of determining protein quality, from biological value to protein effeciciency ratio, to the PDCAAS (protein digestibility-corrected amino acid score). If one considers the PDCAAS the ‘gold standard’ as many do, he can see that several proteins score very highly. Still, I try not to get bogged down by these ratings and consider the whole food and all it entails. For example, meats are solids and give one something tasty to chew on and enjoy, which is important for dietary compliance.
SNI:  Is there a finite amount of protein one should consume per meal?
Dr. Lowery: Fairly recent research on egg protein suggests the number is 20 grams per feeding – about three eggs or one scoop of protein powder. That dose could be different for other protein types. It’s not so much a question of ‘How much can I digest at one time?’ as many persons wonder, but rather the limitation stems from one’s internal anabolic environment. Once those amino acids enter the blood, there’s a certain requirement for anabolic hormones for example. Any amino acids not used for protein synthesis will just be stripped of their nitrogen and oxidized (burned) or used to make new blood sugar. Some dietitians will tell clients that excess protein becomes body fat but that’s mostly just a plausibility argument based on protein’s 4 kcal per gram. Ask yourself this; How many persons do you know who became obese eating skinless chicken breasts, egg whites and low-fat cottage cheese?
Also, some persons over-conclude that at a 20g ‘ceiling’, even with six meals per day, one would only ever need 120g of protein daily. Although this is a good number for many healthy persons, I personally think athletes with particular goals such as fat loss or recomposing their bodies, could consume more. And for those who feel ample protein intakes are unhealthy (which they are not), consider this; one has to eat *something* when he’s hungry! Protein foods are rich in other nutrients, satiating (filling, satisfying) and have a much higher thermic effect of food (TEF) than carbohydrates and fats.
SNI: What is your opinion on soy protein?
Dr. Lowery: I don’t think soy is a bad protein. Its PDCAAS is very high. Still, I remain a little wary that soy foods bring with them phytoestrogens that are still being studied as far as all of their health effects (breast cancer risk, etc.). Plus, after it’s track record of blunders, the agro-food industry doesn’t instill confidence in me. From this industry there is a LOT of promotion of soy – for example through sponsorship of professional dietetic events – and I sometimes worry about bias in the positive messages that get promulgated. I think that, for those who may be concerned but strive for dietary variety, going meatless once per week (with soy foods and others) can be a nice, moderate policy.
SNI: Why does the myth that high protein diets harm kidney function seem to persist? How do you combat such a myth?
Dr. Lowery: This is controversial but I sometimes think that there are longstanding professional issues of reputation, money and politics – as well as dogma – that tend to keep concerns over ample protein diets around. As Upton Sinclair once said; ”It is difficult to get a man to understand something when his salary depends on his not understanding it.’ For example, for decades dietitians have witheld protein from patients with kidney disease (which is itself less conclusive in the literature than one might think) and this has spilled over erroneously into recommendations for healthy populations. If I were a renal dietitian getting insurance company or government reimbursement for witholding protein from patients, I might not be especially critical of the practice. Or if my lauded and profitable nutrition care of overzealous athletes involved protein dissuasion, I might embrace what my colleagues believe or what introductory textbooks have told me rather than going outside my group to the primary literaure for a current, balanced view. Admitting I’ve been wrong all this time would be rough. I’m not saying this narrow-mindedness always happens but I am saying that my conversations with scientists tend to be very different in tone from the conversations I have with clinicians on the issue. I think there can be a disjoin or lag between the two groups. Change takes time and requires impetus. Maybe the nation’s obesity epidemic will serve as such an impetus to give (satiating, metabolism boosting, muscle-preserving) higher-protein diets a fairer shake.
In summary, consider this: Many clinicians and health educators are busy, are well paid for practicing the status quo, see the world in a bit more black-and-white way than do scientists, and move in fairly insular circles. They thus tend to stick to their guns. Unfortunately, those ‘guns’ can be almost silly when it comes to protein, as we catalogued in a 2009 ISSN paper. This documenting of what’s being taught – and comparing it to the actual (lack of) evidence thereon – is one way to combat the high protein myth.
SNI: What is the difference between a dietitian and a sports nutritionist?
Dr. Lowery: This depends on the state. Nutrition and dietetics licensure differs across the country, with some states requiring the Registered Dietitian credential (with follow-up state licensure) to give nutritional advice or to use titles like Nutritionist. Some states do not require this. There is also the more specific sports dietetics certificate but this is more optional, depending on one’s educational background. As a dietitian with a Masters in Nutrition and three degrees in Exercise Physiology including a doctorate, I for example would feel a bit silly going back to get this certificate in order to justify my involvement in exercise and sports nutrition.
I personally am glad that certificates from any particular group are not legal requisites. I do not feel that study for a four-hour exam on a Saturday is equivalent to a four-year degree (or more) in the field of interest. The university degree should obviously carry more weight. Certificates simply help document one’s expertise if he or she wants to do so. A sports nutrition certificate, from whichever group, is simply a way to prove one has successfully met the competency requirements in the included topics. It helps other professionals and consumers judge one’s expertise. I feel that certificates in a free market, with healthy competition, help consumers overall by presenting options and preventing monopoly by one potentially opinionated or insular group. Having said that, it is important for the public to have some idea which groups and which certificates are most rigorous and most legitimate.