Protein, and the amino acids that form it, support key functions in our bodies so we do need to make sure we get enough. Depending on whom you talk to or what you read, however, you might get some different ideas regarding how much is too much or what is too little, and sometimes there are dire warnings given about people who fall out of the range. I was sent this article for critique by alert reader Jennifer that contained some warnings and reasonings that may or may not be accurrate: Are High Protein Diets Safe?
The author of this post does actually give a nice overview of the role protein plays in our body and of the need to get all the essentially amino acids. I also liked that it was pointed out that some sources of protein contain all of the essential amino acids (usually animal sources of protein), making them more efficient sources of protein, and some do not contain all the essential amino acids and so they are less efficient (Usually vegetable sources of protein). (This doesn't mean that they are bad or that they shouldn't be eaten every, just that they are less efficient). One of the things that was not pointed out, however, is that there are some health conditions and lifestyle choices in which a more "efficient" source of protein might be beneficial. Currently I work with a population of people tend to have poor appetites related to dementia, medications, surgeries, cancer treatments, etc. They may not have the desire to eat enough variety of beans, etc (or they don't have the energy level or assistance to cook these type of foods) to get all of the amino acids, so including eggs and other animal protein sources would usually allow them to get more protein with less patient/caregiver burden. I also work with a lot of people that have diabetes and have to carefully control their carbohydrate intake and would rather deal with eating animal protein sources so that they don't have to deal with the carbohydrates found in lentils, etc. I also have friends and relatives that are elite ultra-marathoners and triahtletes that require extra protein because of the additional stress their body goes through and don't want to eat all day so they choose to get their protein from animal sources. And then there are people, like yours truly, who have bowel/intestinal conditions that do not tolerate legumes or grains. (Please note that I am not AGAINST vegetarian diets for any of these conditions, it just depends on the level of work you can/want to do. I have math minded diabetic vegetarian clients who carefully controlly their legume intake so they can control the carb intake/blood sugar. There are vegan athletes who are willing to eat more often and eat more volume at one sitting to get their full contingent of amino acids. You can make this as simple or as complicated as you wish).
One of the other problems is the emphasis on saturated fat being all bad all the time. There have been multiple studies detailing this flawed assumption, and I will point you to this particular summary of the research here: What if saturated fat isn't so bad? Remember, we do actually need some fat for satiety and to make sure we get some omega-3 (and omega-6) which are essential fats--meaning our body needs to acquire them from food sources. You still want to avoid deep fried foods in order to avoid refined carbs, oxidated fats, excess omega-6s, and extra calories period, but that doesn't mean you have to avoid lamb and only eat oysters.
One thing I found interesting was the reaction that his advice to include soy caused a mild explosion on social networking sites. I have covered some of the myths regarding soy in a previous post, including that eating all soy, all day, all the time might not be a good idea (and neither is an overconsumption of anything else). Notice he said "soy is a way to get protein" not "eat soy in everything." Just a reminder for those of you feeling too lazy to follow my links, throwing some tofu or tempeh in as meat sub sometimes probably won't hurt you, but using processed soy all day might not be ok.
Before I address the comments about kidney function, etc, I want to address what a "high protein" diet actually is. First of all, most adults need roughly about 0.8-1 gm protein per kilogram body weight (Divide your weigh in pounds by 2.2 to get your weight in kg). (If you are overweight or obese I would find an online lean body mass calculator and use the same calculation but with your lean body mass). If you are an elite athlete, you probably need to go up to 1.5-2 gm protein per kg body weight. I have also seen a few small studies that use roughly about 1.5 grams of protein per kg in obese people, the reason being that people who are going to have to "diet" longer than those of us trying to lose 5-10 pounds will have to work harder at preserving their lean body mass. Just as a reference point, I have a weight and body fat in ranges that I am content with and my protein requirement is ~53-66 gm of protein per day. For me a "high protein" intake would be upwards of 80 or more grams of protein per day.
Back to kidney function, if you are a healthy individual in so much that you do not already have kidney disease, there is no evidence that a high protein intake will cause kidney damage (Link). Wait, go back and read that again--no evidence for healthy individuals. Now, if you already have known kidney damage the story does change, but it's only a slight change in that you probably just want to stay around 0.8 gm/kg. Unfortunately I am old enough to remember the days when we as healthy care providers used to put people on low protein diets (0.6 gm/kg) when they had decreased kidney function, but fortunately we had the opportunity to study this and find out a) there was no benefit and b) people who are in stage 3 and 4 kidney disease (where you are just about to go on dialysis) have a decreased appetite anyway and we just want them to eat--so telling people "you can't eat that" really does help the cause. I do want to state another caveat; sometimes the people who are going on carb controlled diets like Atkin's, etc are people who have been obese and/or had uncontrolled diabetes and high blood pressure for quite some time (this would be the population I work with); so while I have to applaud them for finally deciding to take better care of themselves, the damage to their kidneys is already done, so they need to be careful to get adequate protein but not go overboard. How do you know if you have kidney damage? If you have known prediabetes, diabetes Type 1 or 2, and/or high blood pressure, your physician should be doing the appropriate blood and urine exams on a regular basis and can tell you if you have any degree of kidney failure (so if you haven't been seeing a physician on regular basis, go!).
As far as protein intake and kidney stone formation, we are back to another gray area thanks to conflicting studies (Link). It appears that some people might have a genetic propensity to have uric acid stone formation and a high protein diet might exacerbate this. Since genetic testing is still not routinely done for this sort of condition, you have to look at your history and ask:
1) Do I have a history of uric acid kidney stones?
2) Do I have a near relative that has a history of kidney stones?
3) Do I have a condition like inflammatory bowel disease or bowel surgery (ex. Gastric Bypass surgery) ? (this alters how you absorb nutrients)
4) Do I have a condition like hyperparathyroidism?
If the answer to any of these questions is yes, you probably want to keep your protein intake to "normal" as listed above, drink plenty of water, and make sure you eat enough fruits and vegetables to keep your urine from being acidic.
When it comes to bone loss, we once again have, you guessed it, a gray area. It's entirely possible that the older you get the more careful you have to be about your protein intake to have healthy bones, as demonstrated in this study. Keep in mind that some people have a harder time absorbing nutrients, including protein, once they get to be "older," (which in the literature is usually about 65 years or more), so the higher protein intake might be more beneficial here but not so much for younger people.
One other topic I want to bring up that I didn't addressed in this article is the difference between what is written in books and what people do on their own. If you actually read the content of and look at the sample menus in books like "The New Atkins for the New You" and "Protein Power," etc the recommendation is to make sure you are getting an adequate amount of protein, not to gorge, and the sample menus might only contain about 70ish grams of protein, so even I wouldn't be too far off. So if someone tells you they had "x" problem with a particular diet, you have to wonder if they were really following it or if they went off on their own little excursion.
So what is SkepticRD's take home message from all of this? First of all, that we all need to figure out what our individual protein needs are, taking into account health conditions, health goals, exercise levels, etc. If you have a calculator, can read food labels, and have access to calorieking.com (or the like) you can figure this out and control the amount you eat. Second of all, not all of the scare tactics that have been used in an attempt to keep you off a particular diet might not apply to you or have evidence to back them up. Third, when it comes to making the choice between animal protein and vegetable protein, each individual has to consider their own health conditions and how much effort you are willing to put into getting.