Protein, how much is too much?

TOO MUCH PROTEIN AND THE ACID ASH IT LEAVES AS RESIDUE

Consumers today are bombarded with health and dietary information that is both correct and incorrect, as well as ridiculous. The idea that an abundance of protein is required from several sources including meat, dairy and supplements is primarily generated by the American Dairy Association, United States beef industry, and the pharmaceutical and supplement providers rather than the Food and Drug Administration or the United States Department of Agriculture. During this review I will explain the protein amounts that are required, the findings of various studies and some of the harmful effects of excess ingestion of protein, both short term and long term.
Consumption of protein has an acidifying on the body. Barzel1 in her article “Excess dietary protein can adversely affect bone” explains that once the protein is digested, it leaves an acid ash which the body has to make more basic or alkaline so it can be excreted. Before we get into that, let’s discuss what the protein requirements are. Mahan and Escott-Stump in their book Krause's Food & Nutrition Therapy2(p 465) explain that the United States Recommended Daily Allowance (RDA) for adults is eight tenths of a gram of protein per day for each kilogram of body mass. So that means the RDA of protein for a one hundred eighty pound man is about sixty-five grams of protein for the day. One hundred eighty pounds converted to kilograms is approximately eighty-two kilograms, multiplied by point eight grams gives about sixty-five grams. If this man consumes a breakfast of three eggs, half pound of ham and a glass of milk that far exceeds (approximately seventy-five grams of protein) the daily intake allowance. If the individual has the audacity to actually have lunch and dinner, maybe a couple of quarter pound cheeseburgers and a nice twelve ounce steak with the fixings, they could easily quadruple (or more) the RDA for protein. Enough about the American intake, Mahan and Escott-Stump also include in their book the Dietary Reference Intakes (DRI) which are different for certain groups of people. For example in pregnant women(p 172) “There is an additional protein requirement for a pregnant women to support the synthesis . . . and fetal tissues.” Not enough protein during pregnancy can have bad effects and is usually accompanied with lack of energy intake, as well. Lactating women(p 287) require an additional twenty-five grams of protein which is more than fifty percent increase from a non-pregnant, non-lactating woman’s requirement of forty-six grams per day. Infants and children(p 227) require approximately 1.1 grams and .95 grams per kilogram of body mass, respectively.
Whatever the protein requirements are for any group of individuals, the fact remains that certain foods leave an acid ash1 when metabolized. These foods are cheeses, grains, fish, meat and meat products. While not as severe as those listed above, milk and non-cheese dairy products leave an acid ash as well. When this happens the body must take corrective actions to buffer this acidity. The best way to do this is other than consuming less protein and grains is to consume alkaline ash producing substances. What are alkaline ash producing foods? Table 11 gives the average potential renal acid loads (PRAL) of various substances. The items that have the lowest (negative) PRAL are fruits and vegetables along with red wine, white wine and some mineral waters. Back to the standard American dietary intake, not only is the average diet high in protein; it is low in vegetable and fruit intake. The body will do what it has to do to correct the acidity and survive. The kidneys will not allow urine with a potential for hydrogen (PH) below five to be excreted. They give an example of a 330 mL soda with a PH of about three would require one hundred times that amount of water (approximately 33 liters) to buffer the acid PH of the 1/3 liter of soda. Since this does not happen, the body buffers it chemically. It can use any alkaline substance in the body to buffer the acid. The ones most abundant in the body are calcium, phosphorus, magnesium and sodium. Urinary calcium increases when there is acid that needs to be buffered for expulsion. The test mentioned compares two groups the first with point eight grams of protein per day and the second with 2 grams of protein per day. “Urinary calcium nearly doubled with the higher protein diet.” The calcium has to come from somewhere and the bones are the biggest deposit of calcium around. Lutz and Linkswiler3 found similar results in their research on post-menopausal women. Their study observed eight subjects with dietary protein of fifty milligrams per day, then increased to one hundred and ten milligrams of protein per day. The subjects were supplemented to increase their calcium, magnesium and phosphorus intake up to 713, 323, and 1078 milligrams per day. They found that even when the subjects were receiving over seven hundred milligrams calcium per day, it was still not enough to balance their calcium intake to urinary calcium.
Allen4 in the article “Calcium bioavailability and absorption: a review” contends that the RDA of calcium may not be adequate and definitely does not apply to all groups. Also, that just because the calcium is available for absorption does not mean it will be absorbed. This is dependent on several different factors “such as calcium and vitamin D status, age, pregnancy, lactation, and disease, which affect the absorption of calcium once it is available in the intestinal lumen.” Certain amounts of calcium intake are lost in feces, sweat and sweat. These amounts do not deviate much when the amounts of dietary calcium change. Allen goes on to explain that dietary protein does not affect the bioavailability of calcium nor affect the absorption rate of the calcium. Increase in urinary calcium correlates to the increase of dietary protein, when the protein intake goes up the urinary calcium goes up. “The negative balance is not prevented by a high calcium intake.” The increase in dietary calcium is not adequate to rectify the acid residue from increase protein metabolism.
Kerstetter, O’Brien, and Insogna5 in their article “Dietary protein, calcium metabolism, and skeletal homeostasis revisited,” reviewed over twenty clinical research projects and found on average “for every 50 g increase in dietary protein, there is . . . 1.6 mmol increase in 24-h urinary calcium excretion.” They further state that with medium protein intake (100-150% of RDA) that calcium and skeletal metabolism stabilizes. They also contend that low protein intake leads to poor calcium absorption into the body, yet did not expound on the long term impact on bone health. They conclude that only thirty to fifty percent of Americans had “moderate” intake of protein. They were uncertain whether high protein intake caused increased absorption of dietary calcium. As well as whether the increase in bone resorption and the hypercalciuria were linked and what the long term results were in regards to fracture rate.
When Margen, C’hu, (et al) 6 published their “Studies in calcium metabolism. 1. The calciuretic effect of dietary protein” they directly and positively correlated the increase in urinary excretion of calcium with the increase in protein consumption. The study threw out the first three days of their controlled observations to rule out the affect of previous intake on their results. After that, any increase of protein directly resulted in increase in calciuria. The subject’s higher calcium level maintained itself at the new higher level and did not try to return to the previous average level. The increase in urine calcium was not proportional between subjects on the same diet. Some subjects had a large increase of calciuria with small increases in protein and others required a large increase of protein to increase the urine calcium. They found that “All of them, however, excreted more calcium in the urine whenever the protein intake increased.” On average the increase was over eight times when the subjects had an increase of ninety-six grams per day of nitrogen from protein. They determined that the overall effect of dietary protein on the urinary calcium can be shown as a percentage of urinary calcium during their study. This removes the effect of varying calcium intake from the calculations and directly relates it to the protein intake. This result was only for calcium, not the other minerals they observed such as magnesium, sodium, potassium, and phosphorus. They found no “consistent or significant” correlation to the urinary levels of these other minerals to the protein intake or the increase in urinary calcium.
The overall consensus from the research is that the amount of protein in the American diet can be detrimental. All but one project rule out the increase in dietary calcium as causing the increase in urinary calcium. Not only does the bone resorption required to buffer the acidifying effect of the metabolized protein cause immediate concern, the long term affect of the pulling calcium from the bones may be directly related to the problem of osteoporosis. In addition to that, this excessive buffering of the acid from too much protein causes the kidneys to be overloaded and overworked. This could potentially lead to renal failure. If Americans in general knew the amount of protein required and actually took action to modify their intake protein (and other acid ash producing foods) accordingly, along with increasing their consumption of fruits and vegetables, they could prevent this negative calcium affect of protein.
Reference Section
1. Barzel US, Massey LK. Excess dietary protein can adversely affect bone. J. Ntr. 1998;128:1051–1053.
2. Mahan LK, Escott-Stump S. Krause's Food & Nutrition Therapy, 12th Ed., St. Louis, MO: Saunders Elsevier Pub.; 2008.
3. Lutz J, Linkswiler HM. Calcium metabolism in postmenopausal and osteoporotic women consuming two levels of dietary protein, Am J. Clin. Nutr. 1981;34: 2178-2186.
4. Allen L. Calcium bioavailability and absorption: a review, Am J. Clin. Nutr. 1982;35: 783-808.
5. Kerstetter JE, O’Brien KO, Insogna KL. Dietary protein, calcium metabolism, and skeletal homeostasis revisited, Am J Clin Nutr 2003;78(suppl):584S–592S.
6. Margen S, C’hu JY, Kaufmannz, NA, Calloway DH. Studies in calcium metabolism. 1. The calciuretic effect of dietary protein. Am J Clin Nutr, 1974;27:584-589.