DEAR DR. BLONZ: You mentioned that excess dietary protein could increase mineral losses in a recent column. Can you say more about that? Is excess protein hard on the kidneys that have to filter out all that nitrogen, too?
Many Americans do eat excessive protein, whether because of high-protein diets like paleo, our addiction to and overindulgence in meat, or the intense marketing of protein shakes/bars. Are we harming ourselves via mineral loss while also damaging the environment by raising and consuming so much meat? -- L.F., Pleasant Hill, California
DEAR L.F.: Proteins, which are made up of chains of amino acids, are involved in many functions (for details, see b.link/m6n36h). There is, however, no practical way for the human body to store unused protein for later use.
When we consume more protein than the body needs, the excess gets converted to energy (fat) -- something the body is quite efficient at storing. But before this conversion can take place, the amino group must be removed from every amino acid. This becomes "ammonia" waste, which ends up in queue for disposal through the urine. As long as we are adequately hydrated and nourished, there shouldn't be any problems having our kidneys carrying out this routine assignment.
Amino groups on their own have negative charges, meaning they need to pair with positively charged "escorts" before they can leave the body through the urine. Calcium ions have a positive charge and can serve this purpose, but they are not the primary or only choice for this role. There are plentiful positive buffering compounds in any balanced diet with healthful amounts of fruits and vegetables. If, however, little else is around, calcium -- which is always present in the blood -- can get the call. If significant calcium leaves the body in this way, hormones will cause calcium to be pulled from the bones to maintain the required blood level.
The bottom line is that some calcium can indeed be lost when one eats a high-protein diet, but this will be more of an issue with diets lacking the recommended balance of plant foods. Unfortunately, the people who overdo it with protein often lack such well-balanced diets.
Finally, as to your last point: Shifting from a diet that is heavy on animal/protein foods to one that is more plant-based is, indeed, healthier for the environment. A paper in the August 2015 journal Public Health Nutrition studied this topic. The paper reported that producing a pound of protein from beef required approximately 18 times as much land, 10 times the water, nine times the fuel, 12 times the fertilizer and 10 times the pesticides as producing the same amount of protein from legumes, such as kidney beans.
We should all be aware that even minor dietary shifts to include more plant foods can help us all, if done by enough of us.
Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to email@example.com. Due to the volume of mail, personal replies cannot be provided.