Protein is everywhere on the grocery and pharmacy shelves these days. There are protein shakes, protein bars, high protein cereals – you name it.
One reason for this emphasis on protein is that in the 1980s and 90s we were taught to fear fat, and in the 2000s we were told carbohydrates were bad – so that only leaves protein!
We do indeed need protein for health. There are a number of essential nutrients (specific amino acids) that the body does not manufacture and which come from dietary protein.
How much protein do we really need, and is too much bad for us?
The recommended amount of protein an average adult should eat is 0.8 grams per kilogram of body weight. Almost every adult in western countries gets this much or more. For an adult weighing 165 pounds, this translates to 60 grams protein per day. If you are trying to maintain or gain muscle mass, or if pregnant or nursing, you should increase this by 25%. This would include most older adults, who often lose muscle with aging.
Protein is available from a variety of foods, with fish, fowl and meat the most obvious but far from the only or even the best source. Dairy products, eggs, beans and lentils and nuts provide quality protein, as does soy. What should you avoid? Fatty cuts of meat and most processed meats (cold cuts, sausages, bacon, hot dogs) are bad for your heart and best minimized. If you are choosing hamburger, go for the 90+% lean packages.
Since all of the foods providing protein also provide different additional nutrients that we need, balance is key. Fish provides omega-3 fatty acids; meat provides iron; dairy products provide calcium and vitamins; legumes provide fiber and minerals.
Can you eat too much protein? Clearly yes, for a few reasons. Protein is our only source of nitrogen and tends to make the body acidic; the kidneys eliminate these toxins. If you have any degree of kidney impairment, excess protein can over-tax the body’s ability to cleanse the blood. Excess animal protein can lead to kidney stones. If you increase your protein intake without increasing exercise, you will probably take in too many calories and put on weight.
Most experts agree that the maximum an average adult should eat is 2 grams per kilogram body weight. For our average 165-pound adult, this is 150 grams per day. Take a look at your intake, and if you are way over this, probably wise to cut back.
And be sure to get your nutrition from a variety of sources. Protein, carbohydrates and healthy fats are all necessary for good health.
Edward Hoffer MD is Associate Professor of Medicine, part-time, at Harvard.
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