My diet includes 100 grams of protein a day from protein powder, that's on top of the protein I get from foods. Should I be concerned about eating too much protein? Is too much from supplements harmful? I am healthy and exercise most days, but I do have a family history of kidney failure.
Eating enough protein – from foods or supplements – can have many desired effects. A protein-rich diet can help build muscle, slow age-related muscle loss, maintain healthy bones, stave off hunger and, at least in the short-term, facilitate weight loss.
Protein's oft-touted promises have lead many people to think that more is better. Unlike a diet that's high in refined carbohydrates or fat, there's no downside to one that's packed with protein, right?
Not so fast.
A diet that's too heavy-handed in protein can lead to weight gain and perhaps, as recent research suggests, more serious health risks, prompting some experts to advise caution.
How much protein?
Protein foods (e.g., meat, poultry, fish, eggs, dairy, soy, legumes, nuts and seeds) supply amino acids which the body uses to build and maintain muscle, connective tissue, skin, tendons and bone. Amino acids are the building blocks of enzymes, hormones, immune compounds and brain neurotransmitters.
For sedentary people, the recommended dietary allowance (RDA) is 0.8 grams of protein per kilogram of body weight a day. So, if you weigh 190 pounds (86 kilograms) you need 69 g of protein each day, an amount that's found in six ounces of chicken plus three-quarters cup of Greek yogurt and one-half cup of lentils.
According to data gathered by Health Canada in 2004 and published in 2012, we're doing okay on the protein front. Ninety-nine to 100 per cent of adults – males and females – met daily protein requirements.
Who needs extra protein
The official RDA for protein may not be an optimal intake for muscle health.
Findings from a study published this month in the American Journal of Clinical Nutrition found that among 2,986 adults, average age 40, those who consumed the most protein (1.8 g per kg per day), whether from animal or plants, had significantly higher muscle mass and strength than those whose diets provided the RDA of 0.8 g per kg.
Older adults are thought to need more protein – about 1.2 g per kg per day – to preserve muscle mass and muscle function.
If you work out regularly, you do need more protein than the RDA. Depending on your sport, a daily intake of 1.2 to 2 g per kg body weight is needed to repair muscle breakdown that occurs during exercise.
Low-calorie dieters also need to rely on extra protein to prevent muscle loss that occurs from dieting. Research has shown that consuming protein in excess of the RDA, combined with resistance training, preserves muscle mass in people following a calorie-restricted diet.
Health risks of eating too much protein
There's a limit to how much protein your body can use. Eat more than you need and those protein calories will be tucked away as body fat. Not good if you're trying to shed a few pounds.
The kidneys filter waste products that come from protein digestion but there's no evidence that a higher protein diet damages healthy kidneys in healthy people. (High-protein diets can be harmful to people with kidney disease.)
Still, a family history of renal failure puts you at risk for kidney disease, so I don't recommend that you exceed your protein needs over the long term. (Major risk factors for kidney disease include diabetes and high blood pressure.)
There's concern among some experts that our obsession with protein has pushed us into unknown territory. There's no data on what years and years of eating too-large portions of meat or chicken – or gulping protein shake after protein shake – can do to our bodies.
It may do more than pile on extra calories. A study published in 2014 found that among 6,831 middle-aged adults (aged 50 to 65) those who reported eating a diet high in animal protein were four times more likely to die from cancer during the 18-year study period than those who consumed less protein.
Remember, though, observational evidence doesn't prove cause and effect. Even so, it's thought that excess protein may increase the activity of growth hormone and a growth factor called IGF-1, proteins that fuel the growth of cancer cells as well as healthy ones.
A diet high in animal protein has also been associated with a greater risk of Type 2 diabetes and cardiovascular disease mortality.
What about protein powder?
Despite its convenience, consuming multiple servings of protein powder each day may cause digestive upset, including bloating and diarrhea. A 2010 Consumer Reports analysis of 15 protein powders and drinks found low to moderate levels of heavy metals (arsenic, cadmium, lead, mercury) in most products. Over the long run, heavy metals accumulate in the body and may cause harmful effects.
Of course, by no means does this imply that all protein powders are contaminated.
Filling up on protein powder may also push important nutrients out of the diet that come from whole foods.
What to do?
If you're concerned you're eating more protein that you need, track your usual food intake for a week. Use an app or online tracker to determine the grams of protein you consume each day. Then, do the math to estimate how much protein is right for your body weight. Factor in your exercise level, your age (are you an older adult?) and whether you're on a low-calorie diet.
Consider where you get your protein from, too. Meet most of your needs from whole foods, rather than supplements. Make an effort to get some protein from plants.
Use protein powder to fill in the gaps or when convenience is needed, such as after a strenuous gym workout.