While there are potential benefits to a high-protein diet, like increased satiety and muscle retention, it’s important to be aware of the risks.
Excess protein in the body is related to several health concerns, especially if you follow a high-protein diet for an extended period.
High-protein diets may promise weight loss, but it may only be short term. Excess protein is usually stored as fat while the surplus of amino acids is excreted. This can lead to weight gain over time, especially if you consume too many calories while trying to increase your protein intake.
A 2016 study found that weight gain was significantly associated with diets where protein replaced carbohydrates, but not when it replaced fat.
Eating large amounts of protein can lead to bad breath, especially if you restrict your carbohydrate intake. In a 2003 registry, 40 percent of participants reported bad breath. This could be in part because your body goes into a metabolic state called ketosis, which produces chemicals that give off an unpleasant fruity smell.
Brushing and flossing won’t get rid of the smell. You can double your water intake, brush your teeth more often, and chew gum to counter some of this effect.
In the same 2003 study, 44 percent of participants reported constipation. This is because high-protein diets that restrict carbohydrates are typically low in fiber.
Increase your water and fiber intake. You may wish to track your bowel movements.
Eating too much dairy or processed foods, coupled with a lack of fiber, in your diet can cause diarrhea. This is especially true if you’re lactose intolerant or consume protein sources such as fried meat, fish, and poultry. Eat heart-healthy proteins instead.
To avoid diarrhea, drink plenty of water, avoid caffeinated beverages, and increase your fiber intake.
Your body flushes out excess nitrogen with fluids and water. This can leave you dehydrated even though you may not feel more thirsty than usual. A small 2002 study on athletes found that as protein intake increased, hydration levels decreased.
Increase your water intake to reduce this effect, especially if you’re an active person. Drink plenty of water throughout the day.
Following a high-protein diet for an extended period can increase your risk of kidney damage. Eating too much protein can also affect people who already have kidney disease. This is because of the excess nitrogen found in the amino acids that make up proteins.
Your kidneys have to work harder to get rid of the extra nitrogen and waste products of protein metabolism.
The same 2002 study from above found that consuming high amounts of protein led to abnormal BUN (one measure of kidney function), and a more concentrated urine. This may have been due to dehydration associated with the high protein rather than a direct result of the high protein itself.
Some good news was found in a 2012 study that looked at the effects of low-carbohydrate high-protein versus low-fat diets on the kidney. The study found that in healthy obese adults, a low-carbohydrate high-protein weight-loss diet over two years was not associated with noticeably harmful effects on renal filtration, albuminuria, or fluid and electrolyte balance compared with a low-fat diet.
Increased cancer risk
High-protein diets have been linked to an increase in cancer, possibly due to higher levels of meat-based protein consumption. Eating more meat is associated with colon, breast, and prostate cancer.
Studies have shown a decreased risk of cancer for people who don’t eat meat. Scientists believe this could be due, in part, to hormones, carcinogenic compounds, and fats found in meat.
Eating lots of red meat and full-fat dairy foods as part of a high-protein diet may lead to heart disease. This could be related to higher intakes of saturated fat and cholesterol.
According to this 2010 study, eating large amounts of red meat and high-fat dairy was shown to increase the risk of coronary heart disease in women. Eating poultry, fish, and nuts lowered the risk.
Diets that are high in protein and meat may cause calcium loss. This is sometimes associated with osteoporosis and poor bone health.
A 2013 review of studies found an association between high levels of protein consumption and poor bone health. However, another 2013 review found that the effect of protein on bone health is inconclusive. Further research is needed to expand and conclude upon these findings.