The U.S. federal government has just released a new version of the food pyramid, recommending that Americans eat more protein than previously recommended.
Previously, the recommended daily protein intake was approximately 0.8g per kg of body weight. This recommendation was aimed at meeting the nutritional needs of the average sedentary adult. New dietary guidelines now suggest that you should consume between 1.2 and 1.6 grams of protein per kilogram of body weight per day.
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“It is unclear why this happened, but [Dietary Guidelines for Americans] We have increased our recommendation from 50% to 100%,” Alice Lichtenstein, an American Heart Association fellow and professor of nutritional science at Tufts University, told Live Science in an email.
Notably, scientists previously estimated that average protein intake for U.S. adults generally exceeded older guidelines. A 2013 study estimated 1.2 to 1.4 grams per kilogram of body weight per day, but the 2021 Dietary Data Summary states that men consume 97 grams and women 69 grams per day.
Nevertheless, the change in guidance raises some questions. Is there any benefit to increasing protein intake, and is there an upper limit that should not be exceeded?
Experts told Live Science that there is no single agreed upon maximum amount of protein that can be consumed in a day. That said, increasing your protein intake beyond previous recommendations may not be very beneficial, especially if you’re not active, the researchers said. Additionally, increasing protein intake at the expense of eating other macronutrients such as fat and carbohydrates is harmful.
Why is protein important?
Proteins are the building blocks of the body, forming everything from muscles and hormones to digestive enzymes and hemoglobin, which carries oxygen in the blood.
Protein-rich foods include meat, fish, eggs, tofu, beans, and nuts. The proteins in these foods are broken down by our bodies into their constituent parts, amino acids, which our cells use to make the proteins they need. While some amino acids can be produced by the body on its own, there are nine amino acids that can only be obtained from the diet, called essential amino acids.
A given person’s protein needs vary depending on a variety of factors, but one of the most important is the amount of exercise they do. So, in general, increased protein intake should be accompanied by increased activity levels, Lichtenstein told Live Science.
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“Most of the research I’m aware of does not demonstrate that increasing protein intake beyond current recommendations increases lean muscle mass,” she said. “If so, it needs to be combined with certain types of physical activity, which for most people is not an advantage.” Those types of activities may include, for example, strength training or endurance training.
Historically, it has been recommended that people who exercise regularly consume around 1.1 to 1.5 grams per kilogram per day, while those training for an athletic event may consume up to 1.7 grams per kilogram per day.
Especially active people need to get enough energy from carbohydrates and fats. Otherwise, the body may use amino acids as fuel, effectively increasing the amount of protein needed to compensate for the loss of protein building blocks in the body.
Another factor that affects protein requirements is age. As we age, the body’s ability to build new muscle protein is hindered, leading to muscle loss and weakness. Research suggests that consuming more protein (about 1 to 1.2 grams per kilogram of body weight per day) may help reduce these effects seen in middle-aged and older adults.
Effects of high protein diet
Research has shown that high protein diets, typically considered around 1.2 to 2 grams per kilogram of body weight per day, are linked to both positive and negative health outcomes.
In one review of research on this topic, researchers compared high- and low-protein diets and found that the former led to greater weight loss and therefore lower BMI. However, another review links high protein intake to decreased bone density and increased risk of kidney stones.
A study in humans and lab mice found that overconsumption of protein increases levels of the amino acid leucine, which can interfere with how immune cells clear plaque from blood vessels. This can increase your risk of heart attack and stroke. Based on this finding, the study authors suggested that consuming more than 22% of your daily calories (about 1.6 grams per kilogram of body weight) from protein may do more harm than good.
Leucine is found in a variety of animal and plant-based protein sources. Additionally, eating too many purine-rich protein sources, such as red meat, organs such as the kidneys, and certain types of seafood, can lead to gout and kidney stones.
“It’s important to note that there is no single official upper limit,” Bridget Cassady, RDN, Abbott, told Live Science via email. “The amount that is considered ‘excess’ varies based on your needs, which vary depending on your age, weight, activity level, and health status.”
But broadly speaking, healthy people can safely consume “reasonably high” amounts of protein (about 2 grams per kilogram per day) as long as it’s part of a balanced diet, Cassady said. Protein intake should not come at the expense of other nutrients. Once fiber-rich plants, healthy fats, or whole-food carbohydrates begin to be eliminated, that’s when protein intake can start to become a concern, she says.
In extreme cases, a very high-protein diet can put a strain on the kidneys, which can only filter so much urea, a protein waste product, from the blood at any one time. That’s why people with kidney problems are recommended to avoid high-protein diets, according to the Cleveland Clinic. If your urine is foamy or frothy, it means your urine contains high levels of protein and may indicate kidney damage.
This article is for informational purposes only and does not provide medical or dietary advice.
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