The protein diet has gained immense popularity in recent years, with many individuals seeking to leverage its potential benefits for weight loss, muscle gain, and overall health improvement. While high-protein diets (HPDs) have demonstrated promising outcomes in various clinical trials, it is essential to understand both the advantages and potential risks associated with this dietary approach.
Introduction
Obesity has become a global epidemic, posing serious health risks and contributing to the development of various chronic diseases, including metabolic syndrome, non-alcoholic fatty liver disease, type 2 diabetes, and cardiovascular diseases. In response to this growing concern, many individuals turn to dietary interventions, such as the protein diet, to achieve a negative energy balance and promote weight loss. However, it is crucial to approach such diets with caution and a comprehensive understanding of their potential effects on the body.
Benefits of a High-Protein Diet
Weight Loss and Body Composition
Several clinical trials have demonstrated that consuming more protein than the recommended dietary allowance (RDA) can effectively reduce body weight (BW) and enhance body composition. Specifically, HPDs have been shown to decrease fat mass while preserving fat-free mass (FFM) in both low-calorie and standard-calorie diets. This is particularly beneficial because maintaining FFM during weight loss helps sustain resting energy expenditure, which is crucial for long-term weight management.
A meta-analysis of 24 randomized controlled trials (RCTs) revealed that individuals on HPDs experienced a significant reduction in BW (-0.79 kg), fat mass (-0.87 kg), and blood triglycerides (-20.3 mg/dL), as well as a significant increase in FFM (0.43 kg) and resting energy expenditure (REE; 595.5 kJ/day) compared to those on standard-protein diets (SPDs).
Furthermore, fairly long-term clinical trials of 6-12 months reported that HPDs provide weight-loss effects and can prevent weight regain after weight loss. This is a significant advantage, as many energy-restricted diets carry the risk of post-loss weight regain due to increased hunger and decreased fullness.
Read also: Protein Coffee Smoothie Recipe
Satiety and Appetite Regulation
HPDs have been shown to increase satiety and reduce appetite through various hormonal and metabolic mechanisms. Specifically, HPDs increase the levels of anorexigenic hormones, such as glucagon-like peptide-1 (GLP-1), cholecystokinin (CCK), and peptide tyrosine-tyrosine (PYY), which reduce appetite. At the same time, they decrease the levels of orexigenic hormones, such as ghrelin, which enhances appetite. This results in increased satiety signaling and, eventually, reduced food intake.
Additionally, elevated diet-induced thermogenesis (DIT), increased blood amino acid concentration, increased hepatic gluconeogenesis, and increased ketogenesis caused by higher dietary protein contribute to increased satiety.
Increased Energy Expenditure
HPDs increase energy expenditure through two primary mechanisms:
- Higher Diet-Induced Thermogenesis (DIT): Proteins have a markedly higher DIT than carbohydrates and fats, meaning that the body expends more energy to process and store protein.
- Preservation of Fat-Free Mass (FFM): Protein intake prevents a decrease in FFM, which helps maintain resting energy expenditure despite weight loss.
Bone Health
Contrary to some concerns, HPDs have not been shown to have adverse effects on bone density in healthy adults. In fact, low protein intake is generally considered a nutritional deficiency and has been described as a factor affecting osteoporosis development in older adults.
A meta-analysis of 74 RCTs observed that subjects in the HPD group (16%-45% of total daily energy intake as protein) were not significantly different from low-protein-diet subjects (5%-23% of total daily energy intake as protein) with regard to bone mineral density of the lumbar spine and hips.
Read also: Wound Healing: The Protein Connection
Furthermore, a study reported that protein intake was negatively correlated with bone loss in older adults. Overall, high protein intake can help prevent bone loss in older adults who are prone to nutritional deficiency.
Renal Function
Similarly, concerns that HPDs may deteriorate renal function have not been substantiated in healthy individuals. A study found no declining renal function in obese adults with normal renal function over two years of HPD consumption. Nevertheless, they reported increased calcium level in urine with neither reduction in bone mineral density nor urolithiasis, calling for further studies.
Another study also reported no association of high protein intake with change in glomerular filtration rate (GFR) in females. While HPD does not affect renal function in healthy people, it can adversely affect renal function in people with kidney disease.
Risks of a High-Protein Diet
While HPDs offer several potential benefits, it is crucial to be aware of the potential risks and take appropriate precautions.
Bone and Calcium Homeostasis
A diet that is high in protein generates a large amount of acid in body fluids. The kidneys respond to this dietary acid challenge with net acid excretion, and, concurrently, the skeleton supplies buffer by active resorption of bone resulting in excessive calcium loss. Moreover, acid loading directly inhibits renal calcium reabsorption leading to hypercalciuria in combination with the exorbitant bone loss.
Read also: The ultimate guide to protein coffee benefits.
In a metabolic study an increase in protein intake from about 47 to 112 g caused an increase in urinary calcium and a decrease in calcium retention. The data indicated that protein-induced hypercalciuria was due to an elevation in glomerular filtration rate and a lower fractional renal tubular reabsorption of calcium, the latter of which caused by the increased acid load on the renal tubular cells
In a prospective study, protein was associated with an increased risk of forearm fracture for women who consumed more than 95 g per day compared with those who consumed less than 68 g per day. Women who consumed five or more servings of red meat per week also had a significantly increased risk of forearm fracture compared with women who ate red meat less than once per week
Notably, it has been shown that the consumption of high calcium diets is unlikely to prevent the negative calcium balance and probable bone loss induced by the consumption of high protein diets (protein-induced hypercalciuria).
Kidney Stones
Low fluid intake and excessive intake of protein are important risk factors for kidney stones. Protein ingestion increases renal acid excretion, and acid loads, in turn, may be buffered in part by bone, which releases calcium to be excreted by the kidney. This protein-induced hypercalciuria could lead to the formation of calcium kidney stones
Furthermore, animal protein is also the major dietary source of purines, the precursors of uric acid. Excessive intake of animal protein is therefore associated with hyperuricosuria, a condition present in some uric acid stone formers.
Cancer Risk
Up to 80% of breast, bowel, and prostate cancers are attributed to dietary practices, and international comparisons show positive associations with high meat diet. The association, however, seems to have been more consistently found for red meat or processed meat and colorectal cancer.
Possible mechanisms include the formation of heterocyclic amines in meat when it is cooked. These heterocyclic amines require acetylation by P450 enzymes, and individuals with the fast-acetylating genotype who eat high amounts of meat may be at increased risk of large-bowel cancer.
Moreover, NH3 and N-nitroso compounds (NOC) formed from residues by bacteria in the large bowel are probably also important. NH3 is a promotor of large-bowel tumours chemically induced by NOC, and some of the chromosomal mutations found in human colorectal cancer are consistent with effects of NOC and heterocyclic amines.
In a cohort study subjects who were free of diagnosed cancer completed a validated food frequency questionnaire and provided detailed information on other lifestyle and health-related factors. An elevated risk of colon cancer was associated with red meat intake. Men who ate beef, pork, or lamb as a main dish five or more times per week had an elevated relative risk compared to men eating these foods less than once per month.
Other Potential Risks
In addition to the above risks, HPDs may also lead to:
- Disorders of liver function
- Precipitated progression of coronary artery disease
- Nutrient Imbalances: Focusing too much on protein could mean you’re neglecting other important nutrients, like fiber.
- Dehydration: It can lead to an increased risk of dehydration, as the body requires more water to metabolize and eliminate the byproducts of protein breakdown
Recommendations for a Healthy High-Protein Diet
To maximize the benefits and minimize the risks of a protein diet, consider the following recommendations:
- Consult with a Healthcare Professional: Before starting any new diet, especially an HPD, consult with a doctor or registered dietitian to ensure it is appropriate for your individual health needs and goals.
- Choose Lean Protein Sources: Opt for lean meats, poultry, fish, eggs, and low-fat dairy products as your primary protein sources.
- Include Plant-Based Protein: Incorporate plant-based protein sources, such as beans, lentils, nuts, seeds, and soy products, to diversify your nutrient intake and reduce your reliance on animal products.
- Balance Your Diet: Ensure your diet includes adequate amounts of fruits, vegetables, and whole grains to obtain essential vitamins, minerals, and fiber.
- Stay Hydrated: Drink plenty of water throughout the day to help your kidneys process the increased protein load and prevent dehydration.
- Monitor Kidney Function: If you have any kidney problems, closely monitor your renal function while on an HPD and consult with your doctor if you experience any adverse effects.
- Spread Protein Intake Throughout the Day: Consume protein evenly across three meals, rather than consuming it all in one meal
- Don't Overdo It: Exceeding 2 grams of protein per kilogram of body weight may not offer any extra benefits.
- Start your day with protein: Try adding high-protein Greek yogurt or a serving of nuts to your breakfast or as a mid-morning snack
- Choose carbohydrate foods that also have extra protein For example, choosing quinoa or lentils instead of rice-or doing a mix of beans and rice.
- Befriend high-quality protein powders: You should prioritize whole foods, but do not be afraid to add in a high-quality protein powder to your routine