Would it be harmful for the body to take too much of proteins or vitamins in the diet?
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The Impact of Excessive Protein and Vitamin Intake on Human Health
Excessive Protein Intake: Potential Risks and Safe Limits
Risks of High Protein Diets
High protein diets have been popularized for weight control and muscle synthesis, but they come with potential risks. When protein intake exceeds 35% of total energy intake, it can lead to several health issues, including hyperaminoacidemia, hyperammonemia, hyperinsulinemia, nausea, diarrhea, and even death, a condition known as "rabbit starvation syndrome". Chronic high protein intake, defined as more than 2 grams per kilogram of body weight per day, can result in digestive, renal, and vascular abnormalities.
Safe Protein Intake Levels
For healthy adults, long-term consumption of protein at 2 grams per kilogram of body weight per day is considered safe, with a tolerable upper limit of 3.5 grams per kilogram per day for well-adapted individuals. A suggested maximum protein intake to avoid toxicity is approximately 25% of energy requirements, equating to about 2 to 2.5 grams per kilogram per day.
Special Populations: Athletes and Bodybuilders
In resistance-trained males, a high protein diet of around 2.51 to 3.32 grams per kilogram per day over one year showed no harmful effects on blood lipids, liver, and kidney function. However, bodybuilders engaging in multiple dietary practices, including high protein intake, may face risks such as acute kidney injury and nephrocalcinosis, especially when combined with other supplements and practices.
Excessive Vitamin Intake: Specific Concerns
Vitamin D and Cardiometabolic Health
Vitamin D supplementation, particularly at 20 micrograms per day, has been shown to counteract winter declines in vitamin D levels and reduce LDL cholesterol in children. However, excessive intake of fat-soluble vitamins like A, D, and E can lead to nephrocalcinosis, a condition characterized by calcium deposits in the kidneys, which is particularly risky for bodybuilders.
Vitamin B-6 and Protein Metabolism
The metabolism of vitamin B-6 is influenced by dietary protein intake. In elderly adults, higher protein intake can increase plasma pyridoxal phosphate (PLP) levels, an active form of vitamin B-6, which is crucial for various metabolic functions. However, excessive protein intake without adequate vitamin B-6 can lead to deficiencies and associated health issues.
Bone Health and Protein Intake
Protein and Calcium Balance
Adequate protein intake is essential for bone health, provided that calcium intake is sufficient. A dietary calcium-to-protein ratio of at least 20:1 (mg:g) is recommended to protect the skeleton from the potential negative effects of high protein intake. Systematic reviews suggest that higher protein intake, above the current RDA, can reduce bone loss and hip fracture risk in older adults, as long as calcium intake is adequate.
Protein and IGF-1 Levels
In middle-aged adults, high protein intake is associated with increased IGF-1 levels, which can elevate the risk of cancer and overall mortality. Conversely, in older adults, high protein intake is linked to reduced cancer and overall mortality, highlighting the need for age-specific dietary recommendations.
Conclusion
While protein and vitamins are essential for health, excessive intake can lead to significant health risks. High protein diets should be approached with caution, particularly for individuals with underlying health conditions. Similarly, excessive vitamin intake, especially fat-soluble vitamins, can pose serious health risks. It is crucial to balance dietary intake with individual health needs and consult healthcare professionals for personalized dietary advice.
Sources and full results
Most relevant research papers on this topic
A review of issues of dietary protein intake in humans.
Effects of high dairy protein intake and vitamin D supplementation on body composition and cardiometabolic markers in 6-8-y-old children-the D-pro trial.
Dietary protein intake and human health.
A High Protein Diet Has No Harmful Effects: A One-Year Crossover Study in Resistance-Trained Males
Nutritional and Non-Nutritional Strategies in Bodybuilding: Impact on Kidney Function
The influence of protein intake on vitamin B-6 metabolism differs in young and elderly humans.
Excess dietary protein may not adversely affect bone.
Benefits and safety of dietary protein for bone health—an expert consensus paper endorsed by the European Society for Clinical and Economical Aspects of Osteopororosis, Osteoarthritis, and Musculoskeletal Diseases and by the International Osteoporosis Foundation
Low protein intake is associated with a major reduction in IGF-1, cancer, and overall mortality in the 65 and younger but not older population.
A high whey protein-, leucine-, and vitamin D-enriched supplement preserves muscle mass during intentional weight loss in obese older adults: a double-blind randomized controlled trial.
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