The minimum amount of proteins needed for positive nitrogen balance is –
**Core Concept**
Nitrogen balance is a measure of protein metabolism in the body, reflecting the balance between protein synthesis and degradation. A positive nitrogen balance indicates that the body is retaining more nitrogen (from protein) than it is losing, which is essential for growth, repair, and maintenance of tissues.
**Why the Correct Answer is Right**
The minimum amount of proteins needed for positive nitrogen balance is crucial for maintaining tissue health. A dietary intake of 0.5 grams of protein per kilogram of body weight per day is generally considered sufficient to achieve a positive nitrogen balance in healthy adults. This amount supports the synthesis of new proteins and the repair of damaged tissues. The recommended dietary allowance (RDA) for protein is based on the minimum amount required to maintain nitrogen balance, and exceeding this amount can lead to excessive nitrogen excretion.
**Why Each Wrong Option is Incorrect**
**Option A:** 0.2 grams per kilogram per day is too low to support nitrogen balance, as the body requires a minimum amount of protein to maintain tissue health.
**Option B:** 1 gram per kilogram per day is higher than the minimum required for nitrogen balance but may be more suitable for athletes or individuals with high protein turnover.
**Option C:** 0.8 grams per kilogram per day is the RDA for protein, but it may not be sufficient for individuals with high protein requirements, such as pregnant or lactating women.
**Clinical Pearl / High-Yield Fact**
A positive nitrogen balance is essential for wound healing, and a diet providing at least 0.5 grams of protein per kilogram of body weight per day is recommended to support tissue repair and regeneration.
**Correct Answer: C. 0.8 grams per kilogram per day**