Final answer:
The best lab test to reflect nutritional status is a comprehensive blood test that measures metabolites like lipids and glucose, and analyzes blood cells. Tests for specific nutritional absorption and renal function are also relevant.
Step-by-step explanation:
The lab test that best reflects nutritional status is often a comprehensive blood test. These tests can measure various metabolites in plasma, such as lipid or glucose levels, through chemical assays. Additionally, the number and types of blood cells can be analyzed using automated methods to assess the composition of the blood itself. To specifically evaluate the absorption function of the gastro-intestinal tract, tests using radioactive fatty acids, iron (59Fe), and vitamin B₁₂ are given orally with blood samples analyzed at intervals. Other related tests include renal function tests, which look at blood urea nitrogen and plasma creatinine levels, to monitor different aspects of health related to nutrition.