TABLE 3.
Number of metabolites by chemical class and the association with β-carotene supplementation in the ATBC Study1
| Chemical class | No. of identified metabolites | No. of metabolites associated with β-carotene supplementation at P < 0.05 | P value2 |
| All | 489 | 17 | |
| Xenobiotics | 60 | 9 (15.0) | 0.00004 |
| Lipids | 181 | 3 (1.7) | 0.12 |
| Peptides | 70 | 0 (0) | 0.15 |
| Carbohydrates | 22 | 2 (9.1) | 0.17 |
| Amino acids3 | 20 | 1 (5.0) | 0.51 |
| Nonstandard amino acids3 | 88 | 2 (2.3) | 0.75 |
| Cofactors and vitamins | 21 | 0 (0) | 1.0 |
| Energy metabolites | 7 | 0 (0) | 1.0 |
| Nucleotide metabolites | 20 | 0 (0) | 1.0 |
1
Values in parentheses are percentages. ATBC, Alpha-Tocopherol, Beta-Carotene Cancer Prevention.
2
Calculated by using Fisher's exact test.
3
Amino acids are defined here as the 20 amino acids that are precursors to proteins and that are directly encoded by the universal genetic code. Nonstandard amino acids are those that are either not incorporated into proteins or not directly encoded by the universal genetic code.