An orange plant pigment the body converts unevenly into vitamin A. As food it tracks longer life; as a high-dose capsule it has largely failed. It makes skin harder to burn, eases a rare inherited sunlight intolerance, and supplies vitamin A without overload risk. In smokers and asbestos-exposed people, high doses raise lung cancer and heart death. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Serum beta-carotene | 20–60 µg/dL | Confirms absorption and flags overexposure |
| Serum retinol | 30–65 µg/dL | Shows whether conversion is actually producing vitamin A |
| Retinol-binding protein | 3.0–6.0 mg/dL | Distinguishes true vitamin A shortfall from carrier-protein shortfall |
| Total plasma carotenoids | Below 4.0 mg/L | The threshold above which skin yellowing appears |
| Plasma lutein and zeaxanthin | No established target; track change from own baseline | Detects displacement by high-dose beta-carotene |
| Fasting lipid panel | Triglycerides below 100 mg/dL | Interprets carotenoid values, which ride on lipoproteins |
| ALT | Below 25 U/L in men, below 20 U/L in women | Catches the alcohol-plus-carotene liver interaction early |
| Serum cotinine | Below 3 ng/mL | Objectively settles the one exposure that reverses the risk-benefit sign |
Cadence: Baseline set before dosing; serum beta-carotene and retinol repeated at three months, then annually. Liver enzymes rechecked at three months only where alcohol is present.