Strongest evidence
Three outcomes have moderate evidence strength: reduced AST (5 studies, small effect, 298–1000 IU/day), reduced ALT (4 studies, mixed effect, 400–1000 IU/day), and reduced inflammation (3 studies, mixed effect, no clear dose). All of these studies were conducted in clinical populations, primarily patients with NAFLD or NASH. The liver enzyme findings show a consistent direction of benefit, though the effect may be small and most studies report effects at 8–12 weeks.
Mixed or weaker evidence
Six outcomes have low or very low evidence strength. For pain reduction (4 studies), the highest-quality evidence (a meta-analysis) found no effect, while smaller studies suggested benefit. Improved sperm morphology (3 studies) showed benefit in only 1 of 3 trials, and the benefit may be limited to specific infertile populations. Reduced TNF-α, reduced malondialdehyde, and reduced vitamin E level all had predominantly neutral findings. Sperm motility (3 studies) showed no benefit at all. These results are preliminary and often based on small sample sizes or studies combining vitamin E with other nutrients.
Effective dose patterns
For liver outcomes, the most studied dose range is 400–1000 IU/day. For sperm morphology, doses of 100 mg twice or thrice daily were used. No consistent dose emerged for other outcomes. Many studies did not report a specific effective dose, limiting cross-outcome comparisons.
Population insights
The strongest evidence comes from people with NAFLD/MASLD. Other clinical populations studied include infertile men, patients with osteoarthritis, fibromyalgia, epilepsy, sarcopenia, and various gastrointestinal conditions. There is insufficient evidence to generalize to healthy individuals or to specific subgroups like the elderly.
Notable caveats
- Publication bias is a concern for the moderate-strength outcomes (ALT, inflammation) because all included studies reported benefit, potentially overrepresenting positive results.
- Many studies are small (3–5 papers) and conclusions are preliminary.
- In several studies, vitamin E was combined with other treatments (e.g., vitamin C, M. sativa), making its independent effect unclear.
- Effect sizes vary widely across studies, and statistical significance was not always reached.