Ginger

It depends on the cause. In a small trial, 1,000–2,000 mg before a spinning chair reduced motion sickness. In a 576-patient trial, 0.5–1.5 g a day eased first-day chemotherapy nausea alongside standard medication, but a 119-patient trial at 500 mg twice daily found no difference. After surgery, a meta-analysis found no meaningful effect.

Probably a little. A meta-analysis of four trials found 750–2,000 mg of ginger powder a day, taken during the first 3–4 days of a cycle, reduced pain more than placebo. A Cochrane review rated the evidence low quality, based on three small trials with 266 women, so treat it as promising, not settled.

Only with advance planning. Two trials totaling 74 people found 2 grams a day for 11 days before arm exercise cut next-day pain by roughly 23–25%. An earlier trial of a single 2-gram dose taken after exercise showed no effect within 45 minutes. The studies are small and from one research group.

Ask a doctor first. An NIH reference database says ginger can raise bleeding risk with warfarin. In small studies, 5 grams with a fatty meal and a single 10-gram dose reduced platelet clumping, while 4 grams a day for 3 months did not. The effect is dose-dependent, but the interaction is documented.

No health authority sets a limit, and no trial was built to find one. The highest sustained amount tested was 2 grams a day for 11 days, with no serious adverse events. Concentrated extract is different: 255 mg twice daily caused digestive side effects in 59 people versus 21 on placebo.