Maca is safe for most people, yet it hasn't been tested for safety in pregnant women, some experts advise against drinking maca coffee in case of side effects. Another possible exception may be for people who have thyroid problems, who should use caution and speak to a health professional before consuming it. Your body may take several days to adjust to maca when you add it to your diet. The effects of maca accumulate over time. If you use it consistently, you'll find it to be a much more powerful supplement than if you use it infrequently.