The point is if your skin is naturally dark then it probably wont work, however if it's due to hyperpigmentation then it may well work by clearing your system of unhealthy toxins.There's no actual evidence that it can lighten drastically. It's reported that it makes the skin brighter and slightly lighter in appearance, but nothing else.
Depends what type though. Even if it is caused by the sun, taking care of your health will help a great deal.Hyperpigmentation is typically triggered by overexposure to the sun. It is rarely a 'toxin' issue. Using an exfoliant like RA, a good sunblock & staying out of the sun will help you too.