You can get more information about Giardiasis at wikipedia. In this article we are talking about Giardiasis can be treated naturally. But please before following any advice here, do consult to your doctor.

1. Plant essential oils can work effectively against Giardia. Essential oils like garlic oil, croton cajucara oils can be used as natural treatment of Giardiasis. They are effective and they also offer other benefits.
2. Raw garlic is also good as a natural treatment of giardiasis.
3. You can use grapefruit extract.
4. Use Pippali rasayana, a ayurvedic formulation. This formulation contains Piper longum and Butea monosperma (palash). You can use Pippali rasayana (PR) for the treatment of parasites like Giardia.
5. You can use Piper longum or Indian long pepper as natural treatment of giardiasis. You can make some aqueous solution of peeper in water or ethanol. Keep it for a few days and then use it.
Diet for Giardiasis

Have a high fiber diet to fight against Giardia. Such diet reduces the acute symptoms that are prevalent in case of Giardiasis. Such diet for a long time can clear the problem. Your diet should contain less sugar, fat and lactose and more fiber.

Fiber diet can help because of the very nature of the parasite that causes Giardiasis. Fiber helps in two ways
1. It increases mucous secretion.
2. Fibers are insoluble and their movement restricts the parasite.

These two properties do not let the parasite that cause Giardia, attach to the intestinal mucosa. As it cannot go for musocal colonization, so the disease spread and intensity gets reduced. Parasites are washed away and out from the body in the process which helps the patients get well soon.
Avoid sugars in Giardiasis

Avoid sugars when you are suffering from Giardia. It is bad for your health in such situations.
Avoid Dairy Products in Giardiasis

As Giardia infection reduces lactase production, so your body may not be able to break down and absorb the lactose in the dairy products. So, reduce the amount of dairy products intake when you are suffering from Giardia. Otherwise, you may have to suffer from diarrhea.
Reduce Fat in your diet

Reduce the amount of fat in your diet. It will help you when you are suffering from Giardia and its related problems like steatorrhoea, diarrhea and nausea et cetera. Bile acids are needed by giardia trophozoites for survival. Fat in your diet stimulates the release of bile acids. So, avoid it till you recover from Giardiasis.
Wheat Germ in Giardiasis

Wheat germ may help you a lot in case of giardiasis. It contains lectin, which binds to NAG residues. So, drink wheat germ juice or extract every morning.