However, a small minority of people report becoming sick after eating quinoa, usually after consuming it for some time. This is a real shame, as quinoa is very tasty, extremely nutritious, and easy to cook. It is versatile, and can be used in many ways.
The most likely problem is saponin, which protects the plant from insect and fungal attack. This is a soapy substance which can be washed out of the quinoa pseudograin. It has a bitter taste, and possible minor toxic effects.
Because of the bitter taste and possible toxicity, it is important that you wash out most saponin before cooking the quinoa. It certainly is not a very dangerous substance, nor is it as bitter as fish bile, so you do not have to take the same care with washing your quinoa as you would with preparing a puffer fish or something.
There are several ways to wash quinoa.
You can put it into a sieve, one with a fine enough mesh to trap even the smallest seeds. Then run it under the tap, shaking the sieve gently from side to side, until the water runs clear.
Or you can immerse the sieve in a big bowl of water. Rub the seeds with your fingers to help shift the saponin. Repeat two or three times until the water is clear and no foam forms on the surface.
Or you can put the quinoa in a blender with some water, and pulse it a few times to agitate the mixture, but not actually chop up the seeds. Drain it through a sieve.
Put quinoa in a pot, with water in a 1:2 ratio (twice as much water). It takes approximately 12 minutes to cook. Allow a little longer (15 minutes or so) if cooking with other acidic ingredients.
A dash of salt brings out the flavor, although some people prefer to cook without salt and are used to the reduced flavor.