Natura Si

Healty food store showing the highest prices in Madrid, perhaps due to its positionning in the rich quarter "Nuevas Americas".
Even common products are sold at nearly double the supermarket price (e.g.: pre-washed salad, eggs-free tortilla, etc.).
Offers fresh fruits and vegetables: shocking prices and usually average to low quality.

It's like a mini-supermarket, variety of organic products (food, cleaning, etc.), friendly staff, good ubication.

Very friendly staff, including the woman at the checkout who spoke English. Good selection of non-dairy milks, soy products, household items, snacks and healthy junk food. Very small selection of fresh produce. Things are a bit pricey, but I haven't been to any other health food stores to compare prices. Tucked away in the back of a shopping area across from a children's playground. You may need to walk a bit to locate the place.

Actually a good-sized natural supermarket with lots of high quality organic fruit and vegetables. Also lots of packaged health foods. Not so much in the way of supplements/vitamins. I guess that's not their focus.

They have two locations (see web site). I visited their C/Guzmán El Bueno location in April 2011. It's a very small store with the basics nor is it centrally located.