What is dragon fruit? And is pitaya the same as dragon fruit? Yes, both reference the same plant, there is no difference between the two. At least in the United States, where both names are used to talk about fruits coming from the Hylocereus genus of cacti. The Stenocereus genus produces the sour pitaya, but that's entirely foreign to your average American.
These reddish-purple fruits grow on night-blooming cacti. Those vivid colors are rich in anthocyanins, a specific type of antioxidant which are water-soluble phenolic compounds. Even though pitaya's phenolic concentration is high for forms, its total antioxidant content as measured by the ORAC scale is relatively low, as seen in the table below.
It is important to understand that this ORAC calculation was done using fresh fruit puree, which of course contained a high amount of water. ORAC is based on 100 grams of the food (1 gram in the table, multiplied by 100). If the same test was conducted using dried dragon fruit or pitaya powder, we can safely assume the reading would be a multiple higher since the nutrients would be much more concentrated.
With the name dragon, many assume it must be oriental in origin, but it's native homeland is Central America, not Asia. It is suspected that that Europeans brought it from the New World and some unknown time after, it was exported to the Asia-Pacific region. Because of its popularity there, today it is heavility cultivated for consumption in Thailand, Malaysia, China, Cambodia, Vietnam, Indonesia, Sri Lanka, and the Phillipines.
What is the difference between red vs. white dragon fruit? In the US, it's typically the dried red fruit you encounter for sale branded as a superfood, while the white variety is more often sold fresh. Both come from the same species of cacti, Hylocereus, but there are different varieties of it:
Hylocereus costaricensis - This variety produces the fruit which has both red skin and red pulp inside. It's commonly referred to as red or purple dragon fruit. It also goes by the name Mexican pitaya rojo.
Hylocereus undatus - This is white dragon fruit. It has the red skin with the white pulp inside.
Hylocereus megalanthus - Probably the least popular, the yellow dragon fruit has yellow skin with white pulp.
Research Support, Non-U.S. Gov't: Mahattanatawee K, Manthey JA, Luzio G, Talcott ST, Goodner K, Baldwin EA. Total antioxidant activity and fiber content of select Florida-grown tropical fruits. J Agric Food Chem. 2006;54(19):7355-63.