Researchers studying the properties of supplements provide us with what is often an incomplete profile of the food from which the supplement they are researching is based. For example, for years we were told to take Alpha Vitamin E. Later, it became natural Vitamin E vs the the synthetic form dl). Next, we learned that there was more than one form of Vitamin E and that it was the Gamma form which was doing all of the heaving lifting , even being eclipsed by the Alpha form . Next came the tocotrienols and finally Delta tocotrieonal, at the moment, is king of the mountain.
Now, the Chinese, Japanese and Turks (as I have learned) literally drink gallons of green tea and don't seem to be suffering, Green tea is not my favorite tea, yet I add measure of it to my smoothie three times a day. I use an especially concentrated form of the tea called Matcha. So far there are at least six identified catechin compounds in green tea. Are there others lurking in the background that have yet to be identified? What about my match? Is it superior to other green teas? Lastly, there is the problem of standardization: 5:1, 10:,1 20:1? And the beat goes on. When using supplements to test for efficacy: how does one settle on which one to use, at which does and at what standardization? Impossible.
The difference between Turmeric and Curcumin is that Turmeric is a rhizome while Curcumin is just one active ingredient in it. If you take Turmeric you are getting the entire spice as it appears in nature.
As far as toxicity is concerned, if you are afraid of harming your kidneys or liver, then stop your intake of cacao (dark chocolate) coffee, ginger and other foods that contain hazardous amounts of cadmium, lead, and oxalates.