Turmeric in food and curcumin in capsules are not the same thing. Turmeric is the whole ground rhizome of the Curcuma longa plant, which contains curcumin, other curcuminoids, essential oils, carbohydrates, proteins, fiber, and many other plant substances.
There is no official recommended daily intake of turmeric in teaspoons for a healthy adult. If a practical, rather than regulatory, guideline is desired, a typical culinary use is approximately ¼ to 1 teaspoon of ground turmeric per day, divided between meals.
Curcumin's bioavailability can indeed be significantly increased, but the most reliable way is not simply to increase the dose or necessarily add black pepper, but to use a formulation that specifically enhances solubility and absorption.
Regular curcumin is poorly absorbed by the body. After ingesting standard powder or unmodified extract, only a small portion of curcumin passes through the intestines into the systemic bloodstream, and the absorbed substance is quickly converted in the intestinal wall and liver.
Curcumin is combined with piperine primarily to increase its bioavailability—that is, to make more curcumin or its metabolites available to the body after oral administration.
Black pepper is added to curcumin primarily to increase its bioavailability—the amount of the substance that is absorbed and becomes available to the body after oral administration.
Turmeric does contain a lot of oxalates, and when consumed in amounts typical of dietary supplements, the oxalate in it can significantly increase oxalate excretion in the urine.
Yes, there is a link, but it primarily concerns large amounts of turmeric and certain food additives, not the usual pinch of the spice in food. Turmeric contains oxalates—salts of oxalic acid. In a small controlled study in humans, supplemental turmeric significantly increased urinary oxalate excretion.
If you have gallstones, bile duct obstruction, cholangitis, or other biliary tract diseases, it is best not to use concentrated turmeric and curcumin preparations without consulting a doctor.
