Researchers are becoming increasingly aware of “plant-derived substances that act as chemopreventive agents.” Chemopreventatives are substances that help prevent cancer, as opposed to chemotherapy agents aimed at treating cancer. These plant-derived substances are not only inexpensive, they are also easily available and may have no or limited toxicity.
Since 1987, the National Cancer Institute has tested more than a thousand different potential agents for chemopreventive activity, of which only a few dozen were moved to clinical trials. Curcumin, present in the Indian spice, turmeric, which is used in curry powder, is one such agent currently under clinical investigation for cancer chemoprevention.
According to their mode of action, chemopreventive agents are classified into different subgroups: antiproliferatives, antioxidants, or carcinogen-blockers. Curcumin belongs to all three, given its multiple mechanisms of action. Curcumin appears to play a role helping to block every stage of cancer transformation, proliferation, and invasion, and may even help before carcinogens even get to our cells.
A study back in 1987, highlighted in my video, Carcinogen Blocking Effects of Turmeric, investigated the effects of curcumin on the mutagenicity (DNA mutating ability) of several toxins and found that curcumin was an effective antimutagen against several environmental and standard mutagenic and cancer-causing substances. However, this was in vitro (from the Latin meaning “in glass,” as in a test tube or petri dish). What about in people? We can’t just take a group of people and expose them to some nasty carcinogen so we can give half of them turmeric and see what happens. We could wait until some toxic waste spill happens or nuclear accident, but otherwise, how could researchers find people who would voluntarily expose themselves to carcinogens—unless, they smoke! That’s why researchers test antimutagenic agents on smokers, who have carcinogens coursing through their veins every day.
If smokers pee on some bacteria, the number of DNA mutations shoot up dramatically. Remember, all life is encoded by DNA, whether bacteria, banana, or bunny rabbit. (When measuring urinary mutagens, it’s easier to just pee on some bacteria.)
The urine of nonsmokers caused far fewer DNA mutations. It makes sense: nonsmokers have fewer chemicals running through their system. If we have nonsmokers eat some turmeric for a month, nothing really happens. But what if we do the same for smokers? In just fifteen days the mutagenic potential of their urine noticeably decreases, and it drops even more by day 30. The turmeric the researchers used was not some concentrated curcumin supplement, but just plain turmeric you might buy at the store. They also used less than a teaspoon of turmeric a day, indicating that dietary turmeric is an effective anti-mutagen.
However, in the same study the researchers found an even more effective anti-mutagen: not smoking. Even after eating turmeric for a month, the DNA-damaging power of smoker pee exceeded that of nonsmokers.
Other foods that may protect DNA include kiwifruit (Kiwifruit and DNA Repair), cruciferous vegetables (DNA Protection from Broccoli), leafy vegetables (Eating Green to Prevent Cancer), garlic (Cancer, Interrupted: Garlic & Flavonoids), green tea (Cancer, Interrupted: Green Tea), but which is better? (Antimutagenic Activity of Green Versus White Tea), and plants in general (Repairing DNA Damage).
Smokers are common research subjects for carcinogen studies. But other groups of people following similar lifestyles are used. For example, see what happens to carcinogen levels when those eating processed meat start eating vegetarian in my video Heterocyclic Amines in Eggs, Cheese, and Creatine.
PS: If you haven’t yet, you can subscribe to my videos for free by clicking here and watch my full 2012 – 2015 presentations Uprooting the Leading Causes of Death, More than an Apple a Day, From Table to Able, and Food as Medicine.
-Michael Greger, M.D.