Antioxidants and aspirin-like compounds in herbs, spices, fruits, and vegetables inhibit growth of colorectal cancer
Worldwide, colorectal cancer accounts for nearly one in ten new cancer cases diagnosed annually. But the geographical distribution of risk is very uneven. The highest rates are found in America, Western Europe, and other developed countries, while India and Africa enjoy the lowest rates.
Researchers attribute these sharp differences in risk to differences in diet. People in Africa and India eat far less red and nitrite-cured cancer-promoting meat than Americans consume, and many more fruits, vegetables, herbs, and spices, intake of which is associated with lower rates of colorectal cancer.
The results of two recently published studies add weight to this dietary hypothesis.
Turmeric is the spice that makes curries bright yellow in color, and the pigment that makes turmeric yellow, called curcumin, possesses potent antioxidant, anti-inflamatory, and anti-cancer powers.
As we reported earlier this year (see “Turmeric Power, Part I”), much of the research into curcumin’s powerful anti-cancer properties has been conducted at The University of Texas M.D. Anderson Cancer Center.
The Center's Web site offers this comment by leading curcumin-cancer researcher Dr. B.B. Aggarwal:
Now we can add another metabolic mechanism to the curry pigment’s anti-cancer portfolio, thanks to research at another medical center in the Lone Star state.
Last month, researchers at the University of Texas Medical Branch at Galveston reported that curcumin blocks production of a gastrointestinal hormone called neurotensin, which the body secretes in response to dietary fat.
This matters because neurotensin promotes production of a potent messenger protein (cytokine) called interleukin-8 (IL-8), which accelerates the growth and spread of colorectal and pancreatic tumor cells.
When the researchers exposed human colorectal cancer to curcumin, it blocked the production of IL-8 and the migration of cancer cells induced by neurotensin. And the yellow curry pigment did it by blocking the same three pathways through which neurotensin promotes release of IL-8 and the growth and spread of cancer:
- Ca2+-dependent protein kinase C
- Activator protein-1 (AP-1)
- Nuclear factor-kappaB (Nf-kappaB)
The Texas team’s findings add to the considerable body of evidence suggesting that turmeric is a powerful ally in the fight to prevent this major killer.
Study #2: Cancer-curbing “natural aspirin” in spices
The history of aspirin dates back some 3,000 years, when Greek physician Hippocrates used a powder made from willow tree bark and leaves to help heal headaches, pains, and fevers.
By 1826, Italian chemists identified salicin as the active ingredient in willow, and 12 years later, another Italian chemist converted salicin into a usable form called salicylic acid. However, its high acidity irritated peoples’ stomachs so badly as to make it useless for pain relief. In 1853, a French chemist solved the problem by adding an acetyl group to salicylic acid to create acetylsalicylic acid (ah-see-tul-sal-ah-sil-ik acid).
However, the discovery went unused until a chemist at the German drug company, Bayer, rediscovered the formula in 1899, and the company marketed acetylsalicylic acid under the trade name “Aspirin”.
In recent decades, aspirin has been proven effective in preventing colon cancer, thanks to its particular anti-inflammatory properties, which block specific metabolic pathways proven to promote cancer growth. People who take about 80 mg of aspirin per day can halve their risk of colorectal cancer.
Like aspirin, salicylic acid appears to reduce cancer risk by inhibiting an enzyme called COX-1, which reduces production of the pro-inflammatory, potentially cancer-promoting messenger chemicals called prostaglandins. Prostaglandin-inhibition is also one of the several ways in which omega-3 fatty acids from fish are believed to inhibit cancer.
Earlier research proved that plant foods contain varying amounts of salicylic acid, with some, as we’ll see, containing large amounts of the anti-inflammatory, anti-cancer compound. Accordingly, population studies show that diets high in plant foods (hence in salicylic acid as well) correlate with lower rates of colorectal cancer.
Culinary herbs and spices lead “natural aspirin” list
The results of a new study confirm prior findings, which indicated that culinary herbs and spices contain unrivaled levels of salicylic acid: amounts that may be large enough to provide significant protection against colorectal cancer (Paterson JR et al 2006).
Scientists from the Dumfries and Galloway Royal Infirmary and the University of Strathclyde in Glasgow ran four experiments:
- Tested spices for their salicylic acid content.
- Tested spicy Indian dishes for their salicylic acid content.
- Tested the blood and urine of European volunteers after they ate spicy Indian dishes.
- Measured the blood salicylic acid levels in villagers in southern India and compared them with average blood levels of salicylic acid in vegetarian and non-vegetarian Europeans.
But the real cause for excitement flows from the comparisons the Scottish team made between average Europeans, European vegetarians, and rural Indians.
Results vindicate cancer-preventive power of vindaloo
The Scottish team found that salicylic acid levels in the blood taken from rural Indians (who have very low rates of colon cancer) were almost three times higher than in Western vegetarians: a finding that strongly suggests spices make a big cancer-preventive difference, even in diets rich in fruits and vegetables.
The champion by far was cumin, which contained 1,629 mg of salicylic acids per 100 gm or 3.5 oz (Cumin is used in very large amounts in Indian cookery). The closest runners up were turmeric, which contained 350 mg of salicylic acids per 100 gm, red chilli powder at 146 mg and paprika at 104 mg.
Accordingly, the researchers found that dishes prepared using “hotter” spice blends such as vindaloo-style curry contained about four times as much salicylic acids, probably because cumin, paprika, and chilies are the ingredients used make curries hotter. The salicylic acids content of the various Indian curry dishes tested ranged from 10 mg (mild curry blend) to 40 mg (super-spicy vindaloo curry blend) per 10 ounce portion.
The Scots also found that blood and urine levels of salicylic acids were higher in the vegetarians tested than in the non-vegetarians, and approximated those of people consuming 150 mg of aspirin per day or more.
The significance of this finding is that blood levels of salicylic acid in vegetarians can be greater than 2000 nmol/ml (nanomoles per milliliter), and, as the Scots said, “...[blood] concentrations as low as 100 nmol/ml can inhibit the transcription of PHGS-2, an enzyme implicated in colon cancer pathogenesis [initiation and growth].”
Organic, pesticide-free growing methods seem to boost salicylic acid levels in foods, since the same Scottish team found higher levels of salicylic acid in organic soup than in soup made from identical conventionally grown ingredients (Baxter GJ et al 2001). The Scots speculated that because plants produce salicylic acids as a defense against pests, foods grown without pesticides would be forced to produce higher levels.
Earlier Aussie study supports Scots’ results
The results of a related study, performed in Australia more than 20 years ago (Swain AR et al 1985), support the new Scottish findings, and provided information on other foods as well:
- As did the Scots, the Aussies found levels of salicylic acids in culinary herbs and spices were much higher than in fruits and vegetables. The winners were the most pungent, flavorful seasonings: curry powder (which is usually rich in turmeric, cumin, and chilies), paprika, thyme, oregano, and rosemary.
- Berries and dried fruits contain significant, but much smaller amounts of salicylic acid. (Interestingly, a prior study by the same Scottish team found substantial amounts of salicylic acid in people’s urine after they drank cranberry juice [Duthie GG et al 2005]).
- Vegetables contained even less salicylic acid than berries.
- Tea provides modest amounts of salicylic acid.
- Cereals, meat, fish, and dairy products contain no salicylic acid or negligible amounts.
But before you start ordering Indian takeout food, we offer an important caveat. Unlike home-cooked Indian meals, food from Indian restaurants often comes soaked in cooking oils that are high in omega-6 fatty acids (soy, corn, canola). Americans already consume too much of these fatty acids, which, in excess, can fuel cancer growth.
Instead of oily, caloric Indian takeout, increase your use of herbs and spices in everyday cooking. You may well cut your risk of colon cancer, and your meals will taste more exciting.
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