For people without a personal history of cardiovascular disease, aspirin’s risks may outweigh its benefits, but aspirin may have additional benefits. “We have long recognized the preventative role of daily aspirin for patients with atherosclerotic [heart] disease; however, it now appears that we can hatch 2 birds from 1 egg. Daily low-dose aspirin may help prevent certain forms of cancer, as well, as I discuss in my video Should We All Take Aspirin to Prevent Cancer? In an analysis of eight different studies involving more than 25,000 people, “the authors found a 20 percent decrease in risk of death from cancer among those randomized to daily aspirin…” The researchers wrote, “[T]he search for the most efficacious and safe treatments for malignant disease remains an enormous and burdensome challenge. If only we could just stop cancer in its tracks—prevent it before it strikes. Perhaps we can.” Indeed, perhaps we can with salicylic acid, the plant phytonutrient that’s marketed as aspirin.
How does aspirin affect cancer? The Nobel Prize for Medicine was awarded to the team who discovered how aspirin works. Enzymes named COX (cyclooxygenase) take the pro-inflammatory, omega-6, fatty-acid arachidonic acid our body makes or we get directly in our diet (primarily from eating chicken and eggs), and turns it into inflammatory mediators, such as thromboxane, which produces thrombosis (clots), and prostaglandins, which cause inflammation. Aspirin suppresses these COX enzymes. Less thromboxane means fewer clots, and less prostaglandin means less pain, swelling, and fever. However, prostaglandins can also dilate the lymphatic vessels inside tumors, allowing cancer cells to spread. So, one way cancer tries to kill us is by boosting COX activity.
We think one way aspirin can prevent cancer is by counteracting the tumor’s attempts to pry open the lymphatic bars on its cage and spread throughout the body. Indeed, reduction in mortality due to some cancers occurred within two to three years after aspirin was started. That seems too quick to be accounted for by an effect only on tumor formation . Cancer can take decades to develop, so the only way aspirin could work that fast is by suppressing the growth and spread of tumors that already exist. Aspirin appeared to cut the risk of metastases in half, particularly for adenocarcinomas, like colon cancer.
Given this, should we all take a daily baby aspirin? Previous risk-benefit analyses did not consider the effects of aspirin on cancer, instead just balancing cardiovascular benefits with bleeding risks, but these new cancer findings may change things.
If daily aspirin use were only associated with a reduction of colon cancer risk, then the benefits might not outweigh the harms for the general population, but we now have evidence that it works against other cancers, too. “[E]ven a 10% reduction in overall cancer incidence…could tip the balance” in favor of benefits over risks.
How does the cancer benefit compare? We know that using aspirin in healthy people just for cardiovascular protection is kind of a wash, but, by contrast, the cancer prevention rates might save twice as many lives, so the benefits may outweigh the risks. If we put it all together—heart attacks, strokes, cancer, and bleeding—aspirin comes out as protective overall, potentially extending our lifespan. There is a higher risk of major bleeding even on low-dose aspirin, but there are fewer heart attacks, clotting strokes, and cancers. So, overall, aspirin may be beneficial.
It’s important to note that the age categories in that study only went up to 74 years, though. Why? Because the “risk of bleeding on aspirin increases steeply with age,” so the balance may be tipped the other way at 75 years and older. But, in younger folks, these data certainly have the research community buzzing. “The emerging evidence on aspirin’s cancer protection highlights an exciting time for cancer prevention…”
“In light of low-dose aspirin’s ability to reduce mortality from both vascular events and cancer to a very notable degree, it is tempting to recommend this measure…for most healthy adults…However, oral aspirin, even in low doses, has a propensity to damage the gastroduodenal mucosa [linings of our stomachs] and increase risk for gastrointestinal bleeding; this fact may constrain health authorities from recommending aspirin use for subjects deemed to be at low cardiovascular risk”—that is, for the general population. “Recent meta-analyses estimate that a year of low-dose aspirin therapy will induce major gastrointestinal bleeding (requiring hospitalization) in one subject out of 833…”
If only there were a way to get the benefits without the risks.
Those who remember my video Aspirin Levels in Plant Foods already know there is. The aspirin phytonutrient salicylic acid isn’t just found in willow trees, but throughout the plant kingdom, from blackberries and white onions to green apples, green beans, and beyond. This explains why the active ingredient in aspirin is found normally in the bloodstream even in people not taking aspirin. The levels of aspirin in people who eat fruits and vegetables are significantly higher than the levels of those who don’t. If we drink just one fruit smoothie, our levels rise within only 90 minutes. But, one smoothie isn’t going to do it, of course. We need to have regular fruit and vegetable consumption every day. Are these kinds of aspirin levels sufficient to suppress the expression of the inflammatory enzyme implicated in cancer growth and spread, though? Using umbilical cord and foreskin cells—where else would researchers get human tissue?—they found that even those low levels caused by smoothie consumption significantly suppressed the expression of this inflammatory enzyme on a genetic level.
Since this aspirin phytonutrient is made by plants, we might expect plant-eaters to have higher levels. Indeed, not only did researchers find higher blood levels in vegetarians, but there was an overlap between people taking aspirin pills. Some vegetarians had the same level in their blood as people actually taking aspirin. Vegetarians may pee out as much of the active metabolite of aspirin as those who take aspirin do, simply because vegetarians eat so many fruits and vegetables. “Because the anti-inflammatory action of aspirin is probably the result of SA [salicylic acid, the active ingredient in aspirin], and the concentrations of SA seen in vegetarians have been shown to inhibit [that inflammatory enzyme] COX-2 in vitro, it is plausible that dietary salicylates may contribute to the beneficial effects of a vegetarian diet, although it seems unlikely that most [omnivores] will achieve sufficient dietary intake of salicylates to have a therapeutic effect.”
Aspirin can chew away at our gut. With all that salicylic acid flowing through their systems, plant-eaters must have higher ulcer rates, right? No. Both vegetarian women and men appear to have a significantly lower risk of ulcers. So, for the general population, by eating plants instead of taking aspirin, we may not only get the benefits without the risks, we can get the benefits with even more benefits. How is this possible? In plants, the salicylic acid can come naturally pre-packaged with gut-protective nutrients.
For example, nitric oxide from dietary nitrates exerts stomach-protective effects by boosting blood flow and protective mucus production in the lining of the stomach—“effects which demonstrably oppose the pro-ulcerative impact of aspirin and other NSAIDs.”
The researcher notes that while “[d]ark green leafy vegetables…are among the richest dietary sources of nitrate…it may be unrealistic to expect people to eat ample servings of these every day,” so we should just give people pills with their pills, but I say we should just eat our greens. People who’ve had a heart attack should follow their physician’s advice, which probably includes taking aspirin every day, but what about everyone else? I think everyone should take aspirin—but in the form of produce, not a pill.
To see the pros versus cons for people trying to prevent or treat heart attacks and stroke, see my video Should We All Take Aspirin to Prevent Heart Disease?.
Does the COX enzyme sound familiar? I talked about it in my Anti-Inflammatory Life Is a Bowl of Cherries video.
Where does one get “dietary nitrates”? See Vegetables Rate by Nitrate and Veg-Table Dietary Nitrate Scoring Method. I also discuss nitrates in Slowing Our Metabolism with Nitrate-Rich Vegetables and Oxygenating Blood with Nitrate-Rich Vegetables.
Do some plant foods have more aspirin than others? Definitely. In fact, some foods have the same amount as a “baby” aspirin. Check out Plants with Aspirin Aspirations.
Michael Greger, M.D.
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