Chapter 160
Salad Days
So industrial meat full of nitrite is clearly out of the question, but what if the amines and amides from unprocessed meat mix with the nitrites from activated vegetable nitrates? Again: Nitrites in and of themselves aren’t carcinogenic; they become so only when they are converted into nitrosamines or nitrosamides in the presence of amines and amides. So what happens if you eat a large salad and then two or three hours later unprocessed meat? Then the nitrites that formed from the salad nitrates on your tongue could mix in the stomach with the amides and amines in the meat. Scientists tested this possibility by having volunteers drink nitrate water with a daily meal of cod, salmon, pollock, or shrimp. (Fish and seafood contain many amines.) During the fish week, carcinogenic nitrosamines in the participants’ blood shot up and dropped back down as soon as they stopped eating fish. A similar reaction was observed in another study not with fish, but with unprocessed chicken and turkey breast. This explains why the urine of omnivores who drink a bottle of beet juice contains enormously elevated levels of these carcinogenic substances in the 24 hours afterward.
On the other hand, vitamin C and other antioxidants from plant foods block the formation of these carcinogens in the stomach. This explains why there is an association between consuming nitrates and nitrites from processed meat and cancer, but no increased risk has been found for nitrates or nitrites from plants. However, it probably takes more than a small side dish. In the study, participants ate vegetables with the fish, but apparently not enough to prevent the formation of the carcinogens. So anyone who wants to get the full benefits from nitrate-rich vegetables should focus on whole plant foods at all meals.
Salad Days
In 1777, General George Washington gave the order that American soldiers should gather wild plants around their camps, “because this vegetable is very conducive to health and prevents all putrid diseases.” Since then, however, most Americans have declared their independence from leafy greens. Today, only one in 25 manages a dozen servings a month; by contrast, I recommend more than a dozen a week.
Leafy greens are said to be one of Okinawa’s longevity secrets. Eating leafy greens almost every day could be a decisive step toward extending lifespan. A study titled “Healthy Lifestyle and Avoidable Death” identified lifestyle factors by which men and women between 60 and 80 can halve their risk of dying in the following twelve years. Alongside factors independent of diet, such as not smoking or taking at least an hour-long walk every day, the only criterion of dietary quality was whether someone “eats leafy green vegetables at least almost daily.”
A Harvard research team analyzed food groups and found the strongest protective effect against major chronic diseases for leafy greens; among other things, each additional serving per day is said to lower the risk of heart attacks and strokes by 20 percent.
No wonder, then, that among all fruits and vegetables, the best scientific evidence for reducing the risk of death from any cause is for leafy greens. Imagine if there were a pill that would extend life and had only positive side effects. Everyone would take it! The fortunate pharmaceutical company that developed it would make billions. Every health plan would include it by law. People from all walks of society and all parts of the world would loudly demand it. But if the “pill” is called “Eat your greens,” most people simply tune it out.
Important warning: Leafy greens and warfarin
Anyone taking warfarin (brand name Coumadin) should talk with their physician before eating more greens. The medication inhibits the enzyme that returns vitamin K to its active form so that it can again participate in blood clotting. If more vitamin K from leafy greens flows into the system, that could undermine the effect of the medication. You can still enjoy greens, but the physician will need to adjust the medication dose.
Berries
All dietary guidelines worldwide contain the same simple core message: Eat more fruits and vegetables. But not all fruits and vegetables are equal. People who consider berries a well-rounded choice live longer; those who prefer bananas do not. I already described the benefits of berries for brain performance, immune defense, and eyesight in the relevant chapters earlier in the book. In research, berries are only rarely studied separately from fruit in general, but if you combine the three existing prospective studies on berries and overall lifespan, it becomes clear that people who eat a lot of berries live significantly longer than those who eat few. They taste delicious and make us live longer? That is exactly what a plant-based diet is about.
Packed to bursting with antioxidants
Berries lower overall mortality risk just as strongly as leafy greens. Leafy greens are the healthiest vegetables, and berries are the healthiest fruits—which is due in part to their respective plant pigments. Leaves contain chlorophyll, the green plant pigment where photosynthesis takes place; that’s why leafy greens contain so many antioxidants that take care of the free radicals produced in the process. Berries evolved in a different direction: They glow in bright colors to attract little fruit-eating critters that then disperse the berry seeds, and those very molecular properties that make them so intensely colorful are also responsible for some of their antioxidant abilities.
In the United States, apples and bananas are the most popular fruits, with an antioxidant capacity of about 60 and 40 units, respectively (daµmol antioxidant units, measured with a modified FRAP experiment). Mangos are the most popular fruit everywhere else and have more antioxidant power at 110 units. (Considering how much more intense the yellow of mango flesh is, that makes sense.) But none of these fruits can hold a candle to berries: Per cup, strawberries have about 310, blueberries 380, raspberries 430, cranberries 490, and blackberries a breathtaking 680 antioxidant units. A few berries from the Arctic tundra, such as the lingonberry, are even more packed with antioxidants, but among what we can buy in the store, the blackberry comes out on top. If you reach for blackberries instead of strawberries, you get double the performance per berry.
Forget the superfruit
Açaí berries had an anti-aging effect in mice, but they did not extend the lifespan of the nematode C. elegans. Fruit flies on a high-fat diet also lived longer with the berries, but what does the fruit offer humans? I outline the disappointing clinical results at see.nf/acai. Even the berries’ antioxidant effect has been exaggerated. Supplement sellers like to advertise that açaí berries would triple the blood’s “antioxidant capacity.” But if you read the study they cite, you find that the antioxidant capacity of the blood in the participants did indeed triple after consuming açaí berries—but the same effect was achieved in a control group that ate plain applesauce.