Chapter 38
Reducing DNA Damage
Unfortunately, most Americans consume many pale foods—white bread, potatoes, white pasta, and white rice—but colorful foods are better for us because of their pigments, which act as antioxidants. Blueberries are among the most intensely colored foods, and the data do not disappoint. A half cup of blueberries can block the drop in our blood’s antioxidant performance in the hours after we have eaten berry-free, sugary breakfast cereal (a quarter cup can’t do that). Randomly assigned blueberry smoothies taken twice a day cut the levels of a potent free radical in the subjects’ blood in half after six weeks, which then translated into greater protection of DNA.
Scientists drew blood from participants before and after they ate two cups of frozen and thawed blueberries, then exposed their white blood cells to free radicals in the form of hydrogen peroxide. The blueberries reduced the resulting DNA damage within an hour after consumption. The protective effect, however, did not last long. After two hours, the DNA was vulnerable again, so, to say it again, we should eat plentiful antioxidants multiple times a day.
In test tubes, lemons, persimmons, strawberries, broccoli, celery, and apples all had a protective effect on the DNA of human cells, but that presupposes that the active components are also absorbed into the bloodstream at the concentration at which the protective effect was observed. For some foods, however, it has been shown that they reduce DNA damage when they are actually eaten:
Kiwis, cooked carrots, and green tea stand out in that they can also repair DNA, something that had been assumed could not easily be influenced by diet. Can we just swallow a pill instead? A supplement with the same amount of alpha- and beta-carotene as carrots did not achieve the same effect.
Whole-food extracts from apples, oranges, spinach, and blueberries have been shown to extend the lifespan of C. elegans, but there are also individual phytonutrients such as gallic acid that not only extend the lifespan of C. elegans but also reduce DNA damage in humans within days—and at a daily dose found in a half cup of strawberries, a half mango, or a few teaspoons of carob powder, although the whole foods would likely work even better. An extract from organic apples increased the average life expectancy of C. elegans by 39 percent, twice as much as individual apple components or individual apple-derived phytonutrients, such as quercetin, which increased average lifespan by only 15 percent. Water with lemon juice—not even the whole fruit—extended the lifespan and healthspan of mice compared with those that drank only water their entire lives, and for amla, cinnamon, cocoa, and turmeric it has all been shown that they extend the lives of fruit flies. For humans, we find the daily dose of antioxidants that is associated with a 7 percent lower risk of premature death in about a cup of cooked spinach or a two-thirds cup of blackberries.
The Spice of Life
Spices protect DNA best. Eating daily for just a week two teaspoons of rosemary or sage, one and a half teaspoons of ground ginger or black cumin, three-quarters of a teaspoon of paprika, or only one-tenth of a teaspoon of cooked turmeric can protect DNA strands from breaking. A quarter teaspoon of amla daily—the dried powder of the Indian gooseberry—was also found to reduce oxidative DNA damage. That is to be expected, since dried herbs and spices are antioxidant heavyweights gram for gram.
For example, herbs and spices have ten times more antioxidant power than nuts and seeds. Of course, it’s easier to eat 30 grams of nuts than 30 grams of nutmeg, but some herbs and spices are so incredibly potent that even a pinch can make a big difference. If, for example, you add a teaspoon of dried oregano to a bowl of whole-wheat spaghetti with Italian tomato sauce and steamed broccoli, it nearly doubles the dish’s antioxidant power. Two-thirds of a teaspoon of marjoram accomplishes the same thing. A half teaspoon of cinnamon increases the antioxidant content of a bowl of oatmeal by more than fivefold, with proven bioavailability. A dozen randomized controlled trials have shown that cinnamon—both Cassia and Ceylon—can increase our blood’s antioxidant capacity and limit free-radical damage, even at just a half to one and a half teaspoons daily.
Don’t forget fresh herbs. A tablespoon of fresh lemon balm leaves roughly doubles the antioxidant content of a salad of head lettuce and tomatoes, as does a half tablespoon of oregano or mint, or a three-quarters teaspoon of marjoram, thyme, or sage. If you blend a dressing, remember that dozens of randomized controlled trials have shown that small amounts of ginger and garlic boost our blood’s antioxidant capacity and reduce free-radical damage, so try adding one of the spices or both.
But the runaway leader? Cloves. One of my favorite recipes takes only a few minutes. I simply microwave a sweet potato and then mash it with some cinnamon and a pinch of cloves, which gives the whole thing a delicious hint of pumpkin pie. An inexpensive, simple, easy snack with more antioxidants than some people get in an entire week on the standard American diet.
What about cocoa? Consuming cocoa has been found to lower both markers of oxidative stress and blood pressure. Dark chocolate can do that too, but white or milk chocolate cannot. Cocoa can neutralize the pro-oxidative effect of cow’s milk, whereas soy milk reduces free-radical damage (rice milk, however, makes everything worse).
Is salt worth it?
Salt is a commonly overlooked pro-oxidative component of the diet. I explain this in detail in my video see.nf/salty, but basically, a single routinely salted meal can significantly impair artery function within 30 minutes by suppressing a strongly antioxidant enzyme called superoxide dismutase, which normally inactivates a million free radicals per second.
DNA-Protective Beverages
Although it is best to eat fruit whole, randomized controlled trials have found that tart cherry, orange, pomegranate, tomato, wheatgrass, and low-sugar cranberry juice reduce free-radical damage. Grape juice can also improve the antioxidant properties of the blood. And wine?
Red wine can actually improve the blood’s antioxidant performance—even to the point that the oxidation spike after a Mediterranean meal with fried fish was reduced (but not eliminated). Chronic wine consumption, however, does not appear to be useful. When smokers were randomly assigned to drink about two glasses of red wine, white wine, or dealcoholized red wine daily for weeks, only those who drank the alcohol-free wine experienced a decline in markers of oxidative stress. The reason was attributed to the well-known oxidative effect of alcohol.
Smokers who drink alcohol suffer twice as much chromosome damage as abstinent smokers, but with all other factors equal, smokers who drink green tea are affected about one third less. (Nonsmokers do even better, because they are damaged ten times less.) Although neither coffee nor green tea blocks the oxidative stress triggered by a high-fat meal, both green and black tea can increase the blood’s total antioxidant performance within just 30 minutes of consumption, which lasts at least two hours. (Green tea provides about a 50 percent bigger boost than black tea.) Although the data on the effect of milk in tea are mixed, most studies have shown that cow’s milk slows or completely blocks tea’s antioxidant properties.