Chapter 158
Which Nut Is the Healthiest?
Maybe peanut butter? The details are available at see.nf/pblongevity, but basically we probably have to say that the longevity benefit associated with nuts (including peanuts) apparently does not extend to peanut butter, perhaps because the cellular structure that supplies our good gut bacteria with lots of prebiotics is no longer intact in the butter. The healthiest nut is probably the walnut. Not only does it have the highest antioxidant and omega-3 content, it is also the only nut that significantly improves arterial function, and it suppressed the growth of cancer cells in vitro better than all other nuts.
Nuts have generally been associated with a reduced risk of impaired flexibility and mobility in older men and a lower risk of impaired overall functioning in older women, but in the Harvard Nurses’ Health Study, a significant association between walnuts and healthy aging was not found until confounding factors were accounted for. Of all the nuts examined in the PREDIMED study, scientists found the greatest benefit with walnuts, especially with respect to cancer. Those who ate more than three servings of walnuts per week cut their risk of dying from cancer in half. A review of the available data concluded: “The far-reaching positive effect of a plant-based diet that includes walnuts could be the most important message for the public.”
Greens
Nuts appear to be superior to vegetables in their life-extending effect, but only when you compare them with vegetables in general. Leafy green vegetables can absolutely hold their own against nuts when it comes to a lower risk of premature death; they are also associated with a reduced risk of heart disease, strokes, and some cancers and might even help prevent some of the leading causes of age-related vision loss (see the chapter “Preserving Eyesight”). Leafy green vegetables can strengthen the immune system, slow metabolism, and protect the body against the effects of air pollution, one of the most common causes of death worldwide.
Broccoli for the Gut’s Immune Defense
The outside world has its greatest influence on us through the gut. If you take into account all the folds of its lining, overall it is about the size of half a badminton court. Yet at one fifty-millionth of a meter, the lining is extremely thin. The barrier between the blood and the outside world is thus many times thinner than a paper tissue. If the gut lining were thicker, nutrients would have difficulty getting through. The skin has to be watertight so we don’t leak out, but the gut lining has to let nutrients and fluids pass through. Because only such a thin layer separates our innermost being from the chaos out there, we need a good defense to keep evil out.
This is where the immune system comes into play—more precisely, the intraepithelial lymphocytes, specialized white blood cells that have two functions: They serve as the gut’s first line of defense against pathogens, and they maintain and repair the thin gut lining. The so-called Ah receptor covers these lymphocytes and activates the cells. This essential receptor is present in significantly increased amounts in 100-year-olds; its loss leads to premature aging (at least in mice). For years, researchers searched for the key to the Ah receptor’s lock. If one knew how to activate these cells, one might be able to strengthen defenses. As it turned out, that key is found in broccoli. More information is available at see.nf/gutdefenses.
The immunity boost we get from eating broccoli and other cruciferous vegetables protects us not only from pathogens in food but also from environmental pollutants such as car exhaust or tobacco smoke. Since dioxins and certain other pollutants exert their toxic effect via the Ah receptor system, components from cruciferous vegetables can inhibit them. Anyone who thinks fear of toxic chemicals wafting around is exaggerated hippie paranoia should be told that they are in fact the fifth-leading cause of death.
Billions of Life-Years Are Lost Every Year
According to the renowned Global Burden of Disease Study, air pollution is the fifth-leading cause of death for humankind and claims about four million victims every year from lung cancer, emphysema, heart disease, strokes, and respiratory infections. Paradoxically, a respiratory infection—Covid-19—may have saved lives in some parts of the world. In the first months after the lockdown, air pollution in China fell so sharply that there were up to 30 000 fewer air-pollution deaths per month. In other words, air quality in China was so bad that Covid 19 may ultimately have saved around 1000 lives a day.
Nine tenths of people live in areas that violate the WHO air-quality guideline. Estimates suggest that global life expectancy would increase by an average of more than two years if air quality were brought into line with these standards. Every year, polluted air robs us of several billion years of life expectancy. Traffic-related air pollution has also been associated with premature skin aging and dementia. What can we do about it?
In 2014, China declared a “war against air pollution,” and since then pollutant levels in the air there have fallen by 29 percent, which likely increased life expectancy by years. Elsewhere, such drastic measures may be “politically unacceptable,” since they “could indirectly impair the population’s comfort.” How can we protect ourselves until there are better vehicle inspections, public transportation, bus lanes, bike paths, and perhaps even congestion charges in cities to finance air-improvement measures?
One could minimize one’s personal exposure to the effects of air pollution by, for example, minimizing physical exertion outdoors on days with high air pollution and in areas with heavy traffic. A randomized crossover study with older men and women found that “the cardiorespiratory benefits of exercise are diminished or even reversed” when one walks along heavily traveled roads. On days with high air pollution, one should even consider wearing respiratory protection, such as a close-fitting FFP2 mask.
Even if you pack up your family and move to the countryside, the ever-larger wildfires triggered by climate change can pollute the air almost everywhere, no matter where you live and breathe. Home air purifiers are increasingly recommended during fires because numerous studies have shown that they reduce fine particulate exposure and are beneficial for the airways and for cardiovascular health. I recommend models with a HEPA filter and warn against air-cleaning technology that could emit harmful byproducts, such as electrostatic filters (ionizers) or negative-ion generators.
However, poor diet still causes more than twice as many deaths as air pollution. Fortunately, you can use the power of a healthy diet against the effects of air pollution.
Detoxification Through Diet
Cruciferous vegetables can stimulate detoxification enzymes in the liver so strongly that people who eat a lot of broccoli have to drink more coffee to get the same caffeine kick. Detoxification enzymes are also found in the lining of our airways. Studies showed that people in whom these enzymes are less effective from birth react extremely allergically to diesel exhaust. This could indicate that these detoxification enzymes actively combat inflammation from air pollution. Does broccoli also strengthen the activity of these enzymes?
The sulforaphane in cruciferous vegetables is the “strongest known activator” of certain important detoxification enzymes, so scientists wanted to know whether it holds its own against inflammation-promoting air pollution. Details are available at see.nf/pollutiondetox, but so much can be said: When participants received diesel exhaust and influenza viruses into their noses, researchers found that after one or two cups of broccoli they got a double benefit: less inflammation from the exhaust and an improved antiviral immune response. It also turned out that broccoli lowers inflammation levels in smokers and massively accelerates the excretion of carcinogenic pollutants such as benzene from the body.