Chapter 24
Lifestyle+ — 15
General conclusions about these results remain elusive. The problem with a strict calorie-restricted diet is that it is hard to adhere to, has been associated with loss of bone density and muscle mass, and slowed brain function. Our brain is only 2 percent of our body mass but consumes 20 percent of our calorie intake. On the other hand, multiple studies support an improved immune response, and, perhaps interrelated, potential antitumor effects show up in experimental models. No calorie-restricted, time-restricted, or intermittent fasting diets have been proven to provide antiaging properties, but a small, randomized trial showed reduction of a biological age score that relied on some improvements of biomarkers (immune system, liver, glucose regulation) with multiple cycles of a fasting-mimicking diet. Until there’s more definitive evidence, perhaps the best practical advice is to eat an early dinner, at least three to four hours before going to bed, and avoid any caloric intake before the next morning’s breakfast.
Several scientists involved in that Lancet Discovery Science study signed on to this perspective: “This fad for fasting—and the perception that it is a clear path to weight-loss and ‘wellness’—creates opportunities for charlatans.”
There’s a tie-in to all of this with our sleep-wake cycle—our circadian rhythm—and gut microbiome. More than half of our gut microbiome flora rhythmically fluctuates throughout the day-night cycle. Our circadian physiology has diverse and important effects on all our organ systems, which include nutrient absorption and gut hormone production. Our central clock, set by light, resides in the brain’s suprachiasmatic nucleus, whereas our peripheral clocks are distributed throughout organs and tissues in the body. Disruption of timing of our meals desynchronizes the clocks and induces glucose intolerance. The immune cells of our gut, the gut barrier, and inflammatory response are affected by our clock system. That’s why it’s helpful to maintain the same pattern of consumption from day to day.
Supplements
Despite their popularity and heavy marketing, there’s little or no hard evidence for the benefit of taking any vitamins or supplements, especially in those who are following a healthy diet. Vitamin D has been advocated for prevention, but a wide variety of randomized trials, and large observational studies have failed to back its benefit. A large, randomized trial of omega-3 fatty acids or placebo in nearly twenty-six thousand participants with over five-year follow-up failed to show any benefit for preventing cardiovascular disease or cancer. A possible exception is that there may be a modest slowing of cognitive aging in older adults taking daily multivitamins, as seen in a randomized trial among 573 participants who took a Centrum Silver multivitamin or matching placebo daily (specifically improved episodic memory and global cognition). The authors added their results to previous randomized trials of about five thousand older adults and then claimed the benefit corresponded to “a two-year reduction in brain aging,” which was met with objection by neuroscience experts. Indeed, randomized trials of multivitamins have shown no effect for preserving cognition, such as one in six thousand men tracked for twelve years. A comprehensive assessment of 277 randomized trials testing vitamins and supplements failed to show survival benefit or reduced cardiovascular mortality for vitamin A, B complex, C, E, selenium, antioxidants, calcium, fish oils, and many others widely used. Furthermore, evidence emerged that calcium plus vitamin D might increase the risk of stroke and cardiovascular mortality, as seen in a large, randomized trial in older women. Niacin intake appears to be associated with increased cardiovascular risk by promoting inflammation. There remain many candidates that have not been adequately tested, some referred to as “longevity vitamins,” such as taurine and choline mentioned earlier and several others. For now, I say take them with a grain of salt.