Chapter 19
Lifestyle+ — 10
I’ve grouped these together because they are at opposite ends of the spectrum for reduced versus increased risk of mortality and relative environmental impact. At one end is processed meats like hot dogs, bacon, and sausages that are linked to the highest risk, deemed carcinogenic by the World Health Organization, and their production leads to large amounts of greenhouse gas emissions. Not far away for increased associated mortality risk are unprocessed meats, pork and beef, which have been labeled “probably carcinogenic.”
Figure 3.3. Association of alcohol intake and cardiovascular conditions. Adapted from Kiran Biddinger et al., “Association of habitual alcohol intake with risk of cardiovascular disease,” JAMA Network Open 5, no. 3 (March 2022): e223849, https://doi.org/10.1001/jamanetworkopen.2022.3849.
In prospective studies of more than fifty-three thousand women and twenty-seven thousand men, with an eight-year follow-up, there was a clear association with increased mortality (fig. 3.4). The environmental impact of the opposite poles represents a marked difference: a switch from high meat to a vegetarian diet would reduce greenhouse gases by 47 percent. But this twofer of putative benefit for health and the environment is not clear-cut. A systematic review of all the studies (nearly 120) did corroborate the increased risk of cancer for processed and unprocessed red meat, but concluded it was small and with low certainty. A similar study made the same point for cardiometabolic outcomes. It certainly isn’t settled. A more recent study of nearly thirty thousand Americans followed for nineteen years concluded that both processed and unprocessed meat, but not poultry or fish, were linked to a small increased risk of all-cause mortality. There was a twist with respect to poultry: two or more servings of unprocessed or processed meat or poultry was associated with a 4 to 7 percent increased risk of developing cardiovascular disease.
In contrast, plant-based foods are plainly healthier. A summary of nine studies in more than three hundred thousand participants linked plant-based diets with 23 percent lowered risk of type 2 diabetes. A meta-analysis of thirty-two studies indicated substantial protection from all-cause mortality, cardiovascular deaths, and type 2 diabetes when processed meat diets were substituted by plant-based foods. Among more than seventy-two thousand participants in Japan, the intake of plant protein was linked to an 11 percent reduced risk of total and cardiovascular-related mortality. Compared with a ketogenic diet, a vegan diet enhanced the immune system responsiveness. Substitution of plant for animal protein for 3 percent of caloric intake was associated with 40 percent less cancer-related mortality. A systematic review added to the reduction of cancer risk linked to plant-based diets. Using DNA methylation markers, a way to assess epigenetic age, a plant-based diet slowed the pace of aging compared with an omnivore diet in a randomized trial of identical twins.