Chapter 17
Lifestyle+ — 8
Arunning theme here is that the subtype of each macronutrient—carbs, protein, or fat—matters. The relationship to all-cause mortality demonstrated among more than 125,000 adults followed for up to thirty-two years is shown in figure 3.2. Note that the shift to unsaturated mono- or polyunsaturated fats is accompanied by more favorable longevity data. The shift from saturated fats to plant-based unsaturated fats was associated with substantial reduction of risk of cardiovascular and type 2 diabetes in four clinical trials.
In the influential Science magazine paper “Dietary Fat: From Foe to Friend?” by David Ludwig and colleagues, the answer depends on the quality of the fat, not so much the content level. The ketogenic diet, which relies on high fat, less than 10 percent carbs, and less than 20 percent protein, has been popular for weight loss. But it is also associated with higher cholesterol and cardiovascular risk, brain fog, flu-like illness (keto-flu), and promoting fatty liver disease. A randomized trial at the NIH Clinical Center compared a ketogenic diet (76 percent fat, mostly animal based) with a plant-based, low-fat diet with no limit on the amount of food eaten. Although it presented less glycemic load to the participants, the ketogenic diet led to about seven hundred calories more ingested per day over two weeks. So it is not surprising that the low-fat diet group lost more weight. This small, rigorous trial defied the expectation for the carbohydrate-insulin model, which shows higher insulin driving more hunger and food intake. A fascinating study in mice showed a high-fat-diet-induced mitochondrial dysfunction, and through mitochondrial RNA, this was transmitted via sperm to male offspring. That is a particularly unnerving reason to be concerned about the impact of high-fat diets.
Figure 3.2. Relationship of dietary fat sources and total mortality. Adapted from Dong Wang et al., “Association of specific dietary fats with total and cause-specific mortality,” JAMA Internal Medicine 176, no. 8 (August 2016): 1134–45, https://doi.org/10.1001/jamainternmed.2016.2417.
Caffeine
Coffee lovers enthusiastically received reports of up to a 30 percent reduced mortality, such as from more than 170,000 participants in the UK Biobank and another UK Biobank study supporting a dose response: the more coffee, the longer the person lived. However, most of the studies converge on about four cups per day linked with maximal benefit. A study of more than 520,000 people in ten countries in Europe followed for over sixteen years found a 12 percent reduction in all-cause mortality and 22 percent reduction for cardiovascular mortality. In three large cardiovascular cohort studies, increasing coffee intake was consistently associated with less heart failure. In well over two hundred meta-analyses of coffee and caffeine consumption, there was an association with less risk of breast, colon, endometrial, and prostate cancer; cardiovascular disease; Parkinson’s disease; and type 2 diabetes. These are all observational studies that have a major caveat that the benefit could be linked to other factors, such as lifestyle, diet, and exercise, that might be contributing. We don’t have a cause-and-effect relationship or unequivocal proof that coffee improves health outcomes.