Many people in the life extension community follow some kind of diet. Historically, caloric restriction (CR) has been the most popular and most discussed option. Other popular diets include the Mediterranean diet and the Paleolithic diet. In one sense, comparing these diets is like comparing apples and pears. The emphasis of caloric restriction is on how much we eat (given adequate nutrition) and the other diets are more concerned with what we eat. People who follow certain diets may also have different aims. In the case of CR, life extension. In the case of the Mediterranean diet, preventing and delaying cardiovascular and neurodegenerative diseases. And many who adopt a low-carb diet are (initially) motivated by securing sustainable weight loss.
Assuming that diet plays some role in longevity and disease, it is rather obvious that cryonicists should take a strong interest in choosing the right diet. As it looks to me, there are a number of important considerations.
1. The most important aim of a diet for cryonicists should be to avoid, or delay, neurodegenerative diseases. Extending your life and ending up with advanced Alzheimer’s Disease is worse than dying young and being cryopreserved under circumstances that optimize preservation of personal identity.
2. The choice to follow a particular diet should work for your genotype. Admittedly, nutrigenetics is a very young field but there is a growing recognition that human evolution has not stopped since the start of agriculture and that different populations respond differently to certain diets. And even within these populations we should expect individuals to respond differently to diet.
3. A decision to follow a certain diet should be based on empirical evidence, not on intuition, abstract theories, or thought experiments. In the case of choosing diets, this means identifying a diet that has shown a favorable ratio of good outcomes in experimental studies, and humans in particular.
Putting this all together, it seems to me that a low calorie diet remains the most defensible choice for most cryonicists because it has been studied longer, studied more extensively, and has the most robust favorable outcomes. CR also seems to stand out favorably in that there are relatively few studies that find detrimental outcomes and its benefits seem to embrace many species and populations. Another advantage of CR is that it can capture all the important goals that life extentionists seeks from a diet: longevity, weight loss and prevention (or delay) of neurodegenerative diseases.
It may be the case that many of the benefits of CR actually come from a reduction of carbohydrates. But one of the problems with a paleolithic diet is that it may be more beneficial for certain populations than others. As Gregory Cochran and Henry Harpending demonstrate in their seminal book The 10,000 Year Explosion: How Civilization Accelerated Human Evolution, human evolution did not stop when hunter gatherers started agriculture, and some populations are more adapted to agricultural products (such as milk) than others. Another concern about the paleolithic diet is the controversy surrounding saturated fat. For life extentionists who carry one or two copies of the ApoE4 gene, a diet high in saturated fat may actually increase the probability of Alzheimer’s disease. Others dispute this and recommend a diet high in (saturated) fat to prevent dementia. In light of this uncertainty, the most prudent course of action may be to incorporate the emerging evidence against carbohydrates into a CR diet without emphasizing saturated fat.
There is an ongoing debate whether the longevity benefits of CR will be as great in humans as in lower species but the evidence so far seems to be that there are at least benefits in terms of delaying the onset of age-associated diseases. Whether these benefits are conferred through a change in gene expression or because they reduce the amount of chemicals that can participate in pathological events is not clear, but our incomplete knowledge about the mechanisms involved should not deter anyone from following CR. As I currently see it, the role of ongoing research into nutrigenetics and other diets should be to further calibrate and refine a low calorie diet to optimize it for a specific individual and to further delay the onset of neurodegenerative diseases.
CR seems to come closer to being a universal diet than other diets but it may be contra-indicated for some people, such as certain athletes and extreme ectomorphs. There are also cases in the life extension community of people who pushed it too hard (or neglected good nutrition), offsetting all the gains from the diet, or even endangering their own health. A diet that does not make a person feel good, is generally not a diet that is good, let alone one that can be sustained over time. The aim of a diet should not be to conform to an impersonal set of recommendations, but to monitor your own response and increase the chance for personal survival.