Longevity, also known as lifespan, is the length of time spent alive. Human longevity varies depending on numerous factors, including socioeconomic status, sex, gender, and lifestyle, but in the United States the average person lives to be about 79 years old.^[1]

Healthy aging is the process of maintaining good health and functional ability during older age. A related concept is healthspan, a term defined as the number of years of life spent in good health, free of the chronic diseases and disabilities associated with aging.^[2]

Diet and maintaining a healthy body weight seem to play a major role in healthy aging and longevity, with different foods and dietary patterns likely capable of increasing or decreasing the risk of various age-associated diseases. It is evident that overweight and obesity increase the risk of many chronic diseases that decrease lifespan and healthspan, including type-2-diabetes, stroke, and more.

Two diets frequently studied in the context of aging and lifespan are caloric restriction (CR) and intermittent fasting (IF). CR involves a (usually at least 10%) reduction in calorie intake relative to typical levels without inducing malnutrition, while IF involves alternating periods of normal food intake with extended periods (usually 16–48 hours) of low-to-no food intake.^[3][4] CR and IF are often found to extend the lifespans of animals (particularly mice) as well as improve risk factors for age-related diseases (e.g, cardiovascular-disease, type-2-diabetes) in humans,^[5][6] but ultimately the effect of these dietary approaches on human lifespan and healthspan has not been completely evaluated.

Supplements that may help reduce the risk of diseases known to shorten lifespan and/or healthspan include cocoa-extract (for cardiovascular-disease),^[7] protein powder (for sarcopenia),^[8] and certain B-vitamins (for cognitive-decline),^[9]. Outside of treating vitamin deficiencies, the evidence for many of these supplements is inconsistent or has important shortcomings.

Studies on animals (e.g., mice) have noted improvements to lifespan and/or healthspan from various supplements, including NAD+ precursors (e.g., nicotinamide riboside and nicotinamide mononucleotide),^[10][11] glycine (sometimes in combination with N-acetyl cysteine),^[12][13] and alpha-ketoglutarate.^[14] Astragalus may be able to lengthen telomeres (the DNA sequences at the end of chromosomes that shorten with age). However, much of the research on these supplements has notable limitations, and there is currently very little quality evidence that they promote healthy aging or increase lifespan in humans.