Diet and longevity

The relationship between diet and longevity encompasses diverse research studies involving both humans and animals, requiring a multidisciplinary analysis of complex mechanisms underlying the potential relationship between various dietary practices, health, and longevity.

Food selection may have an impact on overall health and lifespan. Some dietary practices that may be associated with health and longevity include fasting, calorie restriction, intermittent fasting, the Mediterranean diet, and plant-based diets.

As of 2021, there is no clinical evidence that any dietary practice contributes to longevity.

Regional or cultural diets

The tendency towards longevity in some regions of the world has been attributed to specific regional diets, such as the Okinawa diet and the Hunza diet.

Okinawa diet

The Okinawa diet, which describes the traditional dietary practices of indigenous people of Japan's Ryukyu Islands in the mid-20th century, was asserted to have contributed to a relative longevity.

The dietary intake of Okinawans compared to other Japanese circa 1950 shows that Okinawans consumed fewer total calories (1785 vs. 2068), less polyunsaturated fat (4.8% of calories vs. 8%), less rice (154g vs. 328g), significantly less wheat, barley and other grains (38g vs. 153g), less sugars (3g vs. 8g), more legumes (71g vs. 55g), significantly less fish (15g vs. 62g), significantly less meat and poultry (3g vs. 11g), less eggs (1g vs. 7g), less dairy (<1g vs. 8g), much more sweet potatoes (849g vs. 66g), less other potatoes (2g vs. 47g), less fruit (<1g vs. 44g), and no pickled vegetables (0g vs. 42g). As proportions of total caloric intake, foods in the traditional Okinawa diet included sweet potato (69%), rice (12%), other grains (7%), legumes including soy (6%), green and yellow vegetables (3%), refined oils (2%), fish (1%) and seaweed, meat (mostly pork), refined sugars, potato, egg, nuts and seeds, dairy and fruit (all <1%). Specifically, the Okinawans circa 1950 ate sweet potatoes for 849 grams of the total 1262 grams of food that they consumed, which constituted 69% of their total daily calories. Another low-calorie staple in Okinawa was seaweed, particularly, konbu or kombu. Okinawans ate three grams total of meat — including pork and poultry — per day, substantially less than the 11-gram average of Japanese as a whole in 1950.

As assessed over 1949 to 1998, people from the Ryukyu Islands (of which Okinawa is the largest) had a life expectancy among the highest in the world (83.8 years vs. 78.9 years in the United States), although the male life expectancy rank among Japanese prefectures plummeted in the 21st century. Okinawa had the longest life expectancy in all prefectures of Japan for almost 30 years prior to 2000. The traditional Okinawan diet was widely practiced on the islands until about the 1960s. Dietary practices then shifted towards Western and mainland Japanese patterns, with fat intake rising from about 6% to 27% of total caloric intake and the sweet potato being supplanted with rice and bread. Although many factors could account for differences in life expectancy, calorie restriction and regular physical activity were deemed as prominent factors. People have promoted the "Okinawa diet", believing it to be nutritionally dense yet low in calories, though it is unlikely that the diet alone could explain high life expectancy among seniors on Okinawa in the 20th century.

In addition to their relative longevity identified in the mid-20th century, islanders were noted for their low mortality from cardiovascular disease and certain types of cancers. One study compared age-adjusted mortality of Okinawans versus Americans and found that, during 1995, an average Okinawan was 8 times less likely to die from coronary artery disease, 7 times less likely to die from prostate cancer, 6.5 times less likely to die from breast cancer, and 2.5 times less likely to die from colon cancer than an average American of the same age. In the 21st century, the shifting dietary trend coincided with a decrease in longevity, where Okinawans actually developed a lower life expectancy than the Japanese average.

Overall, the traditional Okinawa diet led to little weight gain with age, low body mass index throughout life, and low risk from age-related disease. In the 1972 Japan National Nutrition Survey, it was determined that Okinawan adults consumed 83% of what Japanese adults did and that Okinawan children consumed 62% of what Japanese children consumed. Since the early 2000s, the difference in life expectancy between Okinawan and mainland Japanese decreased, possibly due to Westernization and erosion of the traditional diet. The spread of primarily American fast-food chains was linked with an increase in cardiovascular diseases, much like the ones noted in Japanese migrants to the United States. No ingredients or foods of any kind have been scientifically shown to possess antiaging properties.

Hunza diet

The Hunza diet consists of a series of selective food and drink intake practiced by the Burusho people (also called the Hunza people) of northern Pakistan. The diet mostly consists of raw food including nuts, fresh vegetables, dry vegetables, mint, fruits and seeds added with yogurt. The cooked meal, daal included with chappati, is included for dinner. It has also been advocated for being inexpensive and mostly self-producible. The Hunza lifestyle was referenced in the Biorhythm Calendar published by the American Health Institute in the late 1970s. In a 1997 book about the Hunza diet, the author postulates that humans should live up to 120 to 150 years, with the Hunza diet as key to this longevity.

Fasting

The concept of fasting and longevity involves abstaining from food to decrease the incidence of diseases and increase lifespan. The use of fasting dates to the 5th century BC, as attributed to Greek physician Hippocrates who suggested that people with certain illnesses should abstain from food or drink as therapy.

Although health can be influenced by diet, including the type of foods consumed, the amount of calories ingested, and the duration and frequency of fasting periods, there is no good clinical evidence that fasting promotes longevity in humans, as of 2021.

Calorie restriction

Calorie restriction is a widely researched intervention to assess effects on aging, defined as a sustained reduction in dietary energy intake compared to the energy required for weight maintenance. To ensure metabolic homeostasis, the diet during calorie restriction must provide sufficient energy, micronutrients, and fiber. Some studies on animals showed that restricting calorie intake resulted in lifespan extension.

According to preliminary research in humans, there is little evidence that calorie restriction affects lifespan.