The food we consume goes a long way in determining the state of our health. Nutrition readily impacts life and health spans. Among other issues, overnutrition can lead to the onset of obesity. But we also need to consider the impact of aging, which cannot be underestimated.
As people age, they become more prone to disease and generally experience a decline in mental or physical capability. So any effort made to interrupt the aging process may also inhibit the onset of disease and optimize the quality of life for the elderly.
Caloric restriction and aging
Probably the most often used non-genetic technique known to extend life and improve health involves the restriction of calories. As far back as the 1930s, researchers found that aging can be slowed. Cutting the caloric intake of mice, while avoiding malnutrition, almost doubled their life span. In the 1980s, other investigators found that when adult-initiated caloric restriction in rats was begun at one year of age, their lifespan increased while their incidence of spontaneous cancer was cut by half.
More recently, it has been found that restricting calories also has a beneficial effect on such organisms as worms, flies, and various rodents, and may involve a common genetic pathway. Scientists are not exactly sure how caloric restriction brings about positive benefits. But many do suggest that the extension of life span that results from restricting calories entails the down-regulation of insulin and insulin-like signaling, amino acid-signaling, and glucose-signaling pathways.
Some believe that to be effective, restricting caloric intake should involve at least 20% to 40% reduction in dietary caloric levels. Self-monitoring our food intake, by counting calories, can play a critical role in attempts to lose weight. But it is a common finding that subjects experience bias which disables them from accurately estimating how many calories they may have actually dropped.
Moreover, the interactions between nutrition, health, and aging in terms of how each impacts and influences the others remain unknown to a certain extent. While restricting one’s intake of calories has been found to improve one’s health, the dietary macronutrient content is also important in determining the outcome.
Macronutrients and fasting
Macronutrients are a family of chemical compounds that provide humans with the bulk of their energy requirements. The three main macronutrients are carbohydrates, proteins, and fat. The body needs these nutrients in large amounts. Carbohydrates can be sourced from grains, dairy, and fruit; proteins from such foods as legumes, eggs, fish, dairy and meat; and fat from oils and nuts, dairy foods, many animal foods, and certain fruits.
Restrict specific macronutrients
A promising fasting strategy that is an alternative to caloric restriction involves restricting specific macronutrients. Some research has shown that cutting protein and amino acid intake may be the most effective approach in terms of extending longevity and health. Moreover, cutting one’s consumption of proteins can strongly influence lifespan in the same manner as restricting one’s diet.
A 2014 analysis conducted by the National Health and Nutrition Examination Survey (US National Center for Health Statistics, Centers for Disease Control and Prevention) found that low protein intake is associated with a significant reduction in Insulin-like growth factor 1 (which may contribute to aging), cancer, and overall mortality for those 65 years old and younger. Also beneficial is a high-carbohydrate, low-protein diet that can lead to a longer lifespan and improved cardio-metabolic health. Research has shown that restricting even one essential amino acid – methionine -- in a normal diet can increase lifespan and resistance to stress,.
Restricting the intake of specific macronutrients may also be beneficial for those with type 1 diabetes mellitus (DM1) where tight metabolic control can inhibit the onset of long-term complications. Carbohydrate counting can enable patients with DM1 to have more flexible food choices.
One study examined the effects of nutrition and short-acting insulin, based on the carbohydrate counting method, on clinical and metabolic control in patients with DM1. The study included 51 patients with DM1. Researchers prescribed a balanced diet, based on limiting carbohydrate intake, and also administered short-acting insulin, based on the total amount of carbohydrate per meal -- 1 unit per 15 grams of carbohydrate.
A significant decrease in HbA1c (which mirrors long-term blood glucose) levels occurred after three months. It appears that the administration of short-acting insulin, based on carbohydrate counting, optimized glycemic control in patients with DM1, at least temporarily. There were no changes in body weight, despite increases in total daily insulin dosage.
Reviewed by Liji Thomas, MD