Nutrition plays a pivotal role in healthy aging, including maintaining cognition. A healthy diet is essential: as well as meeting energy requirements, preventing deficiency diseases and helping to maintain muscle mass, diet affects risk of chronic diseases that affect people as they age. Changes in smell, dentition, cognition or motility can lead to reduced food intakes that further exacerbate the risk of malnutrition in older adults (1). A healthy diet that is rich in fruits, vegetables and whole grain foods, and with adequate intakes of low-fat dairy and protein is associated with better markers of nutrient status for folate, vitamin B12, vitamin C and beta-carotene and an improved quality of life in older adults (2). As well as supporting all-round health, certain nutrients help to maintain cognition in aging (3). Which dietary factors are most important to support seniors’ health and mental functions?
Balancing nutrient and energy needs
As people age, their energy needs tend to decrease (1). Nutrient requirements, however, remain the same or even increase. This places pressure on diets to meet all nutrient requirements on a tighter calorie “budget.” Two situations can arise: the diet remains the same despite lower energy needs leading to weight gain, or energy intakes can decrease leading to dietary deficiencies. Various approaches can be used to increase the nutrient density of the diet. Registered dietitians can offer practical advice regarding how to deal with changing energy and nutrient needs for older people. Swapping fortified foods for other foods that are normally consumed can help to improve nutrient intakes. The use of dietary supplements may be beneficial, especially if particular deficiencies have been identified.
Water is an essential nutrient, and arguably the most important. While it is possible to survive weeks, months and, in a few cases years with a negligible intake of some nutrients, an absence of water can be fatal in only a few days. Even small decreases in body fluid levels can affect cognition (4), and more severe dehydration is a common reason for hospitalization in older adults (5). The elderly may have more difficulty reacting to signals that they are thirsty: not only is their sensation of thirst reduced, they may be less inclined to react to it due to mobility challenges. Seniors can keep their brain sharp by avoiding dehydration.
A nutrient that is consistently found to be lacking in the diet of older people is dietary fiber (1). This is unfortunate because fiber increases bulk in the large intestine and helps to prevent constipation, a common complaint of the elderly and one that reduces quality of life (6). Foods containing a good source of dietary fiber tend to be higher in vitamins, minerals and phytochemicals that can benefit health. Dietary fiber reduces cholesterol levels and may help reduce glucose spikes after a meal, thus contributing to a reduced risk of chronic disease in aged populations. Several mechanisms are proposed for how fiber can help cognition: it can reduce neurotoxicity associated with inflammation. Fiber also changes the production of short-chain fatty acids to alter the functioning of the brain, and increases the number of good bacteria to prevent dysregulation of the response to stress (7).
The elderly may have enhanced protein needs to preserve muscle mass (1). While standard nutrition advice does not recommend that older adults increase their protein consumption, emerging research indicates that enhancing the protein content of the diet can increase muscle (8), improve physical functioning (9) and even ameliorate cognitive functioning (10), especially if combined with a weight-bearing exercise program. As the elderly are at an increased risk of poor protein intakes, extra attention should be placed on providing adequate protein in the diets of older people (11).
Calcium and vitamin D
Both calcium and vitamin D are required to support bone health throughout the life cycle, and are particularly important in older age. Calcium is the most abundant bone mineral, and vitamin D helps calcium to be absorbed. Extra attention to vitamin D is recommended for older people at risk of fractures (12). Aside from maintaining bone, low vitamin D levels are associated with risk of cognitive deficits in seniors (13-16). Deficiency may cause disruption to brain cells, reducing their resistance to damage (17).
Vitamin B12 and folic acid
Deficiency in vitamin B12, symptoms of which include neurological problems, is a relatively common condition in the elderly with approximately one in five elders affected in well-nourished populations (1). Older people are at greater risk of deficiency due to changes in the digestive tract due to the aging process. Seniors with functional vitamin B12 deficiency are more likely to have cognitive impairment and limitations in their daily activities than peers with normal vitamin B12 measures (18, 19). Vitamin B12 deficiency may alter the volume or structure of the brain to cause these functional or cognitive difficulties (20, 21). In individuals with an adequate folate status, the symptoms of frank vitamin B12 deficiency may be masked until irreversible nerve damage has occurred (1). On the other hand, folate deficiency is a direct cause of elevated levels of homocysteine in the blood, which is an independent risk factor for heart disease (22). It is vital that seniors have both an adequate vitamin B12 and folate status in order to maintain cognition and have a healthy heart.
The major fat-soluble antioxidant in cells is vitamin E. It helps prevent oxidation of fatty acids in cells and maintains the integrity of cell walls by preventing oxidative damage, and assists in nerve conductivity (23). Vitamin E deficiency shows neurological symptoms including changes in walking style and nerve damage. Some research suggests that a better status of vitamin E helps to preserve brain white matter (24). Several epidemiological studies have found that higher vitamin E levels are associated with a reduced risk of cognitive impairment in older people (25-27). A randomized, placebo-controlled clinical trial using a very high amount of vitamin E in patients with mild to moderate Alzheimer’s disease found that it delayed disease progression by six months over the course of the two to three year treatment, including a reduced burden on caregivers by two hours per week (28). As vitamin E deficiency is highly prevalent worldwide, attention to vitamin E intakes may be important in supporting cognition in older people (23).
Omega-3 fatty acids
The omega-3 polyunsaturated fatty acids, particularly those from marine sources, support cognition as people age (29-31). These fatty acids are found in high levels in the brain, where they make up part of the cell wall where they can affect the function of cell membranes. They also can regulate the release of neurotransmitters and reduce systemic inflammation. Some research links omega-3 fatty acids with improvements in brain structure (32-34). These structural improvements have translated to supporting cognitive function. Some intervention studies have shown positive cognition results when supplements are given to healthy adults (35-37), although there were differences in length of supplementation, dose and cognitive testing methods. Maintaining a normal status of omega-3 fatty acids may be an important part of healthy aging (38).
All-round good nutrition and an active, social lifestyle
Even though we have looked in detail at individual nutrients important for healthy aging, it is the combination of nutrition, regular physical activity, healthy behaviors such as not smoking, and a brain-stimulating environment that work together to maximize cognitive reserves (39). Attention to all of these factors is important to preserve health and support cognition in aging.