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November/December 2024
November/December 2024 Issue Nutrition’s Impact on Cognitive Decline Strategies for Slowing Progression in Its Beginning Stages Cognitive decline is a normal part of the aging process and occurs on a spectrum from the beginning stages of changes in cognitive and functional impairment through the more severe levels of deficit in dementia or Alzheimer’s disease, leading to a loss of independence and function.1,2 Many people experience a decline in cognitive function starting around age 60.2 Research indicates 67% of individuals likely will experience some amount of cognitive decline by age 70. An estimated 10% of people who have mild cognitive impairment will experience an incremental progression to dementia each year until they receive an official diagnosis. However, not everyone who has mild cognitive impairment develops dementia. The most prevalent type of dementia is Alzheimer’s disease, which is a progressive, neurodegenerative disease that’s the fifth leading cause of death in Americans older than age 65.3 Symptoms of cognitive impairment at the beginning stages can be mild and subjective while daily functioning and independence are maintained.1 Even older adults who perform normally on cognitive tests can report a decline in cognitive functioning when asked about perceived impairment.1,2,4 Researchers have created a framework for subjective cognitive decline in which a person starts to notice a persistent deterioration in cognitive capacity that isn’t related to a specific, acute event. Cognitive decline can include symptoms related to memory, language, processing speed, executive functioning, orientation, attention span, and visual-spatial abilities.1 Defining Mild Cognitive Impairment and Treatments Studies show that the earlier the introduction of lifestyle or pharmaceutical interventions to patients at the beginning stages of cognitive impairment, the more effective they may be at slowing decline. Such patients will have a greater ability to choose and incorporate foods into their diets that can help slow the progression of cognitive decline and increase physical activity.5 Before mild cognitive impairment becomes dementia, some researchers believe it could be reversed or its progression slowed.3,5 Potential treatments for the early stages of cognitive impairment or dementia include interventions related to diet, stress management, sleep quality, mental health, social connection, and exposure to toxins.3 Chronic diseases and nutrition deficiencies may play a role in cognitive impairment, such as insulin resistance, chronic systemic inflammation, and hormonal imbalances, as well as high homocysteine and low vitamin D levels.3 Mild vs Late Stage Cognitive Decline, Nutrition It’s also important to know that as the disease progresses, patients may forget to eat meals and think they have, and report to loved ones that they’ve eaten when they have not, Bruning says. As a result, nutrient deficiencies can follow, compounding the unique nutritional needs of older adults that include adequate protein intake and vitamin B12, which often requires supplementation. “Late- or end-stage dementia may cause dysphagia,” Bruning adds, “leading to aspiration pneumonia, which is one of the leading causes of death in those living with dementia. Refusing to eat, even foods previously enjoyed, may occur, especially towards the end of life.” To be sure, nutrition care is critical in all stages of cognitive decline, but much can be done to empower patients and their families. Los Angeles–based Maggie Moon, MS, RD, a brain health nutrition expert for MIND Diet Meals (minddietmeals.com), an online resource for brain healthy recipes and nutrition news, and best-selling author of The MIND Diet, says that people with age-related mild cognitive impairment often live independently and can still plan meals, shop, prepare healthful foods, though they may need practical or motivational support. Moon says eating foods that maintain brain health in midlife as a preventive measure is key. “Prevention is less painful than cure, and because the onset of disease is decades later, it’s especially critical to eat well for brain health in midlife,” Moon says. “Nutrition is essential to brain health across the lifespan, so it’s never too early to think about nourishing the mind with healthful foods. It’s also never too late, but earlier intervention can be incredibly powerful.” Nutrition support can come in the form of education about which dietary patterns, specific foods, and nutrients can most help people who are experiencing early stages of cognitive decline. Nutrition Considerations Best Supporting Dietary Patterns Moon supports this body of research but emphasizes that although these dietary patterns show promise (some of which have been adapted to cultural diets appropriate for populations worldwide), the MIND diet is the only research-based meal pattern specifically designed for brain health. “From my perspective,” Moon says, “the MIND diet is more adaptable to a greater variety of cultural diets than its two component diets, so the potential for social good is higher, too.” For example, the MIND diet has been adapted to Korean cuisine.6 The MIND diet also has been studied to determine its efficacy in preventing dementia in older adults. A large cohort analysis of 8,353 participants found that adherence to the MIND diet was associated with lower risk of developing dementia in middle-aged and older adults.7 Bruning agrees: “The MIND Diet has been shown to delay or potentially prevent the onset of dementia, especially when [followed] in combination with other healthful lifestyle behaviors like stress management, plenty of movement, good sleep hygiene, sense of purpose, and community connections. [The] Mediterranean [diet] and similar patterns like [the] Nordic [diet] provide anti-inflammatory foods that can help support cognitive health.” Some evidence shows that a keto diet may improve cognition in mild-to-moderate Alzheimer’s, but these results haven’t been studied long-term, Bruning says. The Mediterranean diet has been compared with diets commonly used to improve cardiovascular outcomes, such as a low-fat diet, and has performed better for cognitive decline. A large study of 522 participants was randomly assigned to a Mediterranean diet fortified with either olive oil or mixed nuts. Both interventions improved cognition compared with the low-fat diet in people aged 74.6 ± 5.7.8 Nutrients and Individual Foods “It’s important to stack the diet with omega-3s from foods like walnuts and salmon, B vitamins from foods like leafy greens and lean proteins, and polyphenols from foods like berries and colorful vegetables,” Moon says. “Many of these foods have been independently linked to better cognitive performance in research, and when part of an overall dietary pattern like the MIND or Mediterranean diet.” • Omega-3s. Dietary intake of omega-3s has been studied for its role in slowing cognitive decline and improving cognitive health. Results from a systematic review and meta-analysis of 39 studies on walnuts were inconclusive due to nonuniformity of tests. However, several randomized controlled trials showed improvement in cognitive subdomains or participant subgroups, and observational studies found significant associations between walnut consumption and positive cognitive outcomes.9 Other studies show a dose-response relationship with higher intakes of omega-3s, creating better cognitive protection. A meta-analysis of observational and experimental studies on omega-3 intake through fish consumption found that two portions of fatty fish per week were associated with a 10% reduction in all-cause dementia and a 30% decrease in risk of Alzheimer’s disease.10 • Fruits and vegetables. Fruit and vegetable intake also is an important area of research related to cognitive decline. Berries are a staple in the MIND diet, and guidelines advise eating two 1/2-cup servings per week, though some researchers suggest daily intake. Studies show that berries offer a neuroprotective effect due to their flavonoid content. Berry intake has been associated with improvements in cogitation, attention and concentration, executive functioning, memory, motor skills and construction, and processing speed.11 In other research, 49,493 participants in the Nurses’ Health Study and 27,842 participants from the Health Professionals Follow-Up Study were analyzed over time to determine the association between cognitive outcome and flavonoid intake. Researchers found that higher intakes of total flavonoids, including flavones and anthocyanins, were associated with lower odds of developing subjective cognitive decline.12 This study observed benefits of flavonoid-rich foods beyond berries and saw protective effects from foods such as oranges, grapefruit, apples, pears, celery, peppers, and bananas.12 • Leafy greens and other vegetables contain B vitamins as well as antioxidants and fiber, all nutrients that can benefit cognitive health. Studies have shown that higher intakes of total vegetables are associated with lower risk of developing subjective cognitive function later in life. A large prospective cohort study of 3,718 participants aged 65 and older found that cognitive decline slowed significantly between baseline and annually, with a 40% decrease in those with the highest quintile of vegetable intake (~4 servings/day) compared with the lowest quintile of vegetable intake (~1 serving/day).13 Another large study of 27,842 participants with a mean age of 51 found that vegetable intake in the top vs bottom quintile led to a significant reduction in risk of developing moderate to poor subjective cognitive function.14 Bruning agrees with Moon’s advice for individuals to follow brain-healthy dietary patterns and foods to prevent or delay cognitive decline. According to Bruning, lean protein sources should be recommended to individuals well into their older adulthood to decrease the risk of sarcopenia and other conditions related to falls. “This also is true for those living with dementia, as balance and coordination issues can increase fall risk, leading to fracture or other injury,” Bruning says. Supporting evidence shows that protein intake may play a role in cognitive health and preserve lean body mass in older adults. In a meta-analysis of 4,929 older adults, researchers observed in some studies an association between high protein intake and improved memory, visuospatial, verbal fluency, processing speed, and sustained attention.15 A study of 49,493 women from the Nurses’ Health Study found that higher protein intake compared with total carbohydrate intake was associated with lower odds of developing subjective cognitive decline. However, not all protein was of equal quality in this study. Hot dogs were associated with higher risk of subjective cognitive decline, while lean poultry, fish, and plant-based proteins, such as beans and legumes, were significantly associated with lower odds of subjective cognitive decline.16 Protein intake and cognitive health in the aging population is an emerging area of research with much promise.16 Putting It Into Practice Moon recommends that dietitians partner with patients and caregivers to create a structured and enjoyable eating experience that’s informed by patients’ individual preferences and cultural traditions. As part of this conversation, Moon says dietitians should look for opportunities to provide guidance and recommend greater intake of leafy greens, nuts, beans, berries, seafood, whole grains, liquid oils, and lean poultry, as well as colorful fruits, vegetables, and spices. She recommends creating a schedule to help manage stress among caregivers and patients and says RDs should assess the need for multivitamins or other supplements to close nutrient gaps in those with mild cognitive decline. Bruning agrees that it’s important to take a personalized approach with each patient and their families at the beginning stages of cognitive decline. While beneficial dietary patterns and specific foods can help treat and support those living with dementia, Bruning says, unforeseen difficulties can crop up along the way. “The focus must remain on supporting individuals’ wishes and dignity and not forcing a treatment plan that doesn’t work for their life or their families,” Bruning says. The bottom line, she says, is meeting each person where he or she is in an ever-changing spectrum of health. “You can’t force them to eat what you want them to. Find out what works for them.” Final Thoughts — Ginger Hultin, MS, RDN, CSO, is a nutrition and health writer and board-certified specialist in oncology nutrition based in Seattle. She also runs a virtual concierge nutrition practice, Ginger Hultin Nutrition PLLC.
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