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Colorful diet offers hope for preventing cognitive decline
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by Daniel A. Nadeau, MD, and Harsimran Singh, PhD
Epidemics of diabetes and dementia continue to grow, with diabetes playing an increasing role in cognitive decline, brain atrophy and risk for vascular dementia. Modest cognitive decrements may already be present in patients with prediabetes and those who are in their early stages of type 2 diabetes. Treatment of diabetes should include efforts at brain protection, given that cognitive loss so adversely affects critically needed self-care capability.
Mechanisms for acceleration of cognitive decline in type 2 diabetes include decreased neurogenesis within the hippocampus, leading to brain atrophy, disintegration of the blood-brain barrier, hyperglycemia with advanced glycation end products, oxidative stress and inflammation. Insulin resistance and vascular dysfunction also play key roles in development of dementia and amyloid pathology.
Although amyloid is thought by some to be central to the development of Alzheimer’s disease, a vaccine that dramatically reduced amyloid has been unsuccessful in treating the condition, hence supporting the hypothesis that the abnormal proteins may be the brain’s protective mechanism for fending off the damage done by free radical oxidation.
Role of nutrition therapy
Lifestyle intervention remains a key component in holding back the tide of diabetes and dementia. New research suggests that certain food choices may be especially helpful for those at risk — not just by preventing diabetes, but also by supporting optimal brain function while aging. Emerging evidence supports nutritional interventions, specifically with plant-based foods that protect against age-related decline. Such nutritional interventions can protect behavioral function from age-related decline.
From a bird’s-eye view, plants live in a sea of free-radical oxidation that would destroy anyone forced to face the sun’s enormous tide of energy day after day with no protection. Yet, plants sit unprotected and thrive. Plants eclipse the sun’s free-radical furnace with protective biochemical elements that are both the engines of life and its protectors. The protective elements are often referred to as phytochemicals or phytonutrients.
When animals eat plants, they consume not only their energy, but also the protective elements. Nearly all major degenerative disease stems from oxidative damage and inflammation: cancer from DNA damage from free radicals, cardiovascular disease from LDL oxidation, brain disease from free radical damage, and arthritis from oxidation and inflammation. A lack of plants in the diet and dramatic increases in processed foods are accelerating these degenerative diseases. Recent research suggests that certain plants may be especially helpful for preventing and reversing dementia.
Blueberries , cherries
Blueberries contain a plethora of bioactive phytochemicals that have potential health benefits. In a seminal study conducted by Joseph and colleagues, older animals fed blueberries for 2 months showed improvements in memory and motor skills. The authors concluded that supplementation with fruit extracts that are high in phytonutrient antioxidants can actually reverse some of the age-related neuronal and behavioral dysfunction. Additionally, blueberries have been shown to increase both insulin-like growth factor I and new brain-cell formation.
The first human study to test the translation of polyphenolic compounds in blueberries, mainly anthocyanins, and their antioxidant and anti-inflammatory effects, showed rather robust effects in paired associate learning, word list recall, and trends toward reduced depressive symptoms and glucose control.
Other human studies investigated the effects of cherry juice, also a rich source of anthocyanins, which improved verbal fluency, short- and long-term memory and reduced blood pressure. Pomegranate juice has also been shown to improve verbal memory and task-related brain activation. In a separate study, mobility has also been shown to improve with consumption of two cups of berries per day. Another promising study showed improved cognitive function and task-related brain activation and resting perfusion with 12 weeks of blueberry supplementation.
Green or black tea
The neuroprotective role of tea consumption (green or black) has also been highlighted in a few recent research studies. It is inversely related to risk for cognitive impairment in a 26-study meta-analysis in humans. Accumulating evidence suggests neuroprotective activity of the main catechin, epigallocatechin-3-gallate (EGCG), from tea. Green tea EGCG appears to improve learning and memory deficits in diabetic rats via retardation of oxidative stress and modulation of nitric oxide. In a recent study involving Chinese older adults, long-term benefits of tea consumption were not limited to a particular type of tea as long as the tea was brewed from tea leaves.
Chocolate and cocoa
Unprocessed cocoa products and chocolate are a rich source of flavonoids, which are potent antioxidant and anti-inflammatory agents with established benefits for CV health and increasing evidence of dose-dependent improvements in general cognition, attention, processing speed and working memory. Flavonoids penetrate and accumulate in the hippocampus and brain regions involved in learning and memory. Cocoa, like blueberries, works via neurogenesis, neuronal function and brain connectivity, and via blood-flow improvement and angiogenesis. Although research is still in its early stages, cocoa and chocolate may well have protective benefits and even a therapeutic role in reversal of cognitive decline. There is a clear association between chocolate consumption and Nobel laureates per capita!
Turmeric
Turmeric is a perennial plant of the ginger family and native to Southeast Asia and may help explain a lower risk for cognitive disorders in India. Curcumin is the most active constituent of this spice and is responsible for its yellow, golden color. In Ayurvedic medicine, the therapeutic qualities of turmeric are well-established — from strengthening the body overall to acting as an effective anti-inflammatory agent. The popularity of this spice in modern medicine is also growing, with a variety of studies now demonstrating its value in managing a range of conditions, including asthma, cancer, irritable bowel syndrome and ulcers. In a recent study from Chile, Morales and colleagues demonstrated strong neuroprotective effects of curcumin in neuronal cells, highlighting its potential to prevent establishment and progress of cognitive impairments in Alzheimer’s disease. Human trials point to improved attention and working memory. The anti-inflammatory and neuroprotective qualities of curcumin have also been presented in support for patients with Parkinson’s disease.
Brain diet
An ideal “brain-protection diet” should include one to two cups of fresh or frozen berries, with blueberries being a fruit of choice, possibly as a smoothie. A cup of berries has only 20 g carbohydrate. A blend of berries appears to be synergistic in benefits. It should also include a large multicolored salad every day and tomatoes, which can be served fresh or cooked because lycopene, the main antioxidant in tomatoes, is heat stable.
Other foods most protective against cognitive decline and Alzheimer’s disease include salad dressing, nuts, fish, cruciferous vegetable, fruits, and dark and green leafy vegetables. Foods that present higher risks for development of Alzheimer’s disease include high-fat dairy, red meat, organ meat and butter, supporting the hypothesis that foods with saturated fat increase risk and plant-based foods may be a key to the prevention of cognitive decline. Healthy proteins, such as beans and legumes, nuts and fish, should be emphasized.
For people with diabetes, there sometimes is a move to a low or very low carbohydrate diet, often with more meat and dairy. The risk of such an approach is the unfortunate avoidance of many plant-based foods, which are naturally low in calories and high in antioxidant and anti-inflammatory effects. It is worth our effort to spend some time with our at-risk patients helping them to truly understand the importance of including such foods in their daily diet.
Modern nutrition has largely been premised on a study macronutrients and vitamins and minerals. We have found that encouraging recognition of fruits and vegetables as having inherent healing properties can be a more effective and practical approach. Children especially respond to the concept of including brightly colored fruits and vegetables, but older people interested in maintaining optimal cognition have reason to brighten up their plates as well!
References:
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For more information:
Daniel A. Nadeau, MD , is a practicing endocrinologist with a master’s degree in nutrition and program director at the Mary and Dick Allen Diabetes Center at Hoag Hospital in Newport Beach, Calif. He is co-author of The Color Code, A Revolutionary Eating Plan for Optimal Health. He encourages the consumption of brightly colored vegetables and fruits, especially berries. He can be reached at dnadeaumd@gmail.com.
Harsimran Singh, PhD, is a health psychologist and a clinical research scientist at the Mary and Dick Allen Diabetes Center at Hoag Memorial Hospital Presbyterian in Newport Beach, Calif. The center specializes in offering patient-centered clinical care, education services and psychosocial support for people with diabetes. She can be reached at harsimran.singh@hoag.org.
Disclosures: Nadeau reports he serves on speaker bureaus for AstraZeneca, Boehringer Ingelheim, Eli Lilly, Janssen, Novo Nordisk and Sanofi-Aventis and on the advisory board for Sanofi-Aventis. Singh reports no relevant financial disclosures.