Key Nutrient Deficiencies Linked to Alzheimer’s Disease Development
The burden of Alzheimer's disease is staggering. From an economic perspective, healthcare costs are estimated at more than $170 billion per year just in the United States. Worldwide dementia is as high as 24 million, and it's expected to grow four times higher by the year 2050.
While various models of pathogenesis exist, indicating a multifactorial process, the present theories associated with the development of Alzheimer’s disease link oxidative damage to disease progression. Because of this, a recent study published in the Journal of Alzheimer’s Disease looked at antioxidant levels, specifically carotenoids and tocopherols. The study featured samples of donor brains with confirmed Alzheimer’s disease and compared them to healthy elderly donor brains. The researchers found that there were substantially lower concentration levels of lutein, zeaxanthin, retinol, lycopene, and alpha-tocopherol compared to healthy brain tissue. The two most deficient antioxidants were lycopene and zeaxanthin.
This is the first study to compare levels of retinol, carotenoids, and tocopherols in brains of confirmed Alzheimer’s with those in healthy elderly brains. This most recent study builds upon a strong foundation of previous research.
Diet, Deficiency, and Dietary Supplements
A 2021 cohort of 927 elderly Midwest residents who were followed for seven years found that total carotenoid intake was associated with a 48 percent reduction in the rate of Alzheimer’s disease. Among the 508 deceased participants, those who consumed the most lutein, zeaxanthin, and lycopene did not develop Alzheimer’s disease.
Deficiency in these nutrients has also been studied. A 2023 systematic review and meta-analysis published in BMC Geriatrics concluded that low blood carotenoid levels may be a risk factor for developing mild cognitive impairment and dementia.
Dietary carotenoids have also been studied. Research demonstrates that adherence to the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet, which is high in carotenoids, specifically lutein and zeaxanthin, is associated with better cognition and reduced risk of cognitive decline.
In addition to diet, research also indicates that supplementation is effective. A 2017 randomized placebo-controlled trial involving participants with a mean age of 73.7 found that taking a lutein zeaxanthin supplement improved cognitive function, including memory and executive function. A 2022 randomized, double-blind, placebo-controlled trial involving 90 people aged 40 to 75 with self-reported cognitive dysfunction found that lutein zeaxanthin supplementation resulted in improvements in visual learning and visual episodic memory after six months.
Going Beyond Eye Health
Lutein and zeaxanthin are perhaps most known for their positive impact on eye health. Research demonstrates that lutein and zeaxanthin supplementation can help delay the progression of eye diseases such as age-related macular degeneration and cataracts. Lutein, in particular, has been shown to benefit eye health, especially for age-related macular degeneration. A 2022 review of nine studies involving 855 participants found that lutein supplementation improved macular pigment optical density in patients with age-related macular degeneration.
This latest study builds upon previous research indicating that carotenoids, especially lutein, and zeaxanthin, can not only benefit the eyes but they can also help protect the brain while reducing the risk of Alzheimer's disease.
Encouraging patients to eat a diet high in carotenoids and possibly recommending dietary supplements to high-risk patients appears to be an effective strategy to enhance brain function and reduce the risk of Alzheimer's disease.