알츠하이머 협회에 따르면 미국에는 약 510만 명의 알츠하이머 환자가 있다고 추정되며, 2025년에는 710만명으로 증가할 것으로 예상하고 있다.

최근 알츠하이머의 발병 위험을 줄이는 특별한 식이요법을 설계한 연구들이 주목을 받고 있다.

1. 시카고 소재 러시대학병원(Rush University Medical Center in Chicago)의 연구
- 이 연구는 영양섭취가 어떻게 뇌 건강을 증진시키고, 알츠하이머/치매 유발요인인 인지기능 저하 및 기억손상을 늦추는 지에 대하여 연구한 것이다.
- 연구진은 마인드 다이어트와 심장건강에 좋은 지중해식 식단, 고혈압 조절에 도움이 되는 DASH 다이어트를 비교 연구하였다.
- 2년에 걸쳐 개발한 마인드 다이어트는 인간과 동물을 대상으로 실시한 영양과 뇌 연구 자료를 기초로 하여 지중해식이, DASH 다이어트를 재구성하여 통합한 식단이다. 채식위주 기반의 저지방 식단으로써, 녹황색 채소나 베리류(특히 블루베리) 같은 뇌건강에 좋은 음식 섭취를 강조한다.
- 연구진들은 위의 세가지 식단을 고수하여 섭취한다면 알츠하이머에 걸릴 가능성이 감소할 수 있다는 것을 발견하였다.
- 연구 초기, 치매에 걸리지 않은 58-92세(평균연령 81세)의 대상자 923명이 연구에 참여하였고, 평균 4.5년 동안 참가자들을 추적관찰하였으며, 144종의 식품을 얼마나 자주 섭취하였는지를 매년 조사하였다. 각 식단을 섭취한 집단에 따라 마인드 다이어트는 53%, 지중해식은 54%, DASH 다이어트는 39%까지 알츠하이머의 발병위험이 각각 감소하였다.
- 러시대학의 Morris 교수는 "이것은 심장질환 및 당뇨병과 영양과의 관련성에 비해 상대적으로 새로운 분야라고 할 수 있다. 향후 추가적인 연구를 통해서 마인드 다이어트를 계속 보완 및 교정 할 생각이다"라고 말했다.
- 연구진은 또한 푸른잎이 많은 채소와 인지기능 저하 간의 관련성을 분석하였다. 하루에 녹색 채소를 1-2접시 섭취한 참여자들은 그보다 적게 채소를 섭취한 사람에 비해 인지기능 저하율이 급격하게 감소했다.
- 알츠하이머 권위자인 Doraiswamy 박사는 "마인드다이어트는 치매, 뇌졸중, 심장질환의 위험을 감소시킬 수 있다. 식이가 치매 위험성을 실제로 줄여줄 수 있다면, 그것을 확인할 수 있는 무작위배정 대조연구가 필요하다. 그리고 신체활동, 명상과 같은 생활습관 개선 방안이 접목 된다면, 부가적 이점이 있을 것이다"라고 말했다.

2. 인지장애 예방을 위한 핀란드 노인 대상 연구
   (FINGER; Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability)
- 이 연구는 생활습관이 치매 발병에 미치는 영향에 대한 무작위 대조연구로 60-77세 노인 1,260명을 대상으로 실시하였다.
- 중재그룹의 대상자들은 지중해식과 유사한 식단, 운동 프로그램, 행동수정교육, 신진대사 및 뇌졸중 위험인자에 대해 관리를 받았으며, 대조군의 경우 일반적 건강 조언을 받았다.
- 연구 후 2년 동안의 초기 결과는 최근 Lancet 저널에 발표되었다. 연구진은 중재가 기억력과 처리속도를 포함한 영역에서 명확한 이점이 있다는 것을 발견했다. "대조군은 인지장애 위험이 30% 더 높은 것으로 나타났다"고 이 연구의 책임저자인 Kivipelto 박사는 말했다.
- 후속 단계로 서로 다른 생활습관 중재와 유전자의 다형성에 따른 중재가 사람들에게 어떤 영향을 미치는지 구분하였다. 예를 들어, APOE4 유전자(치매발병 위험인자)의 특정 변이형을 가진 사람은 건강에 해로운 식이에 대해 더 취약한 것으로 나타났다. FINGER 연구의 데이터는 그런 사람들은 건강한 식이의 혜택을 특히 더 받을 수 있는지 여부를 나타낼 수 있다.

3. 웨이크포레스트 의대(Wake Forest School of Medicine in Winston-Salem, N.C.)의 연구
- 2011년 Suzanne Craft 교수는 알츠하이머병의 증상과 식이의 영향에 대해 연구(the Archives of Neurology에 게재)
- Craft 박사와 연구진은 50세 성인을 반으로 나눠 한 집단에게는 포화지방과 설탕이 상대적으로 많은 서양식단을 한달 동안 제공하였고, 나머지 집단은 동일한 양의 심장건강에 좋은 식단을 고수하였다.
- 참가자들의 척수액을 분석한 결과 서양식단은 알츠하이머를 일으키는 염증과 β-아밀로이드단백질 수치가 높아진 것을 발견했다.
- 성인 45-65세 80명을 대상으로 진행 중인 후속연구에서는 뇌 혈류에 관한 다이어트의 효과를 비교하고 있다. 연구진은 알츠하이머를 일으키는 초기 변화를 나타낼 수 있는 바이오마커를 확인하고 있다. "우리가 초기 바이오마커를 식별할 수 있다면, 치료대상이나 취약한 대상들을 판명할 수 있을 것이다"라고 크래프트 박사는 말했다.

Researchers successfully tested a special diet they designed that appears to reduce the risk for developing Alzheimer's disease.
The study compared the so-called MIND diet with the popular, heart-healthy Mediterranean diet and the DASH diet, which is intended to help control high blood pressure. The MIND diet borrows significantly from the other two, and all are largely plant-based and low in high-fat foods. But the MIND diet places particular emphasis on eating "brain-healthy" foods such as green leafy vegetables and berries, among other recommendations.

The study, conducted by researchers at Rush University Medical Center in Chicago, found strict adherence to any of the three diets lessened the chances of getting Alzheimer's. But only the MIND diet seemed to help counter the disease even when people followed only some of the diet's recommendations. The research was observational, not randomized or controlled, and therefore isn't evidence the MIND diet caused a reduced risk for Alzheimer's. Instead, the research shows there is an association between the two.

The study is part of a small body of research investigating how nutrition can improve brain health and stave off the cognitive decline and memory impairment that comes with Alzheimer's disease and other forms of dementia. Experts say there is growing awareness that lifestyle factors?not just genetics?play a prominent role in the development of Alzheimer's, and researchers hope to come up with an optimal diet that will lessen the chances of developing the disease. An estimated 5.1 million people in the U.S. have Alzheimer's, a number expected to grow to 7.1 million by 2025, according to the Alzheimer's Association.
"It's a relatively new field compared with heart disease and diabetes and nutrition," said Martha Clare Morris, a professor of neurological epidemiology at Rush. "As we learn more and more I think we would definitely modify or update the [MIND] diet based on the latest research," said Dr. Morris, who was first author of the study, published recently in the journal Alzheimer's & Dementia.

The MIND diet, which took two years to develop, stands for Mediterranean-DASH Intervention for Neurodegenerative Delay. Researchers modified the Mediterranean and DASH diets based on evidence from animal and human studies looking at nutrition and the brain. DASH stands for Dietary Approaches to Stop Hypertension.

For example, fruits, a common recommendation in heart-healthy diets, haven't been shown to slow cognitive decline or prevent dementia, but berries, and especially blueberries, have, Dr. Morris said. The MIND diet calls for eating berries at least two times a week and doesn't include recommendations for other types of fruit. Research also has shown that green leafy vegetables protect the brain more than other vegetables. The MIND diet includes one serving of greens in addition to eating one or more other vegetables a day. The MIND diet is heavy on nuts and beans, whole grains and olive oil and recommends a glass of wine a day, all of which also are recommended by one or both of the other diets.
The study involved 923 participants who didn't have dementia at the start of the research. Their ages ranged from 58 to 98, with a median age of 81. Participants, who were followed on average for 4.5 years, were questioned annually on how often they ate from among 144 different food items. Subjects whose diet choices adhered closely to the MIND diet had a 53% reduced risk for developing Alzheimer's. Risk was reduced by 54% with the Mediterranean diet and 39% with the DASH diet.

Significantly, even moderate adherence to the MIND diet helped lessen the risk for Alzheimer's, by 35%. By comparison, moderate adherence to the Mediterranean or DASH diets didn't affect the chances of getting the disease. That finding was particularly encouraging, because many people find it easier to follow just some of a diet's recommendations. "I think that will motivate people," Dr. Morris said.
The study controlled for genetic predisposition, physical activity, cognitive activity and education. A further analysis controlled for various chronic medical conditions. It was the first study published on the MIND diet, and researchers expect additional small changes to be made. Cocoa and caffeine, for example, could possibly be added to the diet with more research, Dr. Morris said.

The researchers also analyzed green leafy vegetables in relation to cognitive decline. Participants who ate one to two servings of green vegetables a day had a "dramatic decrease in the rate of cognitive decline" compared with people who ate fewer greens, said Dr. Morris. "It was about the equivalent of being 11 years younger in age," she said.
"The MIND diet may be a triple bonus. It reduces the risk for dementia, strokes and heart disease," said Murali Doraiswamy, a professor of psychiatry at Duke University Medical Center in Durham, N.C., and an Alzheimer's expert. Dr. Doraiswamy, who wasn't involved in the MIND diet study, said a randomized controlled study is needed to determine if the diet really reduces dementia risk, and whether combining it with lifestyle interventions like exercise and meditation could provide additional benefits.

A Swedish study is investigating lifestyle's effect on developing dementia. Finger, for Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability, is a randomized controlled study with 1,260 at-risk participants ages 60 to 77. Subjects assigned to an intervention group were given a diet similar to the Mediterranean diet, an exercise program, cognitive training and management of metabolic and vascular risk factors such as diabetes and hypertension, said Miia Kivipelto, senior geriatrician at the Karolinska Institute in Stockholm. A control group was given general health advice.
"Our hypothesis was that maybe we need to target all these different risk factors simultaneously to get the optimal effect of the intervention," Dr. Kivipelto said.
Initial results, based on the study's first two years, were published recently in the Lancet. The researchers found the intervention had clear benefits in areas including memory function and processing speed. The control group had a 30% higher risk for cognitive impairment, said Dr. Kivipelto, senior author of the study.
The next step is to separate out the effects of different lifestyle interventions and see how interventions may affect people depending on genetic makeup, she said. For example, there is evidence that people with a certain variation of the apoe4 gene?a risk factor for developing dementia?are more vulnerable to unhealthy diets. Data from the Finger study could indicate whether such people might especially benefit from a healthy diet.
Suzanne Craft, a professor at Wake Forest School of Medicine in Winston-Salem, N.C., also studies the effects of diet on Alzheimer's disease symptoms. In a 2011 randomized controlled study published in the Archives of Neurology, Dr. Craft and colleagues assigned about half of 50 older people to a Western diet relatively high in saturated fat and sugar for a month. The other half followed a more heart-healthy diet with the same number of calories. Meals were delivered to the participants.
An analysis of the participants' spinal fluids found that the Western diet increased inflammation and levels of beta-amyloid proteins, which play a role in the development of Alzheimer's. "If you think of the impact of eating with these kinds of patterns over years and years, it's not hard to see how diet can have a profound effect on your risk for Alzheimer's," said Dr. Craft.
A follow-up study currently under way, involving 80 people age 45 to 65 years old, is comparing the diets' effects on blood flow in the brain. The researchers are checking for biomarkers that might indicate early changes that raise a person's risk for Alzheimer's. "If we can identify these really early markers they may turn out to be therapeutic targets or good markers of vulnerability," she said.