研究：谷物有损大脑 可导致痴呆

如果你早餐刚吃了谷类食物或者中饭只嚼了一块三明治，你也许不想读这篇文章，因为根据文中的医生所言，谷物有损你的大脑健康。

佛罗里达州那不勒斯的佩尔穆特健康中心的总裁David Perlmutter是一位颇有声望的神经学家，他认为人们的生活方式、现代饮食和痴呆症之间有十分紧密的联系。

Perlmutter医生刚出的一本新书《谷物——大脑的沉默杀手》已被《纽约时报》评为最畅销书籍，他说碳水化合物有损大脑健康，可引起痴呆、慢性头痛、抑郁、癫痫等健康问题的发生。“即便是被人们大肆追捧的全麦食品也可能导致痴呆、注意力不集中、焦虑、慢性头痛等等问题。”

作为美国营养学院的会员，Perlmutter医生称我们的大脑成长离不开脂肪和胆固醇，但在我们食用谷物时会受到损害。他认为，改变人们的主要生活方式和饮食习惯能有效防止老年痴呆症和其他使人衰弱的疾病的发生。

他认为，通过调整生活方式，减少对碳水化合物的吸收（每日不超过60到80克），在饮食中适度增加脂肪含量，比如初榨橄榄油、椰子油、草饲牛肉和野生鱼等，多做有氧运动，服用DHA补充剂，可以降低痴呆症的风险。

Perlmutter还说，低脂肪的饮食观念已经深入人心，但其实大错特错，而且还需要为大多数现代疾病负重责。

“是时候要重新认识了，早餐你可以吃点蔬菜——末日不会因此来临，你可以吃点熏制鲑鱼、用橄榄油烹饪的放养鸡蛋和有机山羊奶酪。这样你已经为一天做好了准备，而且摄入的碳水化合物也不多。如果早餐摄入碳水化合物过多，一般会导致你上午10点时就迫不及待地跑向自动售货机，因为你体内的血糖正在下降而且大脑也不灵活了。”

It's tempting to call David Perlmutter's dietary advice radical. The neurologist and president of the Perlmutter Health Center in Naples, Fla., believes all carbs, including highly touted whole grains, are devastating to our brains. He claims we must make major changes in our eating habits as a society to ward off terrifying increases in Alzheimer's disease and dementia rates.

And yet Perlmutter argues that his recommendations are not radical at all. In fact, he says, his suggested menu adheres more closely to the way mankind has eaten for most of human history.

What's deviant, he insists, is our modern diet. Dementia, chronic headaches, depression, epilepsy and other contemporary scourges are not in our genes, he claims. "It's in the food you eat," Perlmutter writes in his bestselling new book, Grain Brain: The Surprising Truth About Wheat, Carbs, and Sugar – Your Brain's Silent Killers. "The origin of brain disease is in many cases predominantly dietary."

Perlmutter's book is propelled by a growing body of research indicating that Alzheimer's disease may really be a third type of diabetes, a discovery that highlights the close relationship between lifestyle and dementia. It also reveals a potential opening to successfully warding off debilitating brain disease through dietary changes.

Perlmutter says we need to return to the eating habits of early man, a diet generally thought to be about 75 percent fat and 5 percent carbs. The average US diet today features about 60 percent carbs and 20 percent fat. (A 20 percent share of dietary protein has remained fairly consistent, experts believe.)

Some in the nutrition and medical communities take issue with Perlmutter's premise and prescription. Several critics, while not questioning the neurological risks of a high-carb diet, have pointed out that readers may interpret his book as a green light to load up on meat and dairy instead, a choice that has its own well-documented cardiovascular health risks.

"Perlmutter uses bits and pieces of the effects of diet on cognitive outcomes — that obese people have a higher risk of cognitive impairment, for example — to construct an ultimately misleading picture of what people should eat for optimal cognitive and overall health," St. Catherine University professor emerita Julie Miller Jones, Ph.D., told the website FoodNavigator-USA.

Grain Brain does delve deeply into the neurological effects of dietary sugar. "The food we eat goes beyond its macronutrients of carbohydrates, fat and protein," Perlmutter said in a recent interview with Next Avenue. "It's information. It interacts with and instructs our genome with every mouthful, changing genetic expression."

Human genes, he says, have evolved over thousands of years to accommodate a high-fat, low-carb diet. But today we feed our bodies almost the opposite, with seemingly major effects on our brains. A Mayo Clinic study published earlier this year in the Journal of Alzheimer's Disease found that people 70 and older with a high-carbohydrate diet face a risk of developing mild cognitive impairment 3.6 times higher than those who follow low-carb regimens. Those with the diets highest in sugar did not fare much better. However, subjects with the diets highest in fat were 42 percent less likely to face cognitive impairment than the participants whose diets were lowest in fat.

Further research published in the New England Journal of Medicine in August showed that people with even mildly elevated levels of blood sugar — too low to register as a Type 2 diabetes risk — still had a significantly higher risk of developing dementia.

"This low-fat idea that's been drummed into our heads and bellies," Perlmutter says, "is completely off-base and deeply responsible for most of our modern ills."

This fall, the federal government committed $33.2 million to testing a drug designed to prevent Alzheimer's in healthy people with elevated risk factors for the disease, but "the idea of lifestyle modification for Alzheimer's has been with us for years," Perlmutter says, and it's cost-free.

The author hopes his book and other related media on the diet-dementia connection will inspire more people to change the way they eat. "Dementia is our most-feared illness, more than heart disease or cancer," Perlmutter says. "When you let Type 2 diabetics know they're doubling their risk for Alzheimer's disease, they suddenly open their eyes and take notice.

"People are getting to this place of understanding that their lifestyle choices actually do matter a whole lot," he says, "as opposed to this notion that you live your life come what may and hope for a pill."

As we learn more about the brain's ability to maintain or even gain strength as we age, Perlmutter believes, diet overhauls could become all the more valuable.

"Lifestyle changes can have profound effects later in life," he says. "I'm watching people who'd already started to forget why they walked into a room change and reverse this. We have this incredible ability to grow back new brain cells. The brain can regenerate itself, if we give it what it needs."

What it needs most of all, Perlmutter says, is "wonderful fat." There's no room in anyone's diet for modified fats or trans fats, he says, but a diet rich in extra-virgin olive oil, grass-fed beef and wild fish provides "life-sustaining fat that modern American diets are so desperate for."

Too few of us understand there's "a big difference between eating fat and being fat," he says. People who eat more fat tend to consume fewer carbs. As a result, they produce less insulin and store less fat in their bodies.

Changing minds, however, is an uphill climb. "The idea that grains are good for you seems to get so much play," he says. "But grains are categorically not good for you," not even whole grains.

"We like to think a whole-grain bagel and orange juice makes for the perfect breakfast," Perlmutter continues. "But that bagel has 400 calories, almost completely carbohydrates with gluten. And the hidden source of carbs in this picture is that 12-ounce glass of fresh-squeezed orange juice. It has nine full teaspoons of pure sugar, the same as a can of Coke. It's doing a service with Vitamin C, but you've already gotten 72 grams of carbs.

"It's time to relearn," he says. "You can have vegetables at breakfast – the world won't come to an end. You can have smoked salmon, free-range eggs with olive oil and organic goat cheese and you're ready for the day. And you're not having a high-carb breakfast that can cause you to bang on a vending machine at 10 a.m. because your blood sugar is plummeting and your brain isn't working."

Changing one's diet is a challenge, he acknowledges. Giving up the gluten found in most carbs makes it even tougher. "The exact parts of the brain that allow people to become addicted to narcotics are stimulated by gluten," Perlmutter points out. "People absolutely go through withdrawal from gluten. It takes a couple of weeks."

But the change is worth making, he says, at any age.

"Nutrition matters," Perlmutter says. "The brain is more responsive to diet and lifestyle than any other part of the body and until now it's been virtually ignored. We load up on medications when our mood is off, we hope for an Alzheimer's disease pill when we get older. I submit that we need to take a step back and ask, 'Is this really how we want to treat ourselves?'"