Power Foods for the Brain (6 page)

So it may be that these metals work together, encouraging plaques to form and generating free radicals that attack brain cells. And the problems appear to start early in life, as mild memory problems that pass for everyday forgetfulness, as well as in mild cognitive impairment that for many people is a step toward Alzheimer’s disease.

By now, you are no doubt visualizing toxic metals picking off your brain cells one by one. Well, where are these metals coming from?

Let’s start in your kitchen. What’s under your sink? Copper plumbing has been popular since the 1930s. As copper pipes and brass fittings corrode, copper leaches into drinking water.
¹³

Is there a cast-iron pan on your stove? Iron cookware contributes a significant amount of iron to foods. While that may be beneficial for a young woman with monthly iron losses through menstruation, most other people are more likely to be iron-overloaded than iron-deficient.

Next, take a look in your kitchen cupboard. Do you keep a bottle of multiple vitamins? A One A Day Men’s Health Formula multivitamin has 2 milligrams of copper—more than twice the RDA—in a single pill. It exceeds the RDA for zinc, too. In fact, if you take a look at most any vitamin-mineral supplement, you’ll find copper, zinc, and sometimes iron.

So many of us imagine we are doing a smart thing by taking a daily multiple vitamin, and we are, in many ways. It’s an excellent source of vitamin B
₁₂
and vitamin D, both of which are important for health. But the metals that are often added
are mostly unnecessary, because
you are already getting them in foods
. A better choice is a supplement containing vitamins only, without the added copper, zinc, iron, or other minerals. Or you could choose a B-complex tablet, which limits itself to just B vitamins. We will cover vitamins in more detail in
chapter 4
.

In the 1950s, television commercials pushed Geritol as the answer to “iron-poor tired blood.” The tonic had “twice the iron in a whole pound of calf’s liver.” Doctors promoted iron supplements as an energy booster, too, on the theory that sluggishness was a sign of anemia. Not that they worked very well; fatigue has many causes, and iron deficiency is nowhere near the top of the list.

Take a look at your breakfast cereal. No doubt the food scientists at General Mills imagined you wanted all the iron and zinc they’ve added to a box of Total—a full day’s supply of each in every serving. But you do not need these added metals, and you are better off without them. Many other breakfast cereals are similar, giving you too much of a good thing. I have asked General Mills and the other major cereal manufacturers to limit their supplementation to vitamins and to leave out minerals, which most customers get plenty of already.

So plumbing, cookware, supplement pills, and fortified cereals—these all contribute to an overdose of metals that will do your brain no good. But none of these are the biggest source.

To see the mother lode of metal, stop into any coffee shop in Chicago and order liver and onions. No, don’t eat it. Send it to a laboratory. You would be amazed at what you find.

For comparison, the recommended dietary allowance for
copper is 0.9 milligram, as we saw above. A typical serving of liver (about 3½ ounces) has
more than 14 milligrams
of copper. It also has 7 milligrams of iron and 5 milligrams of zinc, not to mention nearly 400 milligrams of cholesterol.

Now, many people avoid liver because it harbors such an enormous load of cholesterol, among other problems. But they are busily chowing down on beef and other meats. Growing up in North Dakota, I certainly did, and so did my parents and most of the people we knew. Unbeknownst to us, meat-heavy diets are a major source of excess metals.

This is, in fact, a key difference between my North Dakota diet on the one hand, and a plant-based diet on the other. Take iron for starters. Green vegetables and beans contain iron. But it is in a special form called
nonheme iron,
which the body is able to regulate. That is, nonheme iron is more absorbable if you are low in iron and less absorbable if you already have plenty of iron in your body. That is an amazing feature, if you think about it. The amount of iron in a leaf of spinach or a sprig of broccoli does not change from minute to minute. But how much of it your body absorbs does change depending on how much you need. If you happened to have plenty of iron in your blood already, your body is able to turn down its absorption of the nonheme iron in green vegetables. And if you’re running low, your body pulls more of the vegetable’s iron into your bloodstream.

Meats contain some of this kind of iron. But they also contain a great deal of what is called
heme
iron. And heme iron is harder for your body to regulate. Even if you have plenty of iron in your body already, heme iron is still very absorbable compared to nonheme iron. It is like an uninvited guest just barging in on your party. It can tip you into iron overload.

Cows get iron from grass and concentrate it in blood cells and muscle tissue. If we eat meat, we ingest the concentrated iron that animals have stored, and it ends up being more than we need. If instead we were to eat plants directly, we would get the iron we need, without much risk of an overdose.

We’re like the big fish in the ocean. A little fish ingests a bit of mercury from pollutants in the water. A bigger fish then eats the little one and gets all the mercury in the smaller fish’s body. In turn, this fish is swallowed by an even bigger one, who now gets all the mercury that has been accumulating up the food chain. And that’s us. We are the big fish in the ocean, so to speak, ingesting whatever the animals we eat have accumulated during their lives.

It is a good idea to step out of the food chain and take advantage of the nutrition that plants bring us directly. In research studies, we have done exactly that. That is, we have asked people to skip meat and other animal products. So breakfast might be blueberry pancakes or old-fashioned oatmeal topped with sliced bananas. Lunch might be lentil soup with crusty bread, a bean burrito with Spanish rice, a veggie burger, or a spinach salad. Dinner could be a vegetable stir-fry, mushroom Stroganoff with steamed broccoli, or angel-hair pasta topped with artichoke hearts, seared oyster mushrooms, and Roma tomatoes. As we add up the amount of iron in the foods they have chosen, it is usually the same or slightly more than when they were eating meat. However, as these foods pass their lips, their digestive tract has the surprising ability to decide how much or how little iron it needs to absorb. If they have a lot of iron on board already, their iron absorption is automatically reduced. If they need iron, their iron absorption is increased. And that is possible because the iron they are getting is nonheme iron. As a rule, it gives you what you need without the excess.

Plant-based diets also help you avoid the overdose of zinc and copper. There are adequate amounts of these minerals in vegetables, beans, and whole grains. In fact, there may be more copper in these foods than in meats. But if you were to do blood tests on people who avoid meat, you would find that they are slightly lower in iron, copper, and zinc, which is a good thing.
¹⁴
,
¹⁵
The reasons for this are not entirely clear. Aside from your body’s ability to shut out nonheme iron, there is a natural substance called
phytic acid
in many plants that tends to limit copper and zinc absorption.
¹⁴
,
¹⁵

Years ago, all this made nutritionists nervous. After all, we need traces of each of these metals, and many nutrition experts cautioned vegetarians to take extra care to get plenty of iron and zinc. And they reassured meat eaters that they had nothing to worry about.
¹⁶

Today things have turned around. Nutrition researchers have been struck by the observation that people following plant-based diets tend to keep their iron levels in the healthy range. They are no more likely than meat eaters to dip into anemia, but they are much
less
likely to accumulate excess iron.
¹⁴
Vegetarians tend to do fine with copper and zinc, too.

Let me emphasize that it is indeed important to get each of these metals in foods. You need them and do not want to run low. But it is just as important to avoid poisoning yourself with excessive amounts. Getting nutrition from plant sources is the easiest way to stay in the healthy zone.

Growing up in North Dakota, vegetables and beans were not exactly our strong suit. Meat was at the center of our plates 365 days a year. At the time we thought we were doing well. Today we know better.

In the world of Alzheimer’s research, the most hotly debated metal is not any of the ones we’ve discussed so far. It is aluminum.

In the 1970s, researchers analyzed the brains of people who had died of various causes. In people who had not developed Alzheimer’s disease, researchers found very little aluminum. But many of those who had had Alzheimer’s had quite a bit of aluminum in their brains—in one case as much as 107 micrograms of aluminum per gram of brain tissue.
¹⁷
,
¹⁸
Yes, it’s the same stuff that is in soda cans and aluminum foil, and particles of it were inside their brains.

What was it doing there? Our nutritional requirement for aluminum is exactly zero. It has no role in brain function at all, nor does it play a part in any other aspect of human biology.
For many years, public health officials have known that large doses of aluminum are harmful. People exposed to unusually large amounts in the workplace or who have received aluminum in renal dialysis solutions have sometimes developed serious brain damage and have needed a treatment called
chelation
to remove the metal from their bodies.

As a result of these studies, aluminum became a suspect in the Alzheimer’s epidemic.
¹⁹
,
²⁰
Researchers began to debate whether the traces of aluminum we might be exposed to from day to day—in pots and pans or in food additives—could put us at risk.

To this day, the question has not been settled. Some disconcerting evidence came from British researchers who measured aluminum in drinking water. Normally there is almost no aluminum in water as it arrives from wells or streams. But at municipal water purification plants, a process called
flocculation
introduces aluminum as a way of removing suspended particles. In turn, traces of aluminum stay in the water, and they flow from your tap when you fill your drinking glass.

Looking at the tap water in eighty-eight county districts in the UK, the researchers found that the aluminum content varied greatly. In some it exceeded 0.11 milligram per liter. In others it was less than one-tenth that amount. They then looked at Alzheimer’s cases and found they were 50 percent more frequent in the high-aluminum counties.
²¹

A French study found much the same result.
²²
In a group of 1,925 people, those with more aluminum in their drinking water had a faster cognitive decline and were more likely to be diagnosed with Alzheimer’s disease.

Canadian studies added to the accumulating evidence. A high incidence of Alzheimer’s disease in a small part of Newfoundland was hard to explain, except that the local drinking water had particularly high levels of aluminum.
²³
A study in
Quebec linked aluminum in drinking water to a nearly threefold increased risk of Alzheimer’s disease.
²⁴
A study in Newcastle, UK, seemed to disprove the hypothesis, finding no strong relationship between aluminum and Alzheimer’s,
²⁵
,
²⁶
until it became clear that there just was not as much aluminum in the water there compared with areas where the link had been found.
²⁷

Since then, researchers have debated whether aluminum is a problem or not.
¹⁹
,
²⁸
Many feel the evidence indicting aluminum is not particularly strong. The Alzheimer’s Association calls the aluminum-Alzheimer’s link a “myth” and had this to say on its website:

Many authorities agree with this viewpoint. They feel that small amounts of aluminum do little harm and that your kidneys ought to be able to eliminate the incidental traces you might ingest in drinking water and other day-to-day exposures. Perhaps the aluminum deposits found in Alzheimer’s patients’ brains are just a sign that an already-diseased brain can no longer keep toxins out.

However, others have felt the evidence against aluminum is too strong to ignore,
¹⁹
and in 2011 a group of Alzheimer’s researchers published the following comment in the
International Journal of Alzheimer’s Disease
: