Power Foods for the Brain (5 page)

T
he Beatles made an enormous splash in Liverpool. But as big as they were, there was one commodity that was much bigger and much more controversial.

Liverpool is a port city. So ships come and go, carrying coal, timber, grains, steel, crude oil, and endless other commodities. Loaded onto ships leaving Liverpool in the eighteenth century was the most controversial product in English history.

In their holds were bars of copper—that ordinary reddish metal that makes a pot or pan look so shiny and bright. Copper looks innocent enough. But it was the currency of the British slave trade.

The ships sailed from Liverpool to West Africa, where copper and brassware were exchanged for slaves who were then carried across the Atlantic to the Americas. There the human cargo was off-loaded, and rum and sugar from slave plantations were carried back to Britain. This triangular trade route from Britain
to Africa to the Americas and back was fueled by copper from Liverpool. It was what African slaveholders wanted.

Copper also kept the ships afloat. Sailing around the North Atlantic, wooden ships worked out well. But as slave ships entered the Caribbean, they encountered a tiny mollusk, called
Teredo navalis,
which feeds on wood. Or, more accurately, these mollusks have a special organ that carries a bacterium that digests cellulose, dissolving the hulls of ships. A few too many mollusks and your ship is on the ocean bottom.

The answer was to sheathe the hulls in copper. Copper kept the mollusks out, the hulls intact, and the slave ships sailing.

Many Britons called for an end to the slave trade. But copper merchants protested vigorously. They were not getting rich selling pots and pans in Lancashire. The slave trade was the market they wanted to protect. Finally, in 1807, public sentiment turned, and it became illegal for British subjects to traffic in slaves. In 1833, slavery was abolished in all British colonies.

Metals always seem to come in the form of double-edged swords. Lead gave us pipes for plumbing, but it has also poisoned countless children. Mercury gave us thermometers and electrical switches, but it also caused birth defects. Metals build bridges and locomotives, and also bullets, prison cells, and hand grenades.

Metals are a double-edged sword within the human brain, too. In the last chapter, we saw that researchers have found
plaques
and
tangles
within the brains of people with Alzheimer’s disease. If you were to analyze a typical plaque—one of the small deposits that are found among the brain cells—you would discover that much of it consists of
beta-amyloid
protein. But there is something else there, too. Teasing the plaques apart, researchers have found traces of copper. They have found other metals, too, particularly iron and zinc, and perhaps others, as well.
¹

All three of these metals are needed by the body—copper for building enzymes, iron for blood cells, and zinc for nerve transmission, among many other functions. You get them in the foods you eat. But it turns out that if you get too much of any of them, they can damage your brain cells. The difference between a safe amount and a toxic amount is surprisingly small. And that is exactly the problem.

Iron and copper are unstable. Just pour a little water into a cast-iron pan and let it sit for a bit. The rust you see is oxidation. Copper oxidizes, too, which is why a bright shiny penny soon darkens, sometimes combining with other elements and turning green.

Pretty colors, yes. What is not so pretty is when these chemical reactions happen inside your body. That’s when iron and copper spark the production of
free radicals—
highly unstable and destructive oxygen molecules that can damage your brain cells and accelerate the aging process.
²
In a nutshell, iron and copper cause free radicals to form, and those free radicals are like torpedoes attacking your cells.

So, am I saying that memory problems might be caused by ordinary metals like copper, iron, and zinc? To help answer that question, let me take you to Rome, where a research team studied sixty-four women.
³
All were over age fifty but perfectly healthy. The researchers drew blood samples to measure copper in their blood and then gave them a variety of tests to check their memory, reasoning, language comprehension, and ability to concentrate.

Now, overall the women did just fine. None had any major
impairment. But some did noticeably better than others on one test or another. And
those who had the least mental difficulties turned out to be those with lower levels of copper in their blood.
They had adequate copper for the body’s needs but were free of excesses, and that apparently did them a big favor. The difference was especially noticeable on tests that required focused attention.

A study of sixty-four women is not especially large. So let’s next drop in on a research team at the University of California at San Diego that evaluated a much larger group, this one consisting of 1,451 people in Southern California.
⁴
They found much the same thing. People who had lower copper levels in their blood were mentally clearer compared with those with excessive copper. They had fewer problems with short-term and long-term memory. And the same held true for iron. People with less iron in their blood had fewer memory problems.

So even though both iron and copper are essential in tiny amounts, having too much of either one in your bloodstream seems to spell trouble.

If this sounds surprising, it did not entirely surprise the researchers. Every medical student knows that copper is potentially toxic. Your body uses tiny amounts of it in enzymes for various functions, but the amount you need is extremely small. If you get too much of this unstable metal, it can oxidize and encourage free radicals to form. In fact, the only thing that stops copper from destroying your health early in life is that your liver filters much of it out of your blood and eliminates it. In a rare genetic condition called Wilson’s disease, the liver is unable to eliminate copper normally. As copper builds up in the body tissues, it damages the central nervous system and causes all manner of other problems.

Similarly, excess iron has long been known to cause potentially
serious health problems. More on iron in a minute. But first, let’s deal with copper and understand what it is doing to our brains.

I should tell you that copper may contribute to much more serious problems than the minor variations in memory and cognition seen in the Rome and San Diego studies. Starting in 1993, a research team from Rush University Medical Center went door-to-door in three Chicago neighborhoods, aiming to track down the causes of health problems that occur as we age. They invited 6,158 people to join the Chicago Health and Aging Project, and eventually another 3,000 joined in, as well.

The researchers carefully recorded what the volunteers ate. Like people everywhere, some were health conscious, while others were not so particular. The research team then kept in touch with everyone over the years to see who stayed well and who did not—who kept their mental clarity and who had memory problems. They then looked to see if any part of the diet could have predicted who might fall prey to memory loss.

Now, many of the participants got adequate copper in their diets, without excesses. As the years went by, they generally did well on the cognitive tests the researchers gave them. But other participants got quite a bit more of it. Needless to say, none of them were worrying about anything so insignificant as copper. Who would even have known it was in foods, anyway? But as time went on, a particular combination seemed to be especially harmful. Those whose diets included fair amounts of copper along with certain “bad” fats—the fats found in animal products and snack foods—showed a loss of mental function that was the equivalent of
an extra nineteen years of aging
.
⁵
It appears that “bad” fats team up with copper to attack the brain. These fats actually assault the brain in many ways, as we’ll see in the next chapter.

The difference in copper intake between those who generally did well and those who did not was surprisingly small. Here
are the numbers: For comparison, a penny weighs 2,500 milligrams. The people in the Chicago study who generally avoided cognitive problems got around 1 milligram of copper per day. Those who did not do so well averaged around 3 milligrams per day (2.75 milligrams, to be exact). One milligram, three milligrams—what’s the difference? you might be asking. That is still just a tiny speck of copper. But it turned out to be more than enough to cause serious problems. As we will see shortly, the foods that deliver this innocent-looking, bright, shiny metal are right under our noses, and it damages the brain enough to interfere with attention, learning, and memory—and perhaps even cause Alzheimer’s disease. Or so research seems to show.

Researchers have found a surprising link between copper and the APOE e4 allele—that is, the gene linked to Alzheimer’s risk. As you’ll recall, the proteins made by the APOE e2 and APOE e3 alleles are not associated with increased Alzheimer’s risk. It turns out that these two “safer” genes make proteins that
bind copper
. They keep it out of harm’s way. The protein produced by APOE e4 does not do that. As far as APOE e4 is concerned, you are on your own. It does nothing to protect you from copper and the shower of free radicals it causes.
⁶

Copper is not the only problem. Iron builds up in the body in a condition called
hemochromatosis,
causing fatigue, weakness, and pain, and ultimately leading to heart disease, diabetes, liver damage, arthritis, and many other problems.

In the Netherlands, researchers measured iron levels in healthy research volunteers using simple blood tests. Naturally, they varied a bit in their iron levels; some were lower and others were higher. The research team then tested everyone’s memory, reaction speed, and other cognitive abilities. And the results were remarkably similar to the findings with copper. Those who were slowest on cognitive tests were those who had the most iron in their blood.
⁷

Your body packs iron into hemoglobin, the iron-containing protein that gives your red blood cells their color and allows them to carry oxygen. In 2009, a group of researchers checked hemoglobin levels in a large group of older men and women. Those whose hemoglobin levels were in the healthy range did well on cognitive tests. But some people were not in this range.
Some were anemic. They had low hemoglobin levels, and they did not perform well on cognitive tests. And other people were in the opposite situation—they had unusually
high
hemoglobin levels. They did poorly, too. Specifically, they had problems with verbal memory (e.g., recalling words) and perception.
⁸

Following these people for the next three years, those whose hemoglobin levels were in the healthy range tended to retain their mental clarity. Those who were too low or too high in hemoglobin showed more rapid cognitive decline. People with high hemoglobin levels were more than three times more likely to develop Alzheimer’s disease compared with those who were in the healthy hemoglobin range.
⁹
The safest hemoglobin level was around 13.7 grams per deciliter. Going very far above or below that level was linked to problems with brain function as the years went by.

Keep in mind that in these studies hemoglobin was a rough indicator of how much iron people had in their bodies. While you need some iron, it is dangerous to get too much.

Zinc is similar in that your body needs a tiny amount. In fact, your brain cells use zinc to communicate with each other.
¹⁰
,
¹¹
But in even modest overdose, zinc can be potentially toxic.

So let’s return to the question at hand. Could it be that memory problems are caused by getting too much of these seemingly ordinary metals—copper, iron, and zinc? While research is still very active, here’s the picture that is emerging:

All three metals—copper, iron, and zinc—are clearly present in the beta-amyloid plaques of Alzheimer’s disease. The first two—copper and iron—appear to spark the production of free radicals that can damage brain cells.
²
,
¹²
Zinc’s contribution appears to be different. It seems to encourage beta-amyloid proteins to clump together to form plaques.
¹⁰
,
¹¹
Iron and copper
appear to promote clumping, too, but zinc seems to be much more aggressive in this regard.
¹