Oyster Nutrition

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THE OYSTER IS OUR WORLD

Famous Irishman Jonathan Swift once said, “He was a bold man that first ate an oyster,” but there is a the­ory that oysters actually saved humanity. According to the theory, about two hundred fifty thousand years ago, Homo sapiens were reduced to as low as six hundred in number and were confined to an area in South Africa.¹ When anthropologists later studied their caves, they found them full of oyster shells. We call these shell deposits “middens”—layers and layers of oyster shells that furnish evidence of human activity.

Scientists believe these groups of Homo sapiens came out of the forests looking for a better protein source, and with oysters, of course, they hit the jackpot. Oysters were easier to hunt than the large prey that would have been around at the time, so there was less danger and less risk of injury. Those were big advantages to early hunter-gatherers. Moreover, with no legs, wings or fins, oysters don’t move; if you found an oyster bed, it was a bit like an early supermarket. You could come back every day and be guaranteed a good protein meal. Personally, I think it was a bolder man who killed the first woolly mammoth!

Oysters as a regular protein source would have been a huge evolutionary advantage for early Homo sapiens. Oysters are very high in omega-3 fatty acids, zinc and other micronu­trients; so for the first time, we probably had smarter, stronger and possibly sexier cavemen and women. From this period, Homo sapiens outcompeted the Neanderthals, and the rest, as they say, is history.

Oysters may also have helped Homo sapi­ens survive the Ice Age from about one hundred thousand to twenty-five thousand years ago. Game and large animals would have been very scarce, making it a tough time for humanity, and oysters may have been part of the solution. We know that oysters preceded agriculture by at least one hundred thousand years. Oysters are the original “paleo food,” and in some ways, they’re a lost superfood.

OYSTERS THROUGH THE CENTURIES

The Greeks were the first to cultivate oysters, from about 1300 BC to 900 BC, with the Romans subsequently following suit. The Greeks threw pieces of pottery in the water, and oysters would grow on them.² (This same ap­proach is actually being used today as part of the “Billion Oyster Project” to restore oyster reefs in New York harbor.³) Artists often depicted Aphrodite or her Roman counterpart Venus as being born from a shell (think of the famous painting of Venus by Botticelli).

The Romans started delighting in eating oysters around 800 BC though 500 AD. In a fifth-century Roman mosaic depicting a feast, we see lots of oyster shells on the floor, showing their fondness for this delicacy. When oysters became scarce in the Mediterranean, they shipped oysters down from northern Europe and Britain,⁴ which they had strategically invaded. My guess is that oysters were fished two thou­sand years ago where I live on the east coast of Ireland. The Romans transported oysters covered in seaweed to Rome by donkey and cart. Today—even with our modern refrigerated trucks traveling at eighty kilometers an hour— customs delays, bureaucracy and other factors make it challenging to get oysters to Italy. The fact that the Romans did it two thousand years ago is impressive! The Romans who stayed behind in Britain also built villas using a type of concrete made from oyster shells.

After the fall of Rome and throughout the Middle Ages, oysters continued to be a delicacy for the rich but would also have been a staple for ordinary people in some coastal communities. During the Renaissance, we see painters start­ing to depict oyster consumption. Jan Steen’s 1658 painting, The Oyster Eater or Girl Offer­ing Oysters shows a woman preparing oysters. (She has a bit of a dirty look in her eye that makes you wonder what she’s planning for her husband that night.) A painting by Jan Brueghel the Elder, Woman Eating Oysters, shows a woman and her children enjoying oysters. By the seventeenth century, we start to see oyster farming in Europe.

FROM A GOLDEN ERA TO COLLAPSE

Peak production and consumption of oys­ters occurred from about the late 1800s to the early 1900s—the golden era of oysters. The surge in production meant lower prices, which in turn meant that everyone could afford to eat them. In fact, oysters were cheaper than meat, poultry or fish. A picture of Fulton Market in New York City in the 1870s shows ladies and gentlemen strolling around among the oyster vendors. (Unfortunately, oyster stands eventu­ally gave way to hot dog stands, which did not do any wonders for our health.) I also have a 1905 picture from the other side of the world show­ing Aboriginal hunter-gatherers in New South Wales collecting oysters from a river.

In Maryland, “Chesapeake Bay” means “Great Shellfish Bay.” In a picture of the Chesa­peake Bay in the early 1900s, men are standing on top of a mound of oyster shells. The mound represents about two hundred thousand bushels, or about twenty million oysters. That would be the equivalent of 15 percent of Ireland’s annual production today—but that was from a single shucking house in the Chesapeake! This was a colossal area for oyster production. They cut channels through the oyster beds for shipping, and they had shucking houses all along the Chesapeake where they would can oysters to send all over the U.S. and the world.

Other peak areas of production were the San Francisco harbor, New York, the south coast of Australia (which had an oyster reef that was two thousand kilometers long that could have been visible from outer space), the North Sea (an area of oysters that was probably the size of Florida) and a massive area in the Irish Sea where I live.

As a result of the intense level of production, by 1920, oyster populations globally had col­lapsed by 80 percent. Today, no living scientist has seen a living oyster reef, so we don’t even know what they were like. We do know that oys­ter reefs were incredibly important ecosystems for food, biodiversity, coastal protection and all sorts of other functions. That is why oysters are called “ecosystem engineers,” and it is why the disappearance of oyster reefs brought about a wider ecosystem collapse.

To illustrate the extent of collapse, consider that just off the coast where I live, Irish fisher­men recorded a sixty-thousand-barrel catch of oysters in a four-month season in 1860; by 1886, the catch had plummeted to fourteen barrels. In 1860, my town had about three hundred fifty boats and two thousand crew; now, there are about four boats. Obviously, oysters were not just a source of food but also were incredibly important economically to the coastal com­munities.

Factors that contributed to the collapse of oysters varied by place. In San Francisco harbor, for example, the Navy had a huge base, and they would apply tar and creosote to the ships. Ap­parently, the seabed there is covered in tar and creosote, and it will be a long time before that clears itself up. In my region in Ireland, they changed the regulations and said that it was okay to fish into May when the oysters spawn. If you disturb an animal when they’re about to lay an egg or spawn, they will go away. So, the combination of the heavy fishing pressure com­bined with poor management led to the collapse.

There is actually a fascinating history of “oyster wars” in Europe. In my area, the local fishermen fished six days a week (going to the pub on Sundays for a few pints after Mass), but the English fished our area seven days a week. The fishermen in my town wanted to put a heavy cannon on the beach and blow the English boats out of the water; they couldn’t relax on Sundays when the boys from England were still out there fishing!

THE RISE OF AQUACULTURE

Since the 1950s, aquaculture has produced most of the world’s oysters, primarily the Crassostrea species. In 1950, global aquaculture production was 156,000 tons. By 1970, produc­tion had risen to 437,000 tons, continuing to 1.2 million in 1994, 4.3 million in 2003 and around 6 million tons today. However, fully 85 percent of those oysters are produced and consumed in China.

At an oyster farm on the west coast of Ire­land, in a beautiful area with very little agricul­ture and very clean waters, they produce about one hundred tons of oysters a year. Compare that to a large Chinese oyster farm in Qinzhou—the same size as fifteen thousand football fields— that produces 230,000 tons of oysters a year. The scale of production is incredible. People live on rafts with their families, and they farm oysters on them. I don’t know what the industries are in Qinzhou, but whatever they discharge into the water will come out through the estuary and into the oyster beds, so I would be careful to get some analysis done on those oysters before eating them.

Along those lines, I should note that while there are a number of issues with farmed fish, in the case of oysters, there is no qualitative dif­ference between “cultivated” (“farmed”) oysters and “wild” oysters. This is because oysters are “sessile” organisms, meaning they don’t need to move. They are happy to just sit there and filter-feed (hence the phrase, “the patience of an oyster”). Cultivated oysters feed naturally from the sea water they live in, meaning there is no artificial diet involved in farming them, and they get to reproduce once or twice. In terms of animal husbandry, it’s as good as it gets. The quality of farmed oysters is all about whether the water is clean or contaminated.

Europe currently produces about 100,000 tons of oysters annually, and the U.S. produces about 154,000 tons annually. What those num­bers tell us is that a single oyster farm in Qin­zhou produces almost as much as the U.S. and Europe combined. In addition, China imports most of the best grades of oysters coming out of Europe—they are flown into places like Hong Kong, Shanghai and Macau. The Asian casinos are fond of the really good grades of oysters from Europe. Nowadays in the U.S., the average American eats just three oysters a year (a third of a pound); in 1870 in New York City, average annual consumption was about six hundred oysters per person.

A POWERHOUSE OF NUTRITION

In 2000, I founded Marine Health Foods, a family business with twelve staff. We’re located on the east coast of Ireland in County Wicklow, a region nicknamed “the garden of Ireland” because of its lush beauty. I am the owner and CEO of the business but a marine biologist by training, with thirty-five years’ experi­ence working with oysters and shellfish. We started as an artisan producer of gourmet seafood and ran oyster bars, but over time, we shifted our focus to produce food-sourced nutritional extracts. We still employ artisan standards in our manufacturing because we’re passionate about keeping the process clean and pure.

Oysters are an absolute powerhouse of nutrition. They contain literally everything that our body needs. Some of the books that sit on my desk include books on the biochemistry of zinc, copper and selenium, as well as Biology of Oysters by Dr. Brian Bayne,⁵ my old profes­sor from Bangor University who just retired. Bayne’s book has eight hundred forty-four pages on every oyster species and everything you could possibly want to know about oysters—but it doesn’t mention zinc. Meanwhile, Dr. Ananda Prasad, who discovered zinc deficiency in 1963 and was the world’s leading authority on zinc nutrition (he died in 2022 at age ninety-four), wrote a three-hundred-page book on zinc biochemistry that doesn’t say a word about oysters!⁶ This, despite the fact that American researchers discovered zinc in oysters in 1910 and published an early paper in 1919.⁷

These two omissions indicate that there is a disconnect between the understanding of zinc and how it behaves in the body, and oysters. At Marine Health Foods, we’re trying to bring the science and the good qualities of oysters back into people’s lives and increase their understand­ing of what oysters have to offer.

We make about twelve to fourteen batches of product a year, and we monitor the nutrients in every batch. We monitor zinc, copper, manganese, iodine, selenium and vita­min B12 because we make health claims. Oysters are so nutrient-dense and have so many of these elements that we can make over for­ty European Food Safety Authority (EFSA) health claims. This is virtually unheard of for a natural dietary product. You can put ten milligrams of zinc in a synthetic zinc tablet and make health claims, but there is no food you can do that with except oysters. It is the same for the other elements such as copper and manganese. Oysters are very unusual in that respect.

OYSTER BIOLOGY

Why are oysters so unique in the animal kingdom? Oysters live in the intertidal zone—the area between low and high water. When the tide is out, oysters are exposed to the air. The drastic fluctuations in temperature, oxygen and salinity, along with predation from sea birds and humans and lots of pathogens, mean that their environment is very stressful. Moreover, there is no escape; they can’t run away or get back into the water. This leads to a lot of oxidative stress, among other things. However, over the course of three hundred million years, they have evolved to deal with this.

In fact, the extraordinary biology of oysters means they can survive for four weeks out of the water. That is unique in the animal kingdom. How do they do it? They have an open circulation system. Inside, they’ve got a soft body, and it is surrounded by liquid. You might think that the liquid is sea water, but it’s not. It’s actually a “liquor,” hemolymph, which is a primitive type of blood that surrounds the oyster’s body tissue. (It is very nutritious as well, so you definitely should not throw it out when you’re eating oysters.) In the liquor are hemocytes (a primitive form of antibody) that swim around. The hemocytes are like the “police force” for the oyster—the first line of defense if pathogens try to get into the shell.

Out of the water, oysters get weaker and become more susceptible to infection. When pathogens get in, the hemocytes attack them through a process known as phagocytosis, where they engulf the pathogens. However, that process leads to a metabolic burst of free radi­cals, and in particular, superoxide free radicals. These free radicals are now floating around in the blood (the liquor), and they have to be gotten rid of; otherwise, they will cause terrible tissue and DNA damage, which is exactly what free radicals do in the human body. To counteract this, the oysters produce very high levels of antioxidants, which remove the free radicals and restore homeostasis in the shell. It’s by this process that they can survive for up to four weeks out of water.

In Australia, scientists were doing an oyster reef restoration project. They dug some oysters out and killed them, breaking up the shells and putting them back in the water as an experiment. They knew oysters could survive for four weeks, but when they came back fully three months later, some of the oysters were still alive after three months baking in the hot Australian sun! This is more evidence that they are incredibly resilient creatures.⁸

THE ZINC CONNECTION

To do what they do, oysters require a lot of zinc. This is the beauty of the oyster and the key to what I want to discuss in the remainder of this article. Although zinc is involved in about three hundred enzyme reactions and two thousand transcriptional factors, I will focus on just one SOD (see next section, “Antioxidants to the Rescue”).

Oysters are the highest natural source of zinc, with ten times more than the next source, which is beef. At the same time, there is huge variability in the concentrations of zinc in oys­ters—even in two oysters in the same body of water. It’s amazing the way the zinc concentra­tion can change. We’ve seen levels going from three hundred parts per million (ppm) to sev­enteen thousand; for copper, we’ve seen a range from thirty-seven to four thousand ppm. A 1919 paper by American researchers documented the same variability,⁷ with zinc ranging from one hundred forty-five to almost eight hundred ppm, and copper ranging from six to thirty ppm.

You’ll see nutritional information about oysters on the Internet that says “six oysters contain this much zinc,” but you need to know about the potential variability. I can only assume that the people putting up that information are using averages derived from large data sets. The variability is the reason that we analyze every batch of our product. We are transparent with our customers; when they get oyster nutrition from us, we want them to know exactly what they’re getting.

Oysters “hyper-accumulate” zinc and cop­per. If you have an oyster and a mussel living in the same body of water, the oyster will ac­cumulate zinc to much higher levels than the mussel—up to sixty-five times more—even though they are living in the exact same area. It is the accumulation of these two metals that enables oysters’ resistance to the stress of living in the intertidal zone. As filter feeders, oysters also will accumulate heavy metals or persistent chemicals if present in the water (as will any filter-feeding shellfish), but interestingly, their accumulation of zinc is not passive in this way; it’s a preference. They have to do it actively, and it’s done against the chemical gradient, which means the oyster has to expend a lot of energy to do it. That fact raises a question: Why do oysters expend so much energy to store zinc and copper? The answer is that they do it so that they can make important antioxidant molecules.

ANTIOXIDANTS TO THE RESCUE

We know that free radical formation is at the root of much illness. Chronic inflamma­tion from free radicals is linked to autoim­mune disease, heart disease, certain cancers, metabolic disease, type two diabetes and many more conditions.⁹ Free radicals can damage lipids, proteins, carbohydrates and especially DNA. Antioxidants neutralize free radicals and maintain homeostasis and cellular health. Thus, production of antioxidants is vital for health in both oysters and humans.

Oyster antioxidants are very similar in structure to human forms. Zinc, copper and manganese make up the metalloenzymes—the master antioxidants superoxide dismutase, glutathione and catalase—in both oysters and humans. I am going to focus on superoxide dis­mutase (SOD) here. SOD in oysters is 60 percent similar to human SOD, and oyster consumption can promote human production of this master antioxidant. Eating foods that stimulate produc­tion of our own forms of master antioxidants is an important key to good health. Oysters did this for two hundred fifty thousand years, helping us to survive.

Wherever oxygen is metabolized, superox­ide free radicals build up. This happens in every cell of the body, all day, every day. Our first line of defense is SOD, a relatively small protein that has two identical monomers with a zinc and a copper atom at the center of each. If you look at a SOD molecule, you can see how the copper and zinc atoms hold the amino acids together.

SOD functions as a superoxide scavenger in cells throughout the body and especially in the mitochondria where a lot of damage can otherwise be done. Free radical damage in the mitochondria can lead to loss of energy produc­tion. That is at the root of the theory of aging, because from about age forty on, the production of the SOD enzyme starts to decrease, which facilitates more oxidative damage in the mitochondria. That means we have less ATP production, and when there is less ATP in the whole body, we have less energy. Today, fatigue is one of the biggest health complaints; about 80 percent of people going to the doctor complain of fatigue. SOD could be a very important part of that puzzle.

When superoxide forms in the cells, SOD acts on it, breaking it down into hydrogen peroxide. However, hydrogen peroxide is still very danger­ous in the cells and can cause a lot of damage, so then catalase (which relies on iron) and glutathione peroxidase (which is selenium-dependent) together break it down into water and oxygen, making it harmless again.

Oyster SOD cannot function in the human body as is, because the molecule is too big to cross the intestinal lumen; if it could, it would be attacked as a foreign body, even though it is 60 percent similar to hu­man SOD. What happens instead is that it is broken down and digested to provide the building blocks for human SOD. Our intestinal lumen can pull the amino acids, peptides and molecules of zinc and copper across, and then our body builds its own SOD. This is exactly what you want. People talk about taking antioxidant supplements, but it has to be a human antioxidant. The way humans evolved was to eat foods that stimulate our body to make these antioxidants and maintain our antioxidant defense system against persistent threats to our health.

OUR RESEARCH

We decided to do some research to fill the gap left by the books of Dr. Prasad and Dr. Bayne. We took some of our oyster extract powder and tested the effects of oyster nutrition on human cells in vitro (female skin dermal cells). We measured the antioxidant activity by monitor­ing intracellular generation of reactive oxygen species (ROS), that is to say, free radicals. The results showed that oyster nutrition significantly stimulated antioxidant activity.

Next, we decided to dig a bit deeper. Again, we tested the effects of oyster extract on human cells in vitro, using the same human cell line, and this time we focused on SOD production in the cells under stress. The results showed that oyster nutrition significantly stimulated SOD production to counteract the su­peroxide free radical. We plan to continue doing research and eventually would like to do some kind of in vivo trial with human volunteers.

If you haven’t figured this out already, I’m convinced that SOD has important things to tell us, but unfortunately, nobody is doing the kind of research we need. The pharmaceutical companies won’t do it because they can’t pat­ent oysters.

SIZE AND GEOGRAPHY

When it comes to oysters, size matters. Large oysters have much higher nutrient levels; other influences on nutrient levels include age, location and season. In Ireland, we have the largest underground zinc mine in the world, so the waters around Ireland are naturally higher in zinc. In the past, there was also a lot of cop­per mining.

To make our products, we’re constantly trying to select oysters that have really high mineral content. The minerals are lowest when the oysters are ready to spawn and are full of fat and protein, so we harvest just after spawning. That’s when we know the minerals are high; we want to give people really high doses of these valuable minerals so they can make their own antioxidant molecules.

We use large wild oysters (Crassostrea gi­gas) that are not native to Ireland. They escaped from oyster farms that weren’t managed well. They weren’t supposed to be able to spawn in Ireland and survive, but nature found a way. They spawned and settled in a couple of bays on the west coast, and now they have actually become an invasive species. Fortunately, our company’s activity takes them out. The fisher­men are delighted because they’ve got a second fishery; the government is delighted because they don’t have to worry about the invasive problem; and we’re delighted to get this good raw material and excellent source of nutrition.

ZINC-TO-COPPER RATIO

Synergy and nutrient ratios are very im­portant in oysters. Remember, the concept of synergy means that the combined effect of two elements is far greater than their individual ef­fects. A few years ago, a new quality manager joined us, and I asked her to go back through all our batches for the last twenty years and check the zinc-to-copper ratio. On the Internet, referring to synthetic supplements, people say that the ratio should be “such-and-such,” but I thought that the ocean is our laboratory and the oyster has been doing this for three hundred mil­lion years, so let’s ask the oyster. We analyzed all the batches and found a ratio of eleven to one over the twenty-year period. Our conclu­sion: that is nature’s ratio and has nothing to do with us. Interestingly, research suggests that the zinc-to-copper ratio in humans is typically eight-to-fifteen to one, so the oyster’s ratio sits smack in the middle of that.

It’s important to recognize the fact that food sources are always going to be better than synthetic forms of zinc and copper; synthetic forms destroy the all-important synergy be­tween the two. Listen to some of the talks by Morley Robbins,10 who has done phenomenal work on copper and how copper behaves in the body. Robbins describes zinc as an “assassin,” but he is quick to say that he is talking about synthetic zinc supplements, not zinc from food sources, which behaves very differently. Syn­thetic zinc can cause copper deficiency because the two are antagonistic when taken in synthetic forms. Synthetic zinc will pull copper out of the binding sites in the body, and then it floats around in the blood and ceruloplasmin, which makes doctors think people have too much cop­per when they get a blood test. In fact, it’s the opposite—the copper has been pulled out of where it should be doing its work in the body.

I think people are too flippant about taking synthetic zinc without being mindful of the necessary cofactors. It’s quite worrying, because they don’t realize the effects that it can have on their body, upsetting the very delicate balance of minerals that they need to maintain good health. As of 2022, the synthetic zinc market in the U.S. was worth around five billion dollars, which means a lot of it is being sold and consumed.

Dr. Prasad did all his work with synthetic zinc. It is unfortunate that he never studied oysters. I can understand why he would have wanted the precise doses of zinc that a synthetic form can guarantee. As we’ve seen, natural zinc in oysters is quite variable, so it might have been hard to use oysters in controlled experiments. However, because of Prasad’s work, people think that taking synthetic zinc is the way to go, not realizing that oysters are the “caviar” of zinc and copper nutrition. With oysters, you don’t have anything to worry about; there won’t be any antagonism or anything else to create problems.

Interestingly, some French naturopaths who have worked with us have obtained very high “chi” energy measurements on our oyster extract. In comparison, they say that when supplements have been irradiated, as is the case with about 90 percent of supplements on the market, they’re completely “dead”; they can’t raise the “chi” energy above zero.

OYSTERS AND HORMONES

Oysters can play an important role when it comes to fertility and reproductive hormones. A lot of menstrual abnormalities can be due to zinc deficiency; the feedback we’ve received from clients and doctors over the past two decades is that menstrual cramps and pain subside after oyster extract supplementation. Animal studies suggest that zinc deficiency also affects ovarian function and is linked to reduced oocyte quality, so oysters can support healthy ovulation.¹¹ Taking oysters pre­conceptionally (both men and women) can make a difference for anyone trying to conceive. We have had customers who had failed to conceive with in vitro fertilization (IVF) and then were successful after taking high doses of oyster nutrition. During pregnancy and lactation, a woman’s body requires a 50 percent increase in the DRI for many nutrients, and again, oyster is a very good way to get that.¹² Finally, zinc is very important for the secretion of prolactin during breastfeeding.

In men, spermatogenesis requires both selenium and zinc, and high levels of zinc are also needed for prostate health.13 In fact, other than the back of the eye, the prostate has the highest level of zinc in the male body. Zinc is also vital for testosterone production in both men and women.

Oysters as a food-source mineral supplement are very good for skin, hair and nails. Years ago, a client in New York called me. Initially, he had ordered two bottles of oyster extract; a week later, he ordered twenty bottles more, and then two or three weeks later, another fifty bottles. When we spoke on the phone, I asked, “Are you a doctor, or do you have a shop?” He said, “No, I take it myself.” When I said, “You couldn’t be taking that much,” he told me that he was taking from a half to a full bottle every day! It turned out that he had chronic zinc malabsorption, secondary to Crohn’s disease, and the doctors could not get zinc to stay in his body. Whether orally, intravenously or via injection, his body just would not hold on to zinc.

After he found an article that I had written about zinc supplementa­tion, he started taking high doses of the oyster extract. Before taking it, he was emaciated and his hair had gone gray, but when I had the chance to meet him in person about six months later, he was a big, strong guy with black hair! He had completely cured himself, and now he only takes a maintenance dose of oyster. The synergy of the zinc, copper, manganese and so forth was the only way his body would accept it—it would not accept synthetic zinc. This story illustrates both how bad synthetic zinc is and also the importance of food-source zinc.

VEGANS AND BIVALVES

There is a debate going on about whether vegans can eat oysters and mussels. This form of veganism has been dubbed “ostroveganism,” from the Latin word ostrea meaning oyster. One of the big problems with veganism are deficiencies in B12, zinc, vitamin D3, selenium, EPA and DHA—and these are all in the oyster. So, the oyster can cure what I call “MEATabolic syndrome”!

The reason that some of the vegan societies have declared it okay to eat oysters is because oysters don’t have a central nervous system, and so they say oysters are “not sentient.” As a marine biologist, I would argue with that one. We actually have discovered that different species com­municate on the reefs by electrical impulse, and this is a huge advance in our knowledge about oysters. Previously, scientists thought oysters didn’t have any communication at all, other than possibly chemically in the water; people thought they were just a piece of rock sitting there, but they’re actually communicating with each other. This is a fascinating area of emerging research.

OYSTER GASTRONOMY

Gastronomy is where our business started, so I’d like to offer some tips about eating oysters. First and most importantly, savor the moment. Oysters take two to three years to grow, so you don’t want to rush the experience.

More practically, “shucking” is the act of opening oysters—and it’s a bit of an art, too— and “slurping” is the act of eating oysters. Al­ways chew an oyster before swallowing. If you don’t shuck them properly, there could be a sliver of oyster shell in there, and if you swallow that, you’re going to be in trouble. In addition, always make sure there’s plenty of liquor surrounding the oyster—they should be swimming in it. If you order oysters in a restaurant and they’re dry, don’t eat them; give them back, because they’re past their prime. The liquor starts leaking out of the shell about two weeks after being harvested, and then you’re getting close to danger territory. Smell is the number-one safety criterion. A good oyster should smell like a sea breeze, whereas you can smell a bad oyster from ten yards away. My motto is, “If in doubt, chuck it out.”

If oysters are fresh (that is, raw), they must be eaten alive—that’s a legal requirement. If they’re dead in the shell, they will make you sick, unless, of course, they’re cooked, which is a different thing. We had a three-minute rule at our oyster bar where they had to be on a plate in front of you three minutes after being opened.

In terms of ways to cook oysters, two com­mon ways are to smoke or grill them. “Angels on horseback”—oysters wrapped in partially cooked bacon and then grilled or broiled—are delicious, as are deviled oysters and Oysters Rockefeller (oysters on the half-shell topped with a butter-herb sauce and bread crumbs and then baked or broiled). In the EU, we’re a bit snobby and think that oysters always have to be eaten alive, but in the U.S.—perhaps due to the golden era when oysters were so plentiful— cooks historically have been more adventurous with things like oyster stews and gumbos. The problem nowadays is that oysters are no longer a low-budget item; if you want to make an oyster stew, it’s going to be expensive.

We sell our oyster powder as a bulk pow­der, and we’re finding that people like to use it to “turbocharge” broth. It’s a great way to get things like zinc and copper in the broth when ordinarily those metals wouldn’t be there in significant quantities. As for flavor, I like to say, “it tastes like a mermaid crying on your tongue.”

If you are looking for a good pairing of oysters with wine, I recommend Muscadet (a French wine from the Loire Valley) or any very dry white wine. I also recommend always opening the oysters before you starting drink­ing the wine—that’s how you avoid a trip to the emergency room. I made a mistake one night at an event where the event organizers had plied us with free pints; after I sent the knife through my hand, I decided that shucking oysters and drinking is a bit like drinking and driving. “Don’t drink and shuck!”

Oysters will pick up the flavor of the water they live in. They say that “merroir” is to oysters as “terroir” is to wine. In Ireland, there is a lot of peat in the mountains, so the oysters have a “peaty” flavor. At the 2024 Wise Traditions conference, we served oysters from British Co­lumbia, and they had a pine needle taste.

IGNORE OYSTER FEAR-MONGERING

There’s a lot of fear-mongering about oys­ters, but if you follow the proper protocols, you won’t get sick. The benefits of eating oysters far outweigh the risks. We’ve been working with oysters for twenty-four years, following the appropriate protocols for harvesting and production, and we’ve never had an incident with oyster sickness. We also ran oyster bars for years in Dublin. The problem was that people would come to Dublin for a “stag night”; after drinking fourteen pints of Guinness and a bottle of whiskey and eating a single oyster, they would blame the oyster for their hangover.

Only once did a person report us to the health board for making her “nauseous” from oysters. When the health board came in the fol­lowing week, there she was, sitting at the table again. I said, “You reported us for making you sick last week.” She said, “I just felt a little bit nauseous.” I said, “You called the health board. If you got sick in a restaurant eating chicken, would you be back there the next week eating chicken again?” I told the guy from the health board, and he laughed and walked off.

In terms of bacterial contamination, in the U.S. many years ago, there was a problem with the Vibrio species, but they are not particularly resilient and cooking at 150F will destroy them. With oysters, the quality of what you eat is all about where you get them and the quality of the water the oysters are living in. As I mentioned, we get our oysters on the west coast of Ireland where there are no industries and it is very clean.

The U.S. monitors water for marine biotoxins, whereas in Europe, we monitor the shellfish, and if biotoxins have accumulated into the shell­fish, we close off harvesting. That’s why Europe can’t send live shellfish to the U.S.; the regulatory agencies in the two countries can’t reach an agreement, even though both monitoring systems achieve the same end.

As I mentioned, heavy metals will accumulate in oysters if heavy metals are in the water, which is why we test every batch. The levels in ours are about one hundred times less than what’s allowed legally in food. There is an interesting synergy with regard to heavy metals. Zinc reduces heavy metal uptake and causes immobilization and chelation of heavy metals. So, if you have proper zinc homeostasis, the heavy metals can’t get into your body in the first place, and zinc will also kick out heavy metals and chelate them out of the body. So, one very good way to manage your heavy metal load is to make sure you have enough zinc in your diet.

We are getting a growing number of calls about microplastics. This is becoming a bigger issue because of oysters being filter feeders. It is not a requirement to test for microplastics, but we are looking into labs and test methods to see what’s available so that we can do some testing.

OYSTER REEF RESTORATION

About six years ago, I set up Native Oyster Reef Restoration Ireland (NORRI).¹⁴ The team includes Professor Anamarija Frankic, who works in Boston and Croatia; Brecht Stechele, a young PhD student; Nancy Navi jan; and Kealan Doyle, who has a documentary on Netflix called Seahorse Man. Doyle is trying to restore seahorses, but when we explained to him that oysters filter the sea water for eelgrass beds to grow in, he realized that we are never going to have seahorses until we have oysters. He is really into oyster restoration now.

NORRI has applied to the EU Life Fund for funding so that we can get some graduate students working on this. We selected four sites on the east coast of Ireland, including what was, in 1860, one of the biggest oyster fisheries and is now functionally extinct. We are working with three other partners: Oyster Heaven (a company from the Netherlands), University College Dub­lin and Wicklow County Council.

A famous Greek proverb says, “A society grows great when old men plant trees in whose shade they shall never sit.” I don’t know if I will see thriving oyster reefs on the east coast of Ire­land in my lifetime, but I hope my grandchildren will. We’re getting the ball rolling and the idea is catching on. For example, I recently saw that six yacht clubs in Dublin have started putting oysters in and around their marinas.

Professor Frankic did some interesting oys­ter restoration work in Boston Harbor. Before the project, there was just anoxic mud—the place looked like it had been wiped out dead. Two years after they started restoration, an oys­ter reef appeared. Nature is very resilient, and it will recover very quickly if given a chance. In the same bay at high water, they recorded blue sharks and sea turtles—again within two years. In another project in Wellfleet Harbor near Boston, they started with a mud flat, and two years later there were six million oysters. These projects can be very successful. All that is needed is the money and manpower to get things moving.

CREDIT WHERE CREDIT IS DUE

Humans have coexisted with oysters for two hundred fifty thousand years, during which time oysters have served as an important food source, supplying bioactive molecules that have a very positive effect on our health. They have a unique nutritive profile above all other animal products. I call them “the lost organ meat.” Eating oysters is a 100 percent “nose to tail” experience.

In Ireland, people used to put seaweed on the land, which put miner­als back into the soil and hence back into the food chain. Unfortunately, intensive agriculture and chemical fertilizers have depleted the soils. Seafood is a great way to make sure you’re getting all your minerals. I encourage you to make oysters a regular part of your nutrition and try to eat seafood at least two times a week. Remembering that the quality of the sea water is critical, source your oysters wisely. Talk to the sup­pliers and find a good fishmonger or an oyster farm if you are near the sea. Introducing oyster nutrition to your diet is like a tonic for the body’s biochemistry.

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SIDEBARS

OYSTERS AND THE THYROID

A lot of the integrative doctors we work with are using oyster nutrition, notably for thyroid health. Oysters are a very good source of iodine and selenium, and a healthy thyroid requires the correct levels of both. The synergy between iodine and selenium is very important; they interact to produce thyroid hormone. The thyroid has one of the highest levels of selenium in the body, and several selenoproteins are needed for thyroid health. For example, a deiodinase enzyme, which is a selenoprotein, converts T4 to T3. Some people like seaweed for iodine, but a lot of the people we work with donʼt like using it because while it is very high in iodine, it lacks the selenium cofactor, so giving too much iodine in that form can be problematic. Oysters are probably a better source.

TWENTY YEARS OF FEEDBACK

Over the twenty years since we started our work with oyster nutrition, we have received many testimonials. Here are some of the areas where our clients report noticeable improvements:

• Increased energy and less fatigue
• Improved immunity
• Less anxiety and better moods
• Improved thyroid and hormonal health
• Increased libido
• Improved fertility and reproductive success
• Improved prostate health
• Improved skin conditions
• Stronger nails
• Reversed grey hair in those who were copper-deficient
• Stronger hair and faster hair regrowth (“beauty from within”)
• Improved general health

As famous biochemist Linus Pauling once said, “You can trace every sickness, every disease, and every ailment to a mineral deficiency.” With oysters, you’re getting every mineral that your body needs.

A FREQUENTLY ASKED QUESTION

One of the questions we are often asked is, “Are oysters an aphrodisiac?” Part of the answer to that question dates back to something called the “Doctrine of Signatures.” In ancient Greece and Greek medicine, they thought that if a fruit or vegetable resembled a certain part of the human body, then it was good for that part of the body.¹⁵ Walnuts, for example, looked like the brain, so the doctrine taught that walnuts were good for the brain (this might be true because walnuts are high in omega-3s). As another example, anything that looked like a phallus was supposed to be good for male reproductive health. When I heard about this, I wondered, “Is there a female equivalent of the word phallic?” It turns out there is; the Sanskrit word “yonic” refers to a stylized representation of the female genitalia in Hinduism. There is one catch: there is no truly yonic food—except for oysters!

As for scientific proof of the aphrodisiac effects of oysters, some researchers claim that it has to do with the amino acids,¹⁶ but we also know that the minerals in oysters have many effects on bodily functions that support good sexual health, including benefits for spermatogenesis and testosterone production, as well as improved energy levels. Casanova reportedly ate six dozen oysters a day in King Louis XV’s court.¹⁷

OTHER IMPORTANT NUTRIENTS IN OYSTERS

Zinc and copper are just two of the elements that are particularly high, but letʼs not forget about some of the other nutrients in oysters. For example, oysters are an excellent source of vitamin B12; one oyster will give you 100 percent of your Dietary Reference Intake (DRI), although I should mention that mussels are even higher. Here are some other aspects of oyster nutrition that make them such a powerhouse:

• PROTEIN: As we saw at the beginning of this article, oysters are a very good source of protein: 55 to 65 percent when dried and 10 percent by wet weight.
• OMEGA-3s: Oysters are also a very good source of the omega-3 fatty acids EPA and DHA (about three hundred thirty milligrams in a serving of six oysters; four hundred milligrams are recommended daily). There is not as much variation in these elements as with the zinc and copper.
• FATS: Fats in oysters are 9.2 percent by weight.
• TRACE MINERALS: Oysters have fifty-nine trace minerals that the body requires.
• B VITAMINS: In addition to B12, you get B2, B3 (niacin), B5, B6, biotin and B9.
• VITAMINS C and E
• VITAMIN D3: Fish, and especially oysters in the shell, can make vitamin D3 in the dark, whereas humans need sun­light to make it. Oily fish (such as salmon, mackerel) are also a very good source of vitamin D3.
• PHOSPHORUS: Phosphorus is essential for bones and teeth.
• SODIUM: Sodium is important for fluid balance and essential for nerve and muscle function.
• POTASSIUM: Potassium is important for nerve transmission and muscle contraction.
• CALCIUM: There is a lot of calcium in oysters, but if you want an excellent source of biological calcium, grind the shells into a powder. There are a lot of other minerals in the shell as well. We used to make calcium supplements, but itʼs a tough market because itʼs been flooded with cheap stuff from other countries.
• MAGNESIUM: Magnesium is important for bone health.

When it comes to the trace minerals, there is not as much research on these, but they are very important and have known biological effects. Molybdenum, for example, is critical for making certain enzymes that break down toxins. If you donʼt have molybdenum, how does the body make those enzymes? That is a question that Iʼd like answered. Does the body try to make it, but it doesnʼt work properly? We need all of the trace minerals, even if only in tiny amounts.

AN OYSTER POEM

There once was an oyster whose story Iʼll tell

Who found that some sand had got into his shell.

It was only a grain, but it gave him great pain

For oysters have feelings although they are plain.

Now, did he berate the harsh workings of fate

That had brought him to such a deplorable state?

Did he curse at the government, cry for election,

and claim that the sea should have given him protection?

“No,” he said to himself, as he lay on a shell,

“Since I cannot remove it, I shall try to improve it.”

Now, the years rolled round, as the years always do,

and he came to his ultimate destiny—stew.

And the small grain of sand that had bothered him so

was a beautiful pearl all richly aglow.

This tale has a moral, for isnʼt it grand

What an oyster can do with a morsel of sand?

What couldnʼt we do if weʼd only begin

With some of the things that get under our skin?

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REFERENCES

1. Joseph K. Humanity’s primal connection to oysters—from the history to the nutritional value of oysters. Charleston Daily, Dec. 9, 2020.
2. The history of oysters: its rise as a delicacy and a staple food beloved by many. Food Worth Writing For, Jul. 31, 2018.
3. https://www.billionoysterproject.org/
4. Roman oyster “processing site” discovered on banks of Humber. BBC, May 23, 2024.
5. Bayne BL. Biology of Oysters. Academic Press, 2017.
6. Prasad AS. Biochemistry of Zinc. Springer, 1994.
7. Hiltner RS, Wichmann HJ. Zinc in oysters. Journal of Biological Chemistry. 1919 Jun;38(2):205-221.
8. McAfee D, McLeod LD, Carruthers S, et al. Reversing functional extinction: successful restoration of eradicated oyster reefs. Restoration Ecology. 2024 Jul;32(5):e14169.
9. Chandimali N, Bak SG, Park EH, et al. Free radicals and their impact on health and antioxidant defenses: a review. Cell Death Discov. 2025 Jan 24;11(1):19.
10. https://therootcauseprotocol.com/about/morley-robbins/
11. Liu WJ, Li LS, Lan MF, et al. Zinc deficiency deteriorates ovarian follicle development and function by inhibiting mitochondrial function. J Ovarian Res. 2024 May 28;17(1):115.
12. Nichols L. Shellfish: why these nutrient-dense foods are beneficial during pregnancy. Lilynicholsrdn.com, n.d. https://lilynicholsrdn.com/shellfish-pregnancy/
13. Costello LC, Franklin RB. A comprehensive review of the role of zinc in normal prostate function and metabolism; and its implications in prostate cancer. Arch Biochem Biophys. 2016 Dec 1;611:100-112.
14. https://www.norri.ie/
15. Richardson-Boedler C. The doctrine of signatures: a historical, philosophical and scientific view (I). Br Homeopath J. 1999 Oct;88(4):172-177.
16. Casanova was right on about oysters. UPI, Mar. 24, 2005.
17. Star A. Romancing the oyster. Beyond the Acorn, Feb. 1, 2019.

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