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Garlic, broccoli, green tea and turmeric: Health experts keep telling us to consume these foods to fight cancer.
But articles from a New York Times science journalist are challenging the view that diet can prevent cancer. The evidence on the influence of specific foods is weak, George Johnson wrote in a series of recent columns and in a book just released in paperback. Johnson reported that the results of studies connecting diet and cancer were conflicting and the numbers of preventable cases, small.
Ergo, diet doesn’t matter?
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Diet certainly matters, says Stephanie Maxson, senior clinical dietitian at the University of Texas’ MD Anderson Cancer Center, the country’s leading cancer treatment hospital, according to U.S. News & World Report’s most recent rankings. Eating a plant-based diet, as opposed to a diet high in fat or animal protein, is important for preventing cancer as well as all chronic disease, she says.
Faced with this competing points of view, we must make many decisions each day about what to feed ourselves and our families. How do we evaluate the research when it’s not perfect? How do we make the best decisions for our health? Here are five starting points:
1. Why is the evidence is conflicting?
The evidence is often conflicting because the science is complicated, says Maxson.
“It’s true that the research findings regarding individual foods and nutrients are often inconclusive. But this is not because diet has no effect has cancer risk. It’s because the study of food and nutrients is very complex,” she says.
The nutrients contained in a head of broccoli, for example, will depend on the cultivar, where and how it was grown and how it’s prepared, she says. “How the nutrients in a food behave in the body depends on all the other foods it’s consumed with, the genetics of the person consuming it, and the microorganisms in the colon of the person consuming the food.”
Variables like these can explain why one study might find broccoli protective and another not, and as scientists unravel the nuances, they’re able to design better research. “We’re only beginning to understand the complexities of diet, nutrition and cancer relationships,” says Dr. Stephen Clinton, a researcher and physician who, along with a small group of scientists, is currently revising the U.S. government’s dietary guidelines.
2. Are there research-based guidelines on diet and cancer?
If you do a PubMed search, you’ll come up with more than 50,000 studies on diet and cancer. How are we to make sense of them?
The American Institute of Cancer Research and its partner, the World Cancer Research Fund (AICR/WCRF), can serve as guides. These two nonprofit organizations study the studies.
Since the 1990s, a panel of AICR/WCRF experts — researchers and physicians from around the world– have been reviewing the evidence and producing periodic reports as well as broad dietary guidelines, which are used by hundreds of cancer treatment centers, including MD Anderson. “AICR/WCRF is the world’s preeminent organization working to define evidence-based recommendations regarding how diet and nutrition impacts cancer risk and survivorship,” says Clinton.
While the recommendations are for preventing cancer because that’s where most of the research is focused, cancer survivors, they say, should also follow these guidelines once treatment is completed. The suggestions include:
- Be lean. As the columnist points out, obesity increases the risk of many common cancers; body fat produces hormones that drive cancer growth.
- Consume plant foods primarily.
- Eat a variety of them.
Despite the inherent flaws in scientific research, “the evidence that whole diets involving a wide variety of plant foods provides real protection remains as strong as ever,” said AICR’s director of research in response to the columns.
3. What about specific foods and nutrients?
As part of its review process, AICR/WCRF judges the strength of the evidence on various foods and nutrients.
AICR/WCRF reports that there’s “probable” evidence that foods containing lycopene (tomato sauce, for example) or selenium (Brazil nuts, broccoli, garlic) decrease risk of prostate cancer and that diets high in calcium increase risk.
There’s “convincing” evidence that foods with fiber decrease risk of colorectal cancer and that red and processed meat increase it, they say.
Most often, however, the organizations deem the evidence “limited” or “suggestive,” meaning that more study is needed.
“We know of many food constituents that have anti-cancer properties,” says Dr. Steven Zeisel, director of the University of North Carolina’s Nutrition Research Institute and a member of AICR/WCRF’s expert panel that reviews all the studies. Garlic, broccoli, green tea and turmeric, for example, have been shown to fight cancer through extensive good research, he says. “But we do not know precisely which mixture of these constituents works best.”
Guidelines thus focus on patterns that decrease risk, such as plant-based diets, rather than individual nutrients or foods, he says. “What you eat certainly matters.”
4. How much cancer may be preventable?
According to AICR/WRCF estimates, approximately one-third of the most common cancers in the U.S. are preventable by a healthy diet and weight along with physical activity. For some types, the estimates for preventability are particularly high: colorectal, 50%; endometrial and esophageal, almost 60% and 70%, respectively.
In the U.S. alone, that’s nearly 375,000 cases of preventable cancer each year, said AICR’s director of research in a letter to the New York Times.
You can’t just look at each food individually and calculate risk, says its director of communications. “You have to look at the total diet and how all the foods you choose to eat and avoid together impact your cancer risk. You owe it to yourself to play the odds.”
5. What might your plate look like?
Playing the odds according to AICR‘s New American Plate design is fairly straightforward:
Fill at least two-thirds of your plate with plant foods, at most one-third with animal foods. Control portion sizes. Limit red meat to no more than 18 ounces weekly. As for dairy products, however, the evidence is still uncertain.
Meanwhile, as we continue the inevitably long wait for sufficient research-based evidence to warrant public policy on cancer and diet, I’ll be sticking to healthy plant-heavy patterns, lunching on this Mediterranean salad and not worrying about an occasional dollop of tzatziki. A walloping portion? Now that’s another story.
The following recipe is courtesy of The Jittery Cook.
All times are estimates. Cooking time for the pita varies from 7 to 10 minutes.
- ½ small head romaine, torn
- 1 bunch flat leaf parsley, chopped
- 1 bunch mint, chopped
- 2 cups mâche (lamb's lettuce)
- 1 cup arugula
- 6 red radishes, cut into thin half moons
- 12 cherry tomatoes, cut into quarters
- 6 Lebanese cucumbers, cut into chunky half moons (not peeled)
- 1 red onion, cut into small strips
- 1 large whole wheat pita
- 3 teaspoons zataar
- olive oil to lightly coat pita
- 2 lemons, juice only
- ⅓ cup olive oil (or more, if lemons are large)
- 1 heaping tablespoon sumac
- 2 cloves garlic, minced
- salt to taste
- Attack alliums first! Peel onion very gently, then cut it into a few parts and let it sit for a half hour before cutting finely and adding to salad. Smash garlic, let it sit for at least 10 minutes, then mince just before adding it to dressing.
- Separate the pita through the center, into two circular halves. Coat the insides lightly with olive oil and sprinkle on zataar. Cut into long strips, then bake at 350 F for 7-10 minutes, until crisp.
- Combine salad ingredients, dressing ingredients, and toss salad with dressing. Add pita to dressed salad. Either break strips into chips and toss with dressed salad—or serve in long strips for dramatic flair.
Main photo: Garlic is one of the foods that the National Cancer Institute says can reduce the risk of several types of cancer. Credit: Harriet Sugar Miller
Fresh local berries in season are a fleeting pleasure in most regions, and until we can virtually reach through the computer screen and grab them off the bush, the choice will come down to frozen berries or imports from faraway. If they’re not kept cool enough, fresh berries shipped long distances can lose important phytonutrients. Unless you’re up for interrogating suppliers, frozen berries are likely your best option, depending on how they’re frozen and thawed.
How to select and use frozen berries
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1. Reject blobs. Have you ever noticed that some packages of frozen berries feel like one big blob while in others, the berries run freely, resembling a sackful of M&Ms? When berries are frozen en masse, they surrender some of their phytonutrients to the moisture that becomes the blob, says Lila.
What you want are IQF berries — individually quick frozen, meaning they’re laid out on a large tray, berry by berry, and then frozen, a process that retains their healthy compounds, keeps them in singular form and thus makes them easier to thaw. How you thaw is crucial.
2. Defrost only the amount you’re planning to eat, consume them the same day and don’t refreeze them, Lila says. “Minimal handling helps the berries retain their ‘ just picked’ flavor and health protective components.”
3. Thaw berries quickly. A long, slow thaw in the fridge or on the counter activates enzymes that start to degrade phytonutrients, she says.
Lila suggests popping a small amount of frozen berries into the microwave for 15 to 20 seconds max just to get the frost off. She then throws them into her hot morning oatmeal. “The microwave can be devastating if overdone,” she says, so keep the temperature moderate and cooking time short.
4. Gently warm frozen berries on the stovetop, using a double boiler or placing them directly into a pot or pan and stirring continuously so they don’t scorch. A little bit of heat actually breaks down some of the healthy components so they get into your bloodstream faster, Lila says. Again, keep the process short and avoid high heat.
5. Consume the colorful juices left behind. They contain important water-soluble phytonutrients — including anthocyanins, a type of polyphenol that gives berries their red, blue and purple to blackish hues. In nature, anthocyanins protect plants from enemies such as insects and ultraviolet radiation, Lila explained on “The Dr. Oz Show.” In your body, they go straight to your large intestine, where they work with berry fiber and good gut bacteria to fight inflammation.
Lila’s new research suggests that eating berries — any berries — before or after exercising will increase the ability of those anthocyanins to fight inflammation. Her new research also shows that berries have some healthy fat soluble compounds as well, so eat them with a few nuts.
6. How to select and use dried berries.
Dried berries range from the traditional shriveled fruits to the new berries on the block, berry powders and freeze-dried whole fruits.
The traditional dried fruits — the tiny versions dehydrated in the sun — are highly concentrated in natural sugars, and many companies add glucose or other sweeteners. Choose wisely and eat dried fruits in moderation. Wild gojis from the Gobi, for example, are a good option because they’re not sweet and are dense in phytonutrients. All wild berries, if picked when ripe, usually beat out domesticated ones when it comes to producing healthy compounds, says Lila, because wild berries have to struggle in nature on their own, without human help.
Berry powders vary in quality, says Lila, depending on how they’re made. Often they’re spray dried, a process that uses gas to break down the fruits and destroys many phytonutrients.
Whole berries, on the other hand, are freeze-dried, which simply removes the water and retains all the good properties. “It’s the best way to preserve polyphenols,” Lila says. But the sugars become very concentrated and the process is expensive, making them a risky option for anyone with a sweet tooth and an addiction gene.
That would be me. As far as I’m concerned, the best thing about picking frozen berries is that I’m forced to control an unwavering urge to nosh. Have you ever tried biting into an icy fruit?
Main photo: Mary Ann Lila, with colleague Sally Gustafson, at North Carolina State University’s Plants for Human Health Institute. Credit: Courtesy of Plants for Human Health Institute
Broccoli was in the spotlight at the American Institute for Cancer Research’s recent annual conference, where global scientists shared their findings on the connection between diet and cancer. Had the researchers been giving out awards, broccoli’s baby sprouts, not just broccoli, would have snatched gold.
How you prepare broccoli, though, is the key to its cancer-fighting ability, said Elizabeth Jeffery, co-chair of one of the conference’s sessions and a professor in the department of food science and human nutrition at the University of Illinois at Urbana-Champaign. Her latest research could dramatically change your culinary habits.
Queen of the crucifers
You know the stinky smell that fills your kitchen when you’re cooking broccoli? That’s because of healthy sulfur-filled compounds, which exist in all crucifers. An enzyme in crucifers — marked by that kick you get when you bite into a raw one — turns sulfurs into two cancer-fighting categories:
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— Indoles, which help break down hormones as well as target a group of genes that promote prostate cancer. (The latter finding was reported by Wayne State University scientist Fazlul Sarkar at the conference.)
— Isothiocyanates (pronounced eye-so-thigh-o-sigh-a-nates), which counteract carcinogens in general and speed up their removal from the body. (Of course, broccoli also has many more healthy compounds.)
Broccoli bears the crown of queen of the crucifers because compared with other crucifers, it contains more of a particularly important isothiocyanate called sulforaphane.
Because heat degrades the enzyme that produces sulforaphane, many food scientists, until now, have recommended we eat crucifers raw or very lightly cooked. In her recent broccoli research, however, Jeffery has developed a more sophisticated approach to maximizing sulforaphane. Her work shows that how you make the broccoli and what you pair it with are vital.
Tips on handling broccoli
To capitalize on sulforaphane, first cook broccoli lightly, Jeffery said. Steam it in a little liquid for 3 to 4 minutes until bright green, using a steamer so that it doesn’t touch the cooking liquid. Or blanch it for 20 to 30 seconds, no more. Those methods are surprisingly better than eating it raw, she said, because when the enzyme acts on broccoli’s sulfur-containing compounds, the compounds can swing either way — and get turned into sulforophanes, which fight cancer, or nitriles, which don’t. “Every molecule of nitriles formed is a sulforaphane not formed,” Jeffery said. And just a little heat will keep nitriles from forming.
To counteract the enzyme reduction caused by heating Jefferey has a second suggestion:
Eat steamed broccoli along with a little raw crucifer — arugula, watercress, a little wasabi or spicy mustard, or perhaps even better, raw red radish. (The stronger the kick, the more enzyme you’re getting.) Red radishes contain sulforaphane and don’t have the inherent ability to produce nitriles. You don’t need much, Jeffery said — just two to three radishes or a ½ teaspoon of mustard or wasabi. And you don’t have to eat them in the same bite as broccoli, just in the same meal.
Here’s the final and most liberating finding for those of us chained to our kitchens: As long as you eat raw crucifers in the same meal, you can go ahead and cook broccoli any way you want, Jeffery said. The enzymes in the raw crucifers will act on compounds in the cooked ones.
Why broccoli sprouts?
While President George H.W. Bush was banning broccoli on Air Force One back in 1990, Johns Hopkins researcher Paul Talalay was busy exploring the crucifer’s newborn sprouts. What, he wondered, was the ideal number of days needed to germinate seeds to get the best sulforaphane content as well as taste?
The answer: three days. He and his son went on to develop a side business selling young broccoli sprouts. (Talalay, now 91, still collaborates on research and goes to his lab almost every day.)
In contrast to mature broccoli, broccoli sprouts have, on average, 20 times the amount of compounds that develop into sulforaphane, said Yanyan Li, a professor of food science at Montclair State University who is studying sulforaphane. Since the 1990s, researchers have been identifying cancer stem cells in many types of cancer, and Li has recently found that sulforaphane targets breast cancer stem cells at relatively low concentrations.
How much is enough?
To obtain that level of sulforaphane, however, you’d need to eat several pounds of broccoli — or, Li suggested, just a heaping cup of raw sprouts, lightly steamed and consumed along with a few raw radishes. Sulforphane is eliminated from the body relatively quickly, she said, so “eating them three times a day would be ideal to maintain the level.”
For the average person, that’s not really feasible, she acknowledges, and scientists at the conference agreed that eating crucifers four to five times a week is a reasonable goal for most — as long as you chew the vegetables well. By breaking the cell walls, you’re releasing those pungent enzymes.
Jeffery’s lab is now comparing the sulforaphane content in common varieties of broccoli, but that research is not yet ready for prime time.
Broccoli Sprout Salad With Synergy
(Recipe courtesy of Holly Botner, the Jittery Cook)
For the dressing:
½ lemon, juiced
2 tablespoons olive oil
1 clove garlic, minced
½ teaspoon salt
freshly ground black pepper to taste
For the broccoli sprout salad:
2 containers broccoli sprouts
4 red radishes, ½ thinly sliced, ½ julienned
1 handful baby arugula
½ carrot, cut into slivers with a peeler
¼ yellow pepper, finely chopped
1 orange, cut into segments as garnish
1. Combine all ingredients for the dressing and mix well.
2. Steam the sprouts until bright green, then cut off their green tops to use in the salad.
3. Arrange salad ingredients on two small plates. Spoon dressing lightly over salad.
Top photo: Broccoli sprout salad. Credit: Holly Botner / jitterycook.com
Carbs will be out, fats will be in, if a ketogenic diet proves to be a tool in the battle to fight cancer.
A ketogenic diet starves cancer cells of glucose, thereby stunting the disease’s growth and compelling the body to burn fats, which trigger the production of compounds called ketones that, scientists hypothesize, cancer cells can’t use for fuel. The effectiveness of the diet, which should only be used in consultation with a doctor, is in the pilot-study phase of human research.
The diet may work for other reasons: Like a campfire burning wood, cells burning glucose for energy undergo incomplete combustion, thus creating free radicals of oxygen that can damage DNA. In addition, scientists are increasingly studying the insulin the pancreas produces in response to glucose. It appears to trigger a cascade of actions that may stimulate cancer’s growth. Close to a century ago, German scientist Otto Warburg first suggested that glucose may play a role and in 1931 won a Nobel Prize for identifying cancer as a sugar feeder.
Recently, two American scientists collected a smaller prize for their pilot study. Dr. Eugene Fine, a physician and professor at Yeshiva University’s Albert Einstein School of Medicine in the Bronx, N.Y., and his colleague, Richard Feinman, professor of cell biology at State University of New York’s Downstate Medical Center took 10 patients with advanced cancers who had failed or refused standard chemotherapy and put them on ketogenic diets for 28 days, then looked at tumors on PET scans. Patients with the least ketosis (which they defined as least insulin inhibition) showed progressive disease whereas higher levels of ketosis were accompanied by stable disease or partial remission, they reported.
“We think what’s important is that we may have opened a door, long overdue, to studying dietary change as a component of cancer therapy,” Fine said, cautioning against reading too much into a small study.
Ultimately these scientists hope to identify which cancers might best respond to carbohydrate restriction. “For sure, they all won’t,” Fine said. The common slow-growing form of prostate cancer, he said, feeds on fats as well as glucose and glutamate, a protein that’s been implicated in a few cancers. “Even within a single individual with a primary cancer and metastases, the cancer’s behavior … can vary from one cell to the next.”
Ketogenic diet research takes off
Ketogenic diets are actually ancient. That’s how cave dwellers ate, Fine explained, and today’s paleo movement and the similar Atkins approach are bringing them back.
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Johns Hopkins Medicine in Baltimore has been using forms of a ketogenic diet since the 1920s to control epileptic seizures.
But in the cancer field, clinical trials of ketogenic diets are just sprouting up. Among the scientists touting the “fat as fuel” approach is Dr. Craig Thompson, the president and CEO of Memorial Sloan-Kettering Cancer Center in New York City. Thompson founded a private company that’s helping develop drugs to lower glucose and glutamine.
In his recent book, Boston College biology professor Thomas Seyfried takes the ketogenic diet one big step further. He advocates that patients fast periodically. There’s nothing more powerful than calorie restriction in reducing a tumor’s ability to grow blood vessels and spread, he said.
The diet he proposes includes 70% of calories from fat, 12% to 15% from protein, and the rest from carbs. How low carb is that? According to Fine, you need to eat 50 grams of carbs or less a day to get your body into a state of ketosis, where it produces ketones as a result of utilizing fat as its main energy source. The typical U.S. diet provides 250 to 400 grams daily.
Do the types of fat matter? Like the answers to most questions, it depends on whom you ask. Many versions of the ketogenic diet may include bacon and butter, albeit not on toast, but why consume saturated animal fats that are known to promote inflammation and disease? Unsaturated fats, such as those found in avocado and nuts, are good for your heart and may help control insulin. Omega 3 fats, abundant in fatty fish and flaxseed, fight inflammation.
And coconut fats contain medium-chain triglycerides, a type of fat that promotes the production of ketones. How about low-calorie vegetables immersed in high-fat coconut milk? One day that might be just what the doctor orders.
Top photo: A ketogenic diet of fats such as avocados, nuts and seeds is the focus of cancer research. Credit: Harriet Sugar Miller
“So where’s your sushi from?” I asked politely, still sweating the effects of Fukushima on fish from the Pacific Ocean.
“From Japan,” said the waiter.
Well, duh, what should I have expected? We were in a Japanese restaurant.
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For more than a year now, scientists studying the effects of the March 2011 deadly earthquake and tsunami that triggered the disastrous breakdown of the Fukushima Daiichi nuclear plant have suspected that the plant may still be leaking. Levels of radioactivity in the waters and fish around the plant have not been declining, as would be expected. Recently, amid reports of surging radiation levels, Japan finally owned up: The plant has probably been leaking for the past two years, acknowledged Japan’s chief nuclear regulator.
So should we, sitting comfortably across the Pacific, be worried about consuming Pacific fish?
Nicholas Fisher, a State University of New York at Stony Brook professor, has been studying radioactivity and metals in marine life for more than three decades. He’s part of the research team examining Fukushima’s effects on the seas.
Last year he reported small amounts of Fukushima’s cesium in Pacific bluefin tuna caught off California’s coast in summer 2011. Those tuna had spent their early days during that momentous spring off Japan’s Pacific shores, then migrated across the ocean, as some species do.
Last month he published another study saying the amounts of cesium are nothing to worry about. “The biological effects of any contaminant are generally dependent on the dose received,” he wrote. And the dosages of cesium in those 2011 tuna and attendant risks are extremely low, he said — too low to detect any damage and declining in fish caught in 2012. In fact, he’s more concerned about mercury in tuna than radioactivity.
Fisher compares the dosage of cesium you’d get from eating a 200-gram portion of that tuna to the naturally occurring radioactive potassium in one banana: The banana would give you a dose 20 times higher. When’s the last time you had a CT scan? That dosage is at least 1,000 times more — depending on the scan, up to 10,000 times more — than the amount an average American seafood consumer would get eating that contaminated tuna for an entire year, he said.
But what about the fish being exported from Japan?
Seafood from Japan monitored
To its credit, Japan lowered its levels of acceptable cesium in the wake of the disaster from 500 to 100 becquerels per kilogram. The U.S. limit is 1,200 becquerels per kilogram, and the Canadian limit is 1,000 becquerels per kilogram. Japan has been testing fish and posting results on the Internet. Some clear patterns are emerging:
— Some freshwater fish (landlocked salmon, for example) have higher levels of cesium, which is not surprising. Cesium mimics sodium and potassium. both of which are abundant and naturally occurring in the sea, meaning they would displace cesium uptake.
— And some of the ocean’s bottom feeders are showing levels above limits, which again is not surprising. Contaminants are getting trapped in sediments near the Fukushima nuclear plant, experts say, providing a continuous source of food for marine life that feed along the bottom near the shoreline.
The fish that feed in this area include many familiar species: cod, haddock, grouper, bass, halibut, flounder, sole, snapper, shellfish, monkfish, turbot, sturgeon, shark, eel and greenling, which was once a delicacy in Japanese cuisine. Last February, a greenling caught near the plant registered the highest level of contamination yet, which is 7,400 times the amount of radioactive cesium that Japan deems acceptable.
Meanwhile, Japan is working to keep contaminated fish off the market. Immediately after the incident, its fishermen voluntarily agreed to a ban on most commercial fishing off Fukushima prefecture. (The ban did not include fishing for skipjack tuna and some mackerel, all caught far enough offshore that it didn’t seem to worry the decision makers. They’ve been inspecting samples of those species, they say.)
Japan uses a testing program
Today, a few of those restrictions have been lifted. You can now buy Fukushima octopus and snow crab, for example. And the country relies on a testing program that’s managed by the prefectures and depends on the fisherman’s voluntary compliance. The prefectures regularly test samples for cesium, which builds up in muscle (and irregularly test for strontium, which accumulates in bone), at least weekly, often daily, explained a spokesman for Japan’s embassy in Canada. If a fish contains cesium above limits, the fisherman is responsible for keeping that species off the market. That responsibility means they must not sell any fish of that species in that day’s catch.
If a species from a particular area continues to show contamination, the central government can step in and ban fishing for that species in that area of the prefecture, as it has done in several instances. Then, if testing over multiple places within that area shows results consistently below limits, the feds can lift the ban.
Take Japan’s Pacific cod. Today, it’s banned in Fukushima and neighboring Ibaraki prefecture but can still be snagged elsewhere and sold. At one point, it was prohibited in three other prefectures because its contamination levels were above limits, but the ban’s no longer in force. Do fish know prefectural boundaries?
Global efforts to track contamination
In North America, the U.S. Food and Drug Administration and its Canadian counterparts no longer single out imports from Japan for inspection like they did after the incident but they do still monitor radiation in all foods, spokespeople said. The FDA has also issued an order authorizing agents to seize certain foods from certain prefectures that Japan’s central government has already banned from exporting due to high contamination levels. Recently, the American Medical Assn. passed a resolution urging the FDA to monitor seafood carefully, and a group of physician organizations instrumental in that resolution, led by the University of British Columbia’s Dr. Erica Frank, are calling on U.S. and Canadian authorities to be vigilant.
So could Pacific cod that had been feeding in those contaminated sediments make it to your faraway platter? Possibly, assuming it swam a few miles from Fukushima and through a few loopholes. If you indulged on a little sushi, would there be enough cesium to do harm?
Fisher’s now starting to study the levels of radioactivity in those coastal bottom feeders along with the possibility of radiation in other migratory species.
Top photo: Raw tuna. Credit: Holly Botner
Although some Buddhists may swear off onions and garlic because they allegedly arouse both anger and libido, these aromatics have powerful nourishing properties. Experts say you can enhance the many health-promoting and cancer-fighting effects of onions and garlic by adopting certain culinary habits. Are you ready to embrace the almighty bulbs?
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I’ve been involved in a steamy love affair with onions ever since a Thai waitress admired my father’s long, droopy earlobes, a sure sign of longevity in her culture. Other than the hunks of salami he used to beg for at bedtime, what food do I most often associate with my dad? Why, onions, of course!
But what does real science have to say about onions and their garlic cousins? Like leeks, chives and scallions, the other “forbidden spices” of certain Buddhists and Hindus, onions and garlic are members of the allium family of vegetables, so named because they contain the enzyme allinase, which converts the sulfur-containing compound alliin to allicin, its active form.
Alliums have long been prized for their ability to lower cholesterol, blood sugar and pressure, to thin the blood and to attack microbes. Recent research shows they fight cancer, too.
Studies in human populations “suggest that allium vegetable intake reduces the risk of cancer,” writes Italian researcher Carlotta Galeone, “and laboratory investigations have provided convincing evidence that selected substances contained in garlic and other allium vegetables inhibit a variety of chemically induced tumours in animals,” including cancers of the breast, endometrium, colon and digestive tract.
The “selected substances” include those stinky, pungent, tear-inducing molecules of sulfur.
Imagine an insect biting into an allium’s leaf and getting sprayed. “Plant scientists believe that a plant’s chemical system develops as an evolutionary defense against pests,” said Irwin Goldman, an onion expert and professor at the University of Wisconsin. Alliums originated in central Asia, just north of Afghanistan — a rough neck of the woods, by any measure.
In addition to more than 50 variations on sulfur, onions have another trait going for them: They contain flavonoids, compounds that give plants color and contribute to a host of healthy benefits. Quercetin, which acts as an anti-inflammatory, antihistamine and antioxidant, is the most exalted. It’s also has been shown to inhibit estrogen.
Garlic breath and onion sense: Top 5 practices for using them
To maximize the health benefits of onions and garlic, Goldman said, you must adopt some simple culinary habits:
Tip 1: Attack alliums first, as soon as you get to the kitchen.
By cutting onions and garlic, you break their cell walls, thus releasing those allinase enzymes. To develop the full complement of sulfur compounds, you have to let the cut vegetables sit for a while so that the enzymes have time to go to work, Goldman said.
How long is that? Goldman suggested 30 minutes for onions while garlic researcher Suhasini Modem suggested about half that time for cloves of garlic. And sulfur expert Eric Block said shorter times may suffice. In other words, nobody knows for sure, so hedge your bets by choosing the least risky course of action.
You could even cut your onions and garlic far in advance, Modem said, as long as you let them sit on the counter long enough, then refrigerate them to keep the sulfurs stable. Chopped garlic should last six to eight hours on the counter, she said, and two to three days in a cold fridge.
Tip 2: Don’t cut alliums too finely.
If you do, the enzymes will undergo a short-lived reaction and quickly evaporate, Block said. (Crucifers cut too finely react the same way.) But what if you desire a subtle mince? My solution is to keep the cut chunky at first, then cut the vegetables even more just before you’re planning to consume them.
Tip 3: Choose small red and yellow onions grown in colder climates and peel them gently.
Pity the poor Vidalia. She may be southern and mellow, which could be attractive qualities in a mate, but the harsh northern varieties of onions grown in latitudes above 40 degrees are higher in healthy sulfurs, Goldman said. Red and yellow onions, including the small yellow-skinned shallots, also contain more flavonoids than other varieties while white onions appear to have the least.
Quercetin and other flavonoids concentrate in the outer layers of onions, so peel them slightly and throw the skins into soup stock or compost. Smaller onions are simply better value. Why pay for those hunks of flavonoid-free interiors?
Tip 4: Eat alliums raw or slightly cooked.
In the case of garlic, Modem found that cooking it — even a quick saute for two minutes — destroyed its ability to inhibit the growth of cancer cells. Other researchers, however, have found that cooking in the microwave for 60 seconds or even 45 minutes in the oven only partially destroyed garlic’s anti-cancer properties as long as it had time to percolate beforehand. Again, hedge your bets.
Sulfur compounds in all alliums do get destroyed by cooking, Goldman said, but the flavonoids in onions may get enhanced with slight exposure to heat. For that reason, he recommends raw or quickly sautéed onions, cooked for four to five minutes, max.
Tip 5: Combine alliums with alliums and other healthy plant foods.
Even if you insist on cooking your alliums, you can increase their cancer-fighting qualities by throwing in some raw garlic, onions or their juices at the end. Combining garlic with olive oil, said Modem, may also add some anti-cancer synergy. Some studies also suggest you can get a similar boost by combining garlic with tomatoes or with selenium. And if you’re really angling to hedge your bets, you could always snort those piercing fumes. Funny you should bring that up, Goldman said. High on his bucket list is a study of people who work in onion factories–and cry “sulfur” every day.
Green Beans With Brazil Nut-Garlic Paste
This recipe combines raw garlic with Brazil nuts, one of the few food sources of cancer-fighting selenium. Eaten together, the two may pack an even powerful anti-cancer punch.
2 cloves garlic, smashed and allowed to sit 15 minutes before using
5 Brazil nuts
2 tablespoons lemon juice
4 large handfuls raw green beans
Salt to taste
1. Grind garlic and nuts to make a paste.
2. Whisk in lemon juice.
3. Using a steamer and very little water, steam the green beans for a couple of minutes until bright green, then combine with paste.
Top photo: Green beans with Brazil nut-garlic paste. Credit: Harriet Sugar Miller