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The superfoods and diets of the year

Reading time: 17 minutes

Health research in 2021 was dominated by the Covid-19 epidemic, which gave new focus to researchers to explore dietary and nutritional answers to the outbreak. It soon became clear that the epidemic had a lot to do with a poor diet of processed food; the virus singled out the obese and those who suffer from chronic health problems such as heart disease and diabetes, which are also associated with a poor diet.

Here are our highlights of research discoveries during the year that gave new insights into the foods we eat. Although only a small handful looked specifically at the impact of a good diet on Covid, it’s clear that nutrition is one of the key shapers of a strong immune system and so, by default, our best defense against the virus.

Don’t be too upset if your own favorite superfood or drink isn’t included (and certainly don’t stop consuming them), it’s just that they probably weren’t researched in 2021.

#1 Superfood of the Year

The mushroom

It surprised us too—but new studies show that the humble mushroom packs a big health punch. Instead of having it teetering off the edge of the plate, proudly put it center stage.

For one, it’ll halve your chances of getting cancer. People who eat 18 grams of mushrooms—roughly equivalent to four teaspoons—each day reduce their cancer risk by 45 percent. It doesn’t seem to matter much which type of mushroom you eat as they all have a similar protective effect, say researchers from Penn State College of Medicine.1

They’re certainly a superfood, especially because they contain ergothioneine, a powerful antioxidant that protects against cancer, and mushrooms are the richest dietary source around, said lead researcher Djibril Ba. 

He and his colleagues analyzed 17 cancer studies that involved more than 19,500 cancer patients. Those who ate mushrooms daily had the greatest protection, and although shiitake, oyster, maitake and king oyster had the highest levels of ergothioneine, all types of mushrooms seemed to have a similar protective effect. 

Mushrooms are good for your mental wellbeing, too. They appear to be able to lift your spirits and make you less anxious. 

The same team of researchers analyzed the health of around 24,000 adults who were tracked for 11 years to 2016 and found that those who ate mushrooms were less likely to suffer from depression.2 It could be because ergothioneine and other antioxidants in the fungi lower the risk of oxidative stress—a precursor of depression—while they’re also rich in potassium, which lowers anxiety.

Oh yes, and mushrooms even lower your risk for an early death, the researchers add. 

#2 Superfood of the Year


No surprises here. The avocado has for years hovered around the top spot for supreme superfood, and this year we include it because of new research that has revealed even more health-giving qualities of the fruit. So shoot us for not being original.

Avocados contain a compound that could be harnessed to lead the fight against leukemia, the blood cancer, it was discovered last year. The fruit contains a fat molecule, avocatin B, which is being tested on acute myeloid leukemia (AML) cells, one of the most virulent forms of the cancer.

Avocatin B has already been tested as a therapy for preventing type 2 diabetes and managing obesity, and now researchers from the University of Guelph in Ontario are investigating how it interferes with the function of VLCAD, an enzyme critical for the growth and spread of leukemia cancer cells.1

And guess what? Avocado can also help women lose stubborn belly fat, known as visceral abdominal fat.2 As covered in this issue’s News, overweight women—but not men—who ate an avocado a day as part of their daily meal plan saw a reduction in visceral fat and the fat surrounding their organs compared to those who did not have avocado in their diet. These findings are particularly notable because this type of fat is known to be a risk factor for type 2 diabetes.

#3 Superfood of the Year

Green vegetables

Yes, another unoriginal entry, but those green leafy vegetables need to be on your plate every day, and researchers came up with a helping of new reasons why. 

For one, green leafy vegetables will help keep you mentally sharp by the time you reach your late seventies. The vegetables seem to be the most important element of the Mediterranean diet when it comes to maintaining brain health. 

A research team from the University of Edinburgh tested the cognitive skills of more than 500 people who were 79 years old, assessing their ability to solve problems, their memory and word association, and then analyzed what they had been eating in the previous 12 months.

Those who closely followed the Mediterranean diet recorded high cognitive function scores, and those who ate green leafy vegetables and cut down on red meat had the highest scores of all.1

Leafy greens are good for your muscles, too, just as Dr Popeye predicted. It’s the nitrates in vegetables such as spinach, lettuce and kale that are doing all this good work; eating the equivalent of just one cup a day is enough to keep up muscle strength and function.

Eating your greens every day for 12 years will boost lower limb strength by an average of 11 percent, and your walking speed will be 4 percent higher, say researchers from the Edith Cowan University in Western Australia, who tracked the health of 3,759 people.2

These benefits were achieved independent of exercise; just eating your greens every day could be enough, although the ideal scenario would
be to combine the diet with muscle-strengthening exercises including
weight training. 

The diet becomes even more important as we get older. Having strong legs will help reduce the risk of falls and fractures, and our overall health and wellbeing will also improve. It’s especially good for the heart.

But it’s an uphill battle. Fewer than one in 10 people eat their five to six daily servings of vegetables.

Green vegetables also feed the gut, the epicenter of health. Researchers have been tracking the biological processes that take place when we swallow some spinach or chew on broccoli.

Vegetables contain a type of sugar called sulfoquinovose—known as sulfosugar because it contains sulfur (sulphur)—which needs specialized bacteria to break it down. This process produces hydrogen sulfide, a gas that has strong anti-inflammatory effects at low doses.

Researchers from the University of Vienna were the first to track the way the gut deals with sulfosugar. It stimulates the growth of key organisms in the gut microbiome that aren’t affected by other sugars, such as glucose, including E. rectale, one of the 10 most common gut microbes in healthy people.3

The process has a positive knock-on effect. It also produces a sulfur compound, DHPS, that acts as an energy source for other intestinal bacteria.

#4 Superfood of the Year


We’ve always known that legumes—chickpeas, lentils, beans and peas—are good for us, but researchers have come up with another reason why they’re so important: they lower your risk of multiple sclerosis (MS).

The legume family is rich in isoflavones, a phytoestrogen that helps stimulate gut bacteria that seem to protect against the disease.1

MS sufferers are low in the bacteria that break down isoflavones, and an unhealthy gut microbiome is increasingly being suspected as a trigger for the disease.

The bacteria can certainly protect against MS, say researchers from the University of Iowa. And it’s possible that a therapy that includes dietary isoflavones with the metabolizing gut bacteria could even treat the condition.

Newcomer of the Year

Red seaweed

Not exactly a newcomer to Southeast Asia, where the vegetable has been eaten for several thousand years, but researchers in the West have finally caught on to it. Red seaweed protects against cancer and populates the gut with good bacteria, which could explain why Japan’s rates of colon, colorectal and breast cancers are so low.

Researchers at the University of Illinois have analyzed the sugars from red seaweed to understand its health-giving properties. They discovered it contains six different sugars, and three of them have probiotic and anticancer qualities.1

One of the sugars acts as a prebiotic; it encourages the growth of probiotic bacteria in the gut. This could explain why the Japanese generally enjoy better health and longevity than people in the West, said Yong-Su Jin, one of the researchers. 

Another sugar, AHG, has cancer-fighting qualities. “AHG inhibits the growth of human colon cancer cells and yet does not affect the growth of normal cells,” he added. It seems to trigger apoptosis, or cell death, a necessary process that stops cancerous cells growing.

Salad Food of the Year

Celery and beets

It’s a joint award to celery and beets because of their nitrates, which keep your blood vessels and brain healthy. 

The foods promote ‘good’ bacteria in the mouth, which help regulate blood vessels and neurotransmission, or chemical messaging to the brain.

Our diet becomes more important as we get older and our natural ability to produce nitric oxide declines, say researchers from the University of Exeter. 

The foods are rich in inorganic nitrate, and bacteria in our mouth convert this to nitric oxide, which helps maintain vascular and cognitive health.1

#1 Nutrient of the Year

Vitamin D

Nutrients were in the news throughout 2021 as being one of the first lines of defense against Covid. While vitamin C also figured prominently in the debate—with 3 g to 5 g a day being the optimum dose for a healthy immune system—2021 was the year that vitamin D finally came back into the sunlight.

With ‘safe sun’ policies keeping us in the shade, we’ve all become deficient in this essential nutrient. But it’s not just vital in our fight against Covid; it could be key in beating another epidemic, too. Researchers last year discovered that a vitamin D deficiency could be the reason some people have become addicted to opioid painkillers.

A deficiency can make some crave opioids, which increases the risk of dependency and addiction, say researchers at the Massachusetts General Hospital. People with low levels of the vitamin are 50 percent more likely to use opioids in the first place, and this rises to 90 percent in those with a severe deficiency.1

Tests on laboratory mice found that their cravings for opioids diminished when they were given more vitamin D.

But what’s the connection? In 2007, researchers discovered that our skin produces an endorphin, a hormone chemically related to morphine, heroin and other opioids, when it’s exposed to ultraviolet (UV) rays. Endorphins are ‘feel good’ hormones that produce a state of mild euphoria.

Craving this endorphin rush could explain why so many of us sunbathe, the researchers surmise, and opioid painkillers provide a substitute when we don’t get enough sunlight and our vitamin D stores are diminished.

#2 Nutrient of the Year

Fish oils

There’s so much already known about the health-giving qualities of fish and fish oils that you’d think there was nothing more to say. But there is, and researchers have discovered they could be a vital addition to the diet of anyone who has heart disease or cancer. 

The omega-3 fatty acids in fish reduce the chances of a heart attack or stroke by around 17 percent in people who are already at high risk, say researchers from McMaster University. But only if they eat at least two servings a week.

People who were at low risk for cardiovascular disease saw no impact on their risk from eating fish. Strangely, a high-fish diet didn’t help people who weren’t suffering from cardiovascular disease, the researchers found when they took another look at several major studies that had tracked over 190,000 people, which included around 51,000 heart disease patients.1

But what if you prefer to supplement with omega-3s instead of eating more oily fish like mackerel and salmon? Another study published last year provides more insight into the best way to supplement.

When it comes to your heart health, the EPA (eicosapentaenoic acid) form of omega-3 appears to be the most effective. It is more likely to reduce cardiovascular disease and death—and improve survival rates after heart disease—compared to combined EPA+DHA (docosahexaenoic acid) supplements.

Researchers from Brigham and Women’s Hospital took another look at 38 studies to discover a big difference between the two types of fatty acids: they have different chemical properties that influence heart health. The findings build on the Reduce-It trial, which discovered that EPA supplementation dramatically reduces heart attacks and strokes in people who are at high risk.2

However, don’t count out DHA, because it’s not just your heart that will thank you for eating more omega-3s. Eating fish or taking fish oils may protect you against cancer, too.

The omega-3 fatty acid DHA has cancer-fighting qualities, even at low doses. Just 100 mg of DHA every day—less than half the recommended daily allowance of 250 mg—can kill cancer cells.

Researchers from the University of Louvain have discovered that the fatty acid interferes with the growth and spread of cancer cells. In a major advance in the understanding of how cancer spreads, the researchers have found that cancer cells thrive in an acidic environment and replace glucose—the normal energy source for cells—with lipids (fats).

But DHA overwhelms the cells and eventually kills them; in other words, they suddenly have too much fat to feed off. The greater the amount of unsaturated fatty acids in the cell, the greater the risk of oxidation, or cell transformation, the researchers found. In laboratory tests on cancer cells, they discovered the cells were dying in just a couple of weeks.3

With protective effects against heart disease and cancer—the two leading causes of death in the West—it’s no surprise that omega-3s have a positive impact on life expectancy. 

In fact, not taking your omega-3 supplements could be as bad for your longevity as smoking. Cigarettes can take up to five years off your life, and having low stores of the fatty acids can trim four years, say researchers from the University of Guelph in Canada. 

They think that higher levels of omega-3 alone account for the greater life expectancy in Japan, where people typically live five years longer than their counterparts in the West—and it could all be down to their diets, which are rich in fatty fish.

In a study of 2,240 people in their sixties, the researchers said that levels of omega-3 fatty acids were a reliable predictor of life expectancy over the following 11 years.4

#1 Drink of the Year

Green tea/tea

Green tea has for years been recognized as a super drink, and last year even more reasons were discovered.

An antioxidant in the tea could help fight off cancer—and even help protect us from ever getting the disease in the first place.

The antioxidant, EGCG (epigallocatechin gallate), increases our levels of a natural anticancer protein known as p53, which helps repair DNA damage, a precursor of cancer, and destroys cancerous cells.

Around half of all cancer patients have mutations in p53, a protein that researchers at the Rensselaer Center for Biotechnology in New York have described as “arguably the most important protein in human cancer.” It stops cells from growing, activates DNA repair and initiates cell death, known as apoptosis. All three biological processes are involved in the start and spread of cancer.1

The researchers have discovered a direct interaction between the green tea compound EGCG and p53. EGCG stops the protein from degrading,
they say.

And that’s not all. All tea—green and black—is good for keeping high blood pressure (hypertension) under control. This has been known for a few years, but researchers last year figured out how it happens.

Compounds in the teas relax blood vessels by activating a protein known as KCNQ5, say researchers from the University of California at Irvine. These proteins are found in the smooth muscles that line blood vessels, and they are activated by two of the tea’s flavonoid compounds, epicatechin gallate and EGCG.2

It doesn’t seem to matter whether the tea is black or green, if it’s served hot or cold, or if milk is added—all teas have the same beneficial effects on the blood vessels. It’s because they all come from the leaves of the evergreen Camellia sinensis plant, and the differences between the teas are determined by the fermentation process.

#2 Drink of the Year


How could we leave out Adam’s Ale? You’d think there was nothing more to discover about water, but researchers found out last year that drinking up to 3 liters (5 pints) of water every day reduces your chances of heart failure—and probably an awful lot more besides.

Few people drink anywhere near enough water every day—but it’s an essential fuel for the heart’s pumping mechanism. Optimal liquid intake varies between the sexes; women should be drinking between 1.6 to 2.1 liters a day, and the range for men is 2 to 3 liters. 

You know if you’re drinking enough liquids from the amount of sodium in your blood. A high serum sodium reading suggests you should be drinking more water; if you’re not, your body will try to conserve the water it has, and this can eventually lead to heart failure.

Researchers from the US National Institutes of Health tracked the sodium levels of 15,792 adults over a 25-year period. High sodium levels were reliable predictors of heart failure over the duration of the study, with each 1 mmol/L increase in sodium levels increasing the odds of heart failure by around 20 percent.1

#3 Drink of the Year


Last year was quite the rollercoaster ride for wine. It seemed that a 2019 study was pretty much the last word on alcohol; any amount was bad for you, and even one glass could increase your chances of a heart attack or stroke.

But toward the end of the year, researchers took another look at the data behind that study and discovered the calculations were flawed. In fact, drinking in moderation is probably good for our hearts.

Other researchers had already come to a similar conclusion. They discovered that heart attack or stroke survivors who drink a small glass of wine every day reduce their chances of a second attack by around 27 percent compared to teetotalers.1

Those who drink 8 grams of alcohol a day—equivalent to one unit, or a small glass of wine—enjoyed the greatest protection. But you can have too much of a good thing, and those who drank more didn’t lower their risk further, but instead raised their chances of other alcohol-related health problems.

Researchers from University College London studied a database of 14,386 people who had suffered a heart attack, angina or stroke. During the following eight years, 1,640 of the group died and 2,950 suffered a second attack—but the risk was far lower in those who drank moderately.

#1 Diet of the Year

The keto diet

Some find it extreme, but the diet that’s all about filling up on fats and avoiding carbohydrates, or sugars, has many health benefits. The latest news is that it slows the growth of brain tumors and may even reverse the disease. 

Brain tumors are some of the toughest to treat and have a very low survival rate—but a radical change of diet, including occasional fasting, could see all that change.

The tumors feed off glucose for their growth, so it makes sense to starve them of their fuel by dramatically cutting back on carbohydrates, which are the source of glucose. Once the glucose supply is shut off, healthy brain tissue can still feed off ketones, which replace glucose, but tumors can’t adapt, and so they die—or that’s how the theory goes.

A ketogenic diet, with its emphasis on fats, fits the bill—but can people eat just fats for any length of time, and does the diet have any unexpected side-effects?

To find out, researchers from the Johns Hopkins School of Medicine put 25 people with astrocytomas, a type of brain tumor, on the diet for eight weeks. They had all completed their conventional treatment, which included radiotherapy and chemotherapy.

The diet consisted exclusively of bacon, eggs, heavy cream, butter, leafy green vegetables and fish, and this was interrupted with a fast two days a week.

Most of the participants completed the course, and nearly half followed the diet completely. But even those who were less strict still changed their body’s metabolism to use fats and protein for their fuel.1

As expected, this also produced changes in the brain and the tumors. Brain scans revealed an increase in ketones—the replacement fuel for glucose—which could also slow the growth of the tumors given time.

#2 Diet of the Year

The rainbow diet

The rainbow diet is all about eating a rich diversity of vegetables, salads and fruits, such as strawberries, peppers and oranges.

The ‘rainbow’ foods are packed with antioxidant flavonoids—especially flavones and anthocyanins—that help protect our mental capabilities, especially as we get older. Flavonoids are powerhouses that help arrest mental decline, often a forerunner of dementia and Alzheimer’s disease.

Researchers from Harvard University tracked the health and diets of nearly 50,000 women with an average age of 48 and 28,000 men with an average age of 51, all for 20 years. Their ability to recall events or remember short lists was regularly checked through a questionnaire.

Those who ate the most flavonoids—around 600 mg, or half a serving a day—also had the highest scores on the tests and were 20 percent less likely to suffer cognitive decline compared to those eating flavonoid-poor diets.1

Strawberries are especially rich in flavonoids, the researchers said, while flavones, which gave the greatest protection against mental decline, are found in spices and in yellow or orange fruits and vegetables. These alone reduced the risk of cognitive decline by 38 percent, which equates to a brain that is biologically four years ‘younger.’ Anthocyanins, found in blueberries, blackberries and cherries, reduced the risk by 24 percent.

The other piece of good news is that it’s never too late to start. Even those who took up the rainbow diet later in life enjoyed similar protective effects to others who had been eating the diet for 20 years.

#3 Diet of the Year

Intermittent fasting

Fasting takes on many different shapes and sizes, from calorie restriction to shorter ‘eating windows.’ But whichever approach you adopt, it’s collectively known as intermittent fasting—and a review published last year outlined how it helps prevent and manage chronic health problems (see News, page 15, for more).1

Time-restricted eating is a form of intermittent fasting that works with the body’s internal clock. Our genes, hormones and metabolism rise and fall throughout the day, and restricting the time that we eat to within an eight- to 10-hour window keeps us in tune with these rhythms, say researchers at the Salk Institute for Biological Studies in San Diego, and can even help manage chronic health conditions such as diabetes and heart disease.

Snacking throughout the day makes us more prone to disease because it breaks the body’s synchrony with its internal clock, said Satchidananda Panda, the paper’s senior author.

Intermittent fasting reduces the risk of developing obesity, diabetes and heart disease, and it can help manage these chronic problems once they arise. Fasting can also help improve our quality of sleep and overall health.

#4 Diet of the Year

Mediterranean diet

It’s been championed as one of the healthiest diets for 30 years, and last year researchers discovered that eating a Mediterranean-style diet halves our risk of heart disease.

People eating the healthiest diets—which included fruits, vegetables, fish and nuts and excluded processed foods—were 52 percent less likely to develop heart disease. Young people who start eating such a diet by the time they’re 30 and postmenopausal women seemed to get the greatest protection, but it’s a strategy that works for everyone of all ages, researchers say.

The importance of a healthy diet has been underscored by two major studies that examined the link between “plant-centered” eating and heart health. In one, nearly 5,000 young adults were tracked for 32 years, during which time 289 developed heart disease. Those who ate the healthiest diet at the start of the study had the lowest risk of heart disease—and encouragingly, those who took up a healthier diet up to the age of 50 reduced their risk of further disease by 61 percent.1

A similar picture was seen in a separate study of 123,000 postmenopausal women between the ages of 50 and 79. Those who ate a healthy diet were 17 percent less likely to suffer heart failure and had a 14 percent lower risk of coronary artery disease.2 

Bread of the Year

Wholegrain rye

If you’re not gluten-free, you may be tempted to try wholegrain rye, as it may help you lose weight faster. According to one study, you’ll shed those pounds quicker and burn more body fat.

A group of 242 people who were overweight or obese were put on the same low-calorie diet for three months—but half ate wholegrain rye products and the rest were given refined wheat alternatives.

Both groups lost weight—but those eating wholegrain rye lost an average of one kilogram (2.2 lb) more body weight and 0.54 percent more body fat than those in the wheat group.1

Earlier studies that had detected a similar effect from eating rye assumed it was because the volunteers felt less hungry and so ate less, but researchers from Chalmers University of Technology in Sweden say both their groups ate similar amounts, and so rye must be causing a different metabolic reaction that is causing the extra weight loss.


#1 Superfood of the Year – The mushroom
1. Adv Nutr, 2021; nmab015
2. J Affect Disord, 2021; 294: 686–92
#2 Superfood of the Year – Avocado
1. Blood, 2021; blood.2020008551 
2. J Nutr, 2021; 151: 2513–21
#3 Superfood of the Year – Green vegetables
1. Exp Gerontol, 2020; 142: 111117
2. J Nutr, 2021 Mar 24; nxaa415
3. ISME J, 2021; 15(9):2779–91
#4 Superfood of the Year – Legumes
1. Sci Adv, 2021; 7: eabd4595
Newcomer of the Year – Red seaweed
1. Mar Drugs, 2021; 19: 213
Salad Food of the Year – Celery and beets
1. Redox Biol, 2021; 41: 101933
#1 Nutrient of the Year – Vitamin D
1. Sci Adv, 2021; 7: eabe4577
#2 Nutrient of the Year – Fish oils
1. JAMA Intern Med, 2021; 181(5): 631–49
2. EClinicalMedicine, 2021; 38: 100997
3. Cell Metab, 2021; 33(8): 1701–15.e5
4. Am J Clin Nutr, 2021; 114(4): 1447–54
#1 Drink of the Year – Green tea/tea
1. Nat Commun, 2021; 12: 986 
2. Cell Physiol Biochem, 2021; 55: 46–64
#2 Drink of the Year – Water
1. European Society of Cardiology Congress, August 24, 2021


#3 Drink of the Year – Wine
1. BMC Med, 2021; 19: 167
#1 Diet of the Year – The keto diet
1. Neurology, 2021; 97(9): e953–63 
#2 Diet of the Year – The rainbow diet
1. Neurology, 2021; 97: e1041–56
#3 Diet of the Year – Intermittent fasting
1. Endocr Rev, 2021; bnab027
#4 Diet of the Year – Mediterranean diet
1. J Am Heart Assoc, 2021; 10: e020718 
2. J Am Heart Assoc, 2021; 10: e021515
Bread of the Year – Wholegrain rye
1.Clin Nutr ESPEN, 2021; 45: 155–69


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