Month: May 2021

In the US, we are fortunate to have a dizzying array of fruits that fill our grocery stores year-round. They come in all sizes, shapes, and colors, and we have all heard about the recommended five servings of fruits and vegetables a day. So, what are we eating them for? And how does the nutritional value vary between fruits? Is there any difference between whole fruits versus juice, fresh versus dried? Let’s take a look.

Differences between fruits

Just like other foods, different fruits have different nutrient values. Generally, whole fruits are good sources of fiber while fruit juices are not. And one cup of fruit juice, even 100% fruit juice, has a lot more sugar than one piece or one serving of whole fruit. In addition, whole fruits are more satiating than juices. When meeting the recommended fruit and vegetable intake, it is better to eat them (whole) than drink them (juice). However, one should not completely avoid drinking juice — if it is 100% juice — but you should limit consumption to no more than 4 to 8 ounces a day.

The freezer section of the grocery store is often stocked with quite a variety of frozen fruits. These are often peeled and cut already (like mango), which is convenient and often less expensive than fresh fruits. Frozen fruits are usually picked and quick-frozen near the point of harvest, therefore the nutrients are well preserved. Moreover, some seasonal fruits such as blueberries are readily available in frozen form. The key to selection is to choose plain frozen fruits without added sugar.

There are a number of fruits that are available in dried form, such as raisins, apricots, and pineapple — just to name a few. They also have good nutrient values, keep for a long time, are convenient to carry around, and are high in calories, making them a favorite for hikers and campers. However, some often have sugar added in the drying process, particularly mango and pineapple. Dried cranberries almost always have sugar added, as they are naturally very tart. Even for those without added sugar, the compact volume and sweetness make it quite easy to eat a lot in one sitting, and the calories can add up quickly.

Some dried fruits like raisins and apricots are also treated with sulfur dioxide to preserve freshness and color. For most people that is not a concern; however, some individuals are sensitive, especially those with asthma. Sulfur dioxide treatment is labeled on the package, so it is not difficult to avoid if necessary.

What about buying organic?

We have much choice when it comes to organic and conventionally grown fruits, be they fresh, frozen, or dried. Nutritionally, there is not enough difference to choose one over the other, though consumers might choose one over another based on farming practices and environmental impact. The US has regulations on pesticide use, but some fruits tend to have more residual pesticides than others, and it is always recommended that you wash fruits thoroughly before eating.

Differences in nutritional value

Different fruits are good sources of different nutrients. Citrus fruits are high in vitamin C, and other fruits are good sources of nutrients too. A few examples below:

Nutrient	Major functions	Good fruit sources
potassium	fluid and electrolyte balance, maintaining healthy blood pressure	oranges, raspberries, bananas, cherries, pomegranates, honeydew melons, avocados
iron	formation of red blood cells, brain growth in children	dried apricots, raisins
vitamin C	maintaining healthy immune system, wound healing, antioxidant	citrus fruits, strawberries, kiwi
folate	DNA synthesis, formation of red blood cells, early neural tube development in the fetus	oranges, mangos, avocados
vitamin A	night vision, cell growth, immune function	cantaloupe

Besides the above nutrients, certain fruits are also high in flavonoids. This is a diverse group of compounds, some of which are potent antioxidants that protect against oxidative damage, and may reduce the risk of certain diseases such as cardiovascular disease and diabetes. In particular, citrus fruits are high in the flavanones class of flavonoids, and blackberries, blueberries, cranberries, and cherries are high in the anthocyanidins class of flavonoids.

So, what fruits should we eat?

As you can see, there isn’t one fruit that has all the nutrients, so eating a variety is the key to good health. Try something new! Most adults should eat a variety of colors for about 2 cups a day. Prioritize whole fruits over juice. Eat what is in season, as it will be cheaper. And enjoy your fruits: eat mindfully to fully appreciate the smell, texture, and flavor. Bon appetit!

It’s winter, as a glance outside your window may tell you. COVID-19 is circulating at record levels across much of the country. Keeping our immune systems healthy has taken on new importance, as many of us hope to ward off flu and winter colds as well as worrisome variants of the virus that causes COVID-19, whether Delta or Omicron.

Not surprisingly, marketers are taking advantage of our concerns. A whole cottage industry is devoted to chewables, pills, and powders that claim to “boost” or “support” your immune system. Some people even claim that healthy eating and vigorous workouts are all you truly need to avoid getting sick. But are any of these claims true?

The best strategies for staying healthy

I asked Michael Starnbach, professor of microbiology at Harvard Medical School, for his advice on steps that can help us stay in good health this winter.

“Vaccination, skepticism of any other products claiming immune benefits, and staying away from places without universal masking are the best strategies,” he says. Here’s why these approaches count.

Get vaccinated

When it comes to improving your immune response, getting the COVID vaccine and booster shot, along with other recommended vaccinations, is best. Think of vaccination as a cheat sheet for your immune system. When a viral invader makes its way into your body, your immune system prepares to fight. But first it has to figure out what’s attacking, which takes time — time that allows the virus to keep multiplying inside your body.

A vaccine introduces the immune system to the invader ahead of time and allows it to develop a battle plan. So when the virus does show up at the door, your immune system can react quickly, which may mean no symptoms, or at least preventing serious illness. A booster shot is a refresher course to keep those lessons fresh.

While it is possible to become infected even if you are vaccinated, your immune system is primed to clear the virus more rapidly, so the infection is far less likely be severe or life-threatening. “We should get all available vaccines and boosters so that if we do get infected, we have a better chance of having a mild case,” says Starnbach.

Be skeptical

Any number of vitamin formulations and probiotics claim to boost or support your immune system. And while there is a grain of truth to some of those claims, the big picture is that they often don’t work. For example, vitamins do help immune function, but really only in people who have a vitamin deficiency — not in an average, healthy adult.

Probiotics also hold promise. This mini-universe of organisms living in your gut called the microbiome does play an important role in immunity. But experts don’t know enough about that role to create a product that can manipulate the microbiome to enhance immunity. That may change over the next decade — but for now, view probiotic claims with a healthy dose of skepticism, says Starnbach.

Mask up

Ultimately, nothing is better at keeping you well than avoiding exposure to a virus altogether. Wearing a mask isn’t on anyone’s favorites list, but it can help reduce the risk of spreading COVID (and some other viruses) to people who are unvaccinated, including children who aren’t yet eligible for the shot, and people with immune system deficiencies who don’t get adequate protection from the vaccine, says Starnbach. Masks are most effective when everyone around you is wearing one. “We now know clearly that the best way to prevent the unvaccinated from becoming infected is by indoor mask mandates,” says Starnbach.

Practice good health habits

But what about exercise and good nutrition? Do they have a role in supporting your immune system?

The answer is yes. Strategies to improve your overall health are never wasted. Healthy people are more resistant to disease, and often fare better if they are infected. Good health habits can help your immune system operate at its peak. Exercise and good nutrition aren’t the only habits that can help. You should also try to get consistent, high-quality sleep and manage your stress level. Lack of sleep and chronic stress can impair immune function.

But if you hope to avoid COVID-19 and other viruses, these strategies should come in addition to — not as a substitute for — vaccination and other protective measures.

The foundation of a healthy diet is a vibrant rainbow of fruits and vegetables, like rosy red strawberries, dark green spinach leaves, or sunny yellow peppers. Their colors often come from flavonoids, powerful plant chemicals (phytochemicals) that appear to contribute to many aspects of health. And now a large Harvard study published online in Neurology in July suggests that flavonoids may also play a role in protecting cognition.

The investigation

Scientists evaluated the health data and self-reported diet information of more than 77,000 middle-aged men and women, collected over 20 years.

The information included how often participants ate many types of flavonoid-rich foods and whether participants reported cognition changes in their 70s, such as difficulty

• remembering recent events or a short list of items
• remembering things from one second to the next
• understanding instructions
• following a group conversation or TV plot
• finding their way around familiar streets.

Researchers then calculated participants’ intake of six classes of flavonoids:

• flavonols (such as quercetin in onions and kale)
• flavones (such as luteolin in green chile peppers and celery)
• flavanones (such as naringenin in grapefruit and oranges)
• flavan-3-ol monomers (such as catechins in red wine and strawberries)
• anthocyanins (such as cyanidin in blackberries and red cabbage)
• polymers (such as theaflavins in black tea).

What the study found

After accounting for factors that could have affected cognition (such as age, weight, physical activity, alcohol intake, depression, and non-flavonoid nutrient intake), scientists found that people with the highest daily flavonoid intakes were 19% less likely to report trouble with memory and thinking, compared to people with the lowest daily flavonoid intakes.

"Our results are exciting because they show that eating foods high in flavonoids could help prevent or slow down decline in memory and other cognitive processes in late life," says Dr. Walter Willett, one of the study’s authors and a professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health.

"We noticed that earlier consumption of flavonoid-rich foods seemed to improve the protective effect on the brain. But even participants who began eating more flavonoids later in life saw benefits," says Dr. Tian-Shin Yeh, the study’s lead author and a postdoctoral research fellow in the Harvard-Oxford Program in Epidemiology and the department of nutrition at the Harvard T.H. Chan School of Public Health.

The study was only observational, relying on what people remembered about their diets and noticed about cognition, and didn’t prove conclusively that flavonoid intake kept people sharp in older age. But smaller or shorter-term studies have also found a link between flavonoids and cognitive health benefits.

Flavonoid superstars

Some flavonoids in particular appeared to have protective effects on the brain:

• Flavones were associated with a 38% lower risk for self-reported cognitive decline.

• Flavanones had a 36% lower risk for self-reported cognitive decline
• Anthocyanins had a 24% lower risk for self-reported cognitive decline.

Click here (note: automatic download) for a USDA list of top choices for these three types of flavonoids.

The fruits and vegetables in the study most associated with beneficial cognitive effects, listed from strongest to weakest, were:

• Brussels sprouts
• strawberries
• cauliflower
• raw spinach
• yams/sweet potatoes
• blueberries
• yellow/orange winter squash
• cooked spinach
• cooked carrots
• peaches/apricots/plums
• cantaloupe
• tomato juice
• applesauce
• green/red/yellow peppers
• broccoli
• cabbage
• tomato sauce
• romaine lettuce
• tomatoes
• grapefruit
• celery
• beets
• iceberg lettuce
• baked/boiled/mashed potatoes
• orange juice
• raw carrots
• apples/pears
• grapefruit juice
• bananas
• oranges
• onions
• apple juice/cider
• tea
• white wine
• grapes/raisins
• red wine.

What’s the magic in flavonoids?

We don’t know for sure why flavonoids might play a role in protecting cognition. But we do know that flavonoids are powerful antioxidants, which may fight brain inflammation and the accumulation of amyloid — a hallmark of Alzheimer’s disease.

Antioxidants may also play a part in

• keeping the blood vessels healthy (which keeps blood flowing to the brain)
• increasing the production of brain-derived neurotrophic factors, chemicals that repair brain cells, strengthen their connections, promote new brain cell growth, and enlarge the size of your hippocampus (a part of the brain involved in the storage and retrieval of memories).

Plus, we know that flavonoids are associated with fighting inflammation and tumor growth, and in lowering blood pressure.

Setting simple flavonoid goals

With so many potential flavonoid benefits, you may be wondering what kind of levels you should aim for in your diet. In the study, flavonoid intakes ranged from low — about 150 milligrams (mg) per day — to high — about 620 mg per day.

But tracking flavonoids is complicated. They vary greatly depending on the food. For example, half a cup of blueberries contains about 165 mg of anthocyanins; half a cup of peppers contains about 5 mg of flavones. And many fruits and vegetables contain several types of flavonoids, along with many other phytochemicals.

So don’t stress about it. Just eat a diet with a wide variety of fruits and vegetables — the sooner you start, the better. Try to reach the five-a-day fruit and vegetable goal (recent evidence suggests that the most effective combination is two servings of fruits plus three servings of vegetables per day).

Then, as you enjoy foods like strawberries, blueberries, peppers, celery, apples, bananas, oranges, and grapefruit, remember they’re not only tasty and good for general health, but potentially helpful for your brain, too.

"It’s been called ‘eating the rainbow,’ and can lead to a healthier, more delicious diet; and it’s another reason why we should ensure that everyone has access to fresh fruits and vegetables," says Dr. Deborah Blacker, a study co-author and professor and deputy chair of epidemiology at the Harvard T.H. Chan School of Public Health.