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Do you need to eat fruits and vegetables to be healthy? Not necessarily.

Eating fruits and vegetables is often recommended to live longer, healthier lives. Observations show that healthy people who eat fruits and vegetables can consistently live into their 90’s and 100’s.

While this may show that fruits and veggies can be part of a healthy lifestyle for some, it does not prove that they’re required for everyone.

How many fruits and vegetables do we need to eat? Do we need any at all?

Here’s the current scientific evidence on fruits and vegetables.



1. What are fruits?

Fruits are the seed-containing portion of various flowering plants. They grow exclusively above ground.

Different types of fruit

The broad categories of fruit include pome, citrus, tropical, melons, stone fruits, and berries. Most fruits taste sweet, although citrus varieties are often sour or bitter. With the exception of bananas, most domesticated fruits are juicy due to their high water content.

Nutritional composition of fruits

Nearly all of the calories in fruits come from sugar — not surprising, given their sweet taste. Their net carbs span a large range: 5 grams to 20 grams per 100 grams (3.5 ounces) of fruit, depending on the type. A single mid-sized orange has about 12 grams of carbs and a banana has at least 23 grams.

Reviewing the nutrition profiles of different fruits, we see that several provide vitamin C and a few minerals. However, actual nutrient content can vary depending on the type of fruit, how and where it’s grown and stored, and how long it’s been sitting at a stand or grocery shelf.

In addition, all fruits fall short in vitamin D and key minerals like calcium, magnesium, iron and zinc.

2. What are vegetables?

Speaking from a botanical or gardening point of view, vegetables are the leaves, stems or roots of plants. However, many non-sweet fruits are commonly considered vegetables for eating or cooking purposes.

Different types of vegetables

Vegetables can be broadly classified into four categories:

Above-ground vegetables: greens (spinach, lettuce, chard, et cetera), cruciferous vegetables (broccoli, brussels sprouts, cabbage, cauliflower, kale, et cetera), bulbs (onions, garlic), and fungi (mushrooms). Below-ground/root/starchy vegetables: beets, carrots, parsnips, rutabagas, turnips, yams, potatoes, sweet potatoes, et cetera. Gourds: pumpkins, hard-shelled squashes, and other winter squashes. Technically fruits but treated like vegetables: avocados, olives, bell peppers, eggplant, tomatoes, and zucchini. Unlike other fruits, these aren’t sweet and are often prepared and consumed with other vegetables. Avocados and olives are unique among fruits and vegetables because most of their calories come from fat rather than sugar or starch.

Nutritional composition of vegetables

Non-starchy vegetables are keto-friendly foods that provide 5 or fewer grams of net carbs per 100-gram (3.5-ounce) serving. By contrast, root and starchy vegetables have 6 to 17 grams of net carbs per serving.

Vegetables usually contain moderate to high amounts of fiber, especially avocado — which also happens to be among the lowest in net carbs.

Overall, vegetables are more nutrient-dense than fruits, but their vitamin and mineral content can also be affected by factors like growing and storage conditions. Most veggies are good to excellent sources of potassium, and bell peppers and cruciferous vegetables are also high in vitamin C.

3. How many fruits and vegetables should people eat per day?

Looking at official recommendations for fruit and vegetable intake in different countries, it’s clear that they’re basically all variations on “5 a day.” The US dietary guidelines, the UK National Health Service, and the World Health Organization all set minimums that are generally equivalent to two cups of fruit and two and a half cups of vegetables each day.

According to the Centers for Disease Control, only 1 in 10 adults consistently meets the US Dietary Guidelines recommendations for fruit and vegetable intake. But is this really a problem?

Some low-carb diet experts would say no; that if someone is following a diet that meets their needs for essential nutrients, eating several servings of fruits and vegetables every day isn’t necessary.

For instance, Dr. Eric Westman initially recommends two cups of leafy greens and one cup of above-ground vegetables per day — and no sweet fruit of any kind — as part of a very-low-carb diet.

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Other doctors have gone on record as saying that consuming plants is entirely optional — and in some cases may be problematic — including the Paleomedicina Group and Dr. Georgia Ede.

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Health organizations state that their recommendations for fruit and vegetable intake are evidence-based. But as we’ve discussed previously in other guides, there are different levels of scientific evidence. And almost all these fruit and vegetable recommendations are designed for someone who is eating a standard Western diet or a low-fat, high-carb diet.

Let’s explore the high-quality evidence available to see whether eating more fruits and vegetables has actually been proven to improve health.

4. Research on the benefits of eating fruits and vegetables

Obesity

With few exceptions, eating more fruits and vegetables is standard weight-loss advice. But if we look at the results of experimental trials in which people actually ate more — or at least were encouraged to eat more — of these foods, that advice just doesn’t seem to work for everyone.

A 2014 systematic review of eight randomized controlled trials (RCTs) lasting between 4 and 52 weeks found that people assigned to increase their fruit and vegetable intake lost an average of only 1.5 pounds more than those assigned to eat smaller amounts of these foods.

The same year, researchers who published a systematic review of seven different RCTs failed to find any measurable differences in weight change between people who consumed high vs. low amounts of fresh produce.

However, the interventions differed among the RCTs included in both of these analyses. In some cases, people were provided with fresh fruits and vegetables or vouchers to purchase them; in others, they only received advice to consume more of a specific fruit or vegetable.

Furthermore, in most of these studies, researchers relied on reported produce intake from the groups rather than closely monitoring their intake. Often it just wasn’t clear whether people actually ended up eating their assigned amounts of fruits and vegetables or not.

In some cases, people who eat more fruits and vegetables may actually gain weight because they don’t compensate by cutting back on other foods — and juice seems to be especially problematic.

For instance, in one RCT, when overweight and obese people were provided with fresh fruits and vegetables to add to their diets for eight weeks, they gained twice as much weight as lean participants, who responded to increased produce intake by eating less of other foods. But all three groups gained weight after consuming the same amount of produce in juice form during a second eight-week period. Still, obese participants gained the most.

On the other hand, replacing highly processed food with fruits and vegetables is not only a smart choice nutritionally; it might also lead to weight loss.

In a three-month study, overweight women who were given vouchers to purchase fresh produce lost 6 pounds, whereas those who were given vouchers to purchase any type of groceries gained 4 pounds by the study’s end. Overall, eating more fruit and vegetables hasn’t been shown to produce meaningful weight loss in most experimental studies. Overall, eating more fruit and vegetables hasn’t been shown to produce meaningful weight loss in most experimental studies.

Yet we often hear that doing so is the key to achieving and maintaining a healthy weight. What is the basis for this advice?

For decades, it’s mainly been larger yet lower-quality observational (also called epidemiological) research. For instance, a 2015 systematic review analyzing 17 such studies found statistically weak associations between eating a lot of produce and lower body weight and waist size.

In observational nutrition studies, a hazard ratio (HR), odds ratio (OR) or relative risk (RR) that is close to 1 means there is almost no observable difference. That means any OR less than 2 or greater than 0.50 strongly suggests that any association between a behavior (e.g., eating produce) and an outcome (e.g., weight loss) is possibly random and false.

What were the ORs in this study? They were 0.83 for high intake of fruits or vegetables alone and 0.91 for high intake of fruits and vegetables combined. And even the study authors acknowledged that “The present meta-analysis seems to be limited by low study quality.”

Diabetes and metabolic syndrome

Fruits and vegetables are generally considered diabetes-friendly foods. In fact, nearly all types of produce make the “low GI foods” list on the American Diabetes Association website, with the exception of melons and pineapple.

How does adhering to “5 a day” or similar dietary advice affect blood sugar control and insulin resistance? The evidence is mixed.

But how does adhering to “5 a day” or similar dietary advice affect blood sugar control and insulin resistance? The evidence from clinical trials is mixed.

One systematic review of eight RCTs examining the effects of fruit and vegetable intake in people with metabolic syndrome found that although blood pressure slightly improved in those who ate more produce, fasting blood sugar levels were no different among the groups.

The same held true for waist circumference, triglycerides and HDL cholesterol levels — all of which are considered markers of insulin resistance when outside the normal range.

In 2017, researchers analyzed results from four RCTs with fruit and vegetable interventions in people with type 2 diabetes or other health conditions. The groups assigned to eat more fruits and vegetables improved their vitamin C and beta-carotene intake but consumed significantly more carbs and calories. That doesn’t sound very diabetes-friendly, does it?

In one RCT published in Diabetes Care — a journal of the American Diabetes Association — researchers assigned overweight adults to consume two, four, or seven portions of fruits and vegetables per day for 12 weeks. Ultimately, none of the groups experienced any improvement in insulin resistance.

However, results from another RCT suggest that including low-carb vegetables like broccoli and broccoli sprouts may help lower insulin levels and improve insulin sensitivity in adults with type 2 diabetes.

Of course, neither the experimental nor control group were consuming low-carb or keto diets. It’s unknown whether adding broccoli or other green vegetables to a low-carb or keto diet would provide any further benefit on insulin resistance.

Since low-carb diets by definition eliminate two likely offenders behind insulin resistance — sugar and other high-carb foods — there may already be a maximal benefit which may not increase by adding more vegetables. Controlled trials exploring this would need to be done.

What about lower-quality observational studies that suggest eating plenty of fruits and vegetables can help protect against diabetes? Large meta-analyses of these studies have shown very weak associations between fruit and vegetable intake and diabetes risk.

Finally, although results from observational nutrition studies often have such weak correlations that they’re likely due to chance, occasionally there are exceptions.

For example, a 2017 study in pregnant women found that those who reported consuming the highest amount of fruit during their second trimester had a 480% greater risk (OR of 4.82) of developing gestational diabetes than women with the lowest reported fruit intakes.

Controlled studies exploring this relationship are needed. However, it certainly seems possible that eating large amounts of fruit (“nature’s candy”) during pregnancy — a time of dramatic hormonal fluctuations and insulin resistance — could increase a woman’s likelihood of developing gestational diabetes.