A diet rich in fruits and vegetables is universally promoted as a cornerstone of healthy eating. These foods are packed with essential nutrients, dietary fiber, vitamins, minerals, and beneficial plant chemicals. They contribute to overall well-being and can help protect against various diseases. However, relying solely on fruits and vegetables can lead to nutritional imbalances and potential health risks. This article will explore the benefits of incorporating fruits and vegetables into your diet, while also addressing the potential drawbacks of a strictly fruit and vegetable-based dietary approach.
The Benefits of Fruits and Vegetables
Including fruits and vegetables as part of the daily diet may reduce the risk of some noncommunicable diseases (NCDs) including cardiovascular diseases and certain types of cancer. More limited evidence suggests that when consumed as part of a healthy diet low in fat, sugars and salt/sodium, fruits and vegetables may also help to prevent weight gain and reduce the risk of obesity, an independent risk-factor for NCDs. Moreover, fruits and vegetables are rich sources of vitamins and minerals, dietary fibre and a host of beneficial non-nutrient substances including plant sterols, flavonoids and other antioxidants and consuming a variety of fruits and vegetables helps to ensure an adequate intake of many of these essential nutrients.
Evidence shows there are significant health benefits to getting at least 5 portions of a variety of fruit and vegetables every day. That's 5 portions of fruit and veg in total, not 5 portions of each.
Nutritional Powerhouses
Fruits and vegetables are a good source of vitamins and minerals, including folate, vitamin C and potassium. They're an excellent source of dietary fibre, which can help to maintain a healthy gut and prevent constipation and other digestion problems. A diet high in fibre can also reduce your risk of bowel cancer. Fruits and vegetables contribute to a healthy, balanced diet, taste delicious, and offer a wide variety to choose from. They are also usually low in fat and calories, which can help you maintain a healthy weight and keep your heart healthy.
Disease Prevention
A diet high in fruit and vegetables can help protect you against cancer, diabetes and heart disease. A meta-analysis of cohort studies following 469,551 participants found that a higher intake of fruits and vegetables is associated with a reduced risk of death from cardiovascular disease, with an average reduction in risk of 4% for each additional serving per day of fruit and vegetables. The higher the average daily intake of fruits and vegetables, the lower the chances of developing cardiovascular disease. Compared with those in the lowest category of fruit and vegetable intake (less than 1.5 servings a day), those who averaged 8 or more servings a day were 30% less likely to have had a heart attack or stroke. Although all fruits and vegetables likely contributed to this benefit, green leafy vegetables, such as lettuce, spinach, Swiss chard, and mustard greens, were most strongly associated with decreased risk of cardiovascular disease. Cruciferous vegetables such as broccoli, cauliflower, cabbage, Brussels sprouts, bok choy, and kale; and citrus fruits such as oranges, lemons, limes, and grapefruit (and their juices) also made important contributions.
Read also: Explore the pros and cons of fruit juice detoxes.
Blood Pressure Regulation
A diet rich in vegetables and fruits can lower blood pressure, reduce the risk of heart disease and stroke, prevent some types of cancer, lower risk of eye and digestive problems, and have a positive effect upon blood sugar, which can help keep appetite in check. The Dietary Approaches to Stop Hypertension (DASH) study examined the effect on blood pressure of a diet that was rich in fruits, vegetables, and low-fat dairy products and that restricted the amount of saturated and total fat. A randomized trial known as the Optimal Macronutrient Intake Trial for Heart Health (OmniHeart) showed that this fruit and vegetable-rich diet lowered blood pressure even more when some of the carbohydrate was replaced with healthy unsaturated fat or protein. In 2014 a meta-analysis of clinical trials and observational studies found that consumption of a vegetarian diet was associated with lower blood pressure.
Cancer Prevention
Numerous early studies revealed what appeared to be a strong link between eating fruits and vegetables and protection against cancer. A study by Farvid and colleagues followed a Nurses’ Health Study II cohort of 90,476 premenopausal women for 22 years and found that those who ate the most fruit during adolescence (about 3 servings a day) compared with those who ate the lowest intakes (0.5 servings a day) had a 25% lower risk of developing breast cancer. There was a significant reduction in breast cancer in women who had eaten higher intakes of apples, bananas, grapes, and corn during adolescence, and oranges and kale during early adulthood. No protection was found from drinking fruit juices at younger ages.
Farvid and colleagues followed 90, 534 premenopausal women from the Nurses’ Health Study II over 20 years and found that higher fiber intakes during adolescence and early adulthood were associated with a reduced risk of breast cancer later in life. When comparing the highest and lowest fiber intakes from fruits and vegetables, women with the highest fruit fiber intake had a 12% reduced risk of breast cancer; those with the highest vegetable fiber intake had an 11% reduced risk. After following 182,145 women in the Nurses’ Health Study I and II for 30 years, Farvid’s team also found that women who ate more than 5.5 servings of fruits and vegetables each day (especially cruciferous and yellow/orange vegetables) had an 11% lower risk of breast cancer than those who ate 2.5 or fewer servings. Vegetable intake was strongly associated with a 15% lower risk of estrogen-receptor-negative tumors for every two additional servings of vegetables eaten daily. A higher intake of fruits and vegetables was associated with a lower risk of other aggressive tumors including HER2-enriched and basal-like tumors.
A report by the World Cancer Research Fund and the American Institute for Cancer Research suggests that non-starchy vegetables-such as lettuce and other leafy greens, broccoli, bok choy, cabbage, as well as garlic, onions, and the like-and fruits “probably” protect against several types of cancers, including those of the mouth, throat, voice box, esophagus, and stomach. Fruit probably also protects against lung cancer.
Specific components of fruits and vegetables may also be protective against cancer. A line of research stemming from a finding from the Health Professionals Follow-up Study suggests that tomatoes may help protect men against prostate cancer, especially aggressive forms of it. One of the pigments that give tomatoes their red hue-lycopene-could be involved in this protective effect. Although several studies other than the Health Professionals Study have also demonstrated a link between tomatoes or lycopene and prostate cancer, others have not or have found only a weak connection. Taken as a whole, however, these studies suggest that increased consumption of tomato-based products (especially cooked tomato products) and other lycopene-containing foods may reduce the occurrence of prostate cancer.
Read also: Fruit smoothies on a ketogenic diet
Lycopene is one of several carotenoids (compounds that the body can turn into vitamin A) found in brightly colored fruits and vegetables, and research suggests that foods containing carotenoids may protect against lung, mouth, and throat cancer.
Diabetes Prevention and Weight Management
Some research looks specifically at whether individual fruits are associated with risk of type 2 diabetes. A study of over 66,000 women in the Nurses’ Health Study, 85,104 women from the Nurses’ Health Study II, and 36,173 men from the Health Professionals Follow-up Study-who were free of major chronic diseases-found that greater consumption of whole fruits-especially blueberries, grapes, and apples-was associated with a lower risk of type 2 diabetes. Another important finding was that greater consumption of fruit juice was associated with a higher risk of type 2 diabetes. Additionally a study of over 70,000 female nurses aged 38-63 years, who were free of cardiovascular disease, cancer, and diabetes, showed that consumption of green leafy vegetables and fruit was associated with a lower risk of diabetes. While not conclusive, research also indicated that consumption of fruit juices may be associated with an increased risk among women. A study of over 2,300 Finnish men showed that vegetables and fruits, especially berries, may reduce the risk of type 2 diabetes.
Data from the Nurses’ Health Studies and the Health Professional’s Follow-up Study show that women and men who increased their intakes of fruits and vegetables over a 24-year period were more likely to have lost weight than those who ate the same amount or those who decreased their intake. Berries, apples, pears, soy, and cauliflower were associated with weight loss while starchier vegetables like potatoes, corn, and peas were linked with weight gain. Eating non-starchy vegetables and fruits like apples, pears, and green leafy vegetables may even promote weight loss.
Digestive Health
Fruits and vegetables contain indigestible fiber, which absorbs water and expands as it passes through the digestive system. This can calm symptoms of an irritable bowel and, by triggering regular bowel movements, can relieve or prevent constipation. The bulking and softening action of insoluble fiber also decreases pressure inside the intestinal tract and may help prevent diverticulosis.
Eye Health
Eating fruits and vegetables can also keep your eyes healthy, and may help prevent two common aging-related eye diseases-cataracts and macular degeneration-which afflict millions of Americans over age 65. Lutein and zeaxanthin, in particular, seem to reduce risk of cataracts.
Read also: Passion Fruit on Keto: Benefits and Drawbacks
Risks of a Fruits and Vegetables-Only Diet
Although fruits and vegetables are healthy, they do not provide every nutrient your body needs. “It's inevitably going to be unbalanced because it's missing entire food groups,” Ayoob says.
Insufficient Caloric Intake
In the short-term, you may feel uncomfortably full, but still hungry. “Most fruits and vegetables are low in calories and high in volume, due to their fiber and water content,” says Avery Zenker, RD, a registered dietitian in the Toronto, Ontario area. “That means you’d need to eat a very large volume to meet daily energy needs, which isn’t always realistic.”
In the long-term, a lack of calories can lead to malnutrition, excessive weight loss, and muscle mass loss, Zenker says.
Gas and Bloating
If you’re eating just fruits and vegetables, you’ll find yourself consuming a high volume just to feel full. Zenker says this significant increase in volume and fiber may cause digestive woes like excessive bloating, gas, diarrhea, or abdominal cramps when you start your fruits and veggies-only diet.
“In the long-term, if the gut doesn’t adapt to the increase in fiber, digestive symptoms could continue,” Zenker says.
Plus, many fruits and vegetables are high in FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols). Eating high amounts of these fermentable carbohydrates can increase digestive symptoms, particularly in people with irritable bowel syndrome (IBS), Zenker says.
Lack of Protein
Only eating fruits and vegetables means your diet will lack protein, a key component of nutrition. “Without enough protein, you're unable to properly repair and build muscle,” Ayoob says.
Eating more protein in midlife may contribute to better health decades later, with lower odds of major chronic diseases, mental health concerns, and problems with memory or physical function, according to a review published in February 2024 in The American Journal of Clinical Nutrition. Specifically, for every 3 percent increase in calories from protein, researchers found a 5 percent higher odds of healthy aging. Researchers also found that the chances of healthy aging increased by 31 percent for every 3 percent increase in calories from plant proteins.
However, most fruits and vegetables aren’t significantly high in protein, unless you’re including plant-based foods like beans and legumes in the mix, Zenker says.
“Without adequate intake, the body starts breaking down muscle to supply amino acids, leading to health problems including weakness, impaired recovery from injury, and lower immune resilience,” Zenker says.
Iron Deficiency
Plant sources only have non-heme iron, which your body absorbs in much smaller amounts than heme iron that’s found in animal sources.
“Lack of iron can be a concern, particularly for menstruating women, athletes, and growing children,” Zenker says. “Long-term iron inadequacy can lead to anemia, fatigue, hair loss, decreased stamina, and impaired cognition.”
Iron-deficiency anemia is the most common nutrient deficiency globally, affecting 30 percent of people. Poor diet often is the cause, and it can lead to inflammatory conditions like chronic kidney disease, inflammatory bowel disease, and heart failure.
Lack of Other Key Nutrients
Omega-3s (a type of healthy fat) are not present in fruits and vegetables in their long-chain forms - eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), Zenker says. Instead, they primarily contain alpha-linolenic acid (ALA), according to the National Institutes of Health Office of Dietary Supplements. Your body can convert some ALA into EPA and DHA, but usually only small amounts. Cold-water fatty fish is the richest source of EPA and DHA.
“Low EPA and DHA over time is linked to problems such as higher inflammation, mood disorders, and increased cardiovascular risk,” Zenker says. Omega-3-rich foods may help lower the risk of chronic health conditions, including heart disease, rheumatoid arthritis, certain cancers, preterm birth, and depression.
Only eating fruits and vegetables could also lead to other deficiencies, Zenker says.
Recommendations for a Healthy Diet
To get the most out of your diet, aim for variety to get the most nutrients and appeal. No single fruit or vegetable provides all of the nutrients you need to be healthy.
Aim for Variety and Color
At least nine different families of fruits and vegetables exist, each with potentially hundreds of different plant compounds that are beneficial to health. Eat a variety of types and colors of produce in order to give your body the mix of nutrients it needs.
Incorporate Fruits and Vegetables into Every Meal
- Breakfast: Add berries or a sliced banana to your cereal or yogurt.
- Lunch: Substitute vegetables such as lettuce, tomatoes, or cucumbers for some of the cheese and meat in your sandwich, wrap, or burrito.
- Dinner: Include at least two different vegetables with your main course. Replace 1 cup of rice or pasta in your favorite dish with 1 cup of vegetables such as broccoli, squash, or peppers.
Healthy Cooking Methods
Eat fruits and vegetables uncooked or with fat-free or low-fat cooking techniques. Try steaming your vegetables, using low-calorie or low-fat dressings, and using herbs and spices to add flavor. Some cooking techniques, such as breading and frying, or using high-fat dressings or sauces will greatly increase the calories and fat in the dish. Canned or frozen fruits and vegetables are also good options. Frozen or canned fruits and vegetables can be just as nutritious as the fresh varieties. Choose whole fruits over fruit drinks and juices. Fruit juices have lost fiber from the fruit. It is better to eat the whole fruit because it contains the added fiber that helps you feel full.
The Importance of Fiber
Dietary fiber intake was particularly low in their analysis. With the exception of older women (≥51 y), only 0-5% of individuals in all other life stage groups had fiber intakes meeting or exceeding the Adequate Intake (AI)4. Common serving sizes of fruits and vegetables contain 1-5 g of fiber. Traditionally, fiber was measured as “crude fiber,” which includes only the most resistant fibers consumed. As the scientific support for a role for resistant carbohydrates not captured by the crude fiber method such as pectin, glucans, and oligosaccharides was published, additional analytical methods to measure more carbohydrates resistant to digestion and absorption were needed.
The TDF method, or Prosky Method, has become the standard method for the measurement of dietary fiber in the United States. Determining the solubility of fiber was an attempt to relate physiological effects to chemical types of fiber (9). Soluble fibers were considered to have beneficial effects on serum lipids and insoluble fibers were linked with laxation benefits. This division of soluble and insoluble fiber is still used in nutrition labeling. However, despite these commonly used generalizations, scientific evidence supporting that soluble fibers lower cholesterol and insoluble fibers increase stool weight is inconsistent. Many fiber sources are mostly soluble but still enlarge stool weight, such as oat bran and psyllium. Also, soluble fibers such as inulin do not lower blood lipids. Most fruits and vegetables are concentrated in insoluble fiber, not soluble fiber (Table 3). Exceptions to this generalization include cooked potatoes, oranges, and grapefruit.
Viscous fibers are those that have gel-forming properties in the intestinal tract, and fermentable fibers are those that can be metabolized by colonic bacteria. In general, soluble fibers are more completely fermented and have a higher viscosity than insoluble fibers.