Principles of Healthy Eating: Fruits and Vegetables

Principles of Healthy Eating: Fruits and Vegetables

Consuming a variety of fruits and vegetables every day is the second principle of a healthy diet. Just as was the case with whole grains, the value of fruit and vegetables was already recognized in antiquity. In ancient Egypt it was common for people to have their own garden, in which the Egyptians cultivated their own fruits and vegetables. In the biblical Book of Numbers, we read that the Israelites during the journey to the Promised Land mentioned vegetables including onions, leeks and garlic, which they consumed during slavery in Egypt. The popularity of these vegetables in Egypt is confirmed by the description found in the pyramid of Cheops, which details the cost of radishes, onions and leeks, purchased for the slaves who built the pyramids. In ancient Egypt, beans were used as a cure for constipation. Lentils were also used in commercial transactions as currency, such as a payment for lumber. One of the most interesting ancient stories about fruits and vegetables is in the description of the Promised Land. In the book of Deuteronomy, we read that the spies sent by Moses to the Promised Land brought with them various types of produce including a bunch of grapes, which had to be so large and heavy that two people carried it on a stick.

In the Bible, one story clearly demonstrates the health benefits that were attributed to fruit and vegetables. It is found in the book of Daniel that features the prophet Daniel and his three friends. These four young men were taken from Judea into Babylonian captivity. According to the Bible they refused to eat “the portion of the king’s delicacies” and in return asked only for “vegetables to eat and water to drink.” The Bible says that soon they not only looked better physically, but they were smarter than everyone who ate the royal diet.

Eating a variety of fruits and vegetables is especially important due to the fact that there are different categories of fruits and vegetables. These include citrus fruits, such as oranges, lemons and grapefruits, berries including strawberries, blueberries, raspberries, currants, blackberries and cranberries; drupes, which include fruits with one seed, such as plums, peaches, and apricots; pome category includes apples, pears, and many others. In addition, there are green leafy vegetables including lettuce, spinach, kale, turnip greens, and beet leaves; cabbage family vegetables, such as cabbage, Brussels sprouts, broccoli, and cauliflower; root vegetables including carrots, potatoes, beets, celery, and parsnip. Other produce should not be overlooked including onions, radishes, peppers, garlic, tomatoes, cucumbers, legumes and many others. Each of these fruits and vegetables has slightly different content of nutrients, including vitamins, minerals and phytochemicals. Therefore, the consumption of these products is an integral part of a healthy diet.

Intake of fruits and vegetables depends on at least a few factors, such as caloric needs (those in need of more calories, as in case of physically active individuals should eat more fruits and vegetables compared with those leading a sedentary lifestyle). Authorities in the field of nutrition recommend that the daily intake is at least two servings of fruit and three servings of vegetables. An example of a serving includes one banana, an apple, a pear, two plums, etc. One serving of vegetables usually refers to about half cup. For vegetables such as lettuce and spinach, one serving equals one cup. Due to the relatively high content of vitamins and minerals in fruits and vegetables and low content of fat, slightly higher consumption than the recommended number of servings will result in even greater benefits.

In addition to the high content of micronutrients (vitamins and minerals) and phytochemicals (beneficial compounds found in plant products), fruits and vegetables are also rich in dietary fiber, they are low in fat and most of them contain virtually no saturated fat and they have high water content and therefore are low in calories. As a result, adequate intake of fruits and vegetables is associated with the prevention of many different health conditions including cardiovascular disease, cancer, hypertension, stroke, Alzheimer’s disease, Parkinson’s disease, type 2 diabetes, macular degeneration (an eye disease), cataracts, diverticulosis and diverticulitis (diseases of the colon and rectum), arthritis, neural tube defects, osteoporosis, obesity, and certain respiratory diseases.

Fruits and vegetables contain an array of phytochemicals. Phytochemicals are compounds found only in plant foods. To date, scientists discovered more than a thousand phytochemicals. Most likely, there are many more. Studies, which evaluated the health impact of phytochemicals, showed that they have a range of benefits. For example, some of them are anti-inflammatory, some act as antioxidants, many accelerate healing, prevent infection, and have anticancer properties. Phytochemicals are essential in the development and survival of plants and, therefore, fruits and vegetables (as well as other plant products, including seeds, nuts and grains) contain their fair amount.

Phytochemicals have their own distinct color. Therefore, in some cases, the content of the predominant phytochemical can be determined by the color of fruits and vegetables. For example, orange and yellow vegetables, including carrots and pumpkin are rich in carotenoids, of which the best known is beta-carotene. Kale and other green leafy vegetables contain high amount of chlorophyll, which gives them their green color.

Studies on the health effect of beta-carotene in foods can be used as an example of the benefits of eating foods rich in phytochemicals. Beta-carotene belongs to a group of compounds called carotenoids. These compounds can be converted in the human body to vitamin A. Beta-carotene ingested from foods is associated with lower risk of heart disease and cancer. Fruits and vegetables are so rich in beta-carotene that just one serving of some of them exceeds the daily recommendation for vitamin A. For example, only one apricot or one tomato provides 100 percent of the recommended amount of vitamin A for children between 4 and 8 years of age. One cup of spinach has about twice that amount (spinach is rich in carotenoids but even richer in chlorophyll and this is why its color is green rather than red). One serving of carrots contains more than five times the amount of beta-carotene than the daily requirement of vitamin A for children 9 to 13 years.

Fruits and vegetables are packed with a variety of vitamins. One of them is folate also known as folic acid that is needed for the synthesis of the DNA of all cells of the body. Folic acid deficiency is associated with very serious consequences, such as neural tube defects in newborns (e.g. spina bifida [opening in the spine]), anencephaly (without brain), hydrocephalus (water in the cranium), microcephaly (small head/brain size) and others. Folic acid is also important in the prevention of heart disease. One serving of fruit and vegetables such as asparagus, broccoli, avocado, spinach, strawberries and squash contains more than 20 percent of the daily requirement of this vitamin. The figure below shows the content of folic acid in selected fruits and vegetables.

folate content

Many fruits and vegetables are a rich source of vitamin C. They include oranges, kiwi, strawberries, blueberries, peppers, tomatoes, potatoes, cabbage and many others. Just one cup of orange juice contains approximately two times more vitamin C than the daily amount needed for an adult female. Vitamin C is one of three antioxidant vitamins. High intake of this vitamin from foods is linked with the prevention of certain chronic diseases, such as heart disease (intake of vitamin C from supplements do not seem to have the same benefits). Figure 3 lists vitamin C content in selected fruits and vegetables.

vitamin c


Some grapes contain a large amount of the phytochemicals resveratrol and quercetin. The intake of these compounds is linked with a lower risk of heart disease and cancer of certain organs such as the colon. Cherries contain a considerable amount of ellagic acid. Like resveratrol and quercetin, ellagic acid reduces the risk of cardiovascular diseases and cancer, and also protects against arthritis and gout. Berries are rich in anthocyanins and their intake is associated with a lower incidence of cataracts, glaucoma, and some of the health conditions mentioned earlier including cardiovascular diseases and cancer. Apples contain flavonoids, which prevent against cancer of the bladder, and, moreover, may be useful in treating respiratory diseases, including asthma. Onions contain disulfides, trisulfides and cepaene, which among other things show antibacterial activity and seem to prevent cancer. Tomatoes contain lycopene. Studies have shown that people who ingest large amounts of lycopene have a lower risk of colon, rectum, prostate, pancreas and breast cancer. Examples of the health benefits of consuming the recommended amount of fruits and vegetables can be multiplied indefinitely.

Fruit and vegetable intake can be increased in several ways. For example, personally I eat only fruits during dinner at least several times per week. The body does not need large amounts of food at the end of the day. Therefore, after eating a large breakfast and lunch, it is good to reduce the amount of food consumed at the evening meal. For many people, having a small apple, orange and banana will quench the appetite without any problems. People who need a little more caloric intake can add a handful of nuts or a piece of bread with peanut butter.

Frozen vegetables are increasingly available in stores. One of the advantages of including them in our menus is that we can store them in freezers for a relatively long period of time. Some studies have shown that the content of certain nutrients in frozen products exceeded those in fresh fruits and vegetables.

Another way to provide the appropriate amount of fruits and vegetables is the consumption of juices. In our grocery stores there are many fruit and vegetables juice alternatives including punches, cocktails and reduced juice content that are not equivalent to 100% fruit or vegetable juices. Fruit punch or cocktail for example are made of water, sugar, coloring and flavoring agents. Intake of such drinks should be kept to a minimum or better yet, should be completely eliminated. It is worth-while to invest in a juicer or even in a blender to make our own juices. In a blender, fruits and/or vegetables can be blended to make whole fruit or whole vegetable smoothies. Smoothies and 100% juices will play an important role in providing the body with important micronutrients, such as for example, folic acid, vitamin C and potassium.

Dried fruits and vegetables are products that provide the body with concentrated amounts of nutrients. Fruits and vegetables contain a relatively large amount of water. Water evaporates when we dry fruits and vegetables. As a result of water loss, dry fruits and veggies have concentrated amounts of nutrients.

In conclusion, adequate intake of fruits and vegetables plays a key role in human health. It is best to eat seasonal fruits and vegetables that are grown locally. They are fresh, the cheapest, and also contain the most nutrients. Since fruits and vegetables of different color have somewhat different nutritional profile, it is best to consume a variety of them rather than ingesting a few servings of the same fruit or vegetable. They are associated not only with prevention of many health conditions but may also be important in their treatment. Diets low in these products increases the risk of chronic diseases.

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Roman Pawlak, Ph.D, RD

Ph.D, RD is an Associate Professor of Nutrition at East Carolina University in North Carolina. He is the author several books including “Forever young. Secrets of delaying aging and living disease free,” “Healthy diet without secrets,” “In defense of vegetarianism” and “I am the Lord who heals you,” and a co-author of “Vegetarian mother and her baby.”

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