I wanted to write about this topic because it is one that is very near and dear to my heart. I think it is an extremely important one that is not talked about often enough because it seems quite obvious; everyone knows that fruits and vegetables are healthy, right? “Eat your vegetables” is a common thing you hear people say when talking about improving health, but unfortunately most people are not putting this into practice. Some people are going far enough to say that since vegetables are composed mostly of carbohydrates, and we don’t “need” carbohydrates, we therefore do not need vegetables. With the ketogenic and carnivore diets gaining popularity, it seems as though vegetables and fruits are taking a back seat perhaps because they’re not as intriguing. So this begs the questions, how important are vegetables and fruits? What exactly makes them so special? And how many servings are enough to improve health?
Hunter-gatherer societies have been studied profusely in order to gain insight as to how and what humans should be eating, especially those that have longer life-spans and less incidents of illnesses of the western world. One study in particular looked at the macronutrient ratios of 229 hunter-gatherer societies and found that most of them eat 22-40% calories from carbohydrates (plants), 19-35% from protein, and 28-58% from fat. Most of these fell around 30-35% carbohydrates, and this percentage (as well as the populations of the societies) decreased as for the societies located further from the equator and in colder regions, with some outliers consuming as little as 9% carbohydrates in the polar areas. This can give us some insight as to how human diets are meant to be constructed. If you place the 30-35% into practice, plants would consist of about ⅔ to ¾ of your plate.
Living organisms (like ourselves) are constantly exposed to oxidants, some of which may be necessary to sustain life. Some of these come from our environments while others are produced by regular cellular activity. Problems arise when there are too many oxidizing agents within the body without enough antioxidants to balance them out. This leads to oxidative stress which can cause damage to our DNA and increase risks of developing illnesses such as cancers and cardiovascular disease. Antioxidants–some of which include vitamins, minerals, and phytonutrients–which are found in fruits, vegetables, and whole grains (more so in vegetables), help to reduce oxidative stress and therefore reduce risks of cancer and CVD.
The term “phytonutrients” refers to nutrients found in plants–which are not considered vitamins, minerals, carbohydrates, fats, nor proteins–that provide health benefits. These nutrients are found most abundantly in plant foods, although there a few that can be found in animal foods in small quantities. Scientists have discovered over 5,000 phytonutrients, and the list continues to increase along with the knowledge about how they benefit human health. They are also responsible for the physical characteristics that encompass plant foods. Some classes of these nutrients include polyphenols, chlorophyll, carotenoids, and sulfer compounds.
This category includes several subtypes that have been discovered to be extremely important for health improvement and longevity. These are responsible for most of the antioxidants that we consume from our diets.
These phytonutrients provide some of the beautiful red, blue, purple, magenta, and yellow pigmentation in fruits and vegetables. They have been shown to provide antioxidant effects by reducing DNA damage and increasing the activity of the antioxidant enzyme, erythrocyte superoxide dismutase, therefore reducing cancer risks. Some flavonoids are also suspected to have antibiotic, antiviral, and tissue-supportive effects. Anti-inflammatory effects from flavonoids have also been seen in animal studies, particularly in brain cells, which suggests that they can have neuro-protective properties that can aid in the prevention of dementia. Flavonoids have also been found to have cardiovascular benefits by improving blood markers for heart disease risk, reducing blood pressure, and increasing insulin sensitivity.
Tannins also play a role in some pigments, but they contribute more to creating bitter tastes in plant foods. This class of phytonutrients is a bit of a catch 22. While they are sometimes called “antinutrients” because of their tendency to bind to certain vitamins and minerals and thus inhibit our ability to absorb them, they also come with some great benefits. Tannins have been reported to aid in combating microbial infections, especially in regards to dental hygiene.Tannins also provide antioxidant and anticancer effects and can improve cardiovascular health by lowering blood pressure and improving blood lipid levels.
Lignans, a type of phenylpropanoid, have estrogenic properties, which allows them to mimic behaviors of estrogen in the body. Although there is still need for more research in this area, this indicates that they may have the potential to regulate hormones. Some research done on animals and on human cell cultures indicate that phenylpropanoids may aid in reducing inflammation, inhibit tumor growth, and improve immunity.
This is probably the most well-known phytonutrient and is what gives plant foods their green colors. Chlorophyll is the component within plants that allows them to convert sunlight into cellular energy. Chlorophyll has anti-cancer effects because it has the potential to bind to carcinogens. This is particularly important for those that eat red meat because it contains heme, which is what gives it its red color. When metabolized, heme can create carcinogens, but chlorophyll blocks this formation from taking place. This does not necessarily mean that people should refrain from eating red meat (it’s a nutrient-dense food!), but it does mean that red meat should be eaten alongside plenty of richly-green vegetables.
This category of phytonutrients provides some of the oranges and yellows of fruits and vegetables. They are understood to be extremely potent natural antioxidants which can help in preventing CVD and cancer development. Beta-carotene, a type of carotenoid, can be converted by the body into Vitamin A. Lutein and zeaxanthin, two other types of carotenoids, can help prevent eye-related illnesses by protecting the eyes from high energy UV radiation.This can help reduce risks of impaired vision, cataracts, and blindness in older individuals.
These are the phytonutrients responsible for the “smelly” vegetables, including cauliflower, broccoli, cabbage, onions, and garlic. Glucosinolates, thiocyanates, and isothiocyanates are all sulfur-containing compounds and are derived from amino acids, especially tryptophan, methionine, and cysteine. When sulfur-rich foods are chopped, enzymes are activated and convert sulfur compounds into other forms, which results in additional phytonutrients that are associated with cancer prevention, inflammation management, and improved detoxification.
Apart from phytonutrients, fiber is another component that makes fruits and vegetables so beneficial. Fiber is extremely important for human health and can only be found in plant foods. It can be classified as soluble or insoluble. Although insoluble fiber is a carbohydrate, it is not completely digested and thus helps in creating a healthy passage of food. It also helps maintain a proper balance of gut bacteria. It is because of this that fiber helps improve digestion, which is fundamental for well-being because without it, we are unable to absorb any of the nutrients that are necessary for cellular function. Our entire bodily system is dependent on the functioning our cells, which are incapacitated in the presence of nutritional deficiencies. High fiber diets are associated with lower risks of diabetes, cancer, heart disease, and obesity. Although the Institute of Medicine recommends 25-38 grams of fiber per day, the average American only consumes 10 to 15 grams of daily fiber. On top of this, these recommendations are fairly low compared to the fiber consumption of some indigenous peoples (some of whom consume 75-100 grams of daily fiber). Unfortunately, fiber content is lost in food processing, which makes it all the more important to consume fresh/raw whole foods rich in fiber.
Beta-carotene, which can be found in yellow and orange vegetables, as previously mentioned, can be converted into Vitamin A. Our ability to see at night time depends on Vitamin A because it helps us generate the color purple. Vitamin A also aids in our ability to fight infections by helping with the growth and structure of skin cells and the lining of the nose, digestive tract, lungs, bladder, urinary tract, and vagina. Vitamin A also acts as an antioxidant and strengthen the immune system by helping to protect tissue lining and cell membranes from free radical damage, which can lead to heart disease and cancer.
Dark leafy greens, cruciferous vegetables, other green vegetables, and some fruits contain B vitamins. B vitamins are important for maintaining proper energy levels, forming certain neurotransmitters, metabolizing fats, carbohydrates, and proteins, maintaining a healthy digestive tract, and for eye, skin, hair, and liver health. Because there are numerous B vitamins and because they all work synergistically with one another, it is important to include a wide variety of fruits and vegetables to avoid deficiencies.
This vitamin is considered essential because it cannot be created by the body, and therefore must be obtained through consumption. It can only be found in fruits and vegetables and is highest when these foods are raw because it can be easily destroyed in the cooking process. Vitamin C is found in large quantities in citrus fruits, bell peppers, cruciferous vegetables, tomatoes, and dark leafy greens. Vitamin C is important for the formation of collagen, which is needed for the production and maintenance of connective tissues, including skin, cartilage, ligaments, joints, bones, and teeth. Collagen is also needed to heal wounds and to maintain healthy blood vessels. Vitamin C also aids in the production of neurotransmitters and helps to regulate stress hormones. It also works as an antioxidant and helps strengthen the immune system.
Good supplies of Vitamin K can be found in both animal foods and plant foods, some of which include dark leafy greens, cruciferous vegetables, kelp, and alfalfa. This nutrient’s main role in the body is to aid in normal blood clotting, which is necessary for preventing excessive bleeding of injuries.
Calcium can be found in dairy and plant foods, but some research suggests that plant-derived forms are much more easily absorbed. Cauliflower, broccoli, parsnips, butternut squash, and some fruits (including citrus, figs, and raisins) contain moderate to high amounts of calcium. Calcium is important for maintaining and repairing bones and preventing illnesses like osteoporosis and arthritis. It also helps in the contraction of muscles, which is important for a beating heart. Calcium is also the primary contributor in maintaining proper blood pH.
Some copper-containing plant foods include dark leafy greens, mushrooms, winter squashes, pineapple, cherries, avocado, and some dried fruits. Copper helps to metabolize vitamin C and thus helps with the production of collagen. Copper also contributes to proper iron metabolism, which is important for preventing iron-deficiency anemia. It also helps in maintaining healthy hair and skin by contributing to amino acid conversion. Copper also plays a role in thyroid hormone function by aiding in the conversion of triiodothyronine (T3) to thyroxine (T4).
Magnesium is considered an essential nutrient and can be found mostly in plant foods, the majority of which is in vegetables. It is most prominent in dark leafy greens and can also be found in some fruits including avocado and dried apricots. Magnesium is one of the most commonly deficient nutrients in the United States, which is unfortunate because of the important roles it plays in the human body. Magnesium works alongside calcium for maintaining heart health by aiding in muscle relaxation. It has been shown to help normalize heart rhythm and strengthen the heart muscle. It also helps with the elasticity of blood vessels, which is important for preventing high blood pressure. Because of its relaxing effect, magnesium can also aid in inducing sleep in those experiencing sleep troubles.
Most animal foods contain low levels of manganese, so it is best to obtain it from plant foods like leafy greens, beets, sweet potatoes, cruciferous vegetables, kiwis, bananas, and raspberries. Manganese is involved in activating enzymes that contribute to the proper utilization of biotin, thiamin (B1), and vitamin C. It also helps with proper digestion of proteins, is needed for cholesterol and fatty acid synthesis, and aids in glucose metabolism. Some studies also suggest that manganese is necessary for healthy bone formation.
This mineral can be found in high quantities in lots of fruits and vegetables including dark leafy greens, broccoli, tomatoes, potato skins, sweet potatoes, citrus fruits, bananas, apples, and avocados. Potassium is another mineral that helps in maintaining cardiovascular health, particularly in conjunction with sodium. High sodium intake is commonly demonized because of its association with high blood pressure, but this condition is more about sodium-potassium imbalance. Sodium and potassium balance each other out and work synergystically, meaning that hypertension caused by high sodium levels can be reduced more effectively by adding potassium than by reducing sodium intake. Potassium also helps in metabolizing glucose and in building and repairing muscle tissue. Unfortunately, lots of the processed and shelf-stable foods that are consumed today are extremely high in sodium and devoid of potassium.
Zinc can be found in green vegetables and avocados. Zinc aids in liver health by helping with alcohol metabolism. It can also contribute to maintaining healthy skin by aiding in collagen formation and vitamin A metabolism. Zinc is also important for the formation of bones and teeth and energy production. Zinc is particularly important for sexually active men because it contributes to male sex organ function and the formation of male reproductive fluids. It has also been shown to support immunity by regulating white blood cell function and acts as an antioxidant in the body.
Let’s recap the long list of illnesses/conditions that high fruit and vegetable consumption can combat:
- Type II diabetes
- Cardiovascular disease
- Numerous types of cancer
- Dementia/Alzheimer’s disease
- Irritable bowel syndrome
- Autoimmune diseases
- Thyroid disorders
- Liver disorders
- Eye-related disorders
And the list continues to grow as more research expands our understanding of the effects of vegetable and fruit consumption.
So how much should we be eating in order to reap the benefits? Research studies continue to show an association between fruit and vegetable intake and longevity and illness prevention. Some studies have shown that our risk for all cause mortality is reduced by 5% for every additional serving of fruits and vegetables consumed per day. This means that if you consume 5 servings of vegetables per day, you decrease your chances of all cause mortality by 5%x5, which would total to 25%. There also doesn’t seem to be a cap for reaping the benefits of fruit and vegetable consumption, so I recommend eating as much as you would like, always aiming for more.
We also must address what defines a serving. One serving of fruits/vegetables is about 1 cup of raw vegetables, ½ cup of cooked vegetables or fruit, 2 cups of leafy greens, 1 medium sized fruit, or ½ cup of chopped fruit/berries. Personally, I like to aim towards a minimum of 8 servings per day, which really is not all that much. This amounts to about 1.5 cups of cooked vegetables per meal when eating 3 meals per day.
If you are looking to increase your fruit and vegetable consumption, I would suggest increasing it slowly rather than abruptly to ensure that your body is able to adjust and properly digest the foods you are eating, which is important for maximizing the absorption of the nutrients.
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