Phytochemicals in foods
The term phytochemicals comes from the Greek word phyto, meaning “plant”. They are so named because they are chemical substances found in natural sources, particularly in plant foods. Since the beginning of civilization, the use of plants for their health-promoting effects has been common in populations.
Although phytochemicals exist as long as plants exist, we only know about hundred years about their existence. Also, even though phytochemicals are not nutrients, they have important health functions. Simply type the word “phytochemical” into any online search engine and it will return literally thousands of hits. This is a reflection of the role they play in medicine and other areas. They provide many positive health benefits that are useful for maintaining well-being and the normal functions of the body, and increasing life expectancy.
After reading this article you’ll have better understanding of what phytochemicals really are. You’ll also discover the numerous health benefits of these biologically active compounds as well as their food sources.
What is the simplest definition of phytochemicals?
Phytochemicals are health-protecting bioactive compounds of plant origin. They provide flavor and color to the edible, fruits, plants, herbs and beverages. These elements work with the existing nutrients and fiber in fruits and vegetables to boost the body’s immune system to make it resistant to diseases and infections. In laboratory studies, many phytochemicals act as antioxidants, neutralizing free radicals and removing their power to create damage.
What are the most important antioxidant-rich phytochemicals in foods?
The table below summarizes the most important antioxidant-rich phytochemicals with their food sources and health benefits.
| Phytochemicals | Food sources | Health benefits |
|---|---|---|
| Carotenoids | Carrots, tomatoes, parsley, orange and green leafy vegetables, chenopods, fenugreek, spinach, cabbage, radish, turnips | Antioxidants protect against uterine, prostate, colorectal, lung, and digestive tract cancers |
| Phytosterols | Vegetables, nuts, fruits, seeds | Suppress the growth of diverse tumors cell lines via initiation of apoptosis and concomitant arrest of cells in the G1 phase of the cell cycle |
| Limonoids | Citrus fruits | Inhibiting phase I enzymes and inducing phase II detoxification enzymes in liver, provide protection to lung tissue. Detoxify enzymes. |
| Polyphenols >>Flavonoids >>Isoflavonoids >>Anthocyanidins | Fruits, vegetables, cereals, beverages, legumes, chocolates, oilseeds | Action against free radicals, free radicals mediated cellular signaling, inflammation, allergies, platelet aggregation, and hepatotoxins |
| Glucosinolates | Cruciferous vegetables | Protection against cancer of colon, rectum, and stomach |
| Phytoestrogen | Legumes, berries, whole grains, cereals, red wine, peanuts, red grapes | Protection against bone loss and heart disease, cardiovascular diseases, breast and uterine cancers |
| Terpenoids (isiprenoids) | Mosses, liverworts, algae, lichens, mushrooms | Antimicrobial, antiparasitic, antiviral, antiallergic, antiinflammatory, chemotherapeutic, antihyperglycemic, antispasmodic |
| Fibers | Fruits and vegetables (green leafy), oats | Reduces blood cholesterol, cardiovascular disease |
| Polysaccharides | Fruits and vegetables | Antimicrobial, antiparasitic, antiviral, antiallergic, antiinflammatory, lowering serum, enhances defense mechanisms |
| Saponins | Oats, leaves, flowers, and green fruits of tomato | Protection against pathogens, antimicrobial, antiinflammatory, antiulcer agent |
What are the health benefits of phytochemicals?
These biologically active compounds play an important role in human health as antioxidants: they act as antibacterial, antifungal, antiinflammatory, antiallergic, antispasmodic, chemopreventive, hepato-protective, hypolipidemic, neuroprotective, hypotensive, immuno-modulator and carminative agents.
They prevent aging, diabetes, osteoporosis, cancer, and heart diseases; induce apoptosis; act as diuretic, CNS stimulant, analgesic; and protect from UVB-induced carcinogenesis, and many more.
Some of the main roles include:
- substrate for biochemical reactions
- cofactors and inhibitors of enzymatic reactions
- absorbents/sequestrants that bind to and eliminate undesirable contents in the intestine
- ligands that agonize or antagonize cell surface or intracellular receptors
- scavengers for toxic chemicals
- enhance the absorption and/or stability of essential nutrients
- selective growth factor for beneficial bacteria
- fermentation substrate for beneficial bacteria
- selective inhibitors of deleterious intestinal bacteria
Recommended dietary intake levels for phytochemicals: feasible or fanciful?
As you can see from the table above, the different types of phytochemicals include the carotenoids (from green vegetables), polyphenols (from onions and garlic), indoles (from cruciferous vegetables), and allyl sulfides (from garlic, chives, and onions), and numerous other. These biologically active compounds may play an important role in sparking the body to fight and slow the development of some diseases, such as cancer. At this time, however, scientists do not understand the exact mechanisms through which the various phytochemicals reduce the formation of cancer cells.
Although all scientists agree that these foods are important in planning food selections, it’s not possible to give the precise recommendations regarding the amounts of various phytochemical-rich plants.
Current evidence strongly suggests that these compounds may play many key protective roles in the cell, but their specific and unique contribution to this protection is not clear. This fact, together with the generally generic effects of phytochemicals on cellular metabolism, makes it difficult to apply the concept of a key identifiable function for a phytochemical on which a RDI can be based.
The diverse distribution and action of phytochemicals makes it almost impossible to nominate a single key biological role for phytochemicals in general or indeed for individual categories of phytochemicals, or individual compounds.
Should people take phytochemical supplements?
Because it is hypothesized that the beneficial health effects observed from these biologically active compounds are related to the synergistic mixture of phytochemicals and other nutrients found in whole foods and its components, consumption of variety of plant-based foods is encouraged. Natural sources are always preferred over supplements.
In clinical studies, when these bioactive compounds are isolated from the food source and taken alone as a supplement, individual compounds studied do not have consistent preventive health effects. Furthermore, the efficacy and long-term safety of many bioactive compounds as dietary supplements, especially at pharmacologic doses, requires further study.
Closing thoughts
Filling up one’s diet with fruits, vegetables, cereal grains, and plant-based beverages such as tea and wine that are rich in phytochemicals lowers the risk of developing chronic diseases like cancer, heart diseases, and diabetes. Its antioxidant properties also help in protecting the body from free radicals in the environment and the food we eat. As cancer-causing agents are deactivated and controlled, you can live a healthier and happier life. In conclusion, is it important to eat a variety of plant-based foods.
