Antioxidants as Functional Foods in Health and Diseases

Special Article - Antioxidants in Foods

Austin J Nutri Food Sci. 2015;3(3): 1067.

Antioxidants as Functional Foods in Health and Diseases

Suhaila Mohamed*

Institute of BioScience, Universiti Putra Malaysia, Malaysia

*Corresponding author: Suhaila Mohamed, Institute of BioScience, Universiti Putra Malaysia, 43400, Serdang, Selangor, Malaysia

Received: April 22, 2015; Accepted: August 19, 2015; Published: August 25, 2015

Abstract

Antioxidants help protect against oxidation and free radical damage in tissues by neutralizing excess free radicals that eventually induce oxidative stress and degenerative diseases. Many antioxidants are affected by storage, handling and processing, while their combinations may have additive or synergistic effects. Health disorders that are linked to oxidative stress and free radicals include cardiovascular disease, stroke, atherosclerosis, organs ischemia and reperfusion injury, gastrointestinal dysfunctions, cancer, ailments related to AIDS, diabetes mellitus, obstructive sleep apnea, hemorrhagic shock, altered gene expression, hypertension, neurodegenerative diseases (Alzheimer’s disease and Parkinson’s disease), rheumatoid arthritis, osteoporosis, cataracts and some of functional declines associated with aging. Dietary biophenols are more effective antioxidants in vitro than the antioxidative vitamins. The antioxidants in most functional food (fruits, vegetables, cereals, dry legumes, chocolate, and beverages, e.g. tea, coffee or wine) are due to their phenolic compounds. Epidemiological studies show an inverse relation between myocardial infarction and certain cancer risk with the consumption of certain food.

Keywords: Antioxidants; Sources; Polyphenols; Flavonoids; Degenerative diseases

Introduction

What are antioxidants, Free Radicals, nonradical reactive species and the associated diseases?

Antioxidants are compounds that protect against cell oxidation and free radical damage. Antioxidants neutralize harmful free radicals, and help prevent degenerative diseases. Antioxidant levels in food and their bioavailability may be affected by storage, handling and processing. Different antioxidants may have additive and synergistic effects [1].

Free radicals are molecules with highly reactive unpaired electron. Free radicals, Reactive Oxygen Species (ROS) and reactive nitrogen species (RNS, e.g. nitric oxide, NO) have both deleterious and beneficial effects. Excess free radicals and nonradical reactive species cause oxidative stress, and cell structure changes, including lipids and membranes, proteins, and DNA. Oxidative stress induces either a loss of function, a gain of function, or a switch to a different function in a signaling protein [2].

High ROS levels may come from excess NAD(P)H oxidases stimulation or from mitochondrial electron-transport chain. ROS are undesirable by-products of oxidative energy metabolism in the mitochondria. Medium to low ROS/RNS concentrations are needed to regulate cellular responses to noxia, for example in defence against infections, cellular signalling pathways, and mitogenic response induction. Various ROS-mediated actions protect cells against ROS-induced oxidative stress and re-establish or maintain “redox homeostasis or balance”. The physiological functions regulated include vascular tone, signal transduction from membrane receptors, oxygen tension monitoring for controlling ventilation and erythropoietin production [2].

The NO and ROS levels are closely regulated by enzymes such as NO synthase (NOS) and NAD(P)H oxidase isoforms. ROS within cells behave as secondary messengers in intracellular signalling cascades which induce and maintain oncogenic phenotype of cancer cells. However, ROS can also induce cellular senescence and apoptosis, hence can function as anti-tumourigenic species. Chronic oxidative stress and excess free radicals have been implicated in various human diseases. Dietary restriction, metabolic activities, oxygen tension, dietary and pharmacological antioxidants, genetics, affects ROS and human diseases [2].

Health disorders related to oxidative stress and free radicals include cardiovascular disease, stroke, atherosclerosis, organs ischemia and reperfusion injury, gastrointestinal dysfunctions, cancer, ailments linked to AIDS, diabetes mellitus, obstructive sleep apnea, hemorrhagic shock, altered gene expression, hypertension, neurodegenerative diseases (Alzheimer’s disease and Parkinson’s disease), rheumatoid arthritis, cataracts and some of functional declines associated with aging [3].

What are the best sources of antioxidants?

Polyphenols vs. vitamins A, C, E: The antioxidant capacities of most plant products often correlate with their phenolic content. Dietary biophenols are more effective antioxidants in vitro than vitamins E or C. Polyphenols are the most abundant antioxidants in the diet and found in plant products (fruits, vegetables, cereals, dry legumes, chocolate, and beverages, e.g. tea, coffee or wine). Polyphenols (Table 1) have been shown experimentally to prevent cardiovascular diseases, cancers, neuro degeneration, diabetes, or osteoporosis. Epidemiological studies show inverse relation between the risk of myocardial infarction as well as certain cancer risk with the consumption of tea and wine or intake level of some particular flavonoids [4].