Antioxidants are complex molecules that are necessary to perform hundreds of important functions in the human body. There are two classifications of antioxidants: endogenous, or those that the body produces including hormones, DHEA, melatonin and the enzymes superoxide dismutase, glutathione, glutathione peroxidase and catalase; and exogenous that the body gets from foods.
Antioxidants help protect the cells in the body from damage that may occur from reactive oxygen species (ROS) free radicals. Antioxidants can accomplish this by breaking the free radical chain reaction via sacrificing their own electrons, to dismantle the free radical reaction. However, they do not transfer into free radicals themselves. Perhaps the best way to understand how antioxidants are utilized by the body and cells is first to explore the ways in which they are absorbed from the foods that we eat.
The Digestive Process
All nutrients consumed from food undergo intricate processes throughout the digestive system. To assimilate the nutrients from foods, the digestive system undergoes several processes that take approximately six to eight hours to reach the focal point of nutrient absorption or the small intestines.
The mouth. The chemical activity of the digestion process actually begins in the mouth and employs the enzyme lingual lipase to help digest fats, salivary amylase for carbohydrate digestion and a bacterial sentry enzyme called lysozyme. Both chemical and physical activity take place the moment we begin to chew our food. Mastication is a diverse process that alters food particles in the mouth as they are reduced into smaller particles so that they may be assimilated for digestion. Mastication also alters the surface area and density of food so that the enzymes in saliva begin to soften and warm the food mixture into what is called bolus.
Digestive track. The bolus mixture allows for easier swallowing and assimilation as it travels through the digestive track via peristalsis. Peristalsis is the muscle movement in digestion that alters food composition by reducing it into even smaller substances of gastric juices and food particles in the stomach called chime, to be absorbed into the small intestine.
Several acids are found within the stomach and pancreas, along with multiple enzymes that further digest carbohydrates, proteins and lipids. Nutrients must be reduced to the most minuscule state for absorption into the small intestine. The small intestine is a very significant organ responsible for functions that are crucial to life sustaining tasks, namely supplying nutrients to the body. Of great significance is the fact that 90% of food digestion and absorption takes place in the small intestines. Along the wall of the small intestines, specific micro functions are carried out by enzymes that activate across the brush border surface to reduce nutrients to micro particles, so they can be absorbed.
Villi and microvilli are small finger-like projections that further assist in the absorption process. The villi are essential to the process, as their task is to move nutrient components into what are called crypts. The crypts feature many cell structures including absorbent epithelial cells and a mucosal lining to enhance the process of transporting nutrients into the bloodstream. Unfortunately, the transport of nutrients can be greatly reduced due to inflammation, which may blunt the motility and nutrient absorption potential. Conditions such as celiac disease, Crohn’s disease and diverticulitis that involve inflammation greatly influence the efficacy of absorption. It is very important to note that the consumption of healthy foods does not necessarily equate to optimum nutrient absorption. Digestive health, genetics and overall health homeostasis position the potential benefits of antioxidants to be utilized by the body.
Nutrients may enter the cells by passing through the intestinal mucosa by processes referred to as active transport and passive diffusion. The inner and outer portion of a cell is surrounded by water with an inner hydrophobic section featuring a functional barrier for “moving” any large substance, an electrical charge or hydrophilic medium to pass through a concentration gradient. Concentration gradients represent the chemical driving force supporting many activities that occur through cell membranes. It is the process whereby particles travel through a solution (often called a solute) from an area that has a dense or higher number of particles to an area that has a less number of particles typically separated by a membrane, namely the cell wall. This occurs freely as water generally moves through the cell in either direction; however, if the particles inside the cell are barred from moving across the membrane, the process is then called osmosis. When water in the cell travels across the membrane, its goal is to reach balance and equilibrium by having the water concentration the same on both sides of the cell, referred to as osmotic pressure.
Active transport occurs across the cell membrane where thousands of proteins are embedded in the cell’s lipid bilayer (see Phospholipid Bilayer) and are able to cross the bilayer with the help of enzymes and adenosine triphosphate (ATP). Active transport permits molecules and ions to travel in and out of the cell through acquired energy. Passive diffusion is the transport of molecules across the cell membrane that does not require energy. The solubility of lipids is a major factor during passive diffusion, as the molecules must pass through a membrane consisting of a double lipid bilayer as a transport viaduct. The hydrophilic heads are located on the external side of the membrane, and the hydrophobic “tails” are at the interior. Because of the nature of this structure, fatty acids and other substances such as steroid hormones can easily penetrate through the membrane.
Nutrients can also be transported through the cell wall by pinocytosis or phagocytosis. Pinocytosis is an “engulfing” process where liquid substances are captured in a vesicle and pulled in to the cytoplasm. Phagocytosis occurs when cells surround and “envelope” a particle, and signal the cytoskeleton to pull the material into the cell.1 These functions are responsible for the miracle of absorbing nutrients into the cell and also the ability to reduce cellular waste.
The intricate structure of cells includes a specific organelle, the mitochondria. Mitochondria are multifunctional energy centers located in every cell within the body. There may be thousands of mitochondria within one cell, and they may comprise 15–50% volume of the cell itself. Mitochondria perform key reactions and regulatory processes including the production of ATP, intracellular calcium regulation and ROS generation.
Intracellular antioxidants such as glutathione and superoxide dismutase monitor critical ROS concentrations that result in maintaining cell functionality and help to prevent oxidative stress. The super oxide ion is the precursor of most ROS that attacks lipids in the cell membranes, protein receptors, enzymes and DNA that can prematurely kill mitochondria. The important balance of ROS and the functions of the mitochondria involve the monitoring of structural and functional impairments that may trigger cascades of cell apoptosis and lead to mitochondrial related disease such as heart disease, stroke, neurodegenerative diseases and cancer.2
Mitochondrial structure and function deficiencies may impact overall health, aging and tissue disorders including the skin. It is estimated that 10% of patients with primary mitochondrial disorders present skin manifestations that may include hair abnormalities, pigmentation anomalies, inflammation, rashes, pigmentation problems and autoimmune skin diseases.3 Research has supported the practice of calorie restriction and intermittent fasting to assist in reducing the amount of free radicals that may be generated by overeating or eating before bedtime. Late night eating places stress on the body as it is at its lowest metabolic rate a few hours before sleep. Biological biomarkers are driven by the health of our mitochondria, and we may impact the way we age by supporting the health of our mitochondria. Exercise will help to support the mitochondria by requiring them to work harder to support the energy load; however, aggressive exercise may produce oxidative stress to cells and muscles.4 Consuming fresh fruits and vegetables along with specific antioxidants and co-factors such as omega-3 fatty acids, magnesium, CoQ10, acetyl L-carnitine, D-ribose, alpha lipoic acid and B complex vitamins may support mitochondrial health.5
Classification of Antioxidants
There are countless antioxidants in existence with potential benefits for the body and the skin. To help organize them, they are broken down into classes below.
Vitamins. Vitamins are nutrients our bodies need to maintain functions such as immunity and metabolism. Antioxidant vitamins particularly target free radicals to protect cells. Examples include betacarotene and vitamins A, C and E.
Minerals. Minerals are inorganic substances required by the body for the formation of bone and teeth, the constituents of bodily fluids and tissues and are involved in nerve function. Antioxidant minerals particularly target free radicals to protect cells, and examples include copper, zinc and selenium.
Phytochemicals. These botanical and plant compounds number in the thousands. They are responsible for carrying out essential biochemical processes in the body when they are consumed from foods and herbs and work in tandem or singularly with antioxidants, vitamins and minerals.
Enzymes. These large and complex protein molecules are specific to what they will digest or reduce. They run biological processes and functions in the body, whereas vitamins and minerals are co-factors or building blocks. Enzyme antioxidants work with other antioxidants to catalyze reactions and attempt to dismantle free radical activity. Examples include superoxide dismutase and glutathione peroxidase.
Co-enzymes. Co-enzymes are non-protein substances necessary for the function of an enzyme, including selenium, copper, iron, zinc, manganese and betacarotene.
Amino acids. These are made from proteins that catalyze the vast majority of chemical reactions in a cell. Basic amino acids do not have antioxidant activity with the exception of tryptophan, tyrosine, cysteine and homocysteine
Hormones. Made from signaling molecules produced by glands, hormones assist in activity of physiological function and behaviors. Examples include melatonin, which is produced by the pineal gland and assists with sleep, and dehydroepiandrosterone (DHEA) is produced by the adrenal glands to assist in the production other hormones.
Collection and Selection
Antioxidants function and support each other whether as co-factors, reactors or recyclers. This dynamic relationship between antioxidants is referred to as antioxidant synergism and supports the scientific premise that the sum has better activity than the parts alone. Collectively, they may provide the following:6
- Repair damaged molecules;
- Prevent oxidation;
- Chelate metal radical production (cell damage by metal ions);
- Support gene expression (gene synthesis and production);
- Shield DNA;
- Lower LDL cholesterol levels;
- Boost the immune system;
- Prevent cancer in nutrition regimes;
- Regulate DNA cell genetics (epigenetics);
- Serve as precursors to cellular mediators;
- Inhibit cell damaging enzymes;
- Promote apoptosis in cancer cells;
- Regulate cellular redox buffering agents; and
- Modify proteins enzymatically following biosynthesis.
Getting The Good Stuff
Although it is the largest organ of the human body, the skin is the last to receive the benefits of nutrient uptake from the bloodstream. Primary organs receive preferential status.
The ability of skin to absorb topical nutrients has been vastly hypothesized with dermatological science as the means for its rational, “The stratum corneum is the main barrier against permeation and therefore cutaneous absorption is limited by the permeation rate (rate of absorption.”7, 8 Of course, this must factor in the primary mechanisms for transport: inter follicular pathway and lipid pathways within the corneocytes. The structural lipid composition of the stratum corneum serves as a network to protect the skin but also plays a physiological role in the selective absorption of lipids and other materials. The absorption of lipophilic compounds (such as fat based antioxidants) is favored by the lipid composition of the stratum corneum, membranes and intercellular spaces.7, 9 The lipid bilayer structure and its functions including corneocytes, the extracellular matrix, ceramides, cholesterol and free fatty acids foster barrier integrity and are conducive to topical antioxidant potential with sebum as a key player. Sebum consists of varying amounts of triglycerides, squalene and wax esters that act with sebaceous gland activity as a physiological pathway for delivery of surface lipids and antioxidant lipids. Physiological levels of antioxidants that have been detected in the stratum corneum include: vitamin E, vitamin C, and glutathione due to the lipid composition of sebum.10
Topically applied antioxidants may help to prevent the effects of sun damage and oxidative stressors by attempting to quench free radicals, and many studies have demonstrated the highly beneficial effects of these bioactive compounds. However, one of the primary considerations in formulating topical antioxidant products is the potential for instability and oxidation when exposed to light, or that they may lose efficacy due to storage and packaging challenges. The stability in formulation as well as the delivery system are of great significance from both a chemical and physiological perspective. Countless studies have been devoted to the research of novel delivery systems such as micro emulsions, nanoparticles and liposomes to ensure the activity and delivery of antioxidants with favorable results. In particular, vitamin C, A and E, resveratrol, glutathione and alpha lipoic acid have been used in lipid nanoparticle formulations for enhanced delivery with much substantiation.11 Lycopene has also been used as an antioxidant enhancer prized for its ability to bind well with triglycerides and fatty acids thus providing a lipid micro emulsion for delivery.12
Reaping the Benefits
It is important to consume antioxidants to help protect the skin internally by way of antioxidant protection in the cells. Vitamin A, in particular from carotenoids, is a vital source of protection for the skin, as it bolsters the body’s ability to assist in sun protection by supporting some SPF factor (depending on intake of dietary vitamin A), and may reduce the UV induced inflammatory response by reduction of prostaglandin E2, a mediator in arachidonic acid. Additionally, it has been shown that the fibroblasts were significantly capable of reducing lipid peroxidation caused by UVB from beta carotene, lutein, and lycopene.13
Many of us pay close attention to consuming key nutrients in food, including antioxidants. It is no secret that even more individuals rely on the use of supplements to either suffice or substantiate nutrient support. However, many studies indicate that a large percentage of individuals lack the baseline requirements for the recommended daily allowance of daily nutrient intake or are deficient in key vitamins, minerals and antioxidants. In fact, the Center for Disease Control (CDC) and the U.S. Department of Agriculture (USDA) have calculated that when it comes to Americans:14
- 90% are deficient in potassium;
- 70% are deficient in calcium;
- 80% are deficient in vitamin E;
- 50% are deficient in vitamin A, vitamin C and magnesium;
- More than 50% are deficient in vitamin D, regardless of age;
- 90% of higher Fitzpatrick Americans are deficient in vitamin D; and
- 70% of elderly Americans are vitamin D deficient.
A 2009 study estimated that U.S. citizens relied on supplements for 54% of vitamin C, 64% of vitamin E, 14% of alpha- and beta-carotene, and 11% of selenium intake.15
These statistics exemplify the need for individuals to increase their awareness with regard to the intake of daily nutrients, and, in particular, to ensure that critical antioxidants are supplied to help prevent mitochondrial damage. For foods that contain these important antioxidants, see Mineral and Phytochemical Antioxidant Sources. Logging a food diary or utilizing a nutrition tracking application will help you to become more aware of the concentration of nutrient and antioxidant ratios. Food pyramid illustrations are also a great reference tool to assist in taking your personal inventory of the primary nutrients consumed as well as monitoring the frequency of antioxidant intake.
- Handbook of Occupational Dermatology, L Kanerva, P Elsner, JE Wahlberg and HI Maibach, eds., Springer-Verlag: Heidelberg, Germany (2000)
- J Thiele and P Elsner, Oxidants and Antioxidants in Cutaneous Biology, vol. 29 in Current Problems in Dermatology, G Burg, ed., Karger: Basel, Switzerland (2001)
- https://nccih.nih.gov/health/antioxidants/ introduction.htm