In 1956, D. Harman proposed a free radical theory of aging, hypothesizing that oxygen-derived free radicals (reactive oxygen species – ROS) are generated throughout all cells and tissues, resulting in progressive, random damage to enzymes, proteins, unsaturated lipids, cell membranes, and to our genes. The end result is cell senescence. Since then, abundant experimental and observational evidence supports the idea that aging is the sum of all free radical reactions throughout all cells and tissues, or at least they are major contributors to it.
Oxygen-derived radicals (ROS) are produced in abundance in all animal cells and tissues as part of our normal metabolic processes. Fortunately, our body has numerous natural defenses to either prevent their formation or to neutralize them after they are formed. In spite of our natural defenses, it has been estimated that each human cell undergoes 10,000 “hits” by free radicals each day. Although most free radicals are potentially harmful, others are essential to many intracellular metabolic reactions. For example, they are deployed by phagocytic cells to kill ingested microorganisms.
Aging is a complex process which results from cellular, physiological, and psychological changes. While all people show a decline in metabolic activities and organ functions as they age, they exhibit declines differently and at different rates. Why? The theory goes that those who have a closer association with poor health habits, such as smoking, high consumption of alcohol, increased stress, and poor diets do not age well.
Ideally, we should all practice preventive nutritional tactics, eating foods which have minimal processing such as fruits, vegetables, whole grains, legumes, non-fat dairy products, lean meats, and lots of fish. Taking multi-vitamins and mineral supplements in moderate doses can also be beneficial, and there is a lot of talk around the power of antioxidants.
There is evidence showing that antioxidants can potentially delay the aging process, and also protect against the development of age-related diseases.
In a study of centenarians, the plasma levels of vitamins C and E were higher compared to subjects 70-99 years old. Another study evaluated the maximal life-span potential of humans as well as other mammalian species. The authors suggested that carotenoid content of serum and brain tissue may be the most significant factor in determining life span, and there is a link between longevity, antioxidant concentration, and protection against free radical damage.
i) What is beta-carotene (Vitamin A)?
Beta-carotene is probably the most well known of the carotenoids, a phytonutrients family that represents of the one most widespread groups of naturally occurring pigments. It is one of the most abundant carotenoids in the North American diet as well as one of approximately 50 carotenoids known as "provitamin A"compounds, able to be converted in the body into retinol, an active form of vitamin A.
While beta-carotene produces colors in the orange and yellow range, beta-carotene rich foods may be other colors besides from these two. That is because other phytonutrients pigments blend together with the beta-carotene to give the plant food its unique hue that, in addition to orange or yellow, could be other colors including pink, red or white.
How it Functions
What are the functions of beta-carotene?
Preventing Vitamin A Deficiency
Until late in the 20th Century, the functions of carotenoids, including beta-carotene, were discussed only in terms of their potential vitamin A activity. Beta-carotene is one of approximately 50 carotenoids of the known 600, that are called "provitamin A" compounds because the body can convert them into retinol, an active form of vitamin A.
As a result, foods that contain beta-carotene can help prevent vitamin A deficiency. In addition to alpha-carotene and beta-cryptoxanthin, beta-carotene is among the most commonly consumed provitamin A carotenoids in the North American diet.
ii) What is vitamin C?
Because of its widespread use as a dietary supplement, vitamin C may be more familiar to the general public than any other nutrient. Studies indicate that more than 40% of older individuals in the U.S. take vitamin C supplements; and in some regions of the country, almost 25% of all adults, regardless of age, take vitamin C. Outside of a multivitamin, vitamin C is also the most popular supplement among some groups of registered dietitians, and 80% of the dietitians who take vitamin C take more than 250 milligrams. Why is this nutrient so popular?
Vitamin C, also called ascorbic acid, is a water-soluble nutrient that is easily excreted from the body when not needed. It's so critical to living creatures that almost all mammals can use their own cells to make it. Humans, gorillas, chimps, bats, guinea pigs and birds are some of the few animals that cannot make vitamin C inside of their own bodies.
Humans vary greatly in their vitamin C requirement. It's natural for one person to need 10 times as much vitamin C as another person; and a person's age and health status can dramatically change his or her need for vitamin C. The amount of vitamin C found in food varies as dramatically as our human requirement. In general, an unripe food is much lower in vitamin C than a ripe one, but provided that the food is ripe, the vitamin C content is higher when the food is younger at the time of harvest.
How it Functions
What is the function of vitamin C?
Vitamin C serves a predominantly protective role in the body. As early as the 1700's, vitamin C was referred to as the "antiscorbutic factor," since it helped prevent the disease called scurvy. This disease was first discovered in British sailors, whose sea voyages left them far away from natural surroundings for long periods of time. Their body stores of vitamin C fell below 300 milligrams, and their gums and skin lost the protective effects of vitamin C. Recognizing limes as a good shipboard source of vitamin C, the British sailors became known as "limeys" for carrying large stores of limes aboard ship.
The protective role of vitamin C goes far beyond our skin and gums. Cardiovascular diseases, cancers, joint diseases and cataracts are all associated with vitamin C deficiency and can be partly prevented by optimal intake of vitamin C. Vitamin C achieves much of its protective effect by functioning as an antioxidant and preventing oxygen-based damage to our cells. Structures that contain fat (like the lipoprotein molecules that carry fat around our body) are particularly dependent on vitamin C for protection.
iii) What is vitamin E?
Even though its name makes it sound like a single substance, vitamin E is actually a family of fat-soluble vitamins that are active throughout the body. Some members of the vitamin E family are called tocopherols. These members include alpha tocopherol, beta tocopherol, gamma tocopherol, and delta tocopherol.
Other members of the vitamin E family are called tocotrienols. These members include alpha, beta, gamma, and delta tocotrienol. As increasing information has become available about these forms of vitamin E, more and more of them are understood to have unique functions.
How it Functions
What is the function of vitamin E?
Prevention of oxidative stress
Although humans must breathe oxygen to stay alive, oxygen is a risky substance inside the body because it can make molecules overly reactive. When oxygen-containing molecules become too reactive, they can start damaging the cell structures around them. In chemistry, this imbalanced situation involving oxygen is called oxidative stress.
Vitamin E helps prevent oxidative stress by working together with a group of nutrients that prevent oxygen molecules from becoming too reactive. This group of nutrients includes vitamin C, glutathione, selenium, and vitamin B3. Some researchers believe that vitamin E is the most important member of this oxidative stress-preventing group.
Supporting healthy skin
Vitamin E has sometimes been described as the "lightening rod" of the cell, allowing reactive molecules to strike the cell, like lightening, without causing damage. This "lightening rod" function of vitamin E is particularly apparent in the case of the skin, since vitamin E directly protects the skin from ultraviolet radiation (also called UV light). In numerous research studies, vitamin E applied topically to the skin has been shown to prevent UV damage. When the diet contains vitamin E-rich foods, vitamin E can travel to the skin cell membranes and exert this same protective effect.
Protection against Bladder Cancer
One of the benefits of making foods rich in vitamin E—nuts, seeds, spinach, mustard greens, peppers and olive oil—a part of your healthy way of eating is an up to 50% reduction in risk of developing bladder cancer, according to research presented at the annual meeting of the American Association of Cancer Research, Orlando, FL, May 23, 2004.
Bladder cancer, which kills 12,500 Americans annually, is the fourth leading cancer killer among men, and is four times more common in men than women. The study, which included 468 bladder cancer patients and 534 cancer-free controls drawn from residents of Houston, TX, collected data using eating habits questionnaires. Those whose vitamin E intake was in the top 25% had half as much bladder cancer as those in the lowest 25%.