Many colors in fruits and vegetables are antioxidants
Many to most consumers understand they should eat at least three to five servings of fruits and vegetables daily. Few actually do. The dietary recommendations originally were based, in part, on the healthfulness of known components such as vitamins, minerals and fiber found in produce. In the 1980s, research increasingly pointed to the importance of less familiar nutritional phytochemicals in fruits and vegetables.

Today, much of the nutritional news on fruits and vegetables revolves around antioxidants and their role in preventing age-related disease. Now supplement and functional food manufacturers are stepping up to the plate to give consumers what they lack: the antioxidant value that had been obtained from fresh fruit and vegetables, but in more convenient forms.

Therapeutic Conditions

According to Connie Grauds, of the Association of Natural Medicine Pharmacists (ANMP), one of the first products with a high antioxidant level that made headlines for its healthfulness was green tea. After water, green tea is the most-consumed beverage in the world. It contains specific antioxidants, called polyphenols and catechins, of which epigallocatechin is one of the most notable. These antioxidants appear to have the ability to reduce the risk of certain types of cancer, have cardiotonic and anti-atherosclerotic activity, may prevent gingivitis and dental caries and improve resistance to infections. Green tea even is being investigated for its role in weight loss and the treatment of obesity.

Green tea is proving to be a truly health-promoting food. However, it is far from being alone. Just a few of the other products with significant antioxidant levels include yerba mate, grape seed extract, bilberry, cranberries, garlic, capsicum, hawthorn berries, licorice, artichoke and prunes.

Additional areas of health and disease prevention in which antioxidants show promise include skin and connective tissue health, diabetic vascular complications, diarrhea, hemorrhoids, capillary fragility, cardiovascular health, circulation, intermittent claudication, peripheral vascular disorders, venous insufficiency, varicose veins, liver protection and restoration, macular degeneration, retinopathy (microcirculatory), vision, and aging, in general.

Color My World

Many of the compounds in fruits and vegetables that possess antioxidant activity also give them their rainbow of colors, and certain ones are used as natural color extracts in food applications. Anthocyanins are polyphenolic compounds that are potent antioxidants and also exhibit colors in the natural red ranges, from oranges to purples. Carotenoids exhibit colors in the natural yellow ranges, from bright yellows to oranges. The curcuminoids are extracted from the Indian spice turmeric. They possess confirmed health benefits and are used for a natural lemon-yellow color. Chlorophyll (e.g., from spinach) also is used for both health benefits and for its natural green color. Although chlorophyll is used broadly elsewhere in the world as a green colorant, its use is limited in the United States. Food and beverage manufacturers can opt to use spinach powder.

Antioxidant Cross-functionality

Natural Preservatives

Rosemary extract has been used for centuries as a natural preservative for certain types of foods. Today, rosemary extract has created a revolution in the natural preservative field as a potent antioxidant that prevents oxidation of foods, thus protecting flavors and colors. According to Ginny Bank, technical director of a supplier of natural flavors and colors, rosemary is unique in its composition and ability to protect foods from oxidation because it contains the natural compounds carnosic acid and rosmarinic acid. Other sources of rosmarinic acid as a preservative product, such as lemon balm and oregano, are available in the industry. Indeed, extract of oregano (Origanum vulgare), which has been consumed as a dietary supplement, is also beginning to be aggressively marketed to the food industry for its natural preservative abilities.

Arguments for ORAC

ORAC is becoming one industry standard for measuring antioxidants.[1] Developed by researchers at the USDA-ARS Human Research Center at Tufts University, Medford, Mass., the antioxidant test combines a measure of both the time an antioxidant took to react and also its antioxidant capacity in a given sample. ORAC then combines them into one measure, making it the first in vitro assay method for measuring total antioxidant potential.

[2] ORAC looks at the complete reaction between a free radical and a substrate by taking a sample containing a fluorescing chemical marker and combining it with an oxidizing agent (peroxyl radical, hydroxyl radical or metal ions). As the oxidizing agent destroys the antioxidants in the sample, more of the fluorescing chemical is used up until, eventually, none is left and the sample fluoresces no longer.

In the initial examination of food antioxidants by Prior and other Tufts University researchers, ORAC standardized antioxidants were fed to middle-aged rats. Results showed the prevention of long-term memory and learning ability loss. Additionally, human blood samples were measured for increased antioxidant capacity due to the ingestion of certain antioxidant foods/substances, showing the potential of ORAC as a biological assay. According to the research, the intake of between 3,000 to 5,000 ORAC units daily is recommended to help prevent or forestall certain age-related changes. After looking at the typical American diet, the researchers recommended increasing or supplementing our diet by 1,000-2,500 ORAC units daily to reach recommended levels.

Other Antioxidant Tests

Finding the “definitive” and best method to measure antioxidant capacity is difficult because there are numerous biological antioxidant systems, and numerous factors complicating the interpretation of results of any one test. In vivo (in the body) samples containing antioxidants are dynamic and complex systems. For example, in a plasma or blood sample, an increased antioxidant capacity may not be seen as positive if the increased capacity is a response to increased oxidative stress on the system. Using similar reasoning, the decrease in antioxidant capacity may not be seen as negative if this is due to a decreased production of reactive species. Prior and Cao point out that “because of these complications, no single measurement of antioxidant status is going to be sufficient, but a 'battery' of measurements” is needed.

[3] Systems in the body relating to antioxidant reactions involve enzymes (e.g. superoxide dismutase, catalase and glutathione peroxidase), macromolecules (e.g. albumin, ceruloplasmin and ferritin), and independent small molecules (e.g. ascorbic acid, alpha-tocopherol, beta-carotene and reduced glutathione). Antioxidant tests vary in their focus. Below is a brief synopsis of some of the main competing tests in the industry for water-soluble systems:

  • TEAC (I, II and III) — TEAC I analyzes the delay in oxidation; the lag phase is a parameter of antioxidant activity, and the ability to scavenge the radical; TEAC II and III analyze the ability to reduce the radical cation.
  • DPPH — Analyzes the ability to reduce the radical cation.
  • DMPD — Analyzes the ability to reduce the radical cation.
  • TRAP—- Analyzes the delay in oxidation; the lag phase is a parameter of antioxidant activity and the ability to scavenge the radical.
  • FRAP — Uses metal ion to produce oxidation and analyzes the ability to reduce ferric ion.
  • PCL — Analyzes the delay in oxidation; the lag phase is a parameter of antioxidant activity, and the ability to scavenge the radical. Where most tests are able to determine activity in the micromolar range, PCL determines this in the nanomolar range.
Despite the complexity of analysis, antioxidants will continue to be studied by scientists. Driven by research, antioxidants will continue to be “high profile” ingredients among industry and consumers alike.