A) ANTIOXIDANT AND SINGLET OXYGEN-QUENCHING ACTIVITY
As a general category, carotenoids possess significant antioxidant/free radical scavenging activity. For example, beta carotene has been shown to inhibit the oxidation of cholesterol (thus reducing heart disease risk) and protects the thymus (the master gland of immunity) from free radical-induced damage. The carotenoids lutein and zeaxanthin are potent antioxidants within eye tissues and higher intake is strongly associated with reduced risk of age-related macular degeneration. In particular, certain carotenoids neutralise a toxic form of oxygen known as singlet oxygen (typically associated with cigarette smoke, air pollution, UV and ozone exposure). Although beta carotene is a good singlet oxygen quencher, studies show that among others, capsanthin (from paprika and red peppers), lycopene, gamma carotene and alpha carotene are considerably stronger than beta carotene in this respect.
B) CELL PROTECTIVE
Many studies show that the higher the blood levels or dietary intake of carotenoids, the lower the susceptibility to cellular abnormalities. Although the research has focused on statistics measuring specific carotenoids (especially alpha and beta carotene, lycopene and cryptoxanthin), it should be stressed that the people surveyed in such studies acquired carotenoids from food, rather than supplements. Food-derived carotenoids are never found in isolation (i.e. they are present with various other carotenoids and protective compounds). Thus it is likely that much of the cell protection highlighted in this research was associated with the synergistic effect of a wide range of carotenoids and other dietary antioxidants found in the food they were eating. Although in vitro (test tube/petrie dish) and animal studies have shown benefits in cell protection from single carotenoids, it is not yet possible to draw firm in vivo (in the body) conclusions in this respect. The few in vivo human studies (involving synthetic beta carotene supplementation) have not shown the cell protective effects associated with high carotenoid diets. It is likely that some of this disparity is due to the fact that a synthetic form of beta carotene was used* (see below). In any case, diets rich in alpha carotene, lycopene, cryptoxanthin and/or beta carotene are linked to significant cell protection.
C) GAP JUNCTION COMMUNICATION
Gap junctions are a major route by which tissue cells in the body communicate with one another, and a breakdown in gap junctions may lead to cellular damage and/or abnormal cellular function, differentiation and replication. Carotenoids have been found to significantly enhance gap junction communication; it would appear that beta carotene has the greatest gap junction impact, followed by lycopene and lutein.
D) IMMUNE ENHANCEMENT
A high carotenoid intake is strongly associated with a reduced risk of infection and general immune- boosting properties. Although some of the immunological benefits of certain carotenoids are likely to be associated with their vitamin A activity, it appears that a high carotenoid intake may augment immune function irrespective of any influence on vitamin A. For example, beta carotene protects the immune system’s master gland, the thymus, from free radical damage, and supplementation has been shown to significantly boost white blood cell activity.
E) VITAMIN A ACTIVITY
Only 10% or less of the naturally-occurring carotenoids currently identified by scientists fall into the provitamin A category (i.e. can be converted into vitamin A in the body). The production in the body of vitamin A from carotenoids requires adequate levels of thyroid hormone, protein, zinc and vitamin C. Provided that this conversion takes place efficiently, provitamin A carotenoids can be used to provide the functions of vitamin A (as retinol), and without the risk of vitamin A toxicity. However, because the conversion does not exceed the body’s immediate need for retinol, provitamin A carotenoids will not necessarily provide the therapeutic properties of mega-dose retinol supplementation. Beta carotene has the highest vitamin A (retinol) activity of the carotenoids.
• Antioxidant (all – especially alpha and beta carotene and lycopene)
• Singlet oxygen quenching (especially lycopene, astaxantbin, gamma, alpha and beta carotene)
• Cell protection (all – especially lycopene and alpha carotene)
• Vitamin A precursor (some – especially alpha, beta and gamma carotene – see above)
• Skin health (especially beta carotene and mixed carotenoids)
• Respiratory [including lung] health (especially lycopene, alpha carotene, lutein and beta carotene [from natural sources only – not synthetic form])
• Eye health (especially lutein, zeaxanthin and astaxanthin)
• Prostate health (especially lycopene)
• Cardiovascular health (especially beta carotene and mixed carotenoids)
• Female reproductive health (especially alpha and beta carotene and cryptoxanthin)