“Carotenoids” is the term which describes the large range of more than 600 phytochemical pigments from which many plants derive their characteristic red, orange or yellow colourings. Those most commonly found in modern Western diets are alpha-carotene, beta-carotene, lutein, zeaxanthin, and lycopene.
Alpha and beta-carotene have traditionally attracted most attention as they can be synthesised by the body to form vitamin A, one of the body’s most powerful anti-oxidants, immune system boosters and infection fighters. More recently lycopene has won substantial publicity as a possible weapon in the battle against cancer, particularly that of the prostate.
Like lycopene, neither lutein nor zeaxanthin are “pro-vitamin A” active substances in the way that alpha and beta-carotene are, but the evidence now indicates that they also function as valuable fat-soluble anti-oxidants within the body, and as such may be particularly important in preventing free radical damage to the delicate but vital fatty structures of the body’s cells such as the membranes. These fat-soluble anti-oxidants also help to prevent the oxidation of low-density blood lipids (LDL), the so-called “bad cholesterol”, which is implicated as a major factor in the development of cardiovascular disease.
But in addition to sharing the general health giving anti-oxidant properties of carotenoids, lutein and zeaxanthin have been highlighted for their role in maintaining visual health, and particularly in protecting against the principal causes of loss of vision in later life, ie age-related macular degeneration (AMD) and cataracts.
The macula is the centre of the eye’s retina, and its degeneration is the main cause of visual deterioration and ultimately even blindness amongst the elderly in affluent Western societies. Since lutein and zeaxanthin are the only carotenoids found in the retina, particular attention has been paid to their possible role in eye health, and it appears that both may play a role in preventing oxidative damage from blue and ultra-violet light, ie sunlight, in the macula. Like every other structure in the body, the cells of the retina are vulnerable to free radical damage in the absence of sufficient anti-oxidants and research published in the Journal of the American Medical association in 1994 suggests a 43% reduced incidence of AMD for those following a diet rich in lutein and zeaxanthin anti-oxidants as against those whose diet was poorest in these foods.
Lutein and zeaxanthin are likewise the only carotenoids found in the lens of the eye, where ultra-violet light and oxidative damage can cause the growth of the cataracts that frequently obscure the vision of the elderly. Several research studies have demonstrated that diets rich in lutein and zeaxanthin, particularly dark green, leafy vegetables, may reduce the incidence of cataracts by as much as 25-50%.
Conventional medicine nevertheless continues to insist that these findings may be due to elements in a lutein rich diet other than lutein and zeaxanthin themselves, although commonsense would seem to suggest that as these are the only carotenoids present in these vital structures of the eye, nature has probably put them there for a good reason.
The consumption of ample lutein and zeaxanthin requires the consumption of a wide variety of vegetables, particularly the dark, green leafy varieties which are the best dietary source. So a cup of cooked spinach, for example, will provide up to 30,000 mcg, kale around 25,000 mcg, collards or turnip greens perhaps up to 20,000. Squash, peas, sprouts, pumpkin and broccoli, amongst others, may also be useful sources, but will provide rather lower quantities.
As with other carotenoids, the optimum absorption of lutein and zeaxanthin requires the presence of dietary fat. But this is not too tough to achieve so long as the required vegetables are taken as part of a meal also including some meat, particularly red meat.
Supplements containing either lutein, zeaxanthin, or a combination of the two are readily available as an alternative, the combination supplements normally containing significantly more lutein than zeaxanthin. But whilst conventional medicine has largely accepted the value of a diet rich in these carotenoids in helping to ensure continued eye health, it remains sceptical as to the value of such supplementation. Alternative practitioners, of course, admit to no such doubts and urge the benefits, particularly for those with particular reason to fear the onset of age related optical health problems.
And although such practitioners tend to recommend supplements in quantities which ought to be easily achievable through the consumption of a selection of the foods listed above; it appears that many people are still not managing to consume such a diet. This is evidenced by the sad fact that around 25% of the over sixty-five age group show some signs of AMD, and that several hundred thousand people are blinded by it each year.
So as ever, the sensible and cost effective precaution appears to be to combine supplementation with a normal daily diet already well supplied with foods rich in lutein and zeaxanthin.