Key nutrients in the prevention of eye diseases
Optimizing vision throughout the lifespan is a public health priority worldwide, not only because of its central importance to quality of life, but also because of the health care costs associated with the loss of vision in an aging population. Oxidative stress is thought to be a key pathogenic mechanism of compromised vision, and the antioxidant properties of some nutrients show the capacity to modulate disease conditions linked to oxidative stress. Considerable evidence has accumulated showing that vitamins A, C, E, beta-carotene and zinc help support vision and may be protective against the development or progression of some common – especially age-related – eye diseases such as age-related macular degeneration and cataracts. In addition, increased intakes of the carotenoids lutein and zeaxanthin and the omega-3 fatty acid docosahexaenoic acid (DHA) – all concentrated in the eye – have been associated consistently with lower likelihood of sight-threatening conditions. There has also been some promising research with B vitamins in age-related eye diseases and with vitamin A and DHA in the rare disease retinitis pigmentosa.
Controversies in omega-3 fatty acid research
Long chain omega-3 fatty acids play important roles in growth, development, optimal functioning, and maintenance of health and well-being right across the life course. The consumption of omega-3 fatty acids is usually below the recommended intake. Increased intakes are reflected in greater incorporation into blood lipid, cell and tissue pools, modification of the structure of cell membranes and the function of membrane proteins involved as receptors, signaling proteins, transporters, and enzymes. Despite the many promising trials using omega-3 fatty acid supplements, some of the most recent studies conducted have been unable to replicate earlier positive results. In many of these recent trials, the participants already had relatively high levels of eicosapentaenoic acid and docosahexaenoic acid in their blood at the beginning of the study and were also being treated with a pharmaceutical cocktail for their condition.
A new study from Australia reports that an omega-3 fatty acid supplementation of patients with recent onset rheumatoid arthritis seems to reduce the risk of anti-rheumatic drug failure.
According to new US research the recommended dietary allowances (RDAs) of vitamin D is based on a miscalculation and should actually be higher than the tolerable upper level for the nutrient.