Beta-carotene is considered a conditionally essential nutrient and becomes an essential nutrient when the dietary intake of retinol (vitamin A) is inadequate.
Low serum beta-carotene levels have been associated with male gender, younger age, lower non-HDL-cholesterol, greater ethanol consumption and higher BMI (Brady et al 1996), increased lipoprotein density and the presence of inflammation (Kritchevsky 1999), high C-reactive protein (Erlinger et al 2001), high blood glucose (Abahusain et al 1999), hypertension (Coudray et al 1997), exposure to environmental tobacco smoke (Farchi et al 2001), as well as all measures of obesity (Wallstrom et al 2001), including obesity in children (Strauss 1999).
Low serum beta-carotene and/or low beta-carotene intake has also been associated with a number of clinical conditions, such as type 2 diabetes and poor glycaemic control (Abahusain et al 1999, Coudray et al 1997), non-melanoma and melanoma skin cancer (Gollnick & Siebenwirth 2002), breast cancer (Hacisevki et al 2003), rheumatoid arthritis (Kacsur et al 2002), Alzheimers dementia (Jimenez-Jimenez et al 1999) and age-related macular degeneration (Cooper et al 1999a).
Low serum beta-carotene has been independently associated with an increased all-cause mortality risk in older men. Apparently, a synergistic effect occurs between low beta-carotene and high inflammation burden in predicting higher mortality rates (Hu et al 2004). In another study of 668 hospitalised patients aged 70 years or more and 104 healthy controls, the diseased elderly people had reduced plasma levels of retinol, beta-carotene, and alpha-tocopherol (Tebi et al 2000). It is unclear whether these observed low levels of beta-carotene seen in disease states are a cause or result of disease processes.
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