Diabetes and beta-carotene deficiency
Researchers at the Centers for Disease Control and Prevention have
discovered that people with impaired glucose tolerance or newly
diagnosed diabetes also tend to have lower blood levels of the
carotenoid antioxidants (alpha-carotene, beta-carotene,
cryptoxanthin, lutein/zeaxanthin, and lycopene). There is a growing consensus that glucose
intolerance and diabetes are linked to oxidative stress and
increased free radical activity. Earlier research has shown that
diabetics have low levels of vitamin C and vitamin E and that
vitamin E supplementation can help prevent the development of
glucose intolerance (a precursor of diabetes) and diabetes. Their study
involved 1665 people aged 40 to 74 years. The participants took
an oral glucose tolerance test and gave fasting blood samples for
analysis of carotenoid content. One thousand and ten (61 per
cent) of the study participants had normal glucose tolerance, 277
(17 per cent) had impaired glucose tolerance, 148 (9 per cent) had
newly diagnosed diabetes, and 230 (13 per cent) had previously
diagnosed diabetes based on World Health Organization criteria.
Analysis of the blood samples showed that people with impaired
glucose tolerance had a 13 per cent lower level of beta-carotene
(on average) than people with normal tolerance. People with newly
diagnosed diabetes had a 20 per cent lower level of beta-carotene
than did people with normal tolerance. Lycopene content was 6 per
cent lower in the case of impaired tolerance and 17 per cent in
the case of newly diagnosed diabetes. The mean level of
cryptoxanthin was 23 per cent lower in those newly diagnosed.
After adjusting for potentially confounding variables the
researchers also found that both baseline fasting and two-hour
glucose concentrations were inversely related to beta-carotene and
cryptoxanthin concentrations while lycopene concentration was
inversely related to the two-hour glucose concentration only. The
researchers conclude that a low blood level of carotenoids is
associated with diabetes, but caution that more research is
required to determine whether diabetes is caused (at least
partially) by low carotenoid levels or whether the low levels
occur as a result of impaired glucose tolerance or
diabetes.
Ford, Earl S., et al. Diabetes mellitus and serum carotenoids:
Findings from the Third National Health and Nutrition Examination
Survey. American Journal of Epidemiology, Vol. 149, January 15,
1999, pp. 168-76
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