Wednesday, December 30, 2009

Inadequate vitamin D may account for over 1/2 of end-stage renal disease in african americans

New research has shown a significant link between vitamin D status and the risk of advanced kidney disease. In a recent study, individuals with the lowest level of vitamin D were 2.6 times more likely to need kidney dialysis than those with the highest levels.

Kidney failure is more common in African Americans than in Caucasians. This disparity is generally attributable to a greater prevalence of hypertension and diabetes in this population.

In the December 2009 issue of the Journal of the American Society of Nephrology, researchers report a strong association between end-stage renal disease (ESRD) in African Americans and reduced vitamin D levels. Vitamin D deficiencies are more common in this group compared to Caucasians due to increased skin pigmentation, which results in reduced vitamin D synthesis from sun exposure.

Deficiencies in vitamin D (defined as less than 15ng/ml) were found in 34% of African Americans compared to 5% of non-Hispanic Caucasians. Researchers also discovered that individuals with the lowest vitamin D levels were 2.6 times as likely to end up on dialysis compared to those with the highest levels. The researchers determined that vitamin D was responsible for about 58% of the excess risk for renal disease experienced by African Americans.

Follow-up research is needed to confirm the results, but this study adds to previous evidence linking vitamin D deficiency to the progression of kidney disease and the resulting need for dialysis. It also explains a good portion of the increased risk of ESRD in African Americans.

Wednesday, December 16, 2009

Omega–3 fatty acid intake & the incidence of age-related macular degeneration

Results recently published from a long-term study indicate that people at risk for age-related macular degeneration (AMD) may significantly reduce the risk of this disease by increasing their dietary intake of omega-3 fatty acids from oily fish, nuts and seeds, and fish oil supplements.

Omega-3 fatty acids are important for the vascular and neural health of the retina and may influence the risk of developing age-related macular degeneration (AMD). There are two forms of AMD: dry and wet. In the dry form, normal tissue in the macula slowly disappears, leaving a pale area referred to as central geographic atrophy (CGA). In the wet form, or neovascular (NV) AMD, abnormal blood vessels grow underneath the macula. These vessels leak serum or blood and eventually cause the normal macular tissue to be replaced by scar tissue.

Researchers recently investigated whether omega-3 fatty acid intake was associated with a reduced risk of developing both wet and dry forms of AMD. The study involved 1837 people from the Age-Related Eye Diseases Study (AREDS) who were at moderate to high risk of developing AMD. Clinical measurements were obtained in this group over a period of 12 years (from 1992 to 2005).

Participants who reported the highest omega–3 fatty acid intake were 35% less likely than their peers to develop dry (CGA) AMD, and 32% less likely to develop the more common, wet form (NV) AMD.

Over the 12 years of this study, the incidence of CGA and NV AMD was lowest for those reporting the highest consumption of omega-3 fatty acids, which are found primarily in oily fish, nuts and seeds, and fish oil supplements. If these results are applied to the general population, dietary intervention may have a significant preventive effect on the development and progression of AMD.

Wednesday, December 09, 2009

Daily supplement use and brain function in healthy children

A daily multivitamin and mineral supplement may help improve brain function in healthy children

Vitamins and minerals are essential for optimal neural performance. However, national dietary surveys continue to show that a high percentage of adults and children suffer from deficiencies in one or more vitamins and minerals.

A study published in the November 2008 British Journal of Nutrition examined the effects of multivitamin and multimineral supplements on brain function in children. The study involved 81 healthy children between the ages of 8 and 14. The children were randomly assigned to receive a daily children’s multivitamin and multimineral supplement or a placebo.

During twelve weeks of supplementation, the children were given a series of tests to assess brain function. The children who received daily supplements performed better on two tests of attention than did the children who received placebos. Even more surprising was that the improvements in attention scores were seen within a few hours after administering the first vitamin and mineral dose. Mood, another outcome the authors were researching, was not significantly affected by the supplement.

These results suggest that multivitamin and multimineral supplementation may help to improve brain function in healthy children. However, it is impossible to determine whether the improvement in brain function in the children who took the daily supplement was due to a single ingredient in the supplement or whether it was due to the interaction of multiple vitamins and/or minerals. While additional research will be necessary to further elucidate this point, it may be time to reconsider the role of daily multivitamins in maintaining childhood health.

Wednesday, December 02, 2009

Total Vitamin C deficiencies declining, but still a problem for some groups

In the last two decades, vitamin C deficiencies in the U.S. have steadily declined, in part because of increased use of dietary supplements. Unfortunately, some population groups still experience high rates of deficiency.

The National Health and Nutrition Examination Survey (NHANES) is a continuous annual survey conducted in the United States by the National Center for Health Statistics (a division of the CDC). A recent study used data from two separate NHANES surveys – one from 2003-2004 and another from 1988-1994 – to examine whether or not vitamin C deficiencies have increased or decreased over time.

Using serum vitamin C concentration data collected from 7200 individuals (age 6+) in 2003-2004 and 20,600 individuals (age 6+) in 1988-1994, researchers marked individuals as “deficient” or “not deficient”, where deficiency was classified as serum concentration <11.4┬Ámol/l. style="text-align: justify;">
Encouragingly, vitamin C deficiencies declined across most subgroups, and in many groups the declines were substantial. At least part of this improvement is due to vitamin C supplementation. “In prosperous societies, supplement consumption has a significant effect on body stores and circulating concentrations of vitamin C,” the authors reported. “In NHANES 1999–2000, 52% of adults reported consumption of supplements in the past month…these recent data show increased usage since the overall 40% usage reported during NHANES III [1988-1994] and are likely to explain in part the improved vitamin C status of the U.S. population.”

Unfortunately, certain population groups remain at risk of vitamin C deficiency. Smokers are the highest risk subgroup, with 18% of male smokers and 15.3% of female smokers being vitamin C deficient (compared to 5.3% and 4.2% for male and female non-smokers, respectively). Smoking accelerates vitamin C turnover and lowers serum concentrations, which in turn increases the likelihood of deficiency. Lower income groups were also at higher risk for deficiency, and men were more likely to be deficient than women. Children, teens, and adults over the age of 60 were less likely to be deficient than adults between the ages of 20 and 60.

The study concludes by stating: “…the vitamin C status of the US population appears to have substantially improved from 1988–1994 to 2003–2004. Nevertheless, the prevalence of vitamin C deficiency in various subgroups remains a concern.”