In The News: October 2013

The results of a Canadian study published in Occupational and Environmental Medicine reveal a significant association between long-term night shift work and a higher risk of breast cancer.* Although earlier research had uncovered a similar link among nurses, the current study demonstrates the association among members of the general population.

The researchers compared 1,134 women with breast cancer to 1,179 age-matched women who did not have the disease. Questionnaires completed by the participants provided information concerning years spent working night shifts.

Approximately one-third of women in both groups reported a history of night shift work. While no association was found for women who worked night shifts from zero to 29 years, those who worked night shifts for at least 30 years had more than twice the risk of breast cancer than subjects who reported no night shift work.

Editor’s Note: While a reduction in melatonin resulting from nighttime light exposure among night shift workers is one mechanism proposed for their greater risk of breast cancer risk, the authors remark that other mechanisms, including sleep disturbances, clock gene dysregulation and lifestyle differences, could also play a role. It has also been suggested that a decrease in vitamin D production due to reduced sunlight exposure experienced by night shift workers could contribute to increased disease risk.

An article published recently in the American Journal of Clinical Nutrition reveals an association between increased vegetable and fruit intake and a lower risk of dying during 13 years of follow-up.*

The analysis included 38,221 participants in the Cohort of Swedish Men who were recruited between 1997 and 1998, and 33,485 women recruited from 1987 to 1990 to participate in the Swedish Mammography Cohort. Questionnaires completed upon enrollment provided data concerning diet over the previous year, alcohol intake, and other lifestyle factors.

From the beginning of 1998 through 2010, 6,803 men and 4,637 women died. In comparison with subjects who consumed the recommended five servings of fruit and vegetables per day, those who did not consume fruit or vegetables had a 53% greater risk of dying over follow-up.

Editor’s Note: When fruit and vegetable intake were analyzed separately, those who consumed no fruit lived on average 19 months less than subjects who consumed one fruit per day, and those who reported eating three or more servings of vegetables per day survived an average of 32 months longer than those who didn’t consume them.

The FASEB Journal published the discovery of researchers at Boston’s Brigham & Women’s Hospital and Harvard Medical School of a mechanism for docosahexaenoic acid (DHA, an omega-3 fatty acid that occurs in fish oil and algae) in reducing inflammation.*

Charles N. Serhan, PhD, and his colleagues found that human immune cells known as macrophages convert DHA to an intermediate compound labeled 13S, 14S-epoxy-maresin. “Maresins are produced by macrophages from docosahexaenoic acid (DHA) and exert potent proresolving and tissue homeostatic actions,” Dr. Serhan and his coauthors write. “Maresin 1 is the first identified maresin.”

As the result of synthesizing the intermediate molecule, they found that it promoted the conversion of macrophages from the M1 phenotype to the M2 phenotype that does not stimulate inflammation. “We hope that the results from this study will enable investigators to test the relevance of the maresin pathway in human disease,” Dr. Serhan stated.

Editor’s Note: “We’ve known for a long time that DHA tames inflammation; now, we learn exactly how DHA works: via new substances called maresins,” commented Gerald Weissmann, MD, who is The FASEB Journal’s Editor-in-Chief. “We encounter inflammation almost daily, but our body has ways of turning it off. This is an important step toward understanding exactly how this happens. You’re likely to be hearing a lot more about maresins if, or when, new therapies arise from this discovery.”

The results of a meta-analysis described in an article published in the American Journal of Clinical Nutrition reaffirm the benefit of drinking green tea in maintaining glucose control among individuals at risk of metabolic syndrome.*

Researchers in China selected 17 trials that included a total of 1,133 participants for their analysis. Trials were limited to those in which subjects consumed green tea or an extract of green tea for at least two weeks and had fasting glucose or insulin measured before and after treatment, in addition to other criteria. Green tea catechin content ranged from 208 to 1,207 mg per day. Of the trials selected, nine involved participants who were overweight or obese, four included diabetics, two involved subjects with borderline diabetes, and two were limited to healthy participants.

Green tea intake was shown to be significantly associated with reductions in fasting glucose, insulin, and hemoglobin A1c, a marker of long-term glucose control.

Editor’s Note: Subgroup analyses determined that fasting glucose was reduced in participants at risk of metabolic syndrome but not in healthy subjects, and that green tea consumption was beneficial only when providing a level of catechins of at least 457 mg per day. Additional analysis of data extracted from high-quality trials indicated that green tea consumption significantly reduced fasting insulin.

In an article published in Science Translational Medicine, researchers from University Medical Center in Hamburg, Germany, and Lawrence Berkeley National Laboratory report a link between deficient levels of vitamin D and premature aging of the bone.*

Björn Busse and his associates compared bone obtained from 15 normal individuals and 15 men and women with deficient serum 25-hydroxyvitamin D3 levels of less than 20 ng/mL and bone surface osteoidosis indicating the transition to osteomalacia. The researchers found that the increase in osteoid-covered surfaces in bone derived from deficient subjects impaired the remodeling of mineralized bone tissue underneath due to isolation from osteoclasts. These areas of bone continued to age and mineralize, exhibiting the structure of older bone tissue, which is more brittle than young bone. Further testing revealed that being deficient in vitamin D increased the initiation of cracks by 31% and their growth by 22%.

Editor’s Note: “The assumption has been that the main problem with vitamin D deficiency is reduced mineralization for the creation of new bone mass, but we’ve shown that low levels of vitamin D also induce premature aging of existing bone,” stated report coauthor Robert Ritchie of Lawrence Berkeley Laboratory’s Materials Sciences Division.

In a collaboration between scientists from Spain, Venezuela, and England, a benefit for the B vitamin choline on attention and memory has been demonstrated in research involving rats.

Hayarelis Moreno-Gudiño and colleagues gave pregnant rats a standard diet, a diet enriched with choline, or a choline-deficient diet. Ten of the animals’ offspring were selected from each group upon reaching adulthood and tested for memory. While all of the animals were able to remember an object 24 hours after it was shown to them, those born to mothers who received extra choline during pregnancy were better able to recognize the object after 48 hours than animals born to mothers given a standard diet. Rats born to mothers provided with diets deficient in choline were unable to remember the object after two days, indicating a deleterious effect for prenatal choline deficiency on long-term memory.*

Editor’s Note: In another experiment, rats were given a diet supplemented with choline or an unsupplemented standard diet for 12 weeks prior to undergoing tests of attention.* Rats that received the choline-enriched diet maintained better attention than the control group when presented a familiar stimulus and demonstrated an improvement in learning.

Close on the heels of a US study published in May of this year that found an association between reduced vitamin D levels and a greater risk of uterine fibroids, a study of Italian women published in the Journal of Clinical Endocrinology & Metabolism has uncovered a similar finding.*

The current study age-matched each member of a group of 128 women who had at least one fibroid with two control subjects who did not have the condition. Among women with fibroids, serum 25-hydroxyvitamin D3 levels averaged 18 ng/mL, in comparison with 20.8 ng/mL in the control group. Vitamin D deficiency, defined as serum levels lower than 10 ng/mL, occurred in 15% of women with fibroids and in 7% of the controls, resulting in a 2.4 times greater risk of fibroids experienced by deficient women.

Editor’s Note: Uterine fibroids, or leiomyomas, are benign tumors that develop in or around the uterus which occur in a significant number of women. Although the majority of cases do not require treatment, the condition can result in pain, bleeding, urinary frequency, and other complications that can necessitate removal of the fibroids or, in some cases, the entire uterus.

An article published in the Journal of Nutrition reports the finding of an association between higher urinary concentrations of polyphenols measured in older men and women and a reduced risk of dying over a 12-year period.* Polyphenols are compounds that occur in plants that have been found to have antioxidant, anti-inflammatory, anti-obesity, and other effects.

The study included 807 men and women enrolled in the Invecchiare in Chianti study of older adults. Dietary questionnaires administered upon enrollment provided information on polyphenol intake and total urinary polyphenols were measured in urine samples. Over 12 years of follow-up, 66 participants died of cardiovascular disease, 112 died of cancer, and 72 deaths were due to other causes. Among participants whose total urinary polyphenols were among the top one-third of participants, the adjusted risk of dying over follow-up was 30% lower than those whose levels were among the lowest third.

Editor’s Note: While no significant association with mortality was found for dietary intake of polyphenols, the authors remark that validated biomarkers such as urinary polyphenols have an advantage over self-reported intake due to their independence from the biases and errors associated with self-reporting, and they note that food composition tables used to estimate intake were incomplete, resulting in underestimation.

The results of a meta-analysis published in the American Journal of Clinical Nutrition add evidence to a protective role for antioxidants against age-related cataracts.*

Researchers at Guangzhou Medical University and Jinan University in Guangzhou, China, selected 13 studies that included a total of 18,999 participants for their analysis. The studies evaluated the risk of cataracts in association with blood levels of vitamin A, vitamin C, vitamin E, alpha-carotene, beta-carotene, lutein, zeaxanthin, lycopene, and beta-cryptoxanthin.

When comparing lowest to highest blood antioxidant levels, having a high intake of vitamin E was associated with a 25% lower risk, alpha-carotene with a 28% lower risk, lutein with a 25% reduction, and zeaxanthin with a 30% decrease in the risk of cataract. Among Asian populations, having a high vitamin A and vitamin C levels were associated with a 31 and 33% risk reduction.

Editor’s Note: In their discussion, authors Yu-Hong Cui and associates remark that the results of studies evaluating the association between cataracts and dietary antioxidant intake have been inconsistent, possibly due to the imprecise nature of self-reporting, and they note that blood levels of antioxidants may be a better marker of antioxidant status than dietary intake.

A presentation at the 2013 Institute of Food Technologists Annual Meeting & Expo revealed a profound lack of omega-3 polyunsaturated fatty acids in the North American diet, despite what is known of their benefits.* Physicians and their patients are being made increasingly aware of the role of omega-3 fatty acids in the prevention or reduction of inflammatory disorders and cardiovascular disease, among other conditions.

Bruce J. Holub, PhD, of the University of Guelph, along with Alex Richardson, PhD, of the University of Oxford attribute the widespread omega-3 deficiency to diets that provide little in the way of fish or seafood, which are the best food sources of the omega-3 fatty acids EPA and DHA. The average North American diet provides 200 mg EPA and/or DHA per day, which falls short of the AHA’s recommendation of 500 mg per day for healthy adults and 900 mg per day for those with cardiovascular disease.

Editor’s Note: For children, Dr. Richardson suggests 500 mg omega-3 fatty acids per day.

A study published in the journal Neural Regeneration Research revealed a greater risk of deficient serum levels of vitamin D in patients who had undergone treatment at a neurosurgical intensive care unit (ICU).*

Je Hoon Jeong, MD, PhD, and colleagues evaluated serum 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D in 55 men and women who were hospitalized at a neurosurgical ICU. The results of blood testing for white blood cell count and neutrophil percentage indicated suspected infection in 15 patients, which was confirmed by sputum, urine, or blood bacterial culture in 10 patients.

In comparison with subjects who did not have signs of infection, serum 25-hydroxyvitamin D levels were significantly lower in both those with suspected and confirmed infection at all time points up to 28 days following admission.

Editor’s Note: The authors note that research has demonstrated a role for vitamin D in regulating normal innate and adaptive immunity, and that the active form of the vitamin has been shown to stimulate the innate immune system by elevating the production of interleukin-1 and increasing the proliferation of monocytes (a type of white blood cell).