Eating a diet rich in fibre has long been known to help keep your digestive tract working properly. It’s also thought to lower the risk of heart disease, some cancers and diabetes. Now, a new study suggests it could reduce the risk of death from cardiovascular, infectious and respiratory diseases. People who ate a high-fibre diet decreased their risk of dying over a nine year period compared to those who ate less fibre, according to a new study in the Archives of Internal Medicine.
The findings are based on a diet study from the National Institutes of Health and AARP, which included 219,123 men and 168,999 women ages 50 to 71 when the study began. Researchers from the National Cancer Institute examined food surveys completed by the participants in 1995 or 1996. After nine years about 11,000 people died and researchers used national records to determine the cause.
People who ate at least 26 grams per day were 22 percent less likely to die than those who consumed the least amount of fibre — about 13 grams per day or less. Men and women who consumed diets higher in fibre also had a reduced risk of cardiovascular, infectious and respiratory diseases, the study found. Getting fibre from grains seemed to have the biggest impact, the authors write.
The study has some limitations — mainly, people who ate high-fibre diets might also have been more likely to eat healthier diets overall, attributing to their longevity. Still, the study offers more evidence that fibre is certainly good for you. Federal dietary guidelines recommend people consume at least 14 grams of fibre per 1,000 calories, so about 28 grams for an average 2,000 calorie-per-day diet. But many experts say many people don’t get enough.
The vitamin D levels of newborn babies appear to predict their risk of respiratory infections during infancy and the occurrence of wheezing during early childhood, but not the risk of developing asthma. Results of a study in the January 2011 issue of Pediatrics support the theory that widespread vitamin D deficiency contributes to risk of infections.
“Our data suggest that the association between vitamin D and wheezing, which can be a symptom of many respiratory diseases and not just asthma, is largely due to respiratory infections,” says Carlos Camargo, MD, DrPH, of the Massachusetts General Hospital (MGH), who led the study. “Acute respiratory infections are a major health problem in children. For example, bronchiolitis – a viral illness that affects small airway passages in the lungs – is the leading cause of hospitalization in U.S. infants.”
Although vitamin D is commonly associated with its role in developing and maintaining strong bones, recent evidence suggests that it is also critical to the immune system. Vitamin D is produced by the body in response to sunlight, and achieving adequate levels in winter can be challenging, especially in regions with significant seasonal variation in sunlight. Previous studies by Camargo's team found that children of women who took vitamin D supplements during pregnancy were less likely to develop wheezing during childhood. The current study was designed to examine the relationship between the actual blood levels of vitamin D of newborns and the risk of respiratory infection, wheezing and asthma.
The researchers analyzed data from the New Zealand Asthma and Allergy Cohort Study, which followed more than 1,000 children in the cities of Wellington and Christchurch. Midwives or study nurses gathered a range of measures, including samples of umbilical cord blood, from newborns whose mothers enrolled them in the study. The mothers subsequently answered questionnaires – which among other items asked about respiratory and other infectious diseases, the incidence of wheezing, and any diagnosis of asthma – 3 and 15 months later and then annually until the children were 5 years old. The cord blood samples were analyzed for levels of 25-hydroxyvitamin D (25OHD) – considered to be the best measure of vitamin D status.
Cord blood samples were available from 922 newborns in the study cohort, and more than 20 percent of them had 25OHD levels less than 25 nmol/L, which is considered very low. The average level of 44 nmol/L would still be considered deficient – some believe that the target level for most individuals should be as high as 100 nmol/L – and lower levels were more common among children born in winter, of lower socioeconomic status and with familial histories of asthma and smoking. By the age of 3 month, infants with 25OHD levels below 25 nmol/L were twice as like to have developed respiratory infections as those with levels of 75 nmol/L or higher.
Survey results covering the first five years of the participants' lives showed that, the lower the neonatal 25OHD level, the higher the cumulative risk of wheezing during that period. But no significant association was seen between 25OHD levels and a physician diagnosis of asthma at age 5 years. Some previous studies had suggested that particularly high levels of vitamin D might increase the risk for allergies, but no such association was seen among study participants with the highest 25OHD levels. Camargo notes that very few children in this study took supplements; their vitamin D status was determined primarily by exposure to sunlight.
An associate professor of Medicine at Harvard Medical School, Camargo notes that the study results do not mean that vitamin D levels are unimportant for people with asthma. “There's a likely difference here between what causes asthma and what causes existing asthma to get worse. Since respiratory infections are the most common cause of asthma exacerbations, vitamin D supplements may help to prevent those events, particularly during the fall and winter when vitamin D levels decline and exacerbations are more common. That idea needs to be tested in a randomized clinical trial, which we hope to do next year.”
Co-authors of the Pediatrics paper are Ravi Thadhani, MD, and Janice Espinola, MPH, from MGH; Tristram Ingham, MBChB, Kristin Wickens, PhD, and Julian Crane, FRACP, from University of Otaga, Wellington, New Zealand; Karen Silvers, PhD, Michael Epton, PhD, FRACP, and Philip Pattemore, MD, FRACP, from University of Otago, Christchurch, NZ; and Ian Town, DM, from University of Canterbury, Christchurch, NZ. The study was supported by grants from the Health Research Council of New Zealand, the David and Cassie Anderson Bequest and the MGH Center for D-receptor Activation Research.
“However,” the researcher said, “there is a lack of clinical studies of the effect of vitamin D supplementation for preventing respiratory infections.”
For the current study, Laaksi's team randomly assigned 164 male military recruits to take either 400 international units (IU) of vitamin D or inactive placebo pills every day for six months — from October to March, covering the months when people's vitamin D stores typically decline and when respiratory infections typically peak.
At the end of the study, the researchers found no clear difference between the two groups in the average number of days missed from duty due to a respiratory infection — which included bronchitis, sinus infections, pneumonia, ear infections and sore throat.
On average, men who took vitamin D missed about two days from duty because of a respiratory infection, compared with three days in the placebo group. That difference was not significant in statistical terms.
However, men in the vitamin D group were more likely to have no days missed from work due to a respiratory illness.
Overall, 51 percent remained “healthy” throughout the six-month study, versus 36 percent of the placebo group, the researchers report.
The findings, Laaksi said, offer “some evidence” of a benefit from vitamin D against respiratory infections.
Still, the extent of the benefit was not clear. While recruits in the vitamin group were more likely to have no days missed from duty, they were no less likely to report having cold-like symptoms at some point during the study period.
Moreover, recent studies on the usefulness of vitamin D for warding off respiratory ills have come to conflicting conclusions.
A study of Japanese schoolchildren published earlier this year found that those given 1,200 IU of vitamin D each day during cold and flu season were less likely to contract influenza A. Of 167 children given the supplement, 18 developed the flu, compared with 31 of 167 children given placebo pills.
On the other hand, a recent study of 162 adults found that those who took 2,000 IU of vitamin D everyday for 12 weeks were no less likely to develop respiratory infections than those given placebo pills.
Laaksi said that larger clinical trials looking at different doses of vitamin D are still needed before the vitamin can be recommended for curbing the risk of respiratory infections.
In the U.S., health officials recommend that adults up to the age of 50 get 200 IU of vitamin D each day, while older adults should get 400 to 600 IU. The upper limit is currently set at 2,000 IU per day; higher intakes may raise the risks of side effects.
Symptoms of vitamin D toxicity are often vague and include nausea, vomiting, constipation, poor appetite and weight loss. Excessive vitamin D in the blood can also raise blood pressure or trigger heart rhythm abnormalities.
Some researchers believe that people need more vitamin D than is currently recommended, and that intakes above 2,000 IU per day are safe. However, exactly what the optimal vitamin D intake might be remains under debate.
Food sources of vitamin D include milk, breakfast cereals and orange juice fortified with vitamin D, as well as some fatty fish, like salmon and mackerel. Experts generally recommend vitamin pills for people who do not get enough of the vitamin from food.
SOURCE: Journal of Infectious Diseases
The factors instrumental in triggering latent tuberculosis (TB) infection to progress into active disease have long remained elusive to researchers. New insight into the mystery is provided by Professor David Russell, speaking at the Society for General Microbiology's spring meeting in Edinburgh today. His work could help develop innovative strategies for treating the disease.
Professor Russell and his group at Cornell University in New York, USA, have demonstrated that TB-causing bacteria are able to hijack fat metabolism in the host to drive the progression of the disease. The team's research shows that Mycobacterium tuberculosis (Mtb) is able to stimulate macrophages – the immune cells the bacterium infects – to accumulate fat droplets, turning them into “foamy” cells. This cellular transformation can trigger a reawakening of the TB infection from its latent state.
Following initial infection by Mtb, the infected immune cells in the body can clump together in the lungs in a cellular mass that is surrounded by a fibrous cuff. This containing structure, called a
tubercle, physically protects the bacteria from being destroyed by the immune system. This allows them to persist inside the host for years during a latent period in which the host shows no symptoms. The respiratory infection is reactivated only in a small percentage of individuals (often those who are immunosuppressed) in whom it progressively destroys lung tissue. Very little is known about the exact causes of reactivation and the relative roles of the host and the pathogen.
Professor Russell's group discovered that inside the tubercle, surface molecules of Mtb prompted host macrophage cells to take up vast quantities of cholesterol-type lipids from the surrounding blood
vessels. “We think that the lipids in the newly-formed foamy cell are then expelled into the cellular environment, which contributes to the collapse of the tubercle,” he said.
Once freed from their containing structure, the infectious bacteria are able to leak out into the airways where they can progressively destroy lung tissue. “If our model is correct, it has huge implications for
vaccines and chemotherapy programmes. A more detailed knowledge of the bacterium's life cycle and its host interactions will allow us to spot new targets for drugs – opening up new possibilities for treatment,” said Professor Russell.
For pulmonary ailments, certain mediaeval physicians had a useful medical textbook on hand offering detailed information remarkably similar to those a modern doctor might use today. One of the fathers of medicine, the great Persian scholar Avicenna left a wealth of information in his many works. Iranian academics dust off one of these in an article published today in the SAGE journal Therapeutic Advances in Respiratory Disease, sharing in English details of Avicenna's work that still fascinate both physicians and historians of medicine alike.
Seyyed Mehdi Hashemi and Mohsen Raza dug deep into Avicenna's original ancient text, housed in the Central Library of the Tehran University of Medical Sciences in Iran, where they both work. In particular, they aimed to highlight Avicenna's work on respiratory diseases, which may be informative or interesting to physicians and pulmonologists today.
Avicenna discusses respiratory diseases in volume three of the Canon of Medicine, covering the functional anatomy and physiopathology of the pulmonary diseases that were known in his time in detail. His descriptions of the signs and symptoms of various respiratory diseases and conditions are remarkably similar to those found in modern pulmonary medicine. The topic is covered under five chapters: breathing, voice, cough and haemoptysis, internal wounds and inflammations and principles of treatments.
The authors also highlight both herbal and non-herbal treatments Avicenna recommends for respiratory diseases, and their signs and symptoms from the second volume of the Canon of Medicine. Avicenna suggested 21 herbs to treat respiratory disorders, and today we know that several of these herbs contain bioactive compounds with analgesic, antispasmodic, bronchodilatory or antimicrobial activities. For instance, Avicenna would have prescribed opium at that time for cough and haemoptysis, a practice which today has an established therapeutic basis.
“In the time of Avicenna, the presentation of respiratory diseases, their treatment and their prognosis was much different than in modern times,” says Hashemi. Mediaeval physicians had a greater reliance on history, physical examination (which was mostly based on visual observation), individual variation, environmental factors, diet, and so on, for diagnosis and treatment.
Even so, several of Avicenna's observations related to signs and symptoms, aggravating and relieving factors and the treatment of pulmonary disorders are still valid and can be explained by modern science. For example, one of the important symptoms in the diagnosis of asthma that Avicenna discusses is dyspnea during sleep that leads to awakening. Avicenna also observed plaster-like material in tuberculosis patients' sputum, which is now known as lithoptysis (stone spitting), where a patient coughs up calcified material due to perforated bronchial lymph node.
Despite many limitations and the lack of modern instruments in his day, Avicenna adopted a scientific approach to the diagnosis and treatment, not only of respiratory disorders, but also more generally to illnesses he treated and mentioned throughout the Canon of Medicine.