Exercise helps us to eat a healthy diet

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A healthy diet and the right amount of exercise are key players in treating and preventing obesity but we still know little about the relationship both factors have with each other. A new study now reveals that an increase in physical activity is linked to an improvement in diet quality.

Many questions arise when trying to lose weight. Would it be better to start on a diet and then do exercise, or the other way around? And how much does one compensate the other?

The data from epidemiological studies suggest that tendencies towards a healthy diet and the right amount of physical exercise often come hand in hand. Furthermore, an increase in physical activity is usually linked to a parallel improvement in diet quality.

Exercise also brings benefits such as an increase in sensitivity to physiological signs of fullness. This not only means that appetite can be controlled better but it also modifies hedonic responses to food stimuli. Therefore, benefits can be classified as those that occur in the short term (of metabolic predominance) and those that are seen in the long term (of behavioural predominance).

According to Alonso Alonso, "physical exercise seems to encourage a healthy diet. In fact, when exercise is added to a weight-loss diet, treatment of obesity is more successful and the diet is adhered to in the long run."

The authors of the study state how important it is for social policy to encourage and facilitate sport and physical exercise amongst the population. This should be present in both schools and our urban environment or daily lives through the use of public transport or availability of pedestrianised areas and sports facilities.

Exercise modifies the brain

Eating and physical activity are behaviours and are therefore influenced by cognitive processes that are a result of activity in different areas of the brain. Previous studies have already assessed changes in the brain and cognitive functions in relation to exercise: regular physical exercise causes changes in the working and structure of the brain.

The experts point out that these changes seem to have a certain specificity. The Harvard researcher supports the notion that "regular exercise improves output in tests that measure the state of the brain's executive functions and increases the amount of grey matter and prefrontal connections."

Inhibitory control is one of the executive functions of the brain and is basically the ability to suppress inadequate and non-conforming answers to an aim (the opposite of this would be impulsiveness), which makes modification or self-regulations of a behaviour possible.

With regards to losing weight and sustaining weight loss in the long run, various recent studies suggest that executive functions such as inhibitory control and optimal functioning of the brain's prefrontal areas could be the key to success. This success is mainly the fruit of a behavioural change. Inhibitory control could also help to prevent weight gain in healthy people.

The researcher outlines that "in time, exercise produces a potentiating effect of executive functions including the ability for inhibitory control, which can help us to resist the many temptations that we are faced with everyday in a society where food, especially hypercaloric food, is more and more omnipresent."

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The scoop on the dangers of snow shoveling

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Urban legend warns shoveling snow causes heart attacks, and the legend seems all too accurate, especially for male wintery excavators with a family history of premature cardiovascular disease. However, until recently this warning was based on anecdotal reports.

Two of the most important cardiology associations in the US include snow -shoveling on their websites as a high risk physical activity, but all the citation references indicate that this warning was based one or two incidents.

“We thought that this evidence should not be enough to convince us that snow -shoveling is potentially dangerous, ” says Adrian Baranchuk, a professor in Queen’s School of Medicine and a cardiologist at Kingston General Hospital.

Dr. Baranchuk and his team retrospectively reviewed KGH patient records from the two previous winter seasons and discovered that of the 500 patients who came to the hospital with heart problems during this period, 7 per cent (35 patients) had started experiencing symptoms while shoveling snow.

“That is a huge number,” says Dr. Baranchuk. “7 per cent of anything in medicine is a significant proportion. Also, if we take into account that we may have missed some patients who did not mention that they were shoveling snow around the time that the episode occurred, that number could easily double.”

The team also identified three main factors that put individuals at a high risk when shoveling snow. The number one factor was gender (31 of the 35 patients were male), the second was a family history of premature coronary artery disease (20 of the 35 patients), and the third was smoking (16 out of 35 patients). The second two factors may carry much more weight than the first, however, since the team could not correct for high rate of snow shoveling among men in their sample.

A history of regularly taking four or more cardiac medications was found to be preventative.

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Thanksgiving: BPA for Families Using Canned Foods

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Plus, Myths and Facts about BPA in Canned Foods and Recipes for a BPA-Free Thanksgiving at www.breastcancerfund.org/thanksgiving

A new report released today by the Breast Cancer Fund documents the presence of the toxic chemical bisphenol A (BPA) in canned foods used to prepare a typical Thanksgiving meal.

The report, "BPA in Thanksgiving Canned Food," tested Campbell's Cream of Mushroom Soup, Campbell's Turkey Gravy, Carnation Evaporated Milk (by Nestle), Del Monte Fresh Cut Sweet Corn (Cream Style), Green Giant Cut Green Beans (by General Mills), Libby's Pumpkin (by Nestle), and Ocean Spray Jellied Cranberry Sauce. Single servings of almost half of the products tested had levels of BPA comparable to levels that laboratory studies have linked to adverse health effects.

"Preparing your Thanksgiving dinner with these products can deliver a concerning level of BPA," said Jeanne Rizzo, president and CEO of the Breast Cancer Fund. "How many more Thanksgivings will families have to worry about this uninvited guest before manufacturers finally decide to take it out of cans?"

BPA is used to make, among other things, the epoxy-resin linings of metal food cans. The lining forms a barrier between the metal and the food which helps to prevent bacterial contamination. However, the toxic chemical can leach from the resin and make its way into food. BPA has been linked in laboratory studies to adverse health effects such as breast and prostate cancer, infertility, early puberty in girls, type-2 diabetes, obesity and attention deficit hyperactivity disorder.

For this report, the Breast Cancer Fund sent 28 canned food items—four cans of each product tested—to Anresco Laboratories, an independent testing laboratory in San Francisco. The testing revealed tremendous variability among cans of the same product made by the same company, which is consistent with other product testing data.

For instance, BPA levels in Del Monte creamed corn ranged from non-detectable to 221 parts per billion, and levels in Campbell's Turkey Gravy ranged from 5 to 125 ppb. According to scientists at the Breast Cancer Fund, these inconsistencies might be explained by variations in the canning processes across facilities and batches, as well as storage and transportation conditions.

"Consumers have no way of assessing BPA levels just by looking at cans on supermarket shelves," said Gretchen Lee Salter, policy manager at the Breast Cancer Fund. "The findings of this report highlight the urgent need to remove BPA from food packaging so that shoppers can be confident that the food they are purchasing is safe for their families—not only on Thanksgiving, but every day."

The tests detected no BPA in any of the four cans of Ocean Spray Cranberry Sauce. The company has stated that while it does use BPA in its cans, independent tests also indicate no leaching of BPA into the food.

"We know from recent research that a BPA meal creates a spike of this estrogenic chemical in the blood," said William Goodson, M.D., a breast cancer surgeon and senior clinical research scientist at California Pacific Medical Center Research Institute, who in September published a study showing that BPA causes non-cancerous cells to grow and survive like cancer cells. "Natural hormones work by spikes, so this is exactly what you don't want, especially in young kids, who shouldn't have any estrogenic spikes at all." 

As part of the Breast Cancer Fund's Cans Not Cancer campaign, consumers have sent more than 50,000 letters to canned food manufacturers urging them to get BPA out of canned foods and replaced with a safer alternative, and many are beginning to pay attention. A number of companies including some of the can manufacturers featured in this report, such as General Mills and Nestle, have announced that they are working toward alternatives to BPA in canned foods. However, not all of the manufacturers are disclosing the alternative they are exploring. It is imperative that manufacturers are transparent about these alternatives and ensure they are safe.

At the public policy level, 11 states have banned BPA from baby bottles and sippy cups, and three of those states have also banned it from infant formula and baby food. The Breast Cancer Fund is also supporting pending federal legislation authored by Rep. Ed Markey, D-Mass., that would ban BPA from all food and beverage containers including canned foods.

The immediate solution for those preparing Thanksgiving dinner is to seek alternatives to canned foods. Visit www.breastcancerfund.org/thanksgiving for easy recipes for a can-free Thanksgiving meal.

Also available at www.breastcancerfund.org/thanksgiving are the full report and Myths and Facts about BPA in Canned Foods, combating the common industry arguments in favor of BPA.

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Coffee may protect against endometrial cancer

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Long-term coffee consumption may be associated with a reduced risk for endometrial cancer, according to a recent study in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.

Edward Giovannucci, M.D., Sc.D., professor of nutrition and epidemiology at the Harvard School of Public Health, said coffee is emerging as a protective agent in cancers that are linked to obesity, estrogen and insulin.

"Coffee has already been shown to be protective against diabetes due to its effect on insulin," said Giovannucci, a senior researcher on the study. "So we hypothesized that we'd see a reduction in some cancers as well."

Giovannucci, along with Youjin Je, a doctoral candidate in his lab, and colleagues observed cumulative coffee intake in relation to endometrial cancer in 67,470 women who enrolled in the Nurses' Health Study.

During the course of 26 years of follow-up, researchers documented 672 cases of endometrial cancer.

Drinking more than four cups of coffee per day was linked with a 25 percent reduced risk for endometrial cancer. Drinking between two and three cups per day was linked with a 7 percent reduced risk.

A similar link was seen in decaffeinated coffee, where drinking more than two cups per day was linked with a 22 percent reduced risk for endometrial cancer.

Giovannucci said he hopes this study will lead to further inquiries about the effect of coffee on cancer because in this and similar studies, coffee intake is self-selected and not randomized.

"Coffee has long been linked with smoking, and if you drink coffee and smoke, the positive effects of coffee are going to be more than outweighed by the negative effects of smoking," said Giovannucci. "However, laboratory testing has found that coffee has much more antioxidants than most vegetables and fruits."

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Consuming canned soup linked to greatly elevated levels of the chemical BPA

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BPA, found in soup can lining, associated with adverse health effects in humans

A new study from researchers at the Harvard School of Public Health (HSPH) has found that a group of volunteers who consumed a serving of canned soup each day for five days had a more than 1,000% increase in urinary bisphenol A (BPA) concentrations compared with when the same individuals consumed fresh soup daily for five days. The study is one of the first to quantify BPA levels in humans after ingestion of canned foods.

The findings were published online November 22, 2011, in the Journal of the Medical Association (JAMA) and will appear in the November 23/30 print issue.

"Previous studies have linked elevated BPA levels with adverse health effects. The next step was to figure out how people are getting exposed to BPA. We've known for a while that drinking beverages that have been stored in certain hard plastics can increase the amount of BPA in your body. This study suggests that canned foods may be an even greater concern, especially given their wide use," said Jenny Carwile, a doctoral student in the Department of Epidemiology at HSPH and lead author of the study.

Exposure to the endocrine-disrupting chemical BPA, used in the lining of metal food and beverage cans, has been shown to interfere with reproductive development in animals and has been linked with cardiovascular disease, diabetes, and obesity in humans. In addition to the lining of food and beverage cans, BPA is also found in polycarbonate bottles (identified by the recycling number 7) and dentistry composites and sealants.

The researchers, led by Carwile and Karin Michels, associate professor in the Department of Epidemiology, set out to quantify whether canned-soup consumption would increase urinary BPA concentrations relative to eating fresh soup.

They recruited student and staff volunteers from HSPH. One group consumed a 12-ounce serving of vegetarian canned soup each day for five days; another group consumed 12 ounces of vegetarian fresh soup (prepared without canned ingredients) daily for five days. After a two-day "washout" period, the groups reversed their assignments.

Urine samples of the 75 volunteers taken during the testing showed that consumption of a serving of canned soup daily was associated with a 1,221% increase in BPA compared to levels in urine collected after consumption of fresh soup.

The researchers note that the elevation in urinary BPA concentrations may be temporary and that further research is needed to quantify its duration.

"The magnitude of the rise in urinary BPA we observed after just one serving of soup was unexpected and may be of concern among individuals who regularly consume foods from cans or drink several canned beverages daily. It may be advisable for manufacturers to consider eliminating BPA from can linings," said Michels, senior author of the study.

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Low salt intake as bad as high

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For years doctors have warned that too much salt is bad for your heart. Now a new McMaster University study suggests that both high and low levels of salt intake may put people with heart disease or diabetes at increased risk of cardiovascular complications.

The study, published in the Journal of the American Medical Association (JAMA) today, found that moderate salt intake was associated with the lowest risk of cardiovascular events, while a higher intake of sodium was associated with an increased risk of stroke, heart attack and other cardiovascular events and a low intake was associated with an increased risk of cardiovascular death and hospitalization for congestive heart failure.

The research, conducted by investigators in the Michael G. DeGroote School of Medicine at McMaster University and the Population Health Research Institute (PHRI) at McMaster and Hamilton Health Sciences, was co-led by Dr. Martin O'Donnell, an associate clinical professor of medicine, and Dr. Salim Yusuf, a professor of medicine and executive director of the PHRI.

"This research addresses an important population health issue – the association between salt intake and cardiovascular disease," said O'Donnell, who is also appointed at the Health Research Board Clinical Research Facility, National University of Ireland.

"In general, previous observational studies have either reported a positive association, no association or an inverse association between sodium intake and heart disease and stroke. This has resulted in a lot of controversy. Our study is the first to report a J-shaped association between sodium intake and cardiovascular disease, which may explain why previous studies have found different results."

For the McMaster observational study, the researchers examined 28,880 people at increased risk of heart disease from clinical trials conducted between 2001 and 2008. The researchers estimated 24-hour urinary sodium and potassium excretion from a morning fasting urine sample. Follow-up found more than 4,500 cardiovascular events occurred, making this one of the largest studies examining the relationship between sodium excretion (a surrogate measure of sodium consumption), as well as potassium excretion and cardiovascular events. Extensive and careful statistical analytic methods were used to determine the association of urinary sodium and potassium with cardiovascular events, in particular heart attack, stroke, hospitalization for congestive heart failure and death.

Compared with moderate sodium excretion (between 4 to 5.99 grams per day), the researchers found that sodium excretion of greater than seven grams per day was associated with an increased risk of all cardiovascular events, and sodium excretion of less than three grams per day was associated with an increased risk of cardiovascular death and hospitalization for congestive heart failure.

The findings call into question current guidelines for salt intake, which recommend less than 2.3 grams (or 2,300 mg) per day. The guidelines are mostly based on previous clinical trials that found blood pressure is lowered modestly when sodium intake is reduced to this level (which was also found in the present study). However, there are no large studies looking at whether such low levels of sodium intake reduce the incidence of heart attacks and stroke.

Clarifying the optimal daily intake of sodium is particularly important in patients with established heart disease, as they may be especially vulnerable to the cardiovascular effects of very high- and low-salt intake and are most likely to receive recommendations on restricting sodium in their diets, the authors concluded.

"Our study confirms the association between high-sodium intake and cardiovascular disease. Our findings highlight the importance of reducing salt intake in those consuming high-salt diets and the need for reducing sodium content in manufactured foods that are high in salt," said Yusuf, who is also vice-president of research, Hamilton Health Sciences.

"However, for those with moderate (average) intake, whether further reduction of salt in the diet will be beneficial is an open question. We believe that large clinical trials are the most reliable way to determine if reducing sodium intake to lower levels is of benefit."

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L-arginine: fit, young, athletic men - no advantage

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Popular supplement goes under the microscope, reveals no metabolic or hormonal enhancement for athletes at rest

One of the most recent, popular supplements for athletes looking to boost performance comes in the form of a naturally-occurring amino acid called L-arginine.

The reason for its popularity is twofold says Scott Forbes, a doctoral student in exercise physiology. "First, L-arginine is a precursor for nitric oxide that is known to improve blood flow, which in turn may aid the delivery of important nutrients to working muscles and assist with metabolic waste product removal. Secondly, L-arginine has been shown to increase growth hormone levels in the blood."

The benefits of growth hormone are diverse, including increasing the use of fat as a fuel as well as insulin and insulin-growth factor-1 (IGF-1) levels. However, most of the research conducted on L-arginine has been in a clinical setting and the benefits for physically active individuals are not as established. In some cases they are conflicting.

"One of the reasons for this is that the amount an individual has to consume has not been clearly established and this information is rarely provided by the manufacturers of such products," explains Forbes, a doctoral student in exercise physiology.

For Forbes it was a theory worth testing – and he wanted to test two different L-arginine doses on healthy, athletic men – the group most likely to purchase this readily-available supplement.

"L-arginine is interesting for a few reasons," says Forbes. "It can increase growth hormone response, and so can increase muscle mass. Also it has an impact on insulin, which is another anabolic hormone. A recent hot topic has been about nitric oxide as a vasodilator. The theory is that if you can vasodilate your arteries you can potentially enhance blood flow to the muscles and enhance nutrient delivery and waste product removal."

L-arginine is also often prescribed for older adults with cardiovascular disease, endothelial dysfunction or hypertension for its vasodilation properties and is rarely studied in younger, more vigorous populations.

For this study, Forbes recruited 14, active, physically fit men (age: 25±5yrs; weight: 78.0±8.5kg; height: 179.4±4.7cm), who were free of nutritional supplements, to examine a low and high dose of oral L-arginine on blood L-arginine, markers of nitric oxide, growth hormone, insulin, and insulin-like growth factor-1. In the double-blind, randomized, placebo-controlled study participants were first pre-screened, completing a one-day food record which was analyzed for carbohydrates, protein and fat consumption and caloric intake, then required to follow a modified diet to regulate intake of food and water prior to being dosed with L-arginine.

"After a 10-hour overnight fast, and no breakfast, we gave them a different dose of L-arginine – either .075 g per kilogram of body mass for the low dose, .15 g per kg of body mass for the high dose, or a placebo," says Forbes.

Blood samples were drawn with the athlete at rest, every half hour for three hours after the L-arginine or placebo dose. The reason explains Forbes, is that "Previous studies show that two hours after consumption L-arginine tends to reach baseline again."

What Forbes found was that in healthy, young, physically active males the two different doses significantly elevated L-arginine concentrations in the blood at rest, and both a low dose and a high dose were equally effective in doing so, but neither dose promoted a significant increase in nitric oxide, growth hormone, insulin, or insulin-like growth factor-1.

So, according to the study, it appears that L-arginine's impact depends on one's current health status: the more healthy and athletic the person, the less they'll benefit from it.

Now that he's established how L-arginine impacts the fit, young body at rest, he's embarked on two more studies – one with strength-trained athletes and one with aerobically-trained athletes – cyclists in this case – to look at the impacts of L-arginine on the body during exercise. "This time we're looking at the effects of supplements under two extremes: aerobic and strength exercise.

"There's a lot of money in nutritional supplements," he adds. "The industry might not be too happy when they see the results at rest, but who knows, it may be different with exercise."

Forbes has completed both of the exercise studies and hopes to publish the results in the near future.

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