Caffeine Boosts Blood Pressure and Stress Hormones All Day

People who drink four or five cups of coffee throughout the morning have slightly elevated blood pressure and higher levels of stress hormones all day and into the evening, creating a scenario in which the body acts like it is continually under stress, according to a group of Duke University Medical Center scientists.In a study of 72 habitual coffee drinkers, the researchers found that subjects produced more adrenaline and noradrenalin and had higher blood pressure on days when they drank caffeine compared with days they abstained. The two stress hormones are vital to helping the body react quickly in times of danger or stress, but they can damage the heart over a lifetime of heightened production, said James Lane, associate research professor of psychiatry at Duke.

Lane prepared results of his study, funded by the National Heart, Lung and Blood Institute, for presentation Thursday to a meeting of the 1999 Society of Behavioral Medicine.

“Moderate caffeine consumption makes a person react like he or she is having a very stressful day,” Lane said in an interview before the meeting. “If you combine the effects of real stress with the artificial boost in stress hormones that comes from caffeine, then you have compounded the effects considerably.”

During the two-week study, the subjects experienced, on average, a 32 percent increase in adrenalin and a 14 percent increase in noradrenaline on days when they consumed caffeine. Their blood pressure rose an average of 3 points.

Lane’s study builds on smaller ones in which he found that caffeine boosted blood pressure, heart rate and stress hormones in subjects who drank 4 to 5 cups of caffeine per day. In the current study, Lane replicated those findings and added to them by showing that subjects’ blood pressures and stress hormone levels stayed elevated until bedtime, even though they last consumed caffeine between noon and 1 p.m.

Occasional surges of stress hormones temporarily raise heart rate, blood pressure and mental acuity — long enough to accomplish the task at hand. But an excess of stress hormones has been shown to compromise health in a variety of ways, from damaging blood vessels to weakening the immune system.

In addition, even the small boost in blood pressure seen in this study — an average of 3 points during the day and evening — can have clinical significance, Lane said. A review of nine major studies of blood pressure and heart-disease risk showed that a 5-point difference in diastolic blood-pressure — the lower number used to assess health risk — was associated with at least a 34 percent increase in stroke and a 21 percent increase in the incidence of coronary heart disease

While researchers have long known that caffeine can boost stress hormones and blood pressure, Lane said most studies have been conducted in a laboratory setting under tightly controlled circumstances where a single dose of caffeine is compared to none in a short time span. Lane said his body of research is unique because it measures blood pressure, heart rate and stress hormone levels at timed intervals during normal working conditions, while subjects are exposed to a range of moods and activities.

“You can measure how caffeine affects people in the laboratory, but that doesn’t tell you what effects the drug has in the real world when people are exposed to normal stressors and activities,” he said.

In the current study, Lane also studied the effects of caffeine on women taking oral contraceptives, since previous research suggested that this population might be more responsive to the negative effects of caffeine. But Lane found no such effect. In fact, women taking oral contraceptives showed slightly less of a stress response to caffeine than a control group of women.

Lane’s next study will measure the effects of eliminating caffeine from the diets of people with high blood pressure. The goal is to see if stopping caffeine use can be a useful therapy in reducing hypertension, along with diet, exercise and salt reduction.

—————————-
Article adapted by MD Only Weblog from original press release.
—————————-

Contact: Rebecca A. Levine
Duke University Medical Center

Drinking coffee elevates plasma homocysteine raising risk of coronary heart disease

High plasma homocysteine concentration is associated with an increased risk of cardiovascular disease, and consumption of unfiltered and filtered coffee raises homocysteine levels. As yet, it is unclear which substances in brewed coffee are responsible for its homocysteine-raising properties. In an article published in this month’s American Journal of Clinical Nutrition, Verhoef et al. investigated the effects of caffeine alone and in brewed coffee on homocysteine concentrations in a group of healthy volunteers. Brewed coffee increased homocysteine levels within hours of consumption and seemed to have a particularly strong effect when taken after meals.

The 21 male and 27 female participants in the study, aged 19 to 65 years old, were all heavy coffee drinkers who consumed 6 or more cups of filtered or instant coffee daily. Thirty-one percent of the subjects were smokers, who are known to metabolize caffeine more rapidly than non-smokers. Three treatments, administered in random order for a period of 2 weeks each, consisted of either capsules containing 870mg of caffeine daily; 4 cups of strong filtered coffee that contained 870 mg of caffeine; or placebo capsules. Despite the fact that both treatments had a similar amount of caffeine, the average fasting homocysteine concentration rose by 11% after the subjects drank brewed coffee for 2 weeks, compared to a 5% increase after caffeine alone. The paper filter in the brewed coffee retained trace amounts of several substances that were suspected to be responsible for the rise in homocysteine concentrations, including chlorogenic acid (a polyphenolic compound) that is not removed by filtering.

Epidemiologic associatations between coffee consumption and CVD are conflicting; therefore, public health implications of the homocysteine-raising effects of caffeine and coffee will remain unclear until a causal relation between high homocysteine concentrations and CVD is proven.

—————————-
Article adapted by MD Only Weblog from original press release.
—————————-

Contact: Elizabeth Horowitz
American Journal of Clinical Nutrition

Verhoef, Petra et al. Contribution of caffeine to the homocysteine-raising effect of coffee: a randomized controlled trial in humans. Am J Clin Nutr 2002;76:1244-8.

This information should not be construed as medical advice. If you have a medical concern, consult your doctor. To see the complete text of this article, please go to:

http://www.faseb.org/ajcn/Dec2002/13024.Verhoef.PDF

Just Moderate Caffeine Use Boosts Blood Pressure, Potential For Heart Disease

Drinking a few extra mugs of coffee each day can boost blood pressure, heart rate and stress levels enough to increase a person’s risk of developing heart disease over a lifetime of moderate caffeine consumption, according to a Duke University researcher.In a study of 19 habitual coffee drinkers who wore “ambulatory” blood-pressure monitors throughout their daily jobs, the researcher found that the equivalent of four to five cups raised blood pressure an average of five points, compared to days when they consumed only one cup. The effect occurred within an hour of consumption, and the subjects’ blood pressure remained elevated throughout the day, the study found.

The volunteers also reported higher levels of stress during the day when they received the higher, 500-milligram dose of caffeine, and they showed a corresponding increase in heart rate, said James Lane, associate research professor of psychiatry at Duke and lead author of the study. Results of the study, funded by the National Heart, Lung and Blood Institute, are published in the May issue of the journal Psychosomatic Medicine.

While a 5-point increase in blood pressure is not excessive, it can have significant clinical implications over time, Lane said. A review of nine major studies of blood-pressure and cardiovascular-disease risk showed that a 5-point difference in diastolic blood pressure — the lower number used to assess health risk — was associated with at least a 34 percent increase in the incidence of stroke and a 21 percent increase in the incidence of coronary heart disease.

In another unrelated study, called the Hypertension Detection and Follow-up Program, researchers reported that reducing blood pressure by five points through medication was associated with a 20 percent reduction in 5-year mortality, Lane said.

“The relevant message here is that the more caffeine you consume during the day in coffee, tea or soft drinks, the higher your blood pressure is likely to be,” Lane said. “Over many years, this increase in blood pressure may heighten your risk of suffering a heart attack or stroke, even if you don’t have high blood pressure now.”

While researchers have long known that caffeine boosts blood pressure, nearly all the studies have been conducted in a laboratory setting under tightly controlled circumstances where a single dose of caffeine is compared to none in a short time span. Lane said his study is among the first to analyze blood pressure levels at 15-minute intervals during normal working conditions, while subjects were exposed to a range of moods and activities, from sitting to standing to walking.

“You can measure how caffeine affects people in the laboratory, but that doesn’t tell you what effects the drug has in the real world when people are exposed to normal stressors and activities,” he said.

In previous studies conducted over the past 15 years, Lane has shown that caffeine raises levels of adrenalin, the body’s major stress chemical, during everyday work activities, indicating that caffeine made the day more stressful. The question he wanted to answer in the current study was whether or not caffeine acted directly on blood pressure, or whether it elevated blood pressure through its effect on stress and activity levels.

By correlating the blood pressure readings with the subjects’ self-reports of their activities and moods throughout the day, the Duke researchers were able to rule out the possibility that caffeine was simply acting through a stress response or burst of physical activity.

“Essentially, we have demonstrated that the effects of caffeine on ambulatory blood pressure cannot be accounted for by changes in activity, posture (sitting, standing or walking) or perceived stress,” Lane said. “This strengthens the evidence that caffeine is working directly on blood pressure rather than through other mediating factors.”

—————————-
Article adapted by MD Only Weblog from original press release.
—————————-

Contact: Rebecca A. Levine
Duke University Medical Center

High sugar, low caffeine drink make you sleepy

An hour after consuming a high sugar, low caffeine drink you will tend to have slower reactions and experience more lapses in concentration than if you had simply drunk a decaffeinated, nil carbohydrate drink.

This was the finding of research performed at the University of Loughborough and published in Human Psychopharmacology: Clinical and Experimental.

Ten healthy adults had volunteered to restrict their sleep to 5 hours on the day before participating in the trial. An hour after eating a light lunch they were given either an energy drink (42g sugar + 30mg caffeine) or an identically tasting zero-sugar drink. They then performed a monotonous 90-minute test during the afternoon ‘dip’ that assessed their sleepiness and ability to concentrate.

For the first 30 minutes there was no difference in the reaction times or error rates, but 50 minutes after consuming the drinks, the performance of those who had had the energy drink started to slip, and they became significantly sleepier.

Other researched work shows that high energy drinks that contain caffeine will boost concentration.(1)

“A ’sugar rush’ is not very effective in combating sleepiness – so avoid soft drinks that contain lots of sugar but little or no caffeine,” explains Professor Jim Horne, who runs the Sleep Research Centre at the University of Loughborough. “A much better way to combat sleepiness is to have a drink that contains more useful amounts of caffeine and combine this with a short nap”.

—————————-
Article adapted by MD Only Weblog from original press release.
—————————-

Contact: Polly Young
John Wiley & Sons, Inc.

Notes to Editors

• Physiology & Behavior, 2002, 75: 331-335.

• Full citation: C. Anderson & J.A. Home. A high sugar content, low caffeine drink does not alleviate sleepiness but may worsen it. Hum Psychopharmacol Clin Exp 2006; 21: 1-5

• Human Psychopharmacology: Clinical and Experimental provides a forum for the evaluation of clinical and experimental research on both new and established psychotropic medicines. Experimental studies of other centrally active drugs, including herbal products, in clinical, social and psychological contexts, as well as clinical/scientific papers on drugs of abuse and drug dependency are also be considered. While the primary purpose of the journal is to publish the results of clinical research, the results of animal studies relevant to human psychopharmacology are welcome. The journal’s co-editors are Professor Stephen Curran of the University of Huddersfield, UK and Professor C. Lindsay DeVane of the Medical University of South Carolina, Charlestown, USA. Human Psychoparmacology can be accessed at: http://www.interscience.wiley.com/journal/hup

Caffeine Fuels “Unhealthy Pick-me-up” in Energy Drinks

Some carbonated sodas and energy drinks are loaded with caffeine and can give an unhealthy pick-me-up to unsuspecting consumers, University of Florida researchers warn.Because caffeine can pose health risks for people with certain medical conditions, beverages containing the additive should clearly list the amount they contain, a UF toxicologist recommends in a report assessing caffeine levels of cold beverages published this month in the Journal of Analytical Toxicology.

Bruce Goldberger, director of UF’s William R. Maples Center for Forensic Medicine, said the surprisingly high caffeine content in some beverages could present problems for pregnant women and children, and for adults with hypertension, heart disease or mental health ailments such as anxiety.

“We weren’t surprised that there was caffeine in the sodas and some of the other beverages,” said Goldberger, who is also director of toxicology and a professor of pathology and psychiatry at UF’s College of Medicine. The surprise, he said, was the high concentration of caffeine in some of the energy drinks, which exceeded the government’s recommendations for cold beverages.

The Food and Drug Administration recommends a maximum caffeine concentration of 65 milligrams per 12-ounce serving of cola beverages, though it does not regulate caffeine content of these drinks. And although the agency requires the presence of caffeine be disclosed, it does not mandate that caffeine quantity be specified on labeling for energy drinks and cold coffee beverages.

The UF team tested 10 energy drinks, 19 sodas and seven other beverages and found some energy drinks have up to 141 milligrams in a single serving – more than twice the content of some espresso coffee drinks.

The sodas tested, including Coca-Cola and Pepsi products, ranged from 0 to 48 milligrams a serving, well below the maximum recommended amount. A&W Root Beer, Sprite, 7-Up and Seagram’s Ginger Ale were among the caffeine-free drinks. However, the caffeine content of most energy drinks exceeded the maximum recommended limit. One energy drink with the highest caffeine content had a whopping 141 milligrams per serving, more than a double-shot cold espresso drink.

These drinks are often marketed as enhancing performance and stimulating metabolism and are sometimes described as being “highly vitalizing.” Yet in certain people, consumption of caffeine causes serious health effects, such as anxiety, palpitations, irritability, difficulty sleeping and stomach complaints, Goldberger said. Because the amount of caffeine is not labeled on the drinks’ packaging, pregnant women, children, infants or people with certain psychiatric diseases or anxiety conditions may unknowingly ingest too much, he added.

The American Dietetic Association suggests women avoid caffeine while pregnant or breastfeeding, citing findings from studies linking caffeine consumption to miscarriage and low-birth weight babies.

“There are many consequences that are relatively unknown to the general public because they consider the consumption of sodas and other beverages to be relatively safe,” Goldberger said. “People with psychiatric diseases could have manifestations of anxiety when they consume too much caffeine, people with hypertension could increase their heart rate if they consume caffeine.”

Roland Griffiths, a professor of behavioral biology in the Solomon H. Snyder department of neuroscience at Johns Hopkins University School of Medicine, said caffeine is the most widely used mood-altering drug in the world. Although caffeine is not considered highly toxic, physicians often recommend cutting back or eliminating caffeine consumption for patients who are pregnant or who have anxiety, panic attacks, insomnia or some kinds of stomach and heart conditions.

“Daily use of even relatively low doses of caffeine (about 100 milligrams a day) results in physical dependence, with abstinence characterized by withdrawal symptoms such as headache, fatigue, depressed mood and difficulty concentrating,” Griffiths said. “People should then make informed decisions about their caffeine use. Obviously, knowing how much caffeine a given product contains is critical to making an informed decision about use.”

Goldberger said many people are aware of their food’s nutritional content but most know little about the ingredients of their beverage, just whether it is sugar-free or regular. A few energy drinks have labels warning that the product is not recommended for children and pregnant women, but they do not specify the caffeine content.

“This study gives us some enlightenment on the caffeine content of beverages, and the importance of appropriate labeling,” Goldberger said.

—————————-
Article adapted by MD Only Weblog from original press release.
—————————-

Contact: Denise Trunk
University of Florida

Nutrition Standards For “Competitive” Foods and Drinks

Report Recommends Nutrition Standards For ‘Competitive’ Foods and Drinks Sold in Schools 

Spurred by the rising rate of obesity among American youth and the increasing availability of high-calorie, low-nutrient products on school grounds, a new report by the Institute of Medicine proposes a set of nutritional standards for “competitive” foods and drinks available in schools.  The standards promote consumption of fruits, vegetables, whole grains, and nonfat or low-fat dairy products and limit the amount of saturated fat, salt, added sugars, and total calories.  The standards also restrict the sale of caffeinated items. 

Developed by an IOM committee at the request of Congress, the standards apply to a la carte cafeteria items, products sold in vending machines and at school stores, and other foods and drinks that are available outside of — and therefore compete with — federally reimbursable school meals, which already must conform to some nutrition guidelines.  The proposed standards take into account the varying needs and responsibility levels of children and teens — for example, by limiting the sale of caffeine-free diet soda to high schools after school only, and by recommending smaller juice portions for younger children.   

“The alarming increase in childhood obesity rates has galvanized parents and schools across the nation to find ways to improve children’s diets and health, and we hope our report will assist that effort by setting standards for foods and beverages that have so far escaped any requirements,” said committee chair Virginia A. Stallings, Jean A. Cortner Endowed Chair in Pediatric Gastroenterology and director of the Nutrition Center, Children’s Hospital of Philadelphia; and professor of pediatrics, School of Medicine, University of Pennsylvania, Philadelphia.  “Making sure that all foods and drinks available in schools meet nutrition standards is one more way schools can help children establish lifelong healthy eating habits.” 

The committee proposed two tiers of competitive foods and beverages that could be available in schools based on grade level.  The standards apply only to competitive items sold or available on campuses, not to federal school meals or to bagged lunches or snacks that children bring to school.   

Tier 1 products should be allowed at all grade levels during the regular school day and during after-school activities involving students.  The foremost criterion of foods and drinks included in this category is that they provide at least one serving of fruits, vegetables, whole grains, or nonfat or low-fat dairy.  In addition, Tier 1 snacks contain no more than 200 calories per portion, and entrée items that could be sold a la carte do not exceed calorie limits on comparable school lunch program items.  Tier 1 items have no more than 200 milligrams of sodium per snack portion or 480 milligrams per a la carte entrée item.  They contain no more than 35 percent of total calories from fat; less than 10 percent of total calories from saturated fats; no trans fats; and no caffeine except in naturally occurring trace amounts.  They also contain no more than 35 percent of calories from total sugars; exceptions to this guideline are flavored milk, which may contain up to 22 grams of sugars per 8-ounce serving, and yogurt, which should not exceed 30 grams of sugars per 8-ounce portion.  

Examples of Tier 1 foods include whole fruit; raisins; carrot sticks; whole-grain, low-sugar cereals; some multigrain tortilla chips; some granola bars; and nonfat yogurt with no more than 30 grams of added sugars.  Examples of entrée items that meet the criteria are a fruit salad with yogurt or a turkey sandwich.  Tier 1 beverages are plain water, skim or 1 percent milk, soy beverages, and 100 percent fruit or vegetable juice.  Because of their calorie content, juices are capped at 4-ounce servings for elementary and middle-school students and 8-ounce portions for high school students.  

Unlike Tier 1 items, Tier 2 competitive foods and beverages do not necessarily provide a serving of vegetables, fruits, whole grains, or low-fat or nonfat dairy, but they otherwise conform to the U.S. Dietary Guidelines for Americans.  These items should be available to high school students only and after school only.  Like Tier 1 items, Tier 2 foods contain 200 calories or less per portion, 200 milligrams or less of sodium per portion, 35 percent or less of total calories from fat, less than 10 percent of total calories from saturated fats, no trans fats, no caffeine except in naturally occurring trace amounts, and no more than 35 percent of calories from total sugars.  Tier 2 drinks contain five or fewer calories per portion and no caffeine; they are not vitamin- or mineral-fortified, but may be carbonated and may contain flavoring or a sugar substitute.  

Examples of Tier 2 items include single servings of baked potato chips, low-sodium whole wheat crackers, graham crackers, pretzels, caffeine-free diet soda, and seltzer water.  Tier 2 beverages should be available only after school because students may otherwise forgo healthier choices such as milk and juice.  In addition, sports drinks should be available only to students engaged in an hour or more of vigorous athletic activity, at the discretion of coaches, the report says.  The committee recommended against making fortified water available as either a Tier 1 or 2 option.   

The committee did not support the sale of caffeinated products to school-age children because of the potential for negative effects, including headaches, moodiness, and other results that could disrupt students’ abilities to concentrate and learn.  Although caffeine-free diet soda can be an after-school option for high school students, the committee did not recommend for or against foods containing sugar substitutes.  While several studies indicate the overall safeness of consuming sugar substitutes, studies have not explored the effects of long-term consumption of these products starting in childhood.   

Schools should allow only Tier 1 products to be sold as fundraiser items on elementary and middle school campuses; high schools could allow Tier 2 items to be used for on-campus fundraising.  Schools should encourage products used in celebrations such as holiday parties to meet the standards.  Likewise, schools also should encourage foods and beverages sold at after-school and community events that include adults — such as athletic events and PTA meetings — to conform to the standards. The committee was not asked to recommend a plan for implementing the proposed standards.  However, it noted that schools will need technical and financial support.  Federal agencies should work with the food and beverage industries to develop a system for identifying products that meet the Tier 1 and Tier 2 criteria to help food service personnel more readily evaluate items.     

The study was sponsored by the Centers for Disease Control and Prevention.  Established in 1970 under the charter of the National Academy of Sciences, the Institute of Medicine provides independent, objective, evidence-based advice to policymakers, health professionals, the private sector, and the public.  The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies.  A committee roster follows.   

—————————-
Article adapted by MD Only Weblog from original press release.
—————————-

Contact: Christine Stencel
National Academies Press

Copies of Nutrition Standards for Foods in Schools: Leading the Way Toward Healthier Youth are available from the National Academies Press;