Highlight HEALTH

Here’s another reason to enjoy your coffee. A recent study in the July edition of the Journal Hepatology found a significant inverse association (meaning opposingly related; an increase in one variable results in a decrease in another) between coffee drinking and the risk of primary liver cancer [1]. The study also found that serum levels of an antioxidant enzyme, elevated in people with low coffee consumption, were associated with an increased risk of developing the disease.

photo credit: Marcelo Alves

Primary liver and bile duct cancers are the sixth most common cause of cancer death in men and the tenth most common cause of cancer death in women [2]. Hepatitis B and C viral infections have been identified as causative factors in greater than 75% of liver cancers worldwide [3]. Interestingly, incidence rates are low in most developed countries except for Japan, where coffee drinking is relatively uncommon. Several studies have also identified an inverse association between coffee consumption and serum levels of gamma-glutamyltransferase (GGT), an enzyme involved in glutathione metabolism [4-5]. Glutathione plays important roles in antioxidant defense, nutrient defense and regulation of a variety of cellular events [6].

Residents of Finland consume more coffee per capita than the Japanese, Americans, Italians and other Europeans. University of Helsinki researchers examined the associations between coffee consumption and serum GGT levels in 60,323 Finnish participants between the ages of 25 and 74 who were cancer-free at the beginning of the study.

Participants were mailed a questionnaire about their medical history, socioeconomic factors, smoking habits and dietary habits. A subset of participants (n = 37,842) had clinical data available, including alcohol consumption and serum levels of GGT. Study participants were divided into five categories based on their response to the question “How many cups of coffee do you drink daily?”:

• Category 1:   0 — 1 cup
• Category 2:   2 — 3 cups
• Category 3:   4 — 5 cups
• Category 4:   6 — 7 cups
• Category 5:   8 or more cups per day

During a median follow-up period of 19.3 years, 128 participants were diagnosed with primary liver cancer.

The researchers observed that the cumulative incidence curve of liver cancer decreased with increasing amounts of daily coffee consumption (graph). When the analysis was restricted to surveys from participants that had clinical data available, a statistically positive association was found between serum GGT level and liver cancer risk. Joint association of coffee consumption and serum GGT level with liver cancer showed that participants who drank 0 — 1 cups of coffee and were in the top 25% of subjects sampled with respect to serum GGT had about 9.2 times increased risk for liver cancer compared to participants who drank at least 6 cups of coffee daily and were in the bottom 75% of subjects sampled with respect to serum GGT.

The study results are consistent with two meta-analyses published last year demonstrating an inverse relation between coffee consumption and liver cancer [7-8]. While a previous investigation found an inverse association between coffee consumption and serum GGT level, this study is the first large prospective study to suggest that a high level of serum GGT is a risk factor for primary liver cancer. The authors discuss a mechanism for the association between coffee drinking and serum GGT on liver cancer risk [1]:

Several other putative mechanisms behind the association of coffee drinking and serum GGT on liver cancer risk have also been proposed. Coffee contains many compounds, such as chlorogenic acid, which may have the potential to influence glucose metabolism processes to prevent hyperglycemia, and consequently oxidative stress.

Indeed, chlorogenic acid, a chemical largely responsible for coffee’s bitterness, may also be responsible for coffee’s effect on serum GGT level and, ultimately, coffee’s health benefits.

More information and support for patients with “Liver cancer” can be found at Organized Wisdom and MDJunction. Additionally, the American Liver Foundation, the nation’s leading nonprofit organization promoting liver disease prevention and liver wellness, provides research, education and advocacy for those affected by liver-related diseases.

References

1. Hu et al. Joint effects of coffee consumption and serum gamma-glutamyltransferase on the risk of liver cancer. Hepatology. 2008 Jul;48(1):129-36. DOI: 10.1002/hep.22320
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2. A Snapshot of Liver and Bile Duct Cancers. American Cancer Society. Atlanta, Ga. 2007.
3. Ferlay et al. GLOBOCAN 2002: Cancer Incidence, Mortality and Prevalence Worldwide. IARC CancerBase No. 5. version 2.0. Lyon, France: International Agency for Cancer Research; 2004.
4. Casiglia et al. Unexpected effects of coffee consumption on liver enzymes. Eur J Epidemiol 1993;9:293-297.
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5. Tanaka et al. Coffee consumption and decreased serum gamma-glutamyltransferase and aminotransferase activities among male alcohol drinkers. Int J Epidemiol 1998;27:438-443.24.
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6. Wu et al. Glutathione metabolism and its implications for health. J Nutr. 2004 Mar;134(3):489-92.
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7. Larsson and Wolk. Coffee consumption and risk of liver cancer: a meta-analysis. Gastroenterology. 2007 May;132(5):1740-5. Epub 2007 Mar 24.
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8. Bravi et al. Coffee drinking and hepatocellular carcinoma risk: a meta-analysis. Hepatology. 2007 Aug;46(2):430-5.
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Answering seems simple enough. For many people however, the need to avoid criticism and seek praise causes them to respond in a manner consistent with expected norms. Self-reports of dietary intake can be biased by these tendencies, tainting consumption data collected by the health community. Everyone knows they should eat five or more servings of fruits and vegetables a day, so that’s what they say when they’re asked — many even really believe it to be true.

The findings, published in the Nutrition Journal, demonstrate that self-reports of fruit and vegetable consumption are susceptible to substantial social approval bias [1]. Such biases are the presence of social desirability (the tendency to respond in such a way as to avoid criticism) and social approval (the tendency to seek praise) [2-3].

photo credit: karimian

Researchers from the University of Colorado Denver randomly selected 163 women to complete what they were told would be a future telephone survey about health. Randomly half the women were sent a letter prior to the interview describing it as a study of fruit and vegetable intake. Included with the letter was a brief statement on the benefits of fruit and vegetable consumption, a 5-A-Day sticker and a 5-A-Day refrigerator magnet. The other half of the women in the study recieved the same letter but it described the study purpose only as a more general nutrition survey and contained neither the fruit and vegetable message nor the 5-A-Day materials.

Within 10 days of receiving the letters, each of the women answered a food frequency questionnaire and were asked how many fruits and vegetables they had eaten in the last 24 hours. Since the two groups were randomly selected, fruit and vegetable consumption should have been the same in each group. However, those women that recieved the fruit and vegetable message and the 5-A-Day materials reported a significantly higher intake of total fruits and vegetables, and 40% of individuals were categorized as eating 5 or more servings of fruits and vegetables a day compared to just 18% in the other group.

In response to the 24-hour recall questions, 61% of women who received the fruit and vegetable message and the 5-A-Day materials reported eating fruits and/or vegetables on three or more occasions throughout the previous day compared to 32% in the other group. These percentages were independent of age, race, educational level, self-perceived health status and time since last medical check-up.

According to the authors of the study [1]:

This study therefore suggest that social approval bias might well be a substantial problem in the interpretation of nutritional intervention effects that are dependent on education and awareness to affect behavior change. The magnitude of this bias is similar to the intervention effects reported in many studies evaluating changes in fruit and vegetable intake (ranging from 0.93 to 1.25 servings per day). Thus, a major challenge facing nutritional intervention researchers is assessing true behavioral change based on self-reports from reporting bias.

This doesn’t mean that health questionnaires are useless. Rather, it means that many people simply aren’t being entirely truthful when it comes to how many fruits and vegetables they eat. The authors suggest that, in large dietary intervention trials, subgroups can be evaluated with biomarkers or other independent assessments to estimate the reporting bias size. Additionally, bias can also be controlled to some degree by assessing different intensities of an intervention, whereby everyone receives at least a minimal prompt for change instead of one group not receiving any prompt at all.

A growing body of evidence shows that fruits and vegetables are critical to promoting good health. Here’s 5 tips to help you eat more:

1. Keep fruits and vegetables on the counter or at eye level in the refridgerator. Make them easy to find and you’ll be more likely to eat them.
2. If you’re worried about fruits and vegetables spoiling, try canned and frozen fruits and vegetables.
3. Eat fruits and vegetables at every meal. For snacks, try carrot sticks, raisins or apple slices.
4. Buy precut fruits and vegetables. They may cost a bit more than unprepared fruits and vegetables, but there’s less work and they’re ready to eat.
5. Skip the potatoes. They have a high glycemic index compared to other vegetables such as broccoli, cauliflower, asparagus, string beans or peas.

Fruits and vegetables contain essential vitamins, minerals and fiber. In addition to the numerous health benefits of eating more fruits and vegetables, increased consumption lowers your risk of developing several cancers.

Additional resources can be found in the Nutrition category of the Highlight HEALTH Web Directory.

How about you? Do you lie to yourself about the fruits and vegetables you eat?

References

1. Miller et al. Effects of social approval bias on self-reported fruit and vegetable consumption: A randomized controlled trial. Nutr J. 2008 Jun 27;7(1):18. [Epub ahead of print] DOI: 10.1186/1475-2891-7-18
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2. Hebert et al. Social desirability bias in dietary self-report may compromise the validity of dietary intake measures. Int J Epidemiol. 1995 Apr;24(2):389-98.
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3. Hebert et al. Gender differences in social desirability and social approval bias in dietary self-report. Am J Epidemiol. 1997 Dec 15;146(12):1046-55.
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Mind over matter may really work when it comes to managing appetite. Researchers at the University of Birmingham, U.K. have found that recalling foods eaten at lunch has an inhibitory effect on subsequent snacking later the same day. The study is currently in press and will be published in the journal Physiology & Behavior [1]. The effect was observed regardless of the type of snack eaten or palatability. The study also found that meal recall was only effective in decreasing the amount eaten if participants did not have a tendency to overeat.

photo credit: Perfecto Insecto

The study conclusions are based on the results of three experiments described below. Participant eating behavior was determined in these experiments using a questionnaire that included scales assessing dietary restraint (meaning the conscious determination and effort to restrict food intake and calories to control body weight) and tendency toward dietary disinhibition (meaning the tendency to overeat in certain situations). The studies evaluated the inhibitory effects of lunch recall and were conducted to examine the influence of (1) snack palatability, (2) individual dietary traits and (3) the time elapsed since lunch.

Experiment 1: Recall of today’s lunch and subsequent intake of popcorn

The first experiment investigated whether recall of the last meal decreased intake of popcorn differing in added salt and participant-rated pleasantness. Participants took part in one of two experimental conditions:

• The Lunch Today condition, in which participants were asked to recall what they had eaten for lunch that day immediately before tasting and rating the afternoon snack.
• The Lunch Yesterday condition, in which participants were asked to recall what they had eaten for lunch the previous day immediately before tasting and rating the afternoon snack.

Participants (14 young healthy male students) were tested between 2:30 and 4:30 in the afternoon. Upon arrival, those in the Lunch Today condition were asked to write down in ask much detail as possible what they ate for lunch that day. Participants in the Lunch Yesterday condition were asked to do the same for lunch the previous day. Following an assessment of hunger, fullness, desire to eat and mood, participants completed a popcorn taste test. Three large bowls of popcorn were offered with varying amounts of salt (no salt, low salt and high salt) to provide a scale of palatability. After tasting and rating each of the popcorn types, participants were told they could help themselves to any popcorn left over.

The researchers found that when participants were asked to recall lunch eaten earlier that day, intake of all three popcorn types (measured by weighing the bowls of popcorn consumed by each participant before and after each test) was reduced compared to when participants were asked to recall lunch eaten the previous day.

Experiment 2: Recall of today’s lunch and subsequent snack intake: effects of dietary restraint and disinhibition

The second experiment investigated whether the effect of meal recall on snacking is dependent on the tendency towards disinhibition, specifically the tendencies to consciously restrict food intake and to overeat when tempting food is present or other people are eating. Participants (75 young healthy female students) were separated into four groups based on dietary restraint and tendency toward disinhibition:

• Low restraint/Low disinhibition
• High restraint/Low disinhibition
• Low restraint/High disinhibition
• High restraint/High disinhibition

Two participants were excluded because they reported having diabetes or food allergies, were smokers or had a body mass index (BMI) outside the normal range.

Participants again took part in two experimental conditions, the Lunch Today or Lunch Yesterday condition. However, prior to the main test, they attended an introductory session to taste and rate the popcorn, providing the researchers with a baseline measurement of snack intake for each of the four groups. Participants ate their lunch at least 2 hours prior to the test session.

The researchers found no evidence that dietary restraint affected the response to meal recall. However, only participants scoring low in the tendency toward disinhibition decreased their snack intake after recalling lunch. Participants scoring high actually ate as much or more of all three popcorn types! The researchers hypothesized that participants with a tendency towards disinhibition (overeating) may have impairments in working memory related to preoccupying thoughts of food and body shape, as has been shown previously [2]. These impairments would thus interfere with memory encoding or retrieval of the recent meal.

Experiment 3: Recall of today’s lunch and subsequent snack intake: effect of time elapsed since the lunch

The aim of Experiment 3 was to test the hypothesis that the effect of meal recall on snack intake is dependent on memory. Introduction of a delay between a prior event and a later task is typical in memory testing. Thus, researchers examined whether the effect of meal recall is time dependent. Researchers again excluded participants if they reported having diabetes or food allergies, were smokers, had a body mass index (BMI) outside the normal range, or were not habitual breakfast eaters (to control for food intake prior to the controlled lunch). The sample comprised 47 healthy young female students who were asked to remember either their lunch eaten earlier that day or their trip to the test session. Instead of popcorn, the effect of meal recall on cookie intake was measured after a short delay (1-hour post lunch) or a longer delay (3-hour post lunch).

Based on the results of Experiment 2, researchers also assessed whether the effect of meal recall is moderated by dietary traits. Prior to the main test, participants attended an introductory session to taste and rate the cookies that would be eaten in the main experiment, providing the researchers with a baseline measurement of snack intake.

Participants were divided into two groups: half were asked to recall the lunch they had eaten earlier that day (Lunch Today condition) and half were asked to recall their journey to the University campus (Journey Control condition). Within each group, participants attended two test days, each comprising two sessions: a lunch session, which took place between 12:00 and 1:30 p.m., and a snack tasting session, which took place either 1 hour or 3 hours after lunch. Approximately half the participants completed the 1-hour post lunch test followed by the 3-hour post lunch test and the remaining participants experienced the tests in the reverse order.

Replicating the results of Experiment 2, researchers again found an effect of lunch recall on snacking for participants that scored low in tendency toward disinhibition. They also found that the effect of snack intake was time dependent, with participants significantly decreasing their snack intake after recalling lunch in the 3-hour delay condition, but not the 1-hour delay condition. According to the lead author of the study, Psychologist Dr. Suzanne Higgs [3]:

The women who had been asked to recall their lunches and who took the taste test after three hours showed significantly reduced appetites compared to those who had detailed their journeys. This may be because after just one hour, the memory of eating lunch was still vivid enough to affect all the women’s appetites.

Taken together, the results of these experiments show that recall of a recent meal before eating a snack can decrease the amount of snack eaten. The results also suggest that this effect is likely to be related to memory of the meal. The effect of recent meal recall is delay-dependent; snacking was reduced when testing took place 3-hours post lunch and not after 1-hour post lunch. While these results identify the phenomenon, they don’t address how recollection of a recent meal affects subsequent intake. The authors speculate that changes in participants “feeling full” are cognitively mediated and are dependent on a number of factors, including food-related sensory cues, current internal state cues, how participents “felt” after the recent meal, and how they anticipate “feeling” following a snack.

As paradoxical as it sounds, these results suggest that by concentrating on a recent meal, you can reduce your desire to snack. If you’re up to the challenge, give it a try and let me know how you do!

References

1. Higgs et al. Recall of recent lunch and its effect on subsequent snack intake. Physiol Behav. 2008 Mar 4 [Epub ahead of print].
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2. Kemps and Tiggemann. Working memory performance and preoccupying thoughts in female dieters: evidence for a selective central executive impairment. Br J Clin Psychol. 2005 Sep;44(Pt 3):357-66.
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3. Focus on Food — Thinking About Your Last Meal Could Reduce Snacking. University of Birmingham News and Events. 2008 Apr 24.