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Michael and Saul will be happy about this one, since I'm going to criticize Dr. Greger's latest video (embedded below), about happiness titled Which Foods Increase Happiness? I'm also curious what Sthira might have to say :-), if he's still out there...?! In the video, Dr. Greger reviews studies of the link between fruit/vegetable (FV) intake and happiness. In the first part of the video, he reviews a number of studies that have (not surprisingly) found a positive association between FV consumption and positive mood / happiness. Then, to his credit, he asks the perennial question for these kinds of observational studies, namely the direction of causality. Does FV intake increase happiness, or do happy people eat more FVs? He points to evidence for the latter. For example, study  found that people in a good mood are more likely than unhappy people to prefer healthy food alternatives (e.g. grapes) over unhealthy ones (e.g. M&Ms) when given the choice. But then he goes on to argue for causality in the other direction (FV intake -> happiness) as well, based in large part on study . Here is where my criticism comes in. In , researchers tracked (via an internet questionnaire) the FV intake and mood of nearly 300 young adults (avg. age of 20), for three weeks. Affect was gauged each day by having them rate how closely their current mood matched each of 9 positive and 9 negative adjectives (e.g. relaxed, excited, happy, ... vs. depressed, anxious, sad, ...) on a 1-5 scale. The self-rated scores for the positive (and negative) adjectives were averaged together to form a positive (and negative) affect score for each subject each day. These details will be important below, in case you are wondering why I'm going into so much detail... What they found was that higher reported FV intake on a given day was associated with a better mood on the same day. No surprise there, but also no insight as to causality. To try to get at causality, they then looked at FV intake on one day vs. mood on the next day, and visa versa - mood on one day vs. FV intake on the next day. What the found was that FV intake on one day predicted better mood on the next day, but better mood on one day didn't predict more FV intake on the next. So case closed right? Doesn't this tells us that it is FV intake that causes (future) happiness? That's (more or less) Dr. Greger's conclusion. But the key comes in the last few seconds of the video, when Dr. Greger says: How many fruits and vegetables [to increase happiness]? Seems we need to consume approximately 7.2 daily servings of fruit or 8.2 servings of vegetables to notice a meaningful change. So what does that somewhat ambiguous last statement actually mean, and how does it relate to the findings in the rest of the paper? That last statement is based on this sentence from : Because the typical daily consumption in our sample was 1.7 servings of fruit and 2.5 servings of vegetables, our data suggest that young adults would need to consume approximately 7.2 daily servings of fruit or 8.2 servings of vegetables to notice a meaningful change in positive affect. In other words, because of the small size of the effect, the researchers found that a person would need to eat about 5.5 extra servings of FVs per day relative to their normal intake to experience a "meaningful change" in happiness level. What do they consider a "meaningful change"? Here is the footnote from the paper on their definition: A meaningful change in positive affect was defined as an increase in 0.16 points (i.e., increasing from the mean of 2.59 –> 2.75 points on the positive affect scale). A change of 0.16 points reflects a Cohen’s d of 0.20, a small effect, which was computed by the formula 0.20 = (2.75–2.59)/0.80, where 0.80 equals the average within-person standard deviation in positive affect. So they're defining a "meaningful change" as going from 2.59 to 2.75 on a 1-5 scale. Now if you ask me, that is a pretty tiny improvement from eating an extra 5.5 helpings of FVs. I looked up the Cohen's d measure they used a metric for effects size. Interesting statistical stuff. It seems like in the same way statisticians have agreed that P < 0.05 in a student t-test is 'significant', they've also (sorta supposedly) agreed on a definition for 'small', 'medium' and 'large' effects based on this "Cohen's d" metric. The authors of  equated a "meaningful change" with a "small effect" as measured by Cohen's d, which is basically defined as a change in a variable by 25% of one standard deviation in its data. Below is a helpful graphic to give you a feel for what that kind of "meaningful change" would really look like: Imagine the dark grey gaussian represents the distribution of a single individual's happiness over time on a 1-5 scale - most days they felt a middling amount of happiness, but on a smaller number of days they were happier, and on a smaller number of days they were sadder. The extreme tails would represent the (very rare) best and worst days of their life. Hence the gaussian distribution. The "meaningful change" the authors are postulating that would result from eating an additional 5.5 servings of FVs per day equates to shifting the happiness gaussian from the dark grey rightward to the light blue gaussian. I may be a curmudgeon, and you can judge for yourself, but to me this seems like a pretty small shift in happiness as a result of eating a whole lot more fruits and vegetables. So while Dr. Greger's portrayal of the relationship between FV intake and happiness isn't incorrect per se, he may be tilting the interpretation of the data in favor of fruits and vegetables, sort of like the authors of the apples and mortality study may have done in favor of apples. This perspective appears to be shared by the authors of , as reflected in the title they gave to their paper (my emphasis): "Many apples a day keep the blues away - ..." And to their credit (the authors of  that is, not Dr. Greger), they do say in the discussion that they agree with the authors of the review article , which observed that double-blind, randomized control trials are needed to definitively determine if eating more FVs really does indeed lead to improvements in mood: Of course, inferences about causality should be considered tentative until replicated with an experiment. Although our design allowed us to conduct lagged analyses, and these analyses suggested that fruit and vegetable consumption might be influencing positive affect, we agree that future research needs to include randomized controlled trials (RCTs) evaluating the influence of high fruit and vegetable intake on affect and well-being . Sadly, Dr. Greger doesn't mention the randomized trials of FV intake and mood that have been done. Although small and not double (or single) blinded, this one  was encouraging. It found that, among 100 students randomly assigned to eat either a piece of fruit or a serving of "chocolate/crisps" each afternoon for 10 days, the fruit-eaters reported a better mood at the end of the study. But in truly double-blind randomized control trials of various fruit juices (i.e. blueberry , cranberry  and grape  juice), the effect of fruit juice intake on mood was at best small and non-significant , or missing altogether . This is yet another example of where careful reading of the whole published paper, and looking at its results in the context of other research findings, is important for getting a more complete understanding of the research... --Dean -----------  Fedorikhin, Alexander and Patrick, Vanessa M., Positive Mood and Resistance to Temptation: The Interfering Influence of Elevated Arousal (2010). Journal of Consumer Research, Vol. 37, No. 4, 2010. Available at SSRN: http://ssrn.com/abstract=2086834 -----------  Br J Health Psychol. 2013 Nov;18(4):782-98. doi: 10.1111/bjhp.12021. Epub 2013 Jan 24. Many apples a day keep the blues away--daily experiences of negative and positive affect and food consumption in young adults. White BA(1), Horwath CC, Conner TS. Full text: http://sci-hub.io/10.1111/bjhp.12021 OBJECTIVES: Prior research has focused on the association between negative affect and eating behaviour, often utilizing laboratory or cross-sectional study designs. These studies have inherent limitations, and the association between positive affect and eating behaviour remains relatively unexplored. Therefore, the objective of this study was to investigate the bidirectional relationships between daily negative and positive affective experiences and food consumption in a naturalistic setting among healthy young adults. DESIGN: Daily diary study across 21 days (microlongitudinal, correlational design). METHODS: A total of 281 young adults with a mean age of 19.9 (± 1.2) years completed an Internet-based daily diary for 21 consecutive days. Each day they reported their negative and positive affect, and their consumption of five specific foods. Hierarchical linear modelling was used to test same-day associations between daily affect and food consumption, and next-day (lagged) associations to determine directionality. Moderating effects of BMI and gender were also examined in exploratory analyses. RESULTS: Analyses of same-day within-person associations revealed that on days when young adults experienced greater positive affect, they reported eating more servings of fruit (p = .002) and vegetables (p < .001). Results of lagged analysis showed that fruits and vegetables predicted improvements in positive affect the next day, suggesting that healthy foods were driving affective experiences and not vice versa. Meaningful changes in positive affect were observed with the daily consumption of approximately 7-8 servings of fruit or vegetables. CONCLUSIONS: Eating fruit and vegetables may promote emotional well-being among healthy young adults. PMID: 23347122 ---------------  Blanchflower, D., Oswald, A., & Stewart-Brown, S. (2012). Is psychological well-being linked to the consumption of fruit and vegetables? Social Indicators Research. Advance online publication. doi:10.1007/s11205-012-0173-y. Free full text: Abstract Humans run on a fuel called food. Yet economists and other social scientists rarely study what people eat. We provide simple evidence consistent with the existence of a link between the consumption of fruit and vegetables and high well-being. In crosssectional data, happiness and mental health rise in an approximately dose-response way with the number of daily portions of fruit and vegetables. The pattern is remarkably robust to adjustment for a large number of other demographic, social and economic variables. Well-being peaks at approximately 7 portions per day. We document this relationship in three data sets, covering approximately 80,000 randomly selected British individuals, and for seven measures of well-being (life satisfaction, WEMWBS mental well-being, GHQ mental disorders, self-reported health, happiness, nervousness, and feeling low). Reverse causality and problems of confounding remain possible. We discuss the strengths and weaknesses of our analysis, how government policy-makers might wish to react to it, and what kinds of further research -- especially randomized trials -- would be valuable. ------------  Front Nutr. 2014 Jul 16;1:10. doi: 10.3389/fnut.2014.00010. eCollection 2014. Positive effects of a healthy snack (fruit) versus an unhealthy snack (chocolate/crisps) on subjective reports of mental and physical health: a preliminary intervention study. Smith AP(1), Rogers R(1). Author information: (1)School of Psychology, Cardiff University , Cardiff , UK. BACKGROUND/AIMS: Recent research has shown associations between type of snack and wellbeing. These studies have been cross-sectional and the aim of the present research was to examine this topic using an intervention study. METHODS: A between-subjects intervention study was carried out. Volunteers (100 students, mean age = 19.00 years; 27 male, 73 female) completed online questionnaires measuring anxiety and depression, fatigue, somatic symptoms, cognitive difficulties, and distress at baseline. They were then randomly assigned to one of two snacking conditions - chocolate/crisps or fruit. Volunteers consumed one snack item in the mid-afternoon each day for 10 days. At the end of the intervention, the volunteers completed the questionnaires again. RESULTS: Analyses of the baseline data confirmed that consumption of chocolate was associated with greater emotional eating and depression. Analyses of covariance, with the baseline data as covariates, were carried out on the post-intervention responses. The results showed that consumption of fruit was associated with lower anxiety, depression, and emotional distress than consumption of crisps/chocolate. Similarly, scores for somatic symptoms, cognitive difficulties, and fatigue were greater in the crisps/chocolate condition. CONCLUSION: These results extend findings from cross-sectional studies and give a clearer indication of causal effects of different types of snacks on wellbeing. PMCID: PMC4428353 PMID: 25988113 ------------  J Agric Food Chem. 2010 Apr 14;58(7):3996-4000. doi: 10.1021/jf9029332. Blueberry supplementation improves memory in older adults. Krikorian R(1), Shidler MD, Nash TA, Kalt W, Vinqvist-Tymchuk MR, Shukitt-Hale B, Joseph JA. Author information: (1)Department of Psychiatry, University of Cincinnati Academic Health Center, Cincinnati, Ohio 45267-0559, USA. firstname.lastname@example.org The prevalence of dementia is increasing with expansion of the older adult population. In the absence of effective therapy, preventive approaches are essential to address this public health problem. Blueberries contain polyphenolic compounds, most prominently anthocyanins, which have antioxidant and anti-inflammatory effects. In addition, anthocyanins have been associated with increased neuronal signaling in brain centers, mediating memory function as well as improved glucose disposal, benefits that would be expected to mitigate neurodegeneration. This study investigated the effects of daily consumption of wild blueberry juice in a sample of nine older adults with early memory changes. At 12 weeks, improved paired associate learning (p = 0.009) and word list recall (p = 0.04) were observed. In addition, there were trends suggesting reduced depressive symptoms (p = 0.08) and lower glucose levels (p = 0.10). We also compared the memory performances of the blueberry subjects with a demographically matched sample who consumed a berry placebo beverage in a companion trial of identical design and observed comparable results for paired associate learning. The findings of this preliminary study suggest that moderate-term blueberry supplementation can confer neurocognitive benefit and establish a basis for more comprehensive human trials to study preventive potential and neuronal mechanisms. PMCID: PMC2850944 PMID: 20047325 --------  J Altern Complement Med. 2005 Apr;11(2):305-9. A double-blinded, placebo-controlled, randomized trial of the neuropsychologic efficacy of cranberry juice in a sample of cognitively intact older adults: pilot study findings. Crews WD Jr(1), Harrison DW, Griffin ML, Addison K, Yount AM, Giovenco MA, Hazell J. Author information: (1)Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA. email@example.com OBJECTIVES: The aim of this research was to conduct the first known clinical trial of the short-term (i.e., 6 weeks) efficacy of cranberry juice on the neuropsychologic functioning of cognitively intact older adults. PARTICIPANTS: Fifty (50) community-dwelling, cognitively intact volunteers, > or = 60 years old, who reported no history of dementia or significant neurocognitive impairments, participated in this study. DESIGN: A 6-week, double-blind, placebo-controlled, randomized, parallel-group, clinical trial was utilized. Participants were randomly assigned to receive either 32 ounces/day of a beverage containing 27% cranberry juice per volume (n = 25) or placebo (n = 25) for 6 weeks, and administered a series of neuropsychologic tests at both pretreatment baseline and again after 6 weeks of either cranberry juice or placebo treatment to assess treatment-related changes. OUTCOME MEASURES: Efficacy measures consisted of participants' raw scores on the following standardized neuropsychologic tests: Selective Reminding Test, Wechsler Memory Scale-III Faces I and Faces II subtests, Trail Making Test (Parts A and B), Stroop Color and Word Test, and the Wechsler Adult Intelligence Scale- III Digit Symbol-Coding subtest. A subjective Follow-up Self-report Questionnaire was also administered to participants at the conclusion of the end-of-treatment phase assessments. RESULTS: Two-factor, mixed analyses of variance (ANOVA) revealed no significant group (cranberry juice and placebo) by trial (pretreatment baseline and end-of-treatment assessments) interactions across all of the neuropsychologic tests and measures utilized in this study when a Bonferroni corrected alpha level was used to correct for multiple comparisons (i.e., .05/17 group by trial comparisons = .003). Pearson Chi-Square analyses of the groups' self-reported changes over the 6-week treatment phase in their abilities to remember, thinking processes, moods, energy levels, and overall health on the Follow-up Self-report Questionnaire revealed no significant relationships. However, a nonsignificant trend (X2(1) = 2.373, p = 0.123) was noted for participants' self-reported overall abilities to remember from pretreatment baseline to the end-of-treatment assessment. Specifically, more than twice as many participants in the cranberry group (n = 9, 37.5%) rated their overall abilities to remember by treatment end as "improved" as compared to placebo controls (n = 4, 17.4%). CONCLUSIONS: Taken together, no significant interactions were found between the cranberry and placebo groups and their pretreatment baseline and end-of-treatment phase (after 6 weeks) standardized neuropsychologic assessments. A nonsignificant trend was noted, however, on a subjective, self-report questionnaire where twice as many participants in the cranberry group rated their overall abilities to remember by treatment end as "improved" compared to placebo controls. PMID: 15865497 -----------  Br J Nutr. 2010 Mar;103(5):730-4. doi: 10.1017/S0007114509992364. Epub 2009 Dec 23. Concord grape juice supplementation improves memory function in older adults with mild cognitive impairment. Krikorian R(1), Nash TA, Shidler MD, Shukitt-Hale B, Joseph JA. Author information: (1)Department of Psychiatry, University of Cincinnati Academic Health Center, Cincinnati, OH, USA. firstname.lastname@example.org Concord grape juice contains polyphenol compounds, which have antioxidant and anti-inflammatory properties and influence neuronal signalling. Concord grape juice supplementation has been shown to reduce inflammation, blood pressure and vascular pathology in individuals with CVD, and consumption of such flavonoid-containing foods is associated with a reduced risk for dementia. In addition, preliminary animal data have indicated improvement in memory and motor function with grape juice supplementation, suggesting potential for cognitive benefit in ageing humans. In this initial investigation of neurocognitive effects, we enrolled twelve older adults with memory decline but not dementia in a randomised, placebo-controlled, double-blind trial with Concord grape juice supplementation for 12 weeks. We observed significant improvement in a measure of verbal learning and non-significant enhancement of verbal and spatial recall. There was no appreciable effect of the intervention on depressive symptoms and no effect on weight or waist circumference. A small increase in fasting insulin was observed for those consuming grape juice. These preliminary findings suggest that supplementation with Concord grape juice may enhance cognitive function for older adults with early memory decline and establish a basis for more comprehensive investigations to evaluate potential benefit and assess mechanisms of action. PMID: 20028599