This is a good one. I suggest fast forwarding to the 1:00 minute mark.
Friday, October 24, 2014
Thursday, October 23, 2014
Halloween is almost here. And you know what that means: Candy! It’s one of those Halloween traditions that I just never seem to have grown out of. Those little chocolate bars are seriously dangerous to my waistline. Remember how much Halloween candy you ate when you were a kid? Were you one of those kids who gorged on all that sugary goodness, or were you the type to parse it out and make it last? I was a Trader, that kid that made deals to trade all her bad candy for the good stuff. Anyway, the topic of Halloween candy got me to searching through the scholarly journals in search of an article for today’s post. I came across a paper that asks if children really need all of that candy on Halloween. My first instinct was “Of course they do! It’s Halloween!” But, well, read on…
It seems that being a fat American isn't just limited to adults, childhood obesity has been on the rise over the last 3 to 4 decades. Access to unhealthy foods and the poor nutritional quality of their diets is much to blame for this. The promotion and glorification of high sugar, high fat foods on Halloween is simply a good example. It probably comes as no surprise that research has shown that when children are given free access to tasty food that they eat it, especially if it’s sweet, even when they are not hungry. But is there a good alternative that kids will like? A slightly older paper published in Journal of Nutrition Education and Behavior investigated the option and value of nonfood treats as substitutes for candy on Halloween.
To do this, the researchers gave 284 trick-or-treating children a choice of a toy or candy. The toys included stretch pumpkin men, large glow-in-the-dark insects, Halloween theme stickers, and Halloween theme pencils. The candy choices were recognizable name brand lollipops, fruit-flavored chewy candies, fruit-flavored crunchy wafers, and “sweet and tart” hard candies. All of these toy and candy options ranged between 5 and 10 cents per item. When a trick-or-treating child arrived at a door, they were asked for their age, gender and a description of their Halloween costume (pretty typical…except maybe the gender question). Then they were presented with 2 identical plates: 1 with 4 different types of toys and the other with 4 different types of candy, alternating by site/household which on side the plates were located. Only children between 3 and 14 were included. And, if the child asked for both toy and candy, they were allowed to take both but were excluded from the study, but only 1 little girl did that.
The results of the study showed that children chose toys as often as they chose candy. This suggests that children may forego candy more readily than adults expect. The authors cite Social Cognitive Theory as providing a way for candy alternatives to become more commonplace. According to this Theory, when parents see that children are accepting the candy alternatives they are more likely to continue the new toy giving behavior. Factor in the other fun Halloween activities – dressing up, walking around the neighborhood at night, etc. – and these toy treats become positively associated with the fun and the holiday.
Okay, so what about the Halloween-only-comes-once-a-year argument. I’ll admit it is a good one and it something that the authors spend time to address. They point out that Halloween isn’t the only holiday where food and candy are advertised. Well, isn’t that the truth. They even make a nice list of other food laden holidays and events: weddings, new babies, graduation, back-to-school, birthdays, Christmas, Hanukkah, Valentine’s Day, Easter, St. Patrick’s Day, Cinco de Mayo, Earth Day (wait…you get food on Earth Day?), Mother’s Day, Father’s Day, and Independence Day. What they don’t add in are all of the other food-filled events that come seasonally (picnics, cook-outs, etc.) and socially (happy hours, get-togethers, etc.). Put together, that’s a lot of bad food choices all year long.
Ultimately, what the authors are getting at is promoting healthy choices throughout the year. Part of this is giving children healthier options and traditions. It is almost more of a change for adults than it is for children. Breaking those food habits and associations isn’t easy, y’all. Food isn’t love, no matter how many Hershey’s Kisses you give someone. Wow did that ever sound shrinky!
But I’ll throw in a last little note that I think almost every child on the planet would agree with: Don’t be that house than hands out toothbrushes.
Schwartz, M., Chen, E., & Brownell, K. (2003). Trick, Treat, or Toy: Children Are Just as Likely to Choose Toys as Candy on Halloween Journal of Nutrition Education and Behavior, 35 (4), 207-209 DOI: 10.1016/S1499-4046(06)60335-7
(image and product via epicurious)
Wednesday, October 22, 2014
Thursday, October 16, 2014
Tuesday, October 7, 2014
Tuesday, September 30, 2014
Fall is in the air. Here in North Carolina that means drastic temperature swings that cause me to dress incorrectly on any given day. It also means the arrival of fall colors. Indeed, fall colors are incredibly beautiful, but biologically speaking, you are watching death happen. This autumn splendor got me to thinking about these colors a little closer, specifically the phenology of trees.
Phenology is the study of the annual timing of recurring life cycle events. The timing of these events is typically influenced by seasonal environmental changes. In the case of trees, specifically hardwood forests, this is the leafing-out (flushing) and dropping-off (senescence) of leaves. But what actually triggers a plant to leaf-out? This can vary a bit by species or even individual, but there are a couple of general categories you can look to. The first is changes in air temperature, the chilling in the winter and warming in the spring. The other is photoperiod, or the day length, which often interacts with temperature, allowing plants to quickly respond to changing conditions.
Considering that these events are triggered by environmental changes, it is logical to assume that global climate change can force changes in the phenology of many species and communities. This is another think-about-the-plants moment. How plants respond to climate change has huge consequences for world ecosystems – growing seasons, species ranges, carbon and water cycling, interactions with animals, etc.
A paper published earlier this year in PNAS took a look at variations in leaf flushing and senescence dates in relation to warming. Many phonological studies focus on specific phenophases (like leaf-out in the spring), but this study is unique in that it looks at subsequent phenological events. The authors aimed to see if effects of warming lasted longer than the current growing season. To do this, in December 2009 they took seventy 3-4 year old cloned oak and beech trees and put them in growth chambers where they could very carefully control the winter environmental conditions. They manipulated the temperatures of the growth chambers to create treatment groups of winter-spring warming, winter-only warming, and spring-only warming. Then, in spring of 2010 when the flushing was complete, they moved the trees out of the chambers and into a field. The trees stayed outside and were measured until the following spring of 2011. Leaf-out rates were determined using a scale that went from undeveloped bud to unfolded leaf, and leaf senescence was recorded as the date at which half of the leaves were colored or dropped. These measurements allowed for a quantification of growing season length. Additional measurements of numbers of leaf per tree, specific leaf area, total leaf area per tree, number of buds, dry weights of various parts of the trees, carbohydrate content, and carbon and nitrogen content were taken. They also combined their data with that of the European phenology network to get both a larger sample size and a wider geographic area.
The researchers found both leaf flushing and senescence in both species to be advanced 15-18 days by winter-spring warming. In the long-term, the timing of autumn leaf senescence was found to be positively correlated with spring leaf flushing dates, and advanced leaf flushing lead to earlier leaf flushing the following year. This suggests that the physiological impacts of a warmer winter last longer than just one growing season. Advanced leaf flushing in this winter-spring-warming treatment was also associated with some physiological and morphological changes, particularly in the oaks. These included higher leaf number, higher leaf area per tree, and higher starch accumulation.
The trends of the experiment were also observed in the mature trees in the long-term field-based phenology observations of the European phenology network. The underlying cause in both cases is likely that the plants never really fulfill the winter chilling requirements necessary for them to enter dormancy. Currently, the most widely accepted mechanism for leaf senescence is the environmental control hypothesis, which proposes that leaf senescence is triggered with the unfavorable autumn season comes (changes in photoperiod, temperature, or both). This study shows that perhaps that isn’t all that’s going on.
*sigh* nothing is ever simple is it?
Fu, Y., Campioli, M., Vitasse, Y., De Boeck, H., Van den Berge, J., AbdElgawad, H., Asard, H., Piao, S., Deckmyn, G., & Janssens, I. (2014). Variation in leaf flushing date influences autumnal senescence and next year's flushing date in two temperate tree species Proceedings of the National Academy of Sciences, 111 (20), 7355-7360 DOI: 10.1073/pnas.1321727111
For lots of really great info on the science of leaf-out, I recommend this review article:
Polgar, C., & Primack, R. (2011). Leaf-out phenology of temperate woody plants: from trees to ecosystems New Phytologist, 191 (4), 926-941 DOI: 10.1111/j.1469-8137.2011.03803.x
And you can contribute to leaf phenology research through Project Budburst!