Human Population Biology
Critical Thinking Summaries #2
In a 2017 article, “How Does the Body Metabolize Lactose?” PhD student Sirah Dubois describes the process of how lactose is metabolized in the body. Dubois states that an enzyme called lactase is what breaks down lactose in the intestines. She also notes that it breaks down lactose by breaking them down into galactose and glucose molecules, where glucose is absorbed into the bloodstream and then used by your cells for energy. Dubois points out that the galactose molecule is then broken down further by lactase and other enzymes into glucose in order for it to also be absorbed by the bloodstream.
In a 2018 Animal Science Papers and Reports review, “Physico-chemical Properties of Lactose, Reasons for and Effects of its Intolerance in Humans,” Nina Strzalkowska et al., describes lactose intolerance as the inability to digest lactose. They note that lactose intolerance occurs when the organism is unable to produce the lactase-phlorizin hydrolase enzyme. They also state that one of the most occurring forms of lactose intolerance which is mostly found in adults is known as hypolactasia. Lastly, they describe lactose as a unique disaccharide and list a number of traits that lactose has in the body, such as how it has the ability to “stimulate the development of beneficial intestine microflora, increase the synthesis of short chain fatty acids and promote regeneration processes in the intestine mucous membrane” (Strzalkowska et al. 2018:21).
Takeaway: Lactose tolerance is needed in order to break down lactose to provide energy for cells. The inability to break down lactose leads to the inability to provide energy for cells properly.
In a 2017 article, ” What Effects Does Lactose Have on the Human Body?” Jan Annigan describes how lactose is used as a fuel source for your daily activities. She also explains that the energy you receive from lactose is used instead of the energy you get from protein, which allows the protein to be used to build muscle and perform other functions in the body. Annigan notes that overconsumption of lactose can lead to the body converting that sugar into fatty acids, which can then lead to an extra energy reserve in adipose tissue. She points out that this high intake of lactose can cause weight gain and this excessive amount of weight gain can then lead to obesity. She notes the digestive problems that occur with lactase, saying that without enough lactase your body won’t be able to digest the lactose it acquires which would then lead to lactose intolerance.
Takeaway: Lactose is needed in your day to day activities. The inability to digest it can further lead to one being unable to perform tasks and also lead to obesity if not processed properly.
Referencing back to “Physico-chemical Properties of Lactose, Reasons for and Effects of its Intolerance in Humans,” Strzalkowska et al. (2018) describes lactose as having a significant role in newborn mammals by being an energy source for their organs. In regards to newborns and lactose intolerance, an interesting topic about how lactose intolerance isn’t common in newborns was stated by Doctor Anthony Porto in a 2016 article, “Lactose Intolerance in Infants and Children’s: Parents FAQs”. He describes that lactose intolerance usually shows up after the age of three. He also notes that all newborn babies have lactase, but as they increase with age the enzyme decreases.
In a 2011 article, ” Why is Lactose Intolerance More Common in Adults?” Justin White states that “lactose tolerance may be a function of evolution” (White 2011:2) by explaining how the lactase gene turns off when a baby no longer drinks breast milk. He notes that very few people are born without the lactase enzyme, but lactose intolerance usually occurs after infancy. From studies conducted he states that “more than 25% of children more than age 5 are lactose intolerant”(White 2011:1).
Takeaway: Lactose tolerance is usually prevalent in children up until the age of 2-3, but later decreases overtime as they get older. With age, the lactase enzyme is produced less which in turn can lead to lactose intolerance.
In a review article “From ‘Lactose Intolerance’ to ‘Lactose Nutrition,” Widjaja Lukito et al., discusses how people who herded cattle have evolved to be able to get the complete nutritional value of milk and dairy products. In order to get the full nutritional value of milk, Helen Thompson states in a 2012 NPR article “An Evolutionary Whodunit: How Did Humans Develop Lactose Tolerance?” that Ancient European farmers had to have a genetic mutation that allowed the body to digest lactose after early childhood. She also notes that up until a few thousand years ago, the enzyme lactase was switched off once a person grew from a child to an adult, but the development of this lactose tolerance took an estimate of 20,000 years.
In a 2009 Smithsonian article, “Lactose Tolerance and Human Evolution,” Joseph Caputo notes that before the mutation humans weren’t able to access full energy from their dairy foods. They were forced to remove the sugar from milk, but in essence that ended up removing 20% to 50% of its calories. He also stated “Today, more than 90 percent of all people have some degree of lactose tolerance” (Caputo 2009:1).
Takeaway: Lactose tolerance developed overtime as humans evolved because at first humans weren’t able to digest lactose after childhood. However, in order to get the full nutritional value from dairy foods humans had to develop a genetic mutation.
Referencing back to the 2009 article “Lactose Tolerance and Human Evolution,” Caputo notes that people of certain backgrounds such as African, Asian, and Mediterranean have the inability to process lactose, compared to a third of the population that can digest lactose in some way, but may still experience symptoms of lactose intolerance.
In a 2013 Popular Science article, “What are the Most Lactose Intolerant Places in the World?” Shaunacy Ferro describes lactase persistence as a “European phenomenon, evolving from a single genetic mutation that occurred less than 10,000 years ago.” (Ferro 2013:1). From a 2010 article, “Lactose Intolerance by Ethnicity and Region,” Itan Yuval also notes that in certain populations such as Europeans, Africans, Middle Eastern and Southern Asians, there are a high frequency of individuals with the ability to produce lactase throughout life. My assumptions is that people around these areas were involved with cattle in past lives which in turn led to a mutation being passed down that allowed for the continued production of lactase.
Takeaway: Lactose tolerance is prevalent where cattle have been present and herded for a period of time, in order to get the full nutritional value of dairy products.
Annigan, J. (2017, August 14). What Effects Does Lactose Have on the Human Body? Retrieved from https://www.livestrong.com/article/539602-what-effects-does-lactose-have-on-the-human-body/
Caputo, J., 2009. Lactose Tolerance and Human Evolution WWW Document. Smithsonian.com. URL https://www.smithsonianmag.com/arts-culture/lactose-tolerance-and-human-evolution-56187902/ (accessed 6.10.18).
Dubois, S., 2017. How Does the Body Metabolize Lactose? WWW Document. LIVESTRONG.COM. URL https://www.livestrong.com/article/562140-how-does-the-body-metabolize-lactose/ (accessed 6.10.18).
Ferro, S., 2013. What Are The Most Lactose Intolerant Places In The World? Infographic WWW Document. Popular Science. URL https://www.popsci.com/science/article/2013-08/infographic-day-where-people-can-digest-milk (accessed 6.10.18).
Lukito, W., Malik, S. G., Suruno, I. S., & Wahlqvist, M. L. (2015). From ‘Lactose intolerance to Lactose nutrition’. Asia Pacific Journal Of Clinical Nutrition,24, 1-8.
Porto, A., 2016. Lactose Intolerance in Infants & Children: Parent FAQs WWW Document. HealthyChildren.org. URL https://www.healthychildren.org/English/healthy-living/nutrition/Pages/Lactose-Intolerance-in-Children.aspx (accessed 6.10.18).
Strza?kowska, N., Jasi?ska, K., & Jó?wik, A. (2018). Physico-chemical properties of lactose, reasons for and effects of its intolerance in humans – a review. Animal Science and Papers Report,36, 21-31.
Thompson, H., 2012. An Evolutionary Whodunit: How Did Humans Develop Lactose Tolerance? WWW Document. NPR. URL https://www.npr.org/sections/thesalt/2012/12/27/168144785/an-evolutionary-whodunit-how-did-humans-develop-lactose-tolerance (accessed 6.10.18).
White, J., 2016. Why Is Lactose Intolerance More Common in Adults? WWW Document. Greatist. URL https://greatist.com/health/why-lactose-intolerance-more-common-adults (accessed 6.10.18).
Yuval, I., 2010. Lactose Intolerance by Ethnicity and Region – Milk – ProCon.org WWW Document. Is drinking milk healthy for humans? URL https://milk.procon.org/view.resource.php?resourceID=000661 (accessed 6.10.18).