HumanLifeCycle-BirthtoOldAge.pptxThe Human Life Cycle
Birth to Old Age –
What is the human life cycle?
How does nutrition influence our life cycle?
How have our cultural changes in diet and nutrition influenced our development?
So far we have looked at ways in which human beings vary in their phenotypes. Another way that humans have evolved is in our life cycle. All organisms have a cycle of life and eventually die. In this lecture, we are going to consider how the developmental and maturation cycle for homo sapiens has changed over the course of our evolution. When we were in our human evolution section of this course, we watched as maturation rates slowed as species evolved towards Homo sapiens. We have the longest maturation period of any primate, but when we enter this period and get out of it has been altered.
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Humans are a generalized species
Homo sapiens are very generalized and flexible, we also call this plastic.
We live, eat, and respond to a number of different environments and circumstances.
As environments have changed, our culture has evolved to make us more adaptive.
Drastic cultural changes over the last several decades will have profound impact on our biology.
For this lecture, think back a bit to how flexible and adaptive we are. We have the ability to adapt to many environments and we have. On top of that, we have altered our cultures quite a bit and this has impacted our evolution.
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Does our original body and life cycle match our ancestors 300kya ago?
We are a species that evolved in subtropical Africa some time around 300,000 years ago.
Rapid agricultural and cultural changes have caused major divisions between generations; think how different your life is from your grandparents.
We have to consider both biological and cultural influence on how the cycle of life has changed.
Something we have to consider is that humans haven’t been around very long as a species. Since it takes us so long to reproduce, we haven’t been on the planet long enough for us to really have evolved in any major ways. What this means is that technically, most of us are still evolved to live in sub-tropical Africa, in small, kin-based families, who hunt and gather. Yet we live in a rapidly modernizing world. Is this rapid change affecting the way we develop and at the rate we do? Let’s consider some examples by looking at the normal life cycle.
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Fetal growth
The image above gives you an idea of the course of development in utero. Notice that within the first couple weeks, your neural tube (thus your nervous system) is already developing.
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By 16 days, neural tube has formed…
Most women do not necessarily know that they are pregnant as early as 2 weeks after conception. However, the neural tube and thus the nervous system is already forming. This means that nutrition is an absolutely integral part of daily life. If malnutrition or other nutrition issues affect the child this young, then the nervous system is already being harmed.
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Brain growth
25% of the human brain is developed by birth, with almost all neurons developed by this point
50% is developed by 6 months
75% is developed by 2.5 years
90% is developed by 5 years
95% is developed by 10 years
Our human growth cycle has about 25% of our brain developed at birth, but almost all of our active neurons. You can see from this chart that our brains develop over the course of the first 10 years of our lift. This makes nutrition again, extremely important during pregnancy and through the first decade of life.
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Early childhood growth
After birth, growth is rapid for first 4 years.
The brain and the body grow at quite a fast speed in the first few years. Note that by age 3, a large portion of both boys and girls’ bodies have developed.
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Nutrition & Development
During pregnancy, a malnourished mother causes health issues for children including low birth weight, weak immunity, birth defects, brain damage, and low physical stamina.
Since females get their eggs developed in utero, those eggs can also be damaged for future generations.
“…at risk for later neuropsychological problems, poor school achievement, early school drop out, low-skilled employment, and poor care of their own children…” (Prado, 2012).
Please read the article “Nutrition and Brain Development in Early Life” article for this section. I like to cover nutrition in my biology classes because, as you can see, what we eat is crucial to our development. There is A LOT of misinformation out there about what we should eat and why. In this class, we will approach nutrition from the perspective of how nutrients impact the basic functioning of your cells.
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“Nutrition & Early Development”
http://data.unicef.org/nutrition/malnutrition click for more current data
Notice how many children are malnourished. This is lacking nutrition, but the growth of obese children is enormous, and being obese can also mean a child is malnourished. So we have a new issue to deal with.
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Nutrition & Neural Growth
Nutrients are necessary to create neurons in embryonic development.
They are needed for the growth of axons and dendrites, the formation of synapses, and the myelin covering. “Inadequate availability of energy, protein, fatty acids, and micronutrients impair these neurodevelopmental processes.”
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Nutrients – Essential fatty acids
Our brain is nearly 60% fat.
Essential fatty acids (EFA) like docosahexaenoic (DHA) create parts of the brain tissue and membrane. Without DHA, the membrane cannot form properly.
Omega 3 fatty acids are essential for retina and visual cortex formation.
EFA’s also help create neurotransmitters as well as molecules in the immune system that are responsible for responding to brain injury.
In later life, omega 3 fatty acids seem to be associated with a prevention of Alzheimer's and other neurological disorders.
The following slides discuss nutrients one by one from your article and how they impact the functioning your cells.
http://www.ncbi.nlm.nih.gov/pubmed/20329590
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Nutrients - Micronutrients
Iron: Essential mineral component of blood, which transports oxygen. “Iron deficiency anemia is associated with poor mental and motor development in infancy and poor cognition and school achievement in later childhood.”
Iron is also found on axons to help speed up electrical impulses.
Found in meats, beans, dark leafy greens, and fortified breads, etc.
Nutrients - Micronutrients
Iodine: Mineral essential for synthesis of thyroid hormones, which are essential for the central nervous system development through the regulation of metabolism.
“Severe iodine deficiency before and during pregnancy can lead to underproduction of thyroid hormones in the mother and cretinism in the child.”
Cretinism is characterized by mental retardation, def-mutism, facial deformities, and severely stunted growth.
Found in fish predominantly.
Nutrients - Micronutrients
Zinc: Mineral necessary for DNA and RNA synthesis and metabolism of protein, carbohydrates, and fat.
4th most abundant ion in the brain, where it contributes to brain structure and function through its role in binding proteins.
Low zinc is associated with decreased neuronal survival and is related to poor memory and learning abilities, as well as diseases like coronary heart disease.
Found in wheat, beef, seafood, nuts, spinach, etc.
http://onlinelibrary.wiley.com/doi/10.1002/jtra.10042/abstract
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Nutrients - Micronutrients
Thiamine: vitamin that helps to metabolize carbohydrates for brain energy, helps maintain membrane structure, and helps with synapse formation and function.
Lack of thiamine associated with impaired language learning and conceptual abilities.
Found in enriched whole grain products, beef, eggs, nuts, and seeds.
http://brain.oxfordjournals.org/content/brain/134/6/1720.full.pdf
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Nutrients – Vitamin Folate B
Lack of folate B in pregnancy leads to anencephly, where the child is born without a brain and at a maximum, will survive only a few days outside of the womb.
Modern grains are enriched with folate B, refined, gluten free products are not.
Gluten free products are often overly refined, and are low in nutrients.
Can be found in beans and spinach as well.
http://www.scientificamerican.com/article/most-people-shouldnt-eat-gluten-free/
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Nutrients – Other Vitamins
Vitamins are organic compounds that are required by the body to release energy from food to use in many ways.
Vitamin A – essential for eye and immune health, as well as for growth and development of cells
Found in milk, eggs, fortified grains, dark green/orange fruits and vegetables
Vitamin C – essential for collagen health, bones/teeth, and helps absorb iron to help with healing wounds and for brain development.
Found in citrus fruits, tomatoes, and spinach.
Vitamin D – essential for bone growth
Found in egg yolks and fish.
Vitamins B12 & B6 – essential for hemoglobin and nerve cell production.
Found in meats, milk, and fortified products. B6 also found in bananas, nuts, and beans.
Why is malnutrition an issue?
The diet of foragers…
High in wild animal proteins like fish, with omega 3’s and low in saturated fats like omega 6’s.
Fewer carbohydrates, but high in complex carbs: non-starchy fruits and veggies like lettuce, asparagus, spinach, mushrooms, melons, berries, and citrus.
High in fiber, not from grains, but non-starchy fruits and veggies.
Fiber is a carb that cannot be digested and helps regulate digestion of sugar.
Low levels of salt and no refined sugars, processed oils, grains, and dairy.
Some people argue that most new diseases are a result of a diet that is mismatched from our evolutionary diet, but others argue we have adapted fine.
In modern times the “paleo diet” has a lot of opponents, be careful assuming it’s still the “right” diet for our body.
Now that we know about nutrients and how they impact your body, we have to consider how human cultural innovation has caused us to have such major malnutrition. Take a look at what the diet of foragers once looked like, but don’t be fooled by the idea of “returning to our roots and being foragers.” We are not foragers anymore. We have not been foragers for thousands of years, so it’s not quite that simple.
http://www.huffingtonpost.com/john-berardi-phd/paleo-diet_b_5774200.html
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Additionally, notice that foragers have unique diets based on their environments. The “paleo diet” falsely suggests that we should return to our roots, but no diet in the paleolithic was the same. They very much depended on what resources were accessible and thus contributed to the variation among humans. For instance, the Inuit live in the far north, but have dark skin. This is due to the high amount of vitamin D in their fish diet.
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Our modern diet & malnutrition
Today’s diet:
High in saturated fats
Low in complex carbs and high in simple carbs.
These are basic sugars with low fiber that digest quickly, but provide minimal nutritional value. (white flour, sugars, etc.). Complex carbs are longer, taking longer to digest.
Fruits are actually simple carbs, but due to high fiber, they digest more slowly.
Increase in dairy, which contains saturated fats and despite the folklore, may not help bone health at all.
Increase in cereal grains: most importantly, processed grains that lose nutrients.
Grains fed to animals make their meat more saturated in fat.
40-90% of American food energy comes from grains.
Our diets today are very different than those of foragers. It’s the alteration in a few key ingredients that appears to have made a very big difference in our issues with malnutrition today as well as obesity.
http://www.livescience.com/27847-whole-grains-misleading-labeling.html
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A sugar is a sugar is a sugar
All sugars digest in the same way.
High fructose corn syrup has a high glycemic index, causing blood sugar to rise dramatically, leading you to eat more sugar.
When your liver storage capacity is exceeded, it turns sugar into fatty acids and releases them for storage in the body.
Consider our consumption of sugar. There is a lot of hype out there that natural sugars are better for you than condensed sugars, but research shows that all sugars affect the body similarly. Moderation of sugar is something modern society doesn’t have, but it’s something that we can do to help reduce the chances of diabetes.
http://www.huffingtonpost.ca/rose-reisman/sugar-and-substitutes_b_5533859.html
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Veganism/Vegetarianism/ Paleo diet
Vegan/Vegetarian diets are linked with lower risk for heart disease and cancer, and is tied to easier weight loss.
Both are these are short term only, no long term benefits
Many important nutrients like B12, iron, zinc, and calcium are missing.
Diets heavy in soy produce estrogen effects
Plant diets have omega-3s that require conversion. This conversion requires animal fat.
Paleo diet argues for heavy meat/nuts, no dairy.
Red meat consumption is not directly tied to heart disease/cancer like we once thought.
However, meat consumption should still be limited.
Let’s consider some other diets in modern human society. Is one right? It doesn’t appear to be. Most diets are fads. Here are some examples of diets that are more common now and how they impact the body.
https://www.ncbi.nlm.nih.gov/pubmed/26853923
http://ajcn.nutrition.org/content/89/5/1627S.full
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Keto/Macro
¤Keto diet is a high fat, regular protein, low carb diet, generally used to treat epilepsy.
Consequences include increase cholesterol, less energy for the brain, low blood sugar, potential malnutrition
¤Macro fad diet focuses on calories in three categories: fats (20% of diet), carbs (40% of diet), and proteins (40% of diet).
Diet is based on the myth that a calorie is a calorie is a calorie
A calorie is a unit of energy needed to raise the temperature of 1 gram of water to 1 degree C.
While thermodynamics suggests that a calorie IS a calorie, research in human weight gain suggests the opposite. Calories are not created equal.
The controversy of genetic modification
Organisms can be genetically modified
All things you consume and all domesticated animals are genetically modified by farmers.
Modern lab modifications are the same as domestication, and the consensus among scientists is they’re safe.
Genetic modification also happens in the wild through viral transfer.
145 known human genes we have through horizontal tranfer.
http://www.sciencemag.org/news/2015/03/humans-may-harbor-more-100-genes-other-organisms
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What about GMO’s?
A survey of 1783 studies couldn’t find a single, credible example of GMO’s being harmful.
“The literature considering the effects of biodiversity on non-target species is large and shows little to no evidence of the negative effects of GE crops”
“There is no scientific evidence of toxic or allergenic effects” (7). All GM products are tested against the database of all known allergens before commercialization.
What about the “natural order” being disrupted by creating new kinds of DNA? We consume up to 1 gram a day of DNA both GMO and non-GMO, and there is no evidence it affects the human body or GI tract.
“globally, food-producing animals consume 70% to 90% of genetically engineered crop biomass, mostly corn and soybean. In the United States alone, animal agriculture produces over 9 billion food-producing animals annually, and more than 95% of these animals consume feed containing GE ingredients.”
What did studies find on the study of 100 billion animals? GMO’s are the same as non-GMO’s
http://www.geneticliteracyproject.org/wp-content/uploads/2013/10/Nicolia-20131.pdf
http://www.geneticliteracyproject.org/2013/10/08/with-2000-global-studies-confirming-safety-gm-foods-among-most-analyzed-subject-in-science/
http://www.fass.org/page.asp?pageID=52&autotry=true&ULnotkn=true
http://www.forbes.com/sites/jonentine/2014/09/17/the-debate-about-gmo-safety-is-over-thanks-to-a-new-trillion-meal-study/
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Influences on human health
This poor diet, arguably a result of agriculture, leads to poorer health, new and rampant diseases.
Combine the bad diet with a sedentary life with minimal exercise and you’re no longer burning that energy.
Malnutrition is not just not getting food, it’s getting food that is not nutritious enough, so people in both resource rich and resource poor areas are experiencing this.
Inequality of available food is most important.
https://www.ted.com/talks/josette_sheeran_ending_hunger_now?language=en
The impact of lack of exercise, poor diets, bad foods, and fad diets have caused humans to have various ailments. The following TEDtalk looks at the issue that malnutrition have on our bodies as well as effective ways to respond.
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What do you notice?
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What do you notice? What impact might this have on our species?
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Puberty
Early life is affected by nutrition, but so is later life, including puberty. The rates of puberty have changed dramatically over the last couple centuries, and we’re seeing a new expectation for puberty in boys and girls as a result of cultural changes.
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How has puberty changed?
Puberty is controlled predominantly by genetics.
The GPR54 gene gets turned on, sending signals to the brain that influence the endocrine system.
The hypothalamus sends signals to the pituitary gland to release hormones that stimulate the ovaries or testicles to make sex hormones.
In males, testosterone is responsible for changes in puberty, and estradiol is responsible for puberty changes in females.
In the early neolithic, puberty ages were similar to what they are today.
Between 1830-1962 the average age of menarchy dropped from 17 to 12.8. Why? Poor health & nutrition.
Please reading “Early Arrival” article for this lecture. Nutrition impacts early development, but it also impacts the timing of puberty. Puberty is genetically controlled, but nutrition can play an important role. Consider how the average age of puberty has changed. In the Upper Paleolithic, menstruation began around 12 years old. Around the 1800’s, this age has increased to 17 years old. This is due to massive agricultural famine, where people received minimal nutrition and thus, their bodies didn’t have the energy to enter puberty. “Early Arrival” discusses how nutrition impacts puberty in our next slides.
http://www.mum.org/menarage.htm
http://www.nejm.org/doi/full/10.1056/NEJMoa035322#t=article
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“Early arrival” - Beil
Childhood obesity: Fat cells produce leptin, which tells the brain that body fat percentage is acceptable for puberty and to begin producing hormones.
“treats increased the monkeys’ caloric intake by 30% compared with four monkeys on a regular diet…less than a year later, all the monkeys with extra food had begun menstruating, but none of their cage mates did” (pp. 3).
“Early arrival” - Beil
Environmental hormones: “It’s known that many substances used in plastics, pesticides, detergents, and other products can mimic the effect of estrogen in animals. Exposure to these compounds can even cause male reptile and bird hatchlings to become feminized” (pp. 4).
“Since breast tissue is more sensitive to estrogen than is menstruation, ‘the reason for the development of breast tissue at a much younger age over a short period of time must be of environmental origin.”
“Early arrival” - Beil
Stress: “undercurrent of stress in early life affects timing of puberty, probably by activating hormonal responses to danger” (pp. 5).
When life begins without excess anxiety, “the signal is, this is a safe world and I can delay reproduction.”
Response to fight or flight?
Early puberty & implications in adulthood for women
Early puberty has some consequences to it, largely cultural ones based on our values of sex and adulthood.
Research shows however, that women who have more menstrual cycles in their life have a higher risk of cancer, perhaps due to higher hormonal release in the body?
Are there any issues with girls having their menstrual cycles early? We want to consider how this might impact our evolution.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2001234/
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Development of sexual dimorphism
Puberty is when major differences between the sexes start to appear.
Boys get lots of hair, testicles get larger, voice changes, and height increases. Females see menstrual cycles and breasts start to appear.
What does it mean to be a man or a woman in our species? What makes you a man/woman?
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How do the sexes differ?
Men are taller by about 5 inches on average, have greater grip strength, more muscle, greater bursts of energy, larger organ sizes on average.
Women have more fat percentage overall…that’s not all we get! We also mature faster.
Major differences seem to come from hormones.
Sex hormones
Estrogens: “female hormones” associated with female sex organ creation, menstrual cycles, pregnancy, height, bone formation, and increase in cortisol.
Androgens: “male hormones” associated with male puberty, increased muscle, bone mass, and body hair.
Other hormones exist: oxytocin, our love hormone?
Sex hormones don’t just influence sex
They also influence behavior.
“Some evidence suggests at least a small role of [androgens] in the ongoing maintenance of adult sex differences in empathy and dominance striving. For example…found a negative association of basal testosterone with maternal ambitions in women” (McIntyre, 2009, pp. 85).
“Recent evidence suggests that willingness to enter new contests in influenced by basal testosterone…men’s testosterone levels fall in response to failures in dominance contests” (pp. 86).
Sex hormones influence our behaviors as well. One thing to consider in this discussion is why sexual dimorphism evolved in our species. Let’s consider here how hormones may have evolved as a result of the behaviors selected in our species. One thing we saw with neanderthals was that they didn’t appear to have a major division of labor between males and females. Homo sapiens did. This division of labor may have been sexually selected by choosing mates with certain traits.
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Sex differences in the brain
Consider these differences between men and women.
http://www.ucd.ie/artspgs/langimp/genderbrain.pdf
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What does this all reflect in our evolutionary development?
Men as hunters and women as gatherers, and protectors of children.
These differences are real and enormously influential in our bodies. We even have a discipline called “gender medicine.”
Women have most breast and all ovarian cancer, and have higher rates of osteoporosis and Alzheimer’s. We also have higher rates of depression, bipolar, and anxiety.
Men have all testicular cancer and higher levels of autism and X-linked traits like color blindness. They are also more susceptible to anti-social mental health disorders.
This means we have to understand how the sexes truly differ in order to understand disease and illness among our species.
If you combine more muscle, greater grip, greater burts of energy, target directed motor skills, etc…you get a hunter. When you consider more fat, facial recognition, and bonding you see child rearing. It’s possible that our hormones have impacted our behaviors in order to support a division of labor that protected children.
http://www.sciencedirect.com/science/journal/15508579
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What about the future?
Are women still influencing the evolution of men?
Psychologists and biologists alike see relationships changing through oxytocin. Men are more involved with parenting and monogamous relationships, and that success seems to be dependent on them being more receptive to oxytocin genetically.
This means we could be slowly weeding out the “hunter” tendencies of the men we once preferred, to men who work more functionally in a social unit.
Consider menopause and life expectancy
Something to consider is whether or not we will continue to evolve as a result of sexual selection. According to some research, we are. Women are choosing men with different traits and causing their hormone averages to change as well. What implications might this have for our species?
Remember when we talked about early puberty? Something else to consider here is aging. Women enter menopause in their early 50s, but research shows that those who have menstrual cycles earlier, also enter their menopause earlier.
http://www.scientificamerican.com/article/be-mine-forever-oxytocin/
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What is the process of aging?
Senescence: is the process of deterioration with age.
Aging: the declining ability to respond to stress, inability to maintain homeostasis of body, and increase susceptibility to age related diseases.
Menopause is just one aspect of the aging process. Senescence is the deterioration with age. Aging is the body’s increasing inability to deal with all stress. The rest of this lecture will look at what happens when the body ages and why we have evolved to age.
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Normal Human Aging - Skin
Skin becomes less elastic with more wrinkles.
“After the age of 20, the skin produces 1% less collagen per year” (Obagi, 2005).
Skin becomes thinner and fragile. Less elastin is produced, and sweat and oil glands function less.
Environment causes skin to look harder as well as uneven through things like sun spots.
One of the first changes in an aging body is skin. It becomes less plastic and the collagen begins to deteriorate, causing wrinkles. One thing you can do to prevent loss of collagen is consume vitamin A. Retinol products also appear to be helpful.
http://www.scientificamerican.com/article/why-does-skin-wrinkle-wit/
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Sun damage causes aging of skin
Melanin protects against UV damage as much as it can, but eventually you get a sunburn.
This damage can cause destruction of collagen, discoloration, and a leathery look to the skin.
Sun spots are also a factor with age, but primarily something that happens from UV radiation. UV radiation damages DNA and a cell’s ability to produce collagen. Wear sunscreen and cover your skin!
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Smoking cigarettes causes aging of skin
Nicotine and other chemicals in cigarette smoke promote less oxygen in the skin, narrows the blood vessel size on the skin’s surface, and cause the breakdown of collagen.
Cigarettes are also an environmental factor that causes less oxygen to get to the skin, again causing collagen to stop being produced. Stay away!
http://www.nydailynews.com/life-style/health/photos-twin-study-shows-smokers-age-faster-article-1.1501691
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Normal Human Aging - Hair
Hair becomes thinner due to slower production of proteins that structure the hair.
Hair follicles stop producing melanin slowly, causing it to grey.
Graying hair happens because hair follicle cells stop doing their jobs functionally as they begin to age. There is no real way to prevent this.
http://www.nlm.nih.gov/medlineplus/ency/article/004005.htm
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Stress and grey hair?
Some evidence suggests that stress hormones drive the production of free radicals, which impact melanocytes in hair follicles.
However, some studies have shown that unnecessary stress can harm cells with free radicals, causing them to fail at producing melanin.
http://www.scientificamerican.com/article/fact-or-fiction-stress-causes-gray-hair/
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Normal Human Aging - Height
“Men can gradually lose an inch between the ages of 30 to 70, and women can lose about two inches. After the age of 80, it’s possible for both men and women to lose another inch” (“Do people shrink as they age?, n/d).
Cartilage between the joints wears out and osteoporosis shortens the spine.
Broken and weak bones, as well as slow loss of muscle mass can cause you to become shorter, and hunched.
http://www.uamshealth.com/?id=12264&sid=1
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Why do we age? Evolutionary theories
Evolutionary theories suggest that once you surpass your reproductive ages, you’re essentially expendable and the body no longer invests energy in its maintenance.
Mutation Accumulation: deleterious mutations accumulate and affect you later in life, after you’ve reached your reproductive capacity.
Disposable soma theory: The body has a finite amount of energy. There is a compromise of using this energy towards healing. The need to accelerate gestation limits the time allocated to cellular repair, leading to the above.
Antagonistic pleiotropy: One gene has two or more effects on phenotype, one bad and one good. I.e., genes used for development early on in life can influence ageing later on in life.
Ex. P53 gene can repair DNA damage, or initiate cell death.
Please read the article “Theories of Aging” for this discussion. Now that we have seen what happens to the body when it ages, it helps to consider why. The evolutionary theories of aging describe aging as a process of deterioration once you can no longer reproduce. What this means is that you are essentially expendable when you’re not able to reproduce. You have less biological value and thus, less energy is put into maintaining the body.
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Why do we age? System theories- Loss of system control
Neuroendocrine system theory: All the molecular and cellular effects described slow down our adaptation to the environment, with generally slower responses to change.
Adrenal glands control energy release for life stages, stress slows this control, leading to a loss of the maintenance of the body.
The neuroendocrine system also controls actions of the cells through signals and prevents their disorganization.
Systems theories like the endocrine system look at how hormones, which signal for all our growth and development, stop functioning properly.
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Why do we age? System theories- Loss of system control
Immune system theory: The immune system controls and eliminates foreign organisms in the body, while recognizing the body and not destroying interior cells.
Lower functioning immune system means less resistance to infectious diseases, cancers, and increased failure for immune cells to recognize foreign objects against the body cells.
Immunotherapy
Macrophages identify a cancerous tumor, latch on and inject toxins
Immune system theories look at how the immune system shuts down as cell begins to die or get too old to function properly. This allows disease to impact the body much more quickly and dangerously. One major issue with a poor immune system is an increased susceptibility to cancer.
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Cancer
Cancer is a natural product of the body.
When cells being apoptosis, stimulating cancer growth is one option for the cells parts.
All the effects of aging inhibit the body’s ability to control cancer formation.
In fact, death and aging itself are probably mechanisms that evolved to prevent cancer, and thus, us extending ours lives explains increased rates of cancer in our species.
Tumors are filled with senescent cell parts.
54 environmental carcinogens have been linked to cancers like arsenic and asbestos. Cigarettes account for 30% of all cancer deaths.
Some scientists believe that we age to PREVENT cancer. The time of aging is likely an evolved adaptation because the longer we live, the more cells age, and the more cells become susceptible to turn into cancer.
http://www.nature.com/nature/journal/v448/n7155/full/nature05985.html
http://www.cancer.org/cancer/cancercauses/othercarcinogens/generalinformationaboutcarcinogens/known-and-probable-human-carcinogens
http://www.scientificamerican.com/article/how-many-cancers-are-caused-by-the-environment/
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Why do we age? Molecular theories
Gene regulation: Aging is caused by changes in the expression of genes regulating both development and aging.
Codon restriction: Accuracy of mRNA translation in impaired due to inability to decode codons in mRNA.
Error catastrophe: Decline in accuracy of gene expression with aging results in increased fraction of abnormal proteins.
Ex. Lou Gherig’s disease
Somatic mutation: Molecular damage accumulates primarily to DNA/genetic material.
Dysdifferentiation: Gradual accumulation of random molecular damage impairs regulation of gene expression.
These molecular theories look complicated but consider the chart in the article. Each of these is essentially a malfunction that occurs within the cell’s machinery that prevents the cell from doing it’s job. As more and more of the jobs of the cell malfunction, the cell begins to impact those around it and eventually it will die.
http://www.sciencedaily.com/releases/2013/02/130212121856.htm
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Why do we age? Cellular theories
Free radical theory: While mitochondria produce energy, they also produce free radicals.
Free radicals are oxygen containing molecules with a single, unpaired electron, meaning they are searching to steal and eventually destabilize other parts of the cell.
Oxidative stress is caused, which is the inability of the body to stabilize these reactive molecules.
Antioxidants are molecules that offer electrons free radicals to alleviate their damaging effects.
Be careful with exogenous doses of “antioxidants” like vitamin C as they can become toxic.
The free radicals also have protective effects against cancer formation during apoptosis, so if you have low levels of free radicals, then antioxidants like vitamin C could promote cancer development.
Cells can harm each other easily through their increased failures. One issue is free radicals, which are a product of energy creation by mitochondria. These free radicals are unstable molecules that cause other molecules to malfunction. A large enough collection of these can damage a cell and it’s ability to do its job.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2952083/
http://www.ncbi.nlm.nih.gov/pubmed/11603657
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Why do we age? Cellular theories
Cellular senescence: Cells have a limited number of replications, this is called the Hayflick limit. This leads to apoptosis.
Eventually, a cell reaches its own stage of senescence. Cells age just like we do. Once they reach a certain point, they commit cell suicide, otherwise know as apoptosis. This limit is called the “Hayflick Limit,” or the number of times a cell can divide. The question remaining is, how does a cell know how many times it’s divided and when it has enough damage to enter apoptosis?
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Telomere hypothesis – Immortality?
Telomeres are the end caps to chromosomes, which shorten upon cell replication.
As the caps shorten, the ability to replicate effectively decreases.
Eventually the cell begins apoptosis once the telomeres are gone.
This leads to aging in the body.
The answer to the last question is telomeres. Telomeres are caps on the end of chromosomes that shorten every time a cell divides. Think about the plastic cap on your shoe lace. If it were to shorten every time you tied your shoe, everything the cap would be gone, the lace would fray, and you would no longer be able to lace or tie the shoe. This analogy works for DNA. Once the telomere cap is gone, the DNA will fray and be susceptible to damage. This is the signal to the cell to commit apoptosis. The key to aging is to understand how to maintain our telomeres, the next few slides suggest some ways that have been proven to impact the slowing of the aging process.
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So how do we control aging?
Diet!
Making sure we’re receiving the nutrients necessary for cells to function properly is probably the most important factor in aging.
When nutrients are lacking, cells cannot replicate and properly produce proteins necessary for body structure, development, growth, and healing processes.
Boost your immune system…
This is more complicated than it sounds as we still don’t know every part of the immune system and how different cells work, especially with bacteria, to help battle foreign objects.
Research shows that “micronutrient deficient” diets are associated with poor T-cell and microphage production, meaning lower immune response.
Research in the use of herbs such as Echinacea or “probiotics” have been small and inconclusive.
Exercise has also been studied inconclusively.
http://www.health.harvard.edu/staying-healthy/how-to-boost-your-immune-system
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Reduce caloric intake
“The observation that laboratory rats not only live longer but also have fewer age-associated diseases when their food intake is restricted dates back to the 1930s”.
“Caloric restriction also extends the life span in species as diverse as protozoans, water fleas, spiders, and guppies.3 In chickens, ad libitum feeding increases the incidence of diseases and reduces the life span.13 These studies in animals indicate that caloric intake above an optimal level shortens the life span. (Weindruch, et. all, 1997).
Remember, this is not due to fat deposits, but to oxidative stress.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2851235/
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Stress and Mortality
New study shows a connection between perceived psychological distress and earlier mortality.
“…symptomatic patients were at a 29% increased risk of cardiovascular disease death.”
“Psychological distress in highly symptomatic patients was associated with a 41% increased risk of cancer death.”
“These associations remained after adjustment for age, sex, current occupational social class, body mass index, systolic blood pressure, physical activity, smoking, alcohol consumption, and diabetes” (Russ, et. All, 2012).
http://www.bmj.com/content/345/bmj.e4933
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Can meditation help? The Shamatha Project
Studies at U.C. Davis & U.C. San Francisco have suggested that meditation improves psychological well-being, which is indirectly associated with increased production of telomerase in immune cells.
“We assessed a number of health-relevant biomarkers that may change as a result of meditation training. One of these, telomerase, an enzyme that protects genetic material during cell division and enhances cellular viability, is often suppressed in response to psychological distress. Blood samples obtained at the end of the retreat revealed that telomerase activity was significantly greater in retreat participants (vs. controls) and that telomerase activity was related to meditation-induced changes in well-being”
Current research up for publication suggests that meditation is associated with better impulse control, longer attention spans, and finer visual distinctions.
http://www.ls.ucdavis.edu/dss/news-and-research/shamatha-project-nov10.html
http://mindbrain.ucdavis.edu/labs/Saron/meditation-research/research-areas
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