Adaptation to Biological Stressors, Part 1: (Mal)Nutrition PDF

Adaptation to biological stressors, part 1: (Mal)Nutrition AANT 211: Human Population Biology Introduction Malnutrition/nutrition (today) Infectious diseases (part 2) 2 Malnutrition 1. Too little Protein-calorie malnutrition (PCM) -Periods of s...

Adaptation to biological stressors, part 1: (Mal)Nutrition AANT 211: Human Population Biology Introduction Malnutrition/nutrition (today) Infectious diseases (part 2) 2 Malnutrition 1. Too little Protein-calorie malnutrition (PCM) -Periods of starvation - Total lack of food - Insufficient quantity/quality 2. Too much Overabundance 3. Poorly balanced Chronic micronutrient malnutrition -Unbalanced diet 3 4 Malnutrition undernourished 5 Malnutrition obesity 6 Nutrients vs Food 7 Nutrients Energy and materials Macronutrients – Carbohydrates – Proteins – Fats (lipids) Micronutrients – Vitamins – Minerals 8  Protein Structure Amino acids Peptides Function Highly variable Can be broken down into building blocks 9  Proteins → Amino Acids Protein – When broken down, can be used to make other amino acids Non-essential amino acids Some amino acids cannot be created by us – Essential amino acids must be consumed Deficiency in any essential amino acid causes a general protein deficiency in the body – E.g., reliance on a single plant source 10 Protein Quality of Foods Mesoamerican Diet Maya/Aztecs of the past Mexico and Central America today Beans and maize (corn) Several plants used = less risk for deficient essential amino acids 11 Protein Deficiency 12 Energy Reserves PCM: Total Undernutrition Total diet is reduced – Protein/energy deficiency Three types of energy the body uses 1. Glycogen (stored version of glucose) – Stored in liver and muscles – Short-term source (preferred source) 2. Fat – Lipid molecules – Long-term source/major energy storehouse 3. Protein – Broken down to provide energy – Synthesize glycogen 13  Biology of Deficiency After reserves of glycogen and fat are depleted: – Breakdown of protein begins Muscles Immune system Children at greater risk Growth disruptions Kwashiorkor Marasmus 14  Growth Disruptions Children typically have similar growth patterns Need a lot of protein to sustain growth Stunting - reduction in linear growth Wasting - low weight-for-height Harris lines – bone growth slows due to physiological stress 15  Biology of Deficiency Malnutrition in children Kwashiorkor Protein deficiency Adequate intake in other categories Edema/enlarged liver Made worse due to weak abdominal muscles Marasmus Severe malnutrition in all categories Dehydration Emaciation 16 Overnutrition Accelerated growth during childhood Early menstrual cycles Decelerated growth during adolescence Not just a “developed” world problem 17  Can We Adapt? Compared to other mammals? “Buying time”—short term Central nervous and reproductive systems spared No population differences in the ability to withstand periods of starvation “Thrifty genotype” 18 Micronutrient Deficiencies Vitamins/minerals Occurs due to: Poor quality diet Reliance on a limited range of resources 19 Vitamin A (Retinol) Derived from beta-carotene Stored in the liver Rhodopsin protein deficiency – “night blindness” Epithelium – dry hair, scaly skin, and brittle nails 20 Vitamin B1 (Thiamine) Carbohydrate and protein metabolism – Issues arise for high-carb diets Production of neurotransmitters Myelin production Milled vs. unmilled rice Beriberi disease – Wet (heart, circulatory system) – Dry (nerves and muscles) 21 Vitamin C (Ascorbic Acid) Collagen production Historically affected sailors on long journeys Scurvy Swollen, bloody gums Loose teeth Bulging eyes Severe and easy bruising Scaly, dry, brownish skin Very dry hair that curls and breaks off close to the skin Currently observed in Populations during late winter/early spring Low income with poor diet 22 Vitamin D (calcitriol) Stimulates calcium absorption in the small intestine Bone deposition Osteomalacia (poorly mineralized bones) Rickets 23 Electrolytes Minerals that have an electric charge Present in tissues and body fluids 24 Iron Deficiency One of the most prevalent nutritional problems in the world Anemia – Fatigue, neurological impairment, sore muscles, lower immune functions 25 Iron Deficiency 26 Iodine Needed to make thyroid hormone Regulates development Metabolism Deficiency – goiters Overworked thyroid gland Hypothyroidism 27 Lactose Tolerance Lactose & lactase Lactase activity decreases with age in mammals Lactase restriction (lactose intolerance, lactose malabsorption) Why can some populations continue to digest lactose? 28 Lactose Tolerance Lactase persistence is determined by whether an individual carries one of several alleles in the LCT gene or promoter region For carriers of lactose intolerance-associated alleles the age of onset and severity of symptoms are highly variable Convergent evolution Lactase persistence evolved separately in different regions Distinct genetic events Different SNPs involved Evidence for strong selective pressure over past 5,000- 10,000 years Shared cultural traits: animal domestication and adult milk consumption Proportion of population with lactase persistence Co-evolution of genes and culture Pastoral adaptation Adult milk consumption Animal raising Adaptive benefits Role of milk Carbs, fat, calcium, protein Drawbacks of lactose intolerance Diarrhea, water loss Tinbergen’s Four Questions How can we use them to explain variation in lactase persistence?  Why would human biologists criticize this claim?