Primate Nutrition & Malnutrition

Review of Food Selection Models

• Four types of diet in nonhuman primates:
  • Insectivores: Eat insects.
  • Frugivores: Eat fruit.
  • Folivores: Eat leaves.
  • Gumivores: Eat sap.
• Models of food selection in frugivores and folivores:
  • Protein maximization: Prioritize foods to increase protein intake.
  • Nutrient balancing: Select foods to balance nutritional needs.
  • Energy maximization: Increase energy intake.
  • Fiber minimization: Reduce intake of high-fiber foods to ease digestion.
  • Plant secondary compound (PSC) minimization: Avoid toxins and tannins.
• Limiting nutrient example: Protein is a limiting nutrient for frugivores like humans and chimps.

Introduction to Nutrition

• Nutrition is complex, involving macronutrients (carbohydrates, protein, fat) and micronutrients (vitamins, minerals).
• Nutrients: Required for life, growth, and well-being.
• Macronutrients: Used for energy, cell multiplication, and repair (relevant for growth and reproduction).
• Micronutrients: Minerals and vitamins critical for metabolic processes. Metabolic processes are how you convert food into energy.

The Spectrum of Nutrition

• Nutrition ranges from overnutrition to proper nutrition to undernutrition.
• Proper nutrition: Balanced nutrients, metabolic needs are met, no excess or shortage of food.
• Overnutrition: Often seen as overweight in developed countries.
• Undernutrition: More common in developing countries, results from insufficient food intake.
• Many adults in developed countries, despite overconsuming, underconsume micronutrients (calcium, iron, magnesium, zinc, folate, vitamins).
• Those experiencing over nutrition benefit from fresh fruit and vegetables, while people experiencing under nutrition primarily need protein, animal source foods, and carbohydrates.
• Current dietary habits in high and low-income nations may not align with human biology due to cultivated or processed foods.
• Malnutrition includes both under and over nutrition.
• Overweight and obese are terms on a spectrum, as are underweight, wasting, stunting, and deficiencies.

Assessing Nutritional Requirements in Humans

• Nutritional requirements are determined through extensive observational and experimental studies in humans.
• Studies account for age, sex, and reproductive status (pregnancy and lactation).

Assessing Nutritional Requirements in Non-Humans

• Fewer experimental studies are available for non-human primates.
• Two methods:
  • Basal metabolic rate.
  • Geometric framework

Basal Metabolic Rate

• Basal metabolic rate (BMR): Energy expenditure at rest.
• Measured using isotopes like double-labeled water to track oxygen and hydrogen levels.
  • Limitations: Doesn't provide information about nutrient needs.
• Can be estimated through saline injection.
  • Inject a saline with Oxygen 18 isotope.
  • Take a blood sample.
  • Release animal.
  • Recapture after a week.
  • Take another blood sample.
  • Isotope ratio is measured.
• Example: Howler monkey BMR is $355$ kilojoules per kilogram per day, but depends on age and sex.

Geometric Framework

• Applies geometric framework analysis using a right-angle mixed triangle.
• Identifies nutrient rails: Consistent selection indicates essential nutrient ratios.
• If foods are combined in proportions that result in a diet of similar nutrient balance, then this suggests that the diet selection is driven by nutrient specific regulation.
• Example: Milk in gorillas and marmosets has a consistent protein ratio, suggesting selective mechanisms for healthy offspring.
• Diet determines needs in non-human primates, unlike humans where doctors recommend diet changes based on needs.

NRC Guidelines

• Charts for primate nutrition come from the National Research Center (NRC).
• The NRC interested due to biomedical testing on primates.
• Limited to lab species like macaques.
• Uses diet as the basis for assumed nutritional needs.
• Not available for all species (e.g., pet marmosets).
• Serves as a primary source for measuring nutritional requirements in captivity.

Assessing Adequate Nutrition

• Indirect methods: Population-level assessments.
  • Ecological variables: Crop production, rainfall, drought.
  • Economic factors: GDP, per capita income, housing density.
  • Vital health statistics: Infant mortality, birth rates, reproductive rates.
• Direct methods: Individual assessments.
  • Anthropometry: Height, weight, proportions to evaluate under/over nutrition.

Anthropometry

• Weight for age: Low weight indicates protein-energy malnutrition (PEM).
• Doesn't always differentiate acute from chronic malnutrition.
• Weight for height: Indicates recent weight loss (acute malnutrition).
• Height for age: Stunting indicates chronic malnutrition.
• Measurements in children: Arm circumference, fat folds, head circumference.
• Compared against growth charts (separated by sex).
• Measurements in adults: Height, weight, BMI (Body Mass Index).

Body Mass Index

• BMI:
  • Under 18: Underweight.
  • 25+: Overweight to obese.
  • 18-24: Healthy.
• Waist-to-hip ratio: Assesses body shape. Obese if over $0.8$ for females or $0.95$ for males.
• Waist circumference: Predicts mortality. Risk levels at over $94$ cm for males and $80$ cm for females. Greater danger at $102$ cm for males and $88$ cm for females.

Benefits of Anthropometry:

• Objective, reproducible, numerical results.
• Relevant to nutritional status.
• Minimal training, inexpensive.

Limitations of Anthropometry

• Error between observers.
• Limited nutritional diagnosis.
• Problems with reference standards (based on white Western European populations).
• Arbitrary cutoffs for obesity.

Biochemistry

• Blood tests: Hemoglobin (anemia, deficiencies).
• Feces: Parasites.
• Urine: Albumin (kidney disease), sugar, iodine, blood, creatinine (protein digestion).

Clinical Signs

• Physical signs associated with malnutrition, assessed through observation and questioning.
• Examine hair, mouth, gums, nails, skin, eyes, tongue, muscles, bones, thyroid.
• Fast, easy, inexpensive, non-invasive.
• Hard to use for acute cases; deficiencies take time to manifest.
• Relies on accurate information from the individual.

Dietary Evaluations

• 24-hour dietary recall: Quick but relies on memory and honesty.
• Dietary history: More accurate but requires skilled interviewer and verification.
• Food frequency questionnaire: Relatively inexpensive but requires updating.
• Food diary: Reliable but difficult to maintain.
• Observed food consumption: Highly accurate but expensive (clinical settings).

Application to Non-Human Primates

• Dietary evaluation relies on observation.
• Economic factors relevant to humans but less so for non-human primates where rank and status affect access to nutrition.
• Anthropometry: Easier in captive primates.
• Free-living primates require trapping and anesthetizing, raising ethical concerns.
• Measurements: Weight, body fat.
• Biochemistry: Easier in captivity than in the wild but possible.
• Urine collection is difficult.
• Feces and hair collection are more feasible.
• Blood collection is best in captivity.
• Clinical signs: Hair loss, skin conditions.
• Dietary observation: Estimate food intake, feeding rates, nutrient profiles.
• Methods: Focal follows (detailed observation), scans (group snapshots), full-day follows.

Assessing Adequate Nutrition (Free-living Primates)

• Indirect methods:
  • Dietary switching: Shift to lower-quality fallback foods when preferred foods are scarce.
  • Shift in activity budget: Adjust time spent feeding, traveling, and resting.
  • Shift in sociality: Alter group size or spread out to reduce feeding competition.
  • High ranking: Provides greater access to nutrition; changes in rank affect nutrition.
• Physiological adaptions:
  • Losing and gaining weight.
  • Building up fat reserves.
  • Lactation.
• Multiyear lactation (e.g., orangutans) may buffer infants through periods of low fruit availability.
• Population health: Birth rates, death rates, twinning rates, population density, age class distribution.
• Biomass measurements: Protein-to-fiber ratio.
• Ecological indicators: Drought, rain production.

Malnutrition

• Humans worldwide struggle with inadequate nutrition, including both over and undernutrition.

Protein Energy Malnutrition (PEM)

• Most common form of malnutrition in humans.
• A severe acute malnutrition.
• A result in increased mortality.
• Characterized by:
  • Underweight.
  • Wasting (low weight for height).
  • Stunting (low height for age).
• Moderate wasting and stunting are two to three standard deviations from the mean.
• Can cause cognitive deficiencies, affecting cranial vault capacity, brain weight, and brain composition.

Intervention

• Administer protein, energy, micronutrients, and water.
• Electrolytes.
• Treat Infections (worms).
• Give 3 to 4 grams protein or about 200 calories per kilogram a day, use vitamins and minerals.
• Prevent hypothermia.
• Plan future care with parents.
• Interventions improve physical growth, but cognitive deficiencies are harder to address.
• Deficits during the first thousand days of life (including in utero) are particularly challenging to reverse.

Kwashiorkor

• A form of protein-energy malnutrition.
• Severe lack of protein, leading the body to consume its own proteins while saving fats and makes the body eat it's own proteins, saving fats, resulting in a inflated belly.
• Common Features:. Edema (swelling/water retention), psychomotor changes, growth retardation, muscle wasting skin depigmentation, anemia, moon face, and hair discoloration.

Marasmus

• Inadequate protein, energy, and calorie intake.
• Common in the first year, often due to lack of breastfeeding or diluted animal milk.
• End result of starvation.
• Contributing factors: Poverty, famine, diarrhea, ignorance, poor maternal condition.
• Severe muscle and fat wasting, growth retardation.
• Individual looks older than their age.
• Alert but miserable; hungry and dehydrated.
• Kwashiorkor is a maladaptive response since it uses proteins before fats, whereas merasmus is adaptive since it uses fats before muscles.
• PEM can be comorbid with low sugar, low body temperature, low potassium/sodium, heart failure, dehydration, and infections.
• Most deaths from PEM result from diarrhea, respiratory infections, and perinatal causes, as well as measles and malaria.
• Undernourished individuals benefit from animal source foods for protein and cereal foods.

Protein Energy Malnutrition Among Non-Human Primates

• Marmosets in captivity may engage in coprophagy (eating feces) when protein is lacking.
• Difficult to measure due to lack of knowledge about specific primate requirements.
• Often rely on scaling down human numbers.

Micronutrient Deficiencies

• Micronutrients: Vitamins and minerals.
• Minerals: Inorganic substances from soil and water.
• Vitamins: Organic, from plants and animals.
• Minerals tend to be higher in wild foods rather than cultivated crops.
• Living primates often consume high levels of micronutrients compared to human recommendations.
• May be unavoidable, have low bioavailability, higher assimilation efficiency, or mitigate toxic food effects.
• Micronutrient deficiencies are common in captivity; all deficiencies are possible.
• The New World primates often have high levels of anemia. But a lack of B12 or iron are also often seen.

Common Deficiencies in Humans

• Vitamin A:
  • From tuna carrots and sweet potatoes.
  • Good for eyesight; regulates genes, maintains skin & immune system, and red blood cell production.
  • Deficiency leads to vision problems, susceptibility to disease.
• Vitamin C:
  • From citrus, cranberries, broccoli.
  • Stabilizes free radicals, forms connective tissue & collagen, increases white blood cell production.
  • Deficiency leads to tissue breakdown, bruising, bleeding.
• Vitamin D:
  • From sun, fish, red meat, egg yolks.
  • Helps calcium and phosphorus absorption, maintains immune function.
  • Deficiency leads to weakened immunity, rickets.
• Iodine:
  • From iodized salt, fish, soy sauce, eggs, milk.
  • Helps thyroid production, regulates metabolic processes, temperature regulation.
  • Deficiency leads to mental retardation, enlarged thyroid, intolerance to cold.
• Folic Acid:
  • From citrus fruits and cranberries.
  • Helps red blood cell production, brain function; converts carbohydrates into energy.
  • Deficiency leads to reduced oxygen, forgetfulness, neural tube defects, low growth.
• Zinc:
  • From red meat, fish, poultry, dairy, cereals.
  • Good for cell division, fertility, sex hormones, immunity, hair follicles, and vision.
  • Deficiency leads to slowed growth, delayed sexual maturation, impaired immune, lesions on skin and eyes, diarrhea and hair loss.
• Biotin:
  • From Egg yolks, liver, yeast.
  • Converts carbohydrates into glucose and metabolizes fats and proteins.
  • Deficiency leads to tiredness, brittle hair, and skin, with possible depression.
• Iron:
  • From red meat, leafy greens, apricots.
  • Helps transport oxygen, converts blood sugar to energy, forms red blood cells, produces enzymes, cells & hormones.
  • Deficiency leads to fatigue, dizziness, decreased immunity, anemia.
• Adults in developed countries may benefit from increased fruit and vegetable consumption due to these micronutrient deficiencies.

Clinical Observation

• Hair: Sparse, thin may be protein, zinc, or biotin deficiency; easy to pull out may be protein; coiled may be vitamin C or A.
• Mouth: Inflamed tongue may be B vitamin deficiency; bleeding gums may be vitamin C, A, K, B; sores at corners may be B2, B3, or B6.
• Eyes: Night blindness or protruding eyes may be from vitamin A deficiency; light-sensitive or blurred vision may be vitamin A or B deficiency.
• Nails: Spooning indicates iron deficiency; lines across indicate protein deficiency.
• Skin: Pale may be vitamin B or iron deficiency; bumps on hair follicles may be vitamin B or C; dermatitis or peeling maybe from protein deficiency or vitamin A, B, and zinc. Red and bruising may be from vitamins C, K or B9.
• Human and non-human assessments of their nutrition includes knowledge of their requirements and their direct and indirect testing.
  Direct Testing (clinical testing, physical testing)
  Indirect testing (population estimates)
• Double-labeled water can assess basal metabolic rate.
• The most common human deficiency is the protein energy malnutrition.