Option A: Human Nutrition and HealthA1: Components of a human diet

Jamie Oliver’s TED talk http://www.youtube.com/watch?

v=go_QOzc79Uc

Nutrients

Essential vs. Non-essential Nutrients are chemical substances,

found in foods, that are used in the human body.

Essential: foods are the only possible source of the nutrient. Ex.: some amino acids, calcium, vitamins, water

Non-essential: either another nutrient can be used for the same purpose or they can be made in the body from another nutrient. Ex: some amino acids, glucose.

Types of nutrients

Protein deficiency malnutritionMalnutrition

A diet lacking one or more essential nutrients. Example: scurvy, a disease that causes swollen gums, loose teeth, and small black and blue spots on the skin

Undernutrition A person whose

diet is deficient in Calories. Eventually the body begins breaking down its own protein molecules for fuel.

Protein deficiency malnutrition If there is shortage of one or more essential amino acids

in the diet, then the body cannot make enough proteins such as plasma proteins, extracellular proteins, DNA and plasma membranes in the body.

Protein deficiency malnutrition is a key factor in kwashiorkor. Symptoms include: Stunted growth Muscle and skin problems Impaired mental development Immune system impairment Edema (swelling in the abdomen and legs as plasma

proteins responsible for balancing tissue fluids are not produced, so fluid builds up)

Phenylketonuria PKU is a genetic disease caused by a

mutation of a gene coding for the enzyme that converts phenylalanine into tyrosine. Phenylalanine is not converted into tyrosine.

Phenylketonuria PKU is autosomal (any chromosome

that is not a sex chromosome) and recessive (it only occurs in individuals with two recessive mutant alleles)

This disorder is progressive : its effects build up over time and lead to ongoing deterioration.

Phenylketonuria Since phenylalanine is not converted it

builds up in the body causing potentially serious consequences: skin disorders intellectual disability heart problems microcephaly can also develop in severe

cases.

Phenylketonuria PKU babies are unaffected at birth

because their mother’s metabolism has kept phenylalanine and tyrosine at normal levels. This allows for early diagnosis during the first days after birth.

http://www.nandoperettifound.org/en/page.php?project=143

Phenylketonuria Treatment: A diet low in phenylalanine: small dosis

of meat, fish, dairy, nuts, peas and beans. No aspartame sweeteners.

Tyrosine supplements

Fatty acids

Molecular structure of fatty acids

The difference is in the double bonds!

All possible valences have been occupied

Molecular structure of fatty acids

- High density energy store- Solid at room

temperature- Animal products, palm

and coconut oil.- High risk of coronoary

heart disease (CHD)

- Usually oils at room temperature- Usually from plant sources- Olive oil- Less risk of CHD

Molecular structure of fatty acids

There is also variation in the structure of unsaturated fatty acids. cis- isomers have the hydrogen atoms on the same side of the C=C double bond, whereas trans- isomers have the hydrogen atoms on opposite sides. Most trans- fats are created artificially.

the omega-number indicates the position of the first double bond, from the CH3 group

Summary Saturated vs. Un-saturated fatty acids:

which is healthier? Omega 3 and Omega 6: what’s the

difference? Cis- vs. Trans- fatty acids: what’s the

difference? Which is healthier?

Evaluate the health consequences of diets rich in the various types of fatty acids

Fatty acids and health Many claims about the effects of different

types of fatty acids on human health. Difficult to control experiments to show clear causal links, instead: correlations.

Positive correlation between saturated fatty acid intake and rates of coronary heart disease (CHD).

Ex: Olive oil – contains cis-monounsaturated fatty acids low rates of CHD.

However it could also be other aspects like tu high consumption of tomatoes or genetic factors.

Positive correlation between intake of trans fatty acids and CHD: Fatty deposits in arteries of people who died from CHD were found to contain high concentrations of trans fats.

Other risk factors do not account for the correlation: therefore, trans fats probably cause CHD

Omegas? Several long chain omega-3 fatty acids

are essential, particularly for the development of the brain and the eye.

There’s little or no evidence that supplementation of a normal diet enhances brain or eye development.

Vitamins and minerals

Vitamins: Organic compounds made by plant or animals.Vitamin C: ascorbic acid

Minerals: Inorganic ions, mostly found in water, soil and many organic food types as a result of uptake.

Both are needed in the diet in relatively small quantities – mg or µg per day. If any is lacking from the diet, a deficiency disease results. Ex.: mineral iodine thyroid gland: thyroxin metabolic rate.No iodine iodine deficiency disorder (IDD) goiter development and mental impairment

Vitamin C Needed for the synthesis of the collagen

fibers that form many parts and tissues in the body (cartilage, bones, hair, skin, blood vessel walls).

Linus Pauling, a distinguished chemist and double Nobel laureate, claimed that taking massive doses of vitamin C protects the body against upper respiratory tract infections.

Others have issued counter-claims: if intake is high and later drops down to normal levels, symptoms of scurvy develop: rebound malnutrition.

How to determine the recommended daily intake of vitamin C

Recommended Daily Intakes (RDI) of vitamin C are set at 45-60mg day-1.

These levels were determined based on a number of experiments into levels of vitamin C that gave optimum benefit.

Humans and guinea pigs cannot synthesize vitamin C, so it is possible to measure the effects of varying vitamin C doses in carefully controlled experiments.

Human trials Conscientious objectors from WWII volunteered to take part in a

series of medical trials in Sheffield over a four-year period.

20 volunteers were used to measure the effects of varying vitamin C concentrations.

Weeks 1-6:  No vitamin C in foods, but all given 70mg supplementWeeks 7-end (8 months): 3 kept on 70mg per day, 7 were given 10mg per day and 10 were given no vitamin C at all.

Measurement: periodic incisions were made on volunteer’s thighs, and healing time and strength of healed tissue were observed. Blood and urine vitamin C concentrations were recorded.

Outcomes: no ill effects were recorded in the 70mg or 10mg groups. The 0mg group developed scurvy within 6-8 months and some serious side effects were recorded, including one who experienced heart problems, which were rectified after he was given vitamin C.

Guinea pig trials Observe the effect of vitamin C

concentration on collagen structure

After periods of varying vitamin C supplementation and measurement of blood and urine vitamin C levels, guinea pigs were sacrificed and the structure of collagen fibers observed.

Guinea pigs with restricted vitamin C showed weaker collagen.

Vitamin D Needed for calcium absorption from food in the

intestines. Deficiency in vitamin D is similar to deficiency in

calcium, with children developing skeletal deformities (rickets)

It can be synthesized in the skin with a light source containing UV light (sunlight)

Children, elderly and pregnant women are recommended to eat 10µg/day.

However, UV light has some harmful consequences, like skin cancer. Melanin intercepts and absorbs UV light giving good protection against cancer, but also reducing vitamin D synthesis.

http://www.mja.com.au/public/issues/175_05_030901/grover/grover.html

http://www.fitandhungry.com/fitness/10-foods-that-wont-make-you-fat-or-poor/