Chapter 11: Water and the Major Minerals

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Recap of last lecture

• GM foods
• Vegetarianism
• Proteins
• Diet analysis
• Review session

2
27 Outline for today

• Proteins
• Food additives
• How to find nutrition answers on the web

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Is a High-Protein Diet Harmful?

• Low in plant foods (fiber), vitamins,
  phytochemicals
• Intake of animal protein increases risk for heart
  disease (high in saturated fat)
• Excessive intake of red meat is linked with colon
  cancer
• Burden on the kidney
• Increased calcium loss
• National Academy of Sciences recommends no more
  than 2 x RDA for protein

4
Individual Amino Acid (AA) Supplements

• Supplement may cause imbalances and toxicity
  (especially with methionine and tyrosine)
• Body is designed to handle whole proteins
• Excess of one AA can hamper absorption of other
  AAs

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Plant Protein

• No cholesterol and low in saturated fat
• High in (soluble) dietary fiber, phytochemicals
• Lacking in one or more essential amino acid

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Soy Power

• Lowers blood cholesterol
• Contains isoflavones (genistein and diadzein)
• Sources tofu, soy milk, soy flour, tempeh, miso
• Recommend 2-4 servings a week
• Not recommended for women WITH breast cancer (or
  family history)

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Protein food value

• Quality
• Quantity
• Protein conversion efficiency
• Cost

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• Protein conversion efficiency and cost
• Animals convert plant food into animal protein
  with a low efficiency, i.e. they take in much
  more protein and energy than they produce -
  depending on the animal they may consume as much
  as 50 lb. (usually about 20 lb. for cattle) of
  protein for every lb. of protein they produce.
  (not a problem if cattle grazing on grasslands
  unsuited for other uses, but most beef cattle
  today spend much of their time in stockyards
  being fed corn etc.)
• In fact 76 of the US protein production is used
  to feed livestock. 5 of this goes to feed the
  100 million dogs and cats in the US!
• In general legumes are the cheapest sources of
  protein, and meats the most expensive.

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Biological Value

• Measures how efficiently the absorbed food
  protein can be turned into body tissue
• Measures protein (AA) retention

Nitrogen retained Nitrogen absorbed
BV
X 100
10
Protein Efficiency Ratio

• Compares the weight gained in a growing rat after
  10 days or more eating a standard amount of
  protein
• Measures BV (protein retention)

PER
Gram weight gain Gram protein consumed
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Chemical Score of Protein

• Amount of each essential AA in a gram of protein
  in the food divided by an ideal amount for that
  essential AA
• The lowest AA score is the C.S. for that food

Chem. Score
Mg of ess. AAn per gm of protein Required mg
needs of the ess. AAn per gm of protein

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Protein Digestibility Corrected AA Score (PDCAAS)

• Most widely used (on food labels)
• Maximum value is 1.0 ( milk, eggs, soy protein)
• PDCAAS Chem. Score x (0.9-1.0)
• Range
  of digestibility of that
• protein

13
Food additives

• Intentional
• Contaminants (pesticide residues, rodent debris,
  microorganisms)
• The average American consumes more than 5 pounds
  of additives a year.
• GRAS list

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• Food additives have a very long history. Salt and
  smoke as preservatives, sea-weed as a thickener,
  flavorings etc.
• legitimate uses - maintain and preserve the
  nutritional quality of the food
• Non-legit uses masking an inferior food
  product, making food look more attractive,
  increasing company profits, aiding food
  processing, allowing convenience foods

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Food additive functions

• Preservatives
• Emulsifying agents
• Nutrient supplements
• Sequestrants
• Stabilizers
• Flavorings
• Colorants
• Flavor enhancers
• Leavening agents
• Maturing and bleaching agents

• Acid or Alkaline agents
• Alternative Sweeteners
• Anticaking agents
• Antimicrobial agents
• Antioxidants
• Curing and pickling agents
• Antioxidants
• Sweeteners
• Fat replacements
• Humectants

16
MSG

• Flavor enhancer
• Often used in Chinese foods
• Small percentage of people are sensitive (Chinese
  Restaurant Syndrome)
• Experience dizziness, sweating, rapid heart rate,
  nausea, vomiting, high blood pressure and
  headaches
• Symptoms appear 10-20 minutes after ingestion
• Found naturally in other foods (tomato, mushroom,
  parmesan cheese)

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Common methods of food preservation

• Heat - this kills pests and microorganisms, and
  also denatures enzymes which are usually
  responsible for the spontaneous decay.
• Temperature control - refrigeration or freezing
  the lower temperatures slows all processes down
  and therefore retards the decay.
• Filtration - used to remove microorganisms from
  liquids.
• Oxygen control - its removal means that only
  anaerobic organisms can grow.
• Control of acidity- Many microorganisms can only
  grow under a limited range of pH. Some foods are
  thus made very acid to prevent microbial growth.
• Water - If the water in a food is tied up, e.g.
  with salt, sugar, or by dehydration or freezing,
  it will prevent the growth of microorganisms.

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Common preservatives

• Sorbic acid (sorbate)is a fatty acid (caproic
  acid) and is metabolized by our bodies as a fatty
  acid, hence we use it as a source of food and
  energy.
• These compounds are quite safe based on feeding
  studies and their known metabolic routes (They
  inhibit a mold enzyme required for mold growth).

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Common preservatives

• Sodium benzoate is effective under acidic
  conditions in preventing growth of molds,
  bacteria and yeasts.
• It is used in fruit juices, carbonated soft
  drinks, pickles, salad dressings.
• It occurs naturally in many fruit and vegetables,
  and has been reported to be a natural metabolite
  in our body. All the evidence indicates it is
  quite safe.

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Common preservatives

• Sodium bisulfite and sulfur dioxide have been
  used since the times of the Romans to prevent the
  growth of bacteria, especially in beverages.
• It destroys thiamin, and can restore the red
  color to old meat.
• On the GRAS list, however, recent legislation is
  limiting their use (a significant number of
  people are allergic to sulfites - often
  asthmatics).
• Found in salads (keeps them looking fresh), wine

21
Common preservatives

• Sodium nitrate and nitrite These are used in
  processed meats to prevent the growth of C.
  botulinum. They also give the meat a nice pink
  color.
• Converts to cancer causing nitrosamines in the
  stomach
• Vitamin C added can reduce the formation of
  nitrosamine
• Actual risk is low for normal people

22
Common preservatives

• Anti-oxidants
• The most widely used are BHA and BHT. Their role
  is to prevent the oxidation of unsaturated fats,
  especially PUFA's.
• Propyl gallate is often used along with BHA/BHT
  since the two together seem more effective.

23
Common preservatives

• Sequesterants These are added to complex metal
  ions such as iron which catalyze oxidation, or
  react with other components to form precipitates
  in beverages. EDTA is probably the most common,
  and many acids are also used for this purpose.

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Common preservatives

• Colors
• About 4 million pounds of synthetic dyes go into
  our US food supply each year.
• Used to make foods look acceptable.
• 90 are synthetic, many from coal tar, many
  probably carcinogenic. Among the known "baddies"
  Red No. 40, Citrus Red No. 2. Yellow No. 5, Blue
  No. 1, Orange B, Red No. 3. These are all
  associated with studies demonstrating them to be
  carcinogens in animal studies.

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Natural Toxins

• Occur naturally in foods
• Safrole from sassafras, mace, nutmeg
• Solanine from potato shoots
• Mushroom toxins
• Avidin in raw eggs
• Thiaminase in raw clams and mussels
• Tetrodotoxin in puffer fish
• Oxalic acid in spinach, strawberries, etc.
• Nitrites/nitrates, aflatoxin

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Toxic contaminants

• Heavy metals, especially lead, mercury and
  cadmium dioxin, PCB's, etc.
• Pesticide and herbicide residues. Hazardous ones
  are more likely in imported foods, from other
  countries where the regulations are less
  stringent e. g. many pesticides banned in the US
  are used in Mexico and the food exported to the
  US.

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Lead Poisoning

• A heavy toxic metal
• Causes anemia, kidney disease, damage the nervous
  system, IQ deficits, behavior disorders, slowed
  growth
• Lead from solder joints, lead paint, playground,
  metal containers
• A high fat, low calcium, low iron diet absorbs
  more lead
• Thus, a low fat, adequate calcium and iron diet
  is recommended

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Mercury

• From large predator fish (shark, sword fish)
• Accumulates mercury in the fish
• These fish are tested more frequently for mercury
  level
• Not recommended for women of childbearing years
• Birth defects are common

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Dioxin

• Cancer causing, damaging to reproduction,
  development, and immune system
• From trash burning
• From bottom feeding Great Lakes fish
• Exposure seen in people who consume locally
  caught fish, intake of animal fats

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Urethane

• From fermentation of alcohol
• Increase upon heating (of the alcohol)
• Causes cancer in animal studies

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Polychlorinated Biphenyls (PCBs)

• Used in industrial products
• Linked to liver tumors and reproductive problems
  in animals
• Still found in freshwater fish
• Limit established for uses by FDA

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How to Reduce Your Exposure to Toxins

• Know what foods pose a risk
• Practice moderation and variety
• Trim fat from meat and fish
• Wash fruits, vegetables thoroughly
• Cook meat thoroughly

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Perspective

• Smoking kills 150,000 people a year from lung
  cancer
• Alcohol kills 100,000,
• Motor vehicles 50,000.
• Drunk drivers kill an average of 70 people a day!
  
• A few people die each year from food poisoning -
  either bacterial or toxins (e. g. mushrooms,
  shellfish).
• Definite deaths from food additives and pesticide
  residues have not been documented, at least to
  any extent in the US.
• Thousands die from microbial food poisoning

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Table 19.6