Protein Sources, Quality and Requirements

Question 1

Protein Sources: General

Answer 1

• Protein is found in all whole foods, incl. fruits and honey. Only processed foods (e.g. refined sugar and oils) have no protein.
• A rich and varied diet with sufficient calories supplies a good intake of proteins.
• Specific amino acids and higher protein diets can be therapeutic for certain people or in certain life stages (during pregnancy, athletes, injury recovery etc.) more on this to follow.
• The adult human body reabsorbs about 50g of protein per day from shed mucosal cells and 17g per day from digestive enzymes and glycoproteins these are endogenous sources.

Question 2

Protein Sources

Answer 2

• Abundant dietary sources of protein include legumes, nuts/seeds, greens, whole grains,
eggs, fish, poultry and meats.
• Meat provides more protein than non meat sources, but requires more energy to digest than plant sources. Heavy animal protein can accumulate in the intestinal wall, impairing absorption. In addition what is often added to meat dishes reduces its benefit. e.g., a hamburger with bacon and cheese brings with it high calories, trans fats, heterocyclic amines and nitrosamines (cancer risk factors).

Question 3

Protein Digestibility

Answer 3

• Protein digestibility and amino acid composition are said to determine ‘protein quality’
• The digestibility of most animal protein vs. plant protein is variable due to a variety of factors including gut function (i.e. HCl and digestive enzymes), the presence of fibre and some anti-
nutrient factors in plant sources such as phytates and lectins.
• To support the digestibility of plant protein sources, consider soaking, sprouting and fermenting which can lower anti nutrient factors.
• Plant sources also contain fibre, prebiotics, phytonutrients and other ‘qualities’ which can make them a superior choice for everyday healthy eating.

Question 4

Optimising Protein Digestion

Answer 4

• Chew thoroughly and avoid drinking with meals.
• Support stomach acid levels:
– Zinc and B6 rich foods (need for HCl production).
– Apple cider vinegar in a little water before meals.
– Bitter herbs and foods before meals (e.g. dandelion, rocket, watercress, artichoke, gentian, barberry bark , goldenseal) These also promote the release of pancreatic juice.
– Use betaine hydrochloride supplements with at least 600mg per capsule. Start with one when starting to eat, before increasing one capsule per meal up to a total of 5 max or until a feeling of warmth. If warm, cut one pill back.

Question 5

Protein Quality: Metabolism and Fermentation

Answer 5

• The microbiome contributes to protein metabolism: undigested protein that reaches the colon is fermented, creating toxic metabolites that increase the inflammatory response and
encourages the proliferation of opportunistic pathogens.
• Many of the fermentation products of protein are detrimental to health (e.g. ammonia, amines, sulphides, and N-nitroso compounds), with effects including systemic toxicity, nephrotoxicity , and carcinogenesis .
• Therefore, not overloading the body with protein is an important step. Furthermore, optimising protein digestion is crucial to ensure that as little as possible reaches the colon undigested (see

Question 6

Protein Quality: Amino Acid Composition

Answer 6

• To make proteins, a cell must have all the required amino acids available simultaneously; if one essential amino acid is missing, a cell will have to cease making the protein or must dismantle another protein to obtain it.
• If an essential amino acid is supplied in less than the amount needed to support protein synthesis, it is called a limiting amino acid.
• The limiting amino acids are lysine, threonine, methionine, and tryptophan . They are found in the shortest supply from incomplete proteins. For example, beans are low in methionine. This indicates the importance of rotating the sources to provide balance.

Question 7

Amino Acid Combining: Complete Protein

Answer 7

• Food that contains all nine essential amino acids.
• Vegan foods that are complete proteins includes quinoa, buckwheat, pumpkin seeds, chia seeds, hemp seeds, tempeh.
• Animal foods: meat, poultry, fish, eggs and dairy (except butter)

Question 8

Amino Acid Combining: Incomplete Protein

Answer 8

• Food is low in one or more of the essential amino acids.
• Most plant foods have an incomplete protein profile one or more essential amino acids are missing (i.e. the limiting amino acids).

Question 9

Amino Acid Combining: Plants

Answer 9

• Plant foods can be combined to ensure that the essential amino acids are obtained. This ensures the limiting amino acid in one food is included in a food it is combined with.

Question 10

Limiting AA Food: Beans

Answer 10

Methionine
Complementary Foods: Grains, nuts, seeds

Question 11

Limiting AA Food: Grains

Answer 11

Lysine, threonine

Complementary Foods: Legumes

Question 12

Limiting AA Food: Nuts and Seeds

Answer 12

Lysine

Complementary Foods: Legumes

Question 13

Limiting AA Food: Vegetables

Answer 13

Methionine

Complementary Foods: Grains, nuts, seeds

Question 14

Limiting AA Food: Corn

Answer 14

Tryptohan, Lysine

Complementary Foods: Legumes

Question 15

Animal Proteins

Answer 15

Whilst animal sources of protein contain all essential amino acids, high animal protein diets have the following negative effects:
• Methionine is an amino acid highly abundant in animal proteins and has an immune stimulating effect on T cells, which is, if used in excess associated with over reactive immune responses (autoimmunity and chronic inflammation). Excess methionine also increases homocysteine which is associated with atherosclerosis.
• Unless organic, can contain chemical residues. Occurs either by direct oral or topical dosing of the animal (e.g. pesticides to control lice and fleas) or exposure to crop pesticides in feed.
If eating meat, focus on organic, grass fed sources.

Question 16

Excess Protein: Risks

Answer 16

• The adverse effects associated with high, long term animal protein intake in humans include:
– Osteoporosis
– Kidney disease
– Increased cancer risk
– Disorders of liver function
– Atherosclerosis
– Increased muscle soreness post exercise
• High protein is generally considered to be 20% of calorie intake or more. Alkaline rich fruit and vegetables buffer the protein derived acid load, so always encourage plant based eating.

Question 17

Excess Protein: Cancer

Answer 17

• Both high and moderate animal protein intake increases cancer risk significantly, and is linked to cancer initiation and promotion
• WHO (2015) classified red meat as a probable cause of cancer; processed meats (salted, cured, fermented, smoked) are deemed carcinogens.
• High intakes of red meat (especially processed) are strongly linked to several cancers. Polycyclic aromatic hydrocarbons (PAHs) and heterocyclic amines (HCAs) produced during the high temperature cooking of meat (e.g. frying, BBQ, high temp roasting)are carcinogenic.

Question 18

Excess Protein: Skeletal Disease

Answer 18

Due to the acidic burden of excess animal protein, it can also draw calcium out of bones and increase the risk of osteoporosis. However, because of the collagen structure within bone, a protein deficiency can also negatively impact bone health.

Question 19

Excess Protein: Kidney Disease

Answer 19

The extra acidity from a high animal protein intake needs buffering by the kidneys. The kidneys must also filter the increased urea that is generated.

Question 20

Excess Protein: Cardiovascular Disease

Answer 20

Associated with oxidation and inflammation in the endothelium.

Question 21

Protein Requirements

Answer 21

• It is estimated that the risk of protein deficiency would start at values between 0.4-0.5 g/kg of body weight (e.g. 31.5g or below for a 70kg person)
• The general recommendation for protein intake is 0.75g per kg. To meet the functional needs of athletes , increased protein is recommend in the following range: 1.0, 1.3, and 1.6g protein per kg of body weight per for individuals with minimal, moderate, and intense physical activity, respectively.

For an average client (non- athlete) you can:
• Look up the healthy weight for a person of your client’s height.
• Use the midpoint of the healthy weight range to base your calculations.
• Multiply kg by 0.75 to get your RNI use appropriate values for children, pregnant and lactating women or athletes as required.
• For pregnancy: an additional 6g/day is recommended.
• Lactation: an extra 11 g/day 0 6 months and 8 g/day 6+ months.
• Multiply by 1 for vegans and egg/dairy free vegetarians to accommodate for the lower protein bioavailability.

Question 22

Protein Deficiency

Answer 22

In the developed world deficiency is more likely to affect:
• Children whose diets are rich in highly refined / processed foods, high in sugar and soft drinks and low in high quality wholefoods.
• Teenagers dieting, or consuming only highly refined / processed foods / junk food, soft drinks, sweets etc.
• Older people whose immobility, dentition (poor chewing), digestive health (lower stomach acid and pancreatic juice levels), living situation etc. reduces their intake / digestion / absorption.
• Anorexia nervosa sufferers.
• Recovering patients such as post surgery or trauma (i.e. for repair).
• Homeless and disadvantaged people , including those living in substandard conditions in inner cities and rural areas.
• Those with drug and alcohol addictions.
• Those with chronic digestive conditions and chronic use of proton pump inhibitors (
The lack of HCl impairs the digestion and subsequent absorption of proteins.
• Chronic or active infections ; infections deplete body proteins.

Question 23

Amino Acid Assessment

Answer 23

• The amino acid status of a person can be assessed using plasma or urine samples, to explore insufficiencies / imbalances.
• This can be especially useful in certain cases. For example, chronic fatigue syndrome due to
mitochondrial inefficiency, or following long term PPI use due to reduced amino acid absorption.
• The information can also be helpful in clinic, for example:
– Cardiovascular disease risk screen : higher levels of branched chain amino acids (leucine, isoleucine, valine) and homocysteine, linked to heart disease -> lower dietary intake.

Question 24

Amino Acid Functions

Answer 24

Amino acids are crucial for protein synthesis. However, not all amino acids are protein building blocks for human protein tissues. Individual amino acids also:
• Contribute to the synthesis of hormones and neurotransmitters.
• Act as neurotransmitters themselves e.g. glycine.
• Act as methyl donors e.g. methionine.
• Build bile acids for digestion ( glycine and taurine)
• Act as precursors for nitric oxide production e.g. Arginine.
• Help detoxify thousands of chemicals (i.e. phase 2 liver pathways).
• Act as precursors for the manufacture of endogenous antioxidants.