Protein: Deficiency and Excess

This lesson covers the effects of protein deficiency (not enough protein) and protein excess (too much protein) on the body, as required by AQA GCSE Food Preparation and Nutrition specification 8585 (section 3.2.1). You will learn to identify the symptoms and health consequences of both under- and over-consumption, and understand which groups of people are most at risk.

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Protein Deficiency

Protein deficiency occurs when a person does not consume enough protein to meet the body's needs. This can happen because of:

• Inadequate food intake (poverty, famine)
• A very restricted diet that lacks variety
• Increased requirements not being met (e.g. during growth, pregnancy, or recovery from illness)
• Poor-quality protein sources without complementation

Effects of Protein Deficiency

Effect	Explanation
Kwashiorkor	A severe protein deficiency disease, most common in developing countries. Symptoms include a swollen belly (oedema caused by fluid retention), thin arms and legs, flaky skin, and discoloured hair. Primarily affects young children after weaning.
Slow growth	Children who lack protein may not grow to their expected height and weight. Growth is stunted because the body cannot build new tissues.
Wasting (loss of muscle mass)	The body breaks down its own muscle tissue to obtain amino acids, leading to muscle wasting and weakness.
Weakened immune system	Antibodies are made of protein. Without sufficient protein, the body produces fewer antibodies, making a person more susceptible to infections and illnesses.
Poor wound healing	Repair of damaged tissue requires protein. Deficiency slows down the healing of cuts, wounds, and surgical incisions.
Oedema	Protein helps maintain the balance of fluid in the body. Deficiency causes fluid to leak into tissues, resulting in swelling (oedema), particularly in the abdomen, hands, and feet.
Thin, brittle hair and weak nails	Hair and nails are made of the protein keratin. Without adequate protein, they become thin, dry, and break easily.
Fatigue and weakness	The body lacks the amino acids needed to maintain muscles and produce enzymes, leading to tiredness and physical weakness.

Kwashiorkor in Detail

Kwashiorkor is the most severe form of protein deficiency and is most commonly seen in children aged 1–4 years in developing countries, particularly in sub-Saharan Africa and South Asia.

It typically occurs when a child is weaned from breast milk (which is HBV protein) onto a diet that is high in starchy carbohydrates but very low in protein. The name "kwashiorkor" comes from the Ga language of Ghana, meaning "the disease the first child gets when the second child is born" — referring to the older child being weaned when a new baby arrives.

Key symptoms of kwashiorkor:

• Distended (swollen) abdomen due to oedema and an enlarged liver
• Thin, wasted limbs despite the swollen belly
• Discoloured, sparse hair (sometimes reddish or grey)
• Flaky, peeling skin with dark patches
• Irritability, lethargy, and loss of appetite
• Increased vulnerability to infections
• Can be fatal if untreated

Exam Tip: Kwashiorkor is a protein energy malnutrition disease. Do not confuse it with marasmus, which is caused by an overall lack of food (energy and protein). In kwashiorkor, the child may be getting enough calories from starchy food but not enough protein.

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Who Is Most at Risk of Protein Deficiency?

At-Risk Group	Reason
Children in developing countries	Limited access to protein-rich foods; weaned onto starchy diets
Elderly people	Reduced appetite, difficulty chewing, living alone, poverty
People with eating disorders	Severely restricted food intake
Vegans with poorly planned diets	Risk of insufficient protein if diet lacks variety and complementation
People with digestive disorders	Conditions like Crohn's disease or coeliac disease can impair protein absorption
People recovering from surgery or illness	Increased protein requirements that may not be met

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Protein Excess

In the UK, most people consume more protein than they need. While the body can tolerate a moderate excess, consistently consuming far too much protein over a long period can have negative health effects.

Effects of Protein Excess