Digestive disorders and good health practices – Heterotrophic Nutrition (Senior 3 Biology) | Ganzaa

Heterotrophic Nutrition

Lessons

Senior 3 · Biology

Heterotrophic Nutrition

5 lessons

Lesson 5 of 5

Digestive disorders and good health practices

25 min

Two problems in one country

In Senior 1 you saw that stunting, a sign of long-term undernutrition, has been falling in Rwanda. The same national surveys show a second problem growing at the same time: more adults, especially women, are overweight or obese. Health workers call this the double burden of malnutrition. What people eat, and how well their digestive system copes with it, matters at both ends.

Figure 1: Nutrition in Rwanda, from the Rwanda Demographic and Health Surveys 2019–20 and 2025 (DHS Program STATcompiler). Stunted: too short for their age; overweight or obese: body mass index 25 or more; obese: 30 or more; thin: under 18.5.

Worked example 1: reading the survey

Use Figure 1. (a) By how many percentage points did stunting change between 2019–20 and 2025, and what is that as a percentage of the 2019–20 value? (b) Do the same for women who are overweight or obese. (c) What do the two results together suggest?

(a) $26.8 - 33.1 = - 6.3$ percentage points: a fall. $\frac{6.3}{33.1} \times 100\% \approx 19\%$ lower.
(b) $31.3 - 26.3 = + 5.0$ percentage points: a rise. $\frac{5.0}{26.3} \times 100\% \approx 19\%$ higher.
(c) Undernutrition in young children is falling, but overnutrition in adult women is rising at about the same rate. A good diet for the country has to prevent both: enough of every nutrient for children, without too much energy, sugar and fat for adults.

Definition

Digestive disorder: any condition that stops the digestive system from working normally, such as an infection, an ulcer or a blockage.

Dehydration: a dangerous loss of water and salts from the body, for example through diarrhoea and vomiting.

Oral rehydration solution (ORS): a drink of clean water with exact amounts of salt and sugar, given by mouth to replace the water and salts lost in diarrhoea.

Dietary fibre (roughage): the parts of plant food, mainly cellulose, that human enzymes cannot digest.

Common digestive disorders

Disorder and its cause	Signs	Prevention and treatment
Diarrhoea: mostly infections (bacteria, viruses such as rotavirus, parasites) from dirty water, food or hands	Frequent watery faeces; risk of dehydration	Safe water, handwashing with soap, latrines; treat with ORS, and zinc tablets for children
Constipation: too little fibre and water, too little exercise	Hard, dry faeces, passed rarely and with difficulty	Eat fibre (beans, vegetables, fruit, whole grains), drink water, be active
Stomach (peptic) ulcer: mostly infection with the bacterium Helicobacter pylori; also long use of some painkillers, such as aspirin	Burning pain in the upper abdomen, often when the stomach is empty	See a health worker: antibiotics and medicines that reduce acid
Heartburn (acid reflux): stomach acid rises into the oesophagus	Burning pain behind the breastbone	Smaller meals; don't lie down straight after eating
Food poisoning: bacteria or their toxins in food that was badly stored or undercooked	Vomiting and diarrhoea within hours	Cook food well, keep it covered and cool, and eat it fresh
Worm infestation: roundworm or hookworm (Lesson 1)	Tiredness, stomach pain, anaemia	Latrines, shoes, handwashing, deworming
Obesity: taking in more energy than is used, over a long time	Body mass index of 30 or more	Balanced diet with less sugar and fat; regular exercise

For years, ulcers were blamed on stress and spicy food. In 1982 two Australian doctors, Barry Marshall and Robin Warren, showed that most are caused by a bacterium, Helicobacter pylori, and can be cured with antibiotics. They received the 2005 Nobel Prize in Physiology or Medicine for it.

Worked example 2: why ORS works better than plain water

A child with diarrhoea is losing water and salts. Explain why a drink of ORS, containing salt and glucose, rehydrates the child better than plain water.

The cells lining the small intestine take up sodium from the salt together with glucose, carrying both into the body.
This raises the concentration of dissolved substances inside the lining, so water follows by osmosis (Senior 2).
So ORS replaces both the water and the salts, and is absorbed even while diarrhoea continues. Plain water replaces no salts and is absorbed less well.

Remember: keep feeding the child, and go to a health centre at once if the child is very weak, cannot drink, has blood in the faeces, or does not improve.

Good health practices for the digestive system

Eat a balanced diet, the plate you planned in Senior 1, with plenty of fibre: beans, peas, vegetables, fruit, sorghum, maize meal and cassava leaves. Fibre gives the colon's muscles something to grip.
Cut down free sugars, the sugar added to food and drinks plus the sugar in honey and juices. The World Health Organization advises keeping them below 10% of daily energy, and ideally below 5%.
Drink enough clean water, boiled or treated if it is not safe.
Wash hands with soap after using the latrine and before preparing or eating food.
Store and cook food safely: cover it, keep it cool, cook meat and eggs through, and never eat mouldy grain or groundnuts.
Eat regular meals, slowly, chewing well; avoid large meals just before lying down.
Keep active, and avoid alcohol and tobacco, which damage the stomach and liver.
Care for your teeth (Lesson 2) and get dewormed as health workers advise (Lesson 1).

Worked example 3: one bottle of soda

A 500 cm³ bottle of soft drink contains 53 g of sugar (illustrative label). Sugar provides about 17 kJ per gram. A teenager needs about 8400 kJ a day. What percentage of the day's energy does the bottle give as free sugar, and how does this compare with the WHO advice?

Energy from the sugar: $53\ \text{g} \times 17\ \text{kJ g}^{-1} = 901\ \text{kJ}$ .
Percentage: $\frac{901}{8400} \times 100\% \approx 10.7\%$
Comparison: one bottle alone is above the 10% limit, and more than twice the 5% ideal, before counting any other sugar that day.

Warning

Common mistakes and safety. (1) Giving a child with diarrhoea nothing to drink "to stop it": the danger is dehydration, so give ORS and keep feeding. (2) Thinking antibiotics cure every diarrhoea: most are caused by viruses, which antibiotics do not kill. (3) Thinking fibre is useless because it is not digested: it keeps faeces soft and helps peristalsis. See a health worker for severe or lasting abdominal pain, blood in vomit or faeces, or diarrhoea in a baby.

How to make oral rehydration solutions for diarrhoea, Stanford Center for Health Education. Watch why exact amounts of salt and sugar matter; where you can, use a ready-made ORS sachet from a health centre or pharmacy and follow its instructions.

Tip

Memory hook: the four Fs of spreading diarrhoea: Faeces reach Fingers, Flies and Fluids, and from them food. Block each route: latrines, handwashing, covered food, safe water.

✦

Practice: digestive disorders and good health

What is meant by the "double burden of malnutrition"? Use Figure 1 to give one example of each part.
State the main cause of most stomach ulcers, and how they are treated.
Give two ways of preventing constipation, and explain one.
Why is diarrhoea dangerous for a young child?
Explain why washing hands with soap reduces diarrhoea.
Women who are obese rose from 5.8% to 8.8% between 2019–20 and 2025. Calculate the rise in percentage points, and as a percentage of the 2019–20 value.
A 330 cm³ can of soft drink contains 35 g of sugar. Using 17 kJ per gram and 8400 kJ per day, what percentage of daily energy is this?
A friend says: "I have diarrhoea, so I will stop drinking until it stops." Evaluate this plan.

Show answersHide answers

Undernutrition and overnutrition in the same population: for example, 26.8% of children under five stunted, but 31.3% of women overweight or obese (2025).
Infection with Helicobacter pylori; treated with antibiotics and medicines that reduce stomach acid.
Eat more fibre and drink more water (also exercise). Fibre adds bulk and holds water, so faeces stay soft and the colon's muscles can push them along.
The child loses water and salts faster than they are replaced and can become dehydrated, which can kill quickly.
Soap removes the bacteria, viruses and worm eggs from faeces that are on the hands, so they are not passed to food or the mouth.
$8.8 - 5.8 = 3.0$ percentage points; $\frac{3.0}{5.8} \times 100\% \approx 52\%$ higher.
$35 \times 17 = 595$ kJ; $\frac{595}{8400} \times 100\% \approx 7.1\%$ .
A poor plan: it increases the risk of dehydration. The friend should drink ORS or plenty of safe fluids, keep eating, wash hands, and see a health worker if it is severe or lasts.

Key points

Rwanda faces a double burden: stunting in children is falling, while overweight and obesity in women are rising (DHS 2019–20 and 2025).
Diarrhoea: prevent with safe water, latrines and handwashing; treat with ORS (plus zinc for children). Constipation: more fibre and water. Most ulcers: H. pylori, cured with antibiotics.
A healthy gut needs a balanced, fibre-rich diet low in free sugars, clean food and water, and good hygiene.

1Two problems in one country

2Common digestive disorders

3Good health practices for the digestive system

Two problems in one country

Common digestive disorders

Good health practices for the digestive system