Blood pressure in children
Babies, children and young people usually have lower blood pressure than adults. They have different ranges that are considered healthy. These depend on:
- how old they are
- whether they are a boy or a girl
- how tall they are.
Your child’s doctor or nurse will know the normal ranges of blood pressure for children who are the same age, sex and height as your child. They will let you know what your child’s blood pressure readings mean.
Keeping healthy
Your family can follow some tips to help keep your child’s blood pressure healthy. These include:
- eating less salt
- eating a healthy diet
- staying active.
If your child has a kidney condition, your doctor or nurse will give you more information about how this affects blood pressure. Rarely, children need to take medicines to control their blood pressure.
Blood pressure and kidneys
Kidneys normally control blood pressure to help make sure it is at a healthy level. They do this by regulating how much salt and water is in the blood. If the kidneys are not working properly, they may not be able to control blood pressure well.
The kidneys and other parts of the body are involved in the renin-angiotensin system, which helps control blood pressure. There are two types of chemicals.
- Enzymes speed up chemical reactions in the body.
- Hormones are carried in the blood to send messages to other parts of the body.
The renin-angiotensin system is very complicated, but it is important and works like this.
- The kidneys release an enzyme called renin. The liver releases a hormone called angiotensin.
- Renin changes angiotensin into angiotensin I. When angiotensin I gets to the lungs, some of it is changed into angiotensin II by an enzyme called ACE (angiotensin-converting enzyme).
- Angiotensin II causes the adrenal gland, which sits on top of the kidney, to release another hormone called aldosterone. Angiotensin II also causes the small blood vessels (arterioles) to constrict (squeeze), which raises blood pressure.
- When blood flows into the kidney, the filters (glomeruli) remove most of the water and salts from the blood into long tubes (renal tubules). Some of the water and salts leave the kidney as urine, and some are taken back into the blood. The hormone called aldosterone causes more water and salt to be taken back into the blood, which raises blood pressure
Controlling blood pressure
It is important for your child’s health that his or her blood pressure is controlled so it is in a healthy range. Below are some tips you can follow as a family to keep your child’s blood pressure healthy.
- Reducing the amount of salt you eat can help to control blood pressure. Avoid eating or drinking lots of salted nuts, crisps, crackers, soft drinks, fast food meals, takeaways and processed foods (meals that are pre-prepared, including soups) – these often have more salt than we think. Do not add extra salt to meals that you cook, or at the dining table.
- Eat lots of fresh fruits and vegetables. Swap white bread, rice and pasta for whole-wheat varieties. Avoid food and drinks with lots of added sugar (including sweets, sugary cereals, high-sugar squash and fizzy drinks or sodas). Limit caffeine (which is found in coke drinks, tea and coffee).
- Most children should be physically active for at least 30 minutes a day. Encourage your child to get involved with sports and other activities where they are moving around.
- It is important that your child has a healthy weight for his or her age. Children (and adults) who are overweight are more likely to develop high blood pressure.
- If your child has a kidney condition, he or she may need to make more changes to what he or she eats and how much he or she drinks. A renal dietitian will help you with this.