Cystic Fibrosis

Cystic Fibrosis (CF) is a genetic disease caused by a defect in one particular gene known as CFTR (cystic fibrosis transmembrane-conductance regulator). About 1 person in 25 of European descent has this gene. However your chance of having CF is more like 1 in 3,000, as you only get it if both your parents have the gene. That should roughly be a 1 in 625 (25*25) chance, but because of genetic shuffling that is reduced to about 1 in 3,000 for people of European descent. People with other racial backgrounds have the CF gene less often, and so CF is less common in other racial groups.

There are different types of Cystic Fibrosis, as the gene defects differ. This means that the best medication for different people with CF varies. Diet and exercise advice is more uniform however, and depends more on the persons dietary preferences and fitness.

What are the symptoms of Cystic Fibrosis?

Cystic Fibrosis changes the ability of the epithelial cells lining your lungs, liver, pancreas, digestive tract, reproductive tract and skin to transport chloride ions. In practice this means that chloride ion concentration inside and outside the cell differs from the normal situation. Many of these epithelial cells produce mucus and the abnormal chloride concentration leads to mucus outside cells becoming less watery and more sticky. This leads to problems in the lungs and pancreas. Within the skin, the sweat glands produce more chloride than normal, and this is the basis for one test that can detect CF.

Lung problems:

Typically this sticky mucus can cause a blockage to small airways in the lungs leading to difficulty breathing. Also microbes which are caught on it are not able to be removed as efficiently. The mucus which normally gets shunted up the airways like a travelator is slowed down as it is more viscous. This means that microbes are more likely to establish themselves in the lungs and are more difficult to remove. A chronic inflammatory response is established, which over time leads to scar tissue formation (fibrosis) and the appearence of cysts. Hence the name of the condition "cystic fibrosis". The lung problems are normally treated by inhalation of substances which cause the bronchioles to dilate, such as steroids. Substances that reduce inflammation, such as ibuprofen, can also be used.

Because people with CF can have microbes in their lungs that are harmful to other people with CF, it is generally not recommended that they spend too much time with other people with the condition. In the past inhalers were shared between people with CF and this was particularly damaging to their life chances.

Digestive problems:

The pancreas is an organ that produces pancreatic juice that helps digest your food making absorption of the nutrients possible. With CF the pancreatic juice containing the enzymes that break down fats, carbohydrates and proteins can get blocked in by sticky mucus. This is mostly a problem for fat digestion as carbohydrates (e.g. bread, pasta and cakes) can be broken down in the mouth, and proteins (e.g. chicken, tuna and soya) in the stomach. A small amount of fat can be broken down in the mouth and stomach by the enzymes lingual lipase and gastric lipase respectively. However these enzymes are not normally sufficient to break down fats well enough for efficient absorption. As a result people with CF can become short on essential fatty acids and the fat soluble vitamins A, D, E and K. Nowadays most people with CF get given digestive enzymes, which makes it possible to get sufficient amounts of these nutrients if they eat a good diet.

How genes work:

To understand why a genetic disease like Cystic Fibrosis occurs you need to understand a bit about genetics.

When you are born you are given 23 chromosomes from your mother and 23 from your father. They are duplicate, in that each of the 23 chromosomes pairs up with the equivalent chromosome from your other parent. Look at the picture to the left. The left hand portion of the chromosome could be from mum and the right from dad. At a given point down the chromosome is a gene. Normally it takes more than one gene to create a trait such as hair colour or how much oxygen your blood can carry. However there are cases where only one gene creates a trait.

The widows peak hairline is a single gene trait. If even one parent carries it you'll end up looking like Zidane, because the widow's peak trait is a dominant gene. You'll only end up looking like a Milliband if both parents carry the recessive (non-dominant) gene. Either way you'll end up with either a headbutt or a headache.

Cystic Fibrosis is another single gene trait. If both mum and dad have the gene then there is a good chance you'll get it. If one parent has the gene then you won't get it because you'll use the other parents non-CF gene. It is slightly more complex than this, as when your dad's sperm meets your mum's egg they mix their DNA in a way that can change a CF gene into a non-CF gene, and so your chance of getting CF is reduced.

The CFTR gene, like most genes, makes proteins that your body can use. The normal CFTR gene makes a protein that transports chloride ions into and out of epithelial cells. the transport of some other ions can also be affected. Different errors (or mutations as they are called in genetics) can affect the CFTR gene. The most common (called ðF508) causes it to create a protein that does not fold correctly. It is hard to get this misfolded protein into the cell membrane so that it can allow chloride ions to escape. 

Is exercise good for people with Cystic Fibrosis?

Definitely yes. Exercise, both cardiovascular and strength exercises, help to improve many of the symptoms manifested with CF.

  1. It clears the airways in the lungs. This brings in more oxygen which can slow down the growth of some of the bacteria that can set up camp in the lungs of people with CF.
  2. It increases lung capacity, making it easier to breathe.
  3. It increases strength and endurance. CF does not reduce exercise capacity directly, but lung infection and nutritional deficiency can affect strength and endurance. Cardiovascular exercise and weight bearing exercises that involve using your bodyweight or shifting weights all help. Exercise normally increases appetite which should help prevent nutritional deficiencies.
  4. It increases bone density. This is important as deficiency in vitamins D and K can lead people with CF to develop weaker bones.

A person with CF should be aware that they may sweat out more salt during exercise and for this reason may need to use a sports drink containing plenty of salt. Not all sports drinks contain salt. A list of those that do, in decreasing order of saltiness is: (PowerbarEndurance*;High5 Isotonic*;Isostar;Taut*;High5EnergySource;LucozadeSport;InfinitRide*;Powerade). So of those that aren't powders Isostar may be the best. Remember CocaCola has not much salt in it.

Bear in mind that those with '*' by them are in powder form. For purposes of comparison they are assumed to be watered down to an isotonic strength. Roughly 60grams of powder for every litre of water. Those in bold can be normally be found in shops in liquid form.If you want to avoid artificial sweeteners (Lucozade) and excess calcium (Isostar), then the  Powerbar and High5 powders are good choices. Alternatively, add 1/2 a gram of table salt to a typical 500ml drinking bottle containing fruit juice.

What is the best diet for someone with Cystic Fibrosis?

It is best to eat a diet that includes plenty of the nutrients that are deficient in CF. These are vitamins A, D, E and K as well as the essential fatty acids and salt. Calcium is also often mentioned as being needed, but the evidence is not strong for this. Whether there are grounds for supplementation for the fat soluble vitamins is open to debate. If pancreatic enzyme supplements are being used, then the fat soluble vitamins in the diet should be adequately absorbed. In other words the best approach for most people with CF is to eat a diet containing plenty of the foods mentioned below.

Major Nutrients 

For most people with CF it is important to eat more than other people, as absorption from the gut is not as efficient due to the lack of pancreatic digestive enzymes. There is an increased need for essential fats called omega 6 and omega 3, and so a diet containing good sources of these fats is important. Omega 6 fats are very common in modern diets, whereas omega 3 fats are pretty rare. To keep a good level of omega 3 fats in the diet, include plenty of oliy fish such as trout, salmon, sardines, pilchards and kippers. A supplement containing omega 3, such as cod liver oil could also help. The other major nutrient to eat in good amounts is protein, which is not absorbed so well in most people with CF. It is needed in childhood for growth, and later on for maintenance and repair of the body. Eating plenty of meat, fish and some diary is the most effective way to ensure good protein nutrition. Carbohydrate is used for energy. However it is best not to have too much of it on its own, as it can cause blood sugar spikes which can lead to glucose intolerance and eventually diabetes. My advice is to eat a diet that emphasizes the healthy forms of protein and fat with plenty of vegetables. Eat a moderate amount of starches such as bread, pasta, rice and potato. Fruits and sweet treats are also best eaten in moderation. Do make sure that enough is being eaten in total though.

Vitamin A

This vitamin is needed for good vision, immunity, red blood cell production and growth. It is found at high levels in liver. Dairy foods such as cheese, milk and yoghurt as well as eggs contain good amounts of vitamin A. Dark green and yellow vegetables are also good sources of beta carotene, which the body can turn into vitamin A.

Vitamin D

This important vitamin is needed for good bone health as well as many other important roles in the body such as immunity, growth and cardiovascular health. It is found at high levels in liver. However sunshine is the best way to get vitamin D, so outdoor exercise provides the person with CF a double benefit of airway clearance and a supply of vitamin D also.

Vitamin E

This is found in good amounts in nuts, seeds and their oils, including margarine. Egg yolks and avocados also contain a fair amount as do green leafy vegetables. Most nut and seed oils and margarine contain trans-fats which are not good for health. However nut butters such as peanut butter are probably healthier sources as they normally contain palm oil, which contains less trans fats than sunflower, safflower and vegetable oils. Check the label to be sure. My advice is to stick to nuts, seeds, eggs, avocados and green leafy vegetables with some peanut butter thrown in to keep you vitamin E levels up.

Vitamin K

This vitamin allows blood to clot properly, preventing uncontrolled bleeding. It also helps the formation of strong bones. It is found in green leafy vegetables. Kale, chard, brocolli and parsley are all excellent sources.

Salt

Since people with CF sweat a particularly salty sweat they are prone to lose alot of salt. Unlike the general population eating plenty of salty snacks is a good habit to develop, especially after sweating alot as during hot weather or during and after exercise. Some of the healthiest ways of taking on more salt are by eating more olives or oily fish. Commercial bread also contains a lot of salt. Care should be taken with infants, especially below the age of one as there is a possibilty of salt poisoning at this age.

Calcium

Do people with CF need more calcium? One reason they may not, is that they suffer from kidney stones more often. Excess calcium in the body can supersaturate the kidneys with calcium, and lead to the production of calcium oxalate stones. Traditionally calcium was advised as being needed to strengthen the bones, as people with CF are prone to having weaker bones. However, there is no evidence I've found that good calcium balance is not maintained in people with CF. They can absorb and retain it adequately. The reason they develop weaker bones is much more likely to do with their lack of vitamin D and vitamin K. Certainly calcium supplements are unlikely to be needed. Eating calcium containing dairy foods and sardines should be OK unless excessive amounts are eaten. If kidney stones are already present then cutting down on dairy foods is probably in order.