What is sleep apnoea?
Sleep apnoea is a relatively common condition where breathing is interrupted during sleep by partial or complete collapse of the upper airways. Up to 5% of western populations have this uncontrolled condition (Arbor, 2009).
The following factors make people more prone to sleep apnoea:
- Overweight and obesity
- Nasal congestion
- Excessive alcohol consumption
- Post-menopause (in women)
However, sleep apnoea is an independent risk factor for high blood pressure and other cardiovascular diseases. People who have hypertension or heart disease have a higher incidence of deaths if they also have sleep apnoea.
Besides being a potential cause of death, constantly cutting off the air supply to your lungs while sleeping can also make you very sleepy during the day and reduce your mental sharpness (Arbor, 2009).
Sleep apnoea causes hypoxia (a lack of oxygen in the body tissues), which increases so-called oxidative stress and inflammation, and blood coagulation. It also causes damage to the linings of the blood vessels, and it has been suggested that sleep apnoea contributes to insulin resistance and metabolic syndrome.
Dietary factors and sleep apnoea
A number of studies have attempted to determine if dietary factors can influence sleep apnoea.
Some studies show that overweight/obesity has a dramatic worsening effect on sleep apnoea.
It's been estimated that gaining just 10% more body weight will increase your risk of this night-time illness by up to six times. This could be due to fat deposits around the upper airway and impaired lung function, combined with an increased oxygen demand. The latest research also implicates an increase in leptin and other metabolic factors associated with obesity.
Losing weight is usually associated with an improvement in sleep apnoea and should always be considered if you have a BMI of more than 25.
A Finnish study showed that when 72 overweight patients (average BMI: 32) who had sleep apnoea used either a very-low-calorie-diet (VLCD) or a single dietary counselling session (the control group) the VLCD-group had significantly greater weight loss. Their sleep apnoea also improved markedly.
The group using the VLCD also snored less and had fewer apnoea incidents when they were observed during sleeping (23 incidents compared to 32 incidents for the control group).
b) Fat and protein contents
Other researchers have investigated the effect of the fat and protein contents of diets on sleep apnoea.
A group of 320 adults took part in an American study to determine if the composition of the participants’ diets influenced their sleep apnoea and daytime sleepiness.
The researchers found that those participants who used a diet rich in fat, saturated fat, cholesterol and protein were more likely to suffer from a high frequency of sleep apnoea episodes (more than 50 per night) than the participants who ate less fat and protein (10 episodes per night) (Arbor, 2009).
c) Protective nutrients
In view of the fact that sleep apnoea may also be related to oxidative stress and inflammation, scientists have turned their attention to the effect of antioxidants. These nutrients can help combat oxidative stress.
The leading foods in this category are fruits and vegetables that are rich in a variety of protective nutrients such as beta-carotene, minerals, trace elements, phytonutrients and vitamin C.
The link between fruit and vegetable intake and improvement of sleep apnoea was studied in a recent Norwegian trial where 115 overweight patients (average BMI: 36.7) were either asked to increase their intake of fruit and vegetables, or given no treatment (control group).
The treatment group were encouraged to increase their intakes of fruit to at least 300g per day and their vegetable intake to at least 400g per day.
This increase in fruit and vegetable intake had a dramatic effect on the treatment group, who lost weight and improved their high blood pressure. Disappointingly, this experiment didn't show significant changes in the markers of oxidative stress (Arbor, 2009).
d) Other approaches
There's some evidence that the use of metformin, a drug used for the treatment of insulin resistance in metabolic syndrome, may help with sleep apnoea.
Treatment of gastro-oesophageal reflux, which is often associated with sleep apnoea, may also be beneficial, and the use of tryptophan supplements to improve sleep has shown some promise (Arbor, 2009). Tryptophan is an amino acid that has positive effects on sleep patterns.
At this stage, our knowledge of the interaction of dietary factors and sleep apnoea is still rather rudimentary.
There are indications that losing weight, following a diet that's low in fat and cholesterol and rich in fruit and vegetables, and correcting certain conditions with medications such as metformin (insulin resistance in metabolic syndrome) or antacids (GORD), may help to reduce the frequency and severity of sleep apnoea.
If you have this potentially life-threatening condition, consider losing weight if you're overweight or obese. Also improve your diet: reduce the amount of fat you eat and increase your fruit and vegetable consumption.
If you don’t know whether you have sleep apnoea, but tend to feel sleepy all day long and drop off to sleep in the daytime, or suffer from a lack of mental acuity, combined with hypertension and cardiovascular disease, it's a good idea to ask your doctor to check if you don’t perhaps have the condition.
(Dr I.V. van Heerden, DietDoc, May 2009)
(Arbor (2009). Sleep apnoea and nutrition. Arbor Clinical Nutrition Updates, Issue 302, March 2009)