Studies of high-fat diets show mixed results. Some research suggests eating abundant fats can improve sleep quality, while other studies show high-fat diets linked to more disruptive sleep and trouble falling asleep. (I'll talk about the effects of protein and carbohydrates on fats in a minute.)
There are a small number of studies that look at keto diets and sleep. They show this very low-carb, high-fat diet may offer benefits for sleep, both through weight loss and other pathways. A just-released study on the effects of keto found that adhering to this eating plan helped reduce daytime sleepiness in a group of obese patients. Previous studies have found similar results, along with increases to REM sleep. Other research has shown ketogenic diets increase REM sleep and sleep quality in a group of children with epilepsy. (A ketogenic diet has shown the capacity to reduce seizures, making it an effective dietary therapy for people with epilepsy.)
There's some very interesting emerging research showing that ketogenic diets have an effect on a brain chemical that is important to sleep regulation: adenosine. You've heard me talk about adenosine before, in relation to caffeine. Adenosine builds up in the body throughout the day. It contributes to our feeling increasingly less alert and wakeful as the day goes on, and eventually helps to promote deeper slow-wave sleep at night. Caffeine's ability to block the effects of adenosine is one important way it delivers us that stimulating, alertness-producing mental boost. Studies show a ketogenic diet promotes adenosine activity in the body, helping to relax the nervous system, as well as reducing pain and inflammation — all of which can help improve sleep.
We need to see more research to better understand the relationship of ketogenic diets to adenosine, and to sleep directly. There may be short-term issues on a ketogenic diet that eventually give way to benefits for sleep — but we need to see more research to know.
Sleep issues with high-protein, low-carb diets?
It's tough to find research that specifically addresses the Paleo diet and sleep. (There are currently studies underway, which I'll talk about when they're published.) From talking with my patients and others, I know people who start eating paleo sometimes have a harder time sleeping, similar to people who adopt a ketogenic eating plan.
The shift away from carbohydrates and toward protein may explain these sleep issues. Carbohydrates increase levels of the amino acid tryptophan in the brain, which helps facilitate sleep when it converts to serotonin. Serotonin is necessary for the body to produce the sleep hormone melatonin. Protein, on the other hand, increases levels of tyrosine, an amino acid that triggers the production of stimulating, alerting brain chemicals, including epinephrine and norepinephrine. Reducing serotonin by limiting carbohydrates — while at the same time elevating the alertness-promoting chemicals associated with tyrosine — may result in difficulty falling asleep and getting a full night of rest.
Research on the effects to sleep of high-protein and high-carbohydrate diets is mixed. Some studies have shown people with sleep disorders such as insomnia and sleep apnea tend to consume less carbohydrates than people without these sleep disorders. Other research shows reductions to slow-wave sleep in people who consume high-carb diets, compared to low-carb.
One factor that seems clearly to matter when it comes to carbohydrate intake? Quality. Diets that derive their carbohydrates from healthy, fiber-rich whole foods — as opposed to sugars and processed starches — are associated with better sleep. The Mediterranean diet, which emphasizes whole foods, lean proteins, fresh vegetables and fruits, a moderate amount of grain — while minimizing sugars — is linked to improvements in insomnia and other sleep problems. The effects on sleep from moving from a high-carb to a low-carb diet may depend heavily on the types of carbohydrates you've been eating, the ones you keep in place in your new regimen, and the timing of your eating, especially in the evening.
High protein diets have also shown both benefits and drawbacks for sleep. Some studies show consuming greater amounts of protein is linked to longer sleep times, more consistent sleep patterns, and higher sleep quality. Other research suggests higher protein intake is linked to shorter sleep amounts. Recent research indicates that high-protein diets in people who are overweight may lead to improvements to sleep.
A couple takeaways on low-carb diets and sleep
There isn't a one-size-fits-all message about how these popular diets affect sleep. To navigate sleeping well alongside any new eating plan, keep these things in mind:
Losing weight will help you sleep better. A diet that helps you get safely to a healthy weight and stay there will benefit your sleep. Your risks for obstructive sleep apnea and other sleep disorders will go down. You'll sleep more comfortably, and wake with more energy for the day. But keep this in mind also: losing weight at the expense of a sound, consistent sleep routine is not a smart strategy. The key is to identify the eating habits that allow you to lose excess weight, maintain a healthy weight, and sleep well at every step along the way.
Any dietary change can alter your sleep. Our eating and sleeping lives are deeply connected. What and when we eat affects our circadian rhythms, our gut health, our energy levels, and the hormones and biochemicals that stimulate and sedate us. If you're starting on a new diet, be aware your sleep may change at first. Be prepared to pay extra attention to how you're sleeping. If sleep issues arise in connection with a new diet and don't ease after a few weeks, take a look at modifying your eating strategy in consultation with your doctor, to improve your rest.
There's some exciting research coming on this topic, which we'll return to soon. In the meantime, eat well and sleep well as we head into a fresh new year.
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