How Does Sugar Affect Sleep?


Written by Dr. Michael Breus

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Whether you are considering Paleo, Keto, Whole 30, or intermittent fasting, your new healthy eating and weight-loss strategy is guaranteed to involve reducing sugar.

These days, I’m hearing from a lot of my patients that their sleep has improved a lot since they started their version of eating clean. One of the most potent, underrated benefits of eating well, especially when paired with exercise? A big boost in sleep. Many of my patients tell me that since they gave their diets a reboot they’re finding it easier to fall asleep, they wake less often, and they rise in the morning feeling better rested and much more energized.

For all its benefits, staying away from sugar isn’t easy! I have a serious sweet tooth, so I totally understand this struggle. For a little extra motivation, let’s go over some of the biggest reasons sugar can prevent you from getting your best sleep.

Sugar Reduces Sleep Quality

There is evidence that consuming more sugar is linked to more restless, disrupted sleep. In a 2016 study one group was fed a controlled diet that limited added sugars and fats and emphasized fiber, while a second group was allowed to eat whatever they wanted, in whatever amounts. Researchers found that the second group consumed significantly more sugar and fat—and their diet had an impact on the quality of their nightly rest. The volunteers who consumed diets with more sugar took longer to fall asleep and spent less time in deep, slow-wave sleep. This sleep stage is essential for the body’s physical restoration and healing, as well as for maintaining healthy metabolism and immune function. These volunteers also experienced more restless sleep, with frequent awakenings throughout the night.

Some sugary treats also contain caffeine, which will undermine your sleep, especially if you consume it in the evenings. Together, sugar and caffeine are a one-two combination primed for interfering with your rest.

Sugar Stimulates Cravings

Eating sugar activates the brain’s reward circuitry, and a complex web of hormones related to hunger and metabolism. In response to sugar, the brain releases dopamine—a hormone that delivers powerful feelings of pleasure and satisfaction. The more sugar we eat, the less sensitive our brains become to that dopamine rush. We need to produce more dopamine in order to experience the same feelings of pleasure and satisfaction. And that translates into a need to eat more sugar. The dopamine-activated reward pathways in the brain that are affected by sugar are the same ones affected by alcohol, drugs, and other potentially addictive behaviors.

Eating sugary foods—and the additional body fat that typically comes from a high-sugar diet—reduces the effectiveness of hunger-suppressing and metabolism-regulating hormones. Cravings lead to late-night eating that will disrupt your sleep and, in turn, poor sleep makes our sugar cravings even worse. A wealth of studies show that poor quality and insufficient sleep interfere with the normal production and function of hormones, including leptin and ghrelin. Poor sleep also interferes with insulin, the hormone that is a key regulator of blood sugar. A regular sugar habit can set in motion a cycle of disrupted sleep and overstimulated appetite that is tough to break, and over time leads to weight gain, as well as prediabetes and diabetes.

Sugar Increases Inflammation

Both sleep and inflammation are regulated by our circadian rhythms. When one goes awry, the other is likely to suffer, also. Sleeping poorly, including getting too little or too much sleep, increases the chronic inflammation that is a significant contributor to disease.

Systemic inflammation, in turn, can also undermine healthy sleep by triggering physical and psychological changes that make it harder to get a good night’s rest. Inflammation comes with the presence of cytokines, chemical messengers that have been shown to regulate sleep. Elevated cytokines have been linked to trouble sleeping and to insomnia. Inflammation can create pain and stiffness in the body that make it difficult to fall asleep and sleep soundly. Inflammation involves higher levels of cortisol, a hormone that stimulates alertness and can contribute to feelings of psychological stress. Stress is among the most significant common obstacles to healthy sleep.

Diets high in sugar increase chronic inflammation. Sugar contributes to the formation of harmful biochemical compounds that spike inflammation. Sugar and refined carbohydrates cause unhealthful, inflammation-boosting changes to gut bacteria—now recognized as a key regulator of overall health. Sugar in our diets also elevates cholesterol, which is linked to increased inflammation.

Sugar Hurts a Healthy Gut

The relationship between sleep and gut health is complex. Like sleep, our gut microbiome is regulated by circadian rhythms. We’re still just beginning to understand how gut microbiota affects our health, but this densely populated microbiotic community appears to have a significant influence over our metabolism, immune health, cardiovascular and circulatory function, and mood. There’s an abundance of evidence that a standard Western diet—one that’s high in processed sugars and fats—causes unhealthy changes to the composition of our gut microbiota and to the strength of the intestinal wall which keeps them from entering the bloodstream where they can cause inflammation.

But it is difficult to extract from this research the specific effects of sugar on gut health. We’re only now beginning to see a handful of studies investigating sugar’s effects on the microbiome. A 2018 study found that dietary fructose, found naturally in fruits and juices and also found in processed sweeteners, causes changes to the microbial make-up of the gut. There’s also an interesting 2017 study which showed that consumption of added sugars in childhood and adolescence led to alterations to the gut microbiome.

There are other ways sugar may indirectly affect our gut health. A diet that includes frequent consumption of added sugars is likely to lead to weight gain. People who get calories from sugary foods may be consuming less essential nutrients. For example, fiber is essential for the bacteria and other microbes in our intestines. One recent study in mice showed a low-fiber diet produced significant changes to the diversity of the microbiome and also increased inflammation and blood sugar levels. When the intestinal barrier that holds bacteria within the gut weakens, something called “leaky gut” increases the risk of inflammation and disease.

We have yet to see definitive research, but there are indications that a healthy gut may play an important role in sleep. Keep your gut healthy with a low-sugar, high-fiber diet that focuses on whole, unprocessed foods—and you may also see your sleep improve!

About The Author

Dr. Michael Breus

Clinical Psychologist, Sleep Medicine Expert

Michael Breus, Ph.D is a Diplomate of the American Board of Sleep Medicine and a Fellow of The American Academy of Sleep Medicine and one of only 168 psychologists to pass the Sleep Medical Specialty Board without going to medical school. He holds a BA in Psychology from Skidmore College, and PhD in Clinical Psychology from The University of Georgia. Dr. Breus has been in private practice as a sleep doctor for nearly 25 years. Dr. Breus is a sought after lecturer and his knowledge is shared daily in major national media worldwide including Today, Dr. Oz, Oprah, and for fourteen years as the sleep expert on WebMD. Dr. Breus is also the bestselling author of The Power of When, The Sleep Doctor’s Diet Plan, Good Night!, and Energize!

  • POSITION: Combination Sleeper
  • TEMPERATURE: Hot Sleeper

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