How Does Sugar Affect Sleep?

A lot of us are just about one month into our new year, shape-up, eat-right plans. Whether you’ve started the new year with Paleo, Keto, Whole 30, or intermittent fasting, your new-and-improved 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.

(A lot of today’s popular diets also come with potential hazards for sleep. You can read up on the pros and cons of Keto, Paleo, and intermittent fasting  here, and here.)

For all its benefits, staying away from sugar isn’t easy! I have a serious sweet tooth, so I totally understand this struggle. You know it’s the right thing to do. But cookies, chocolate, and ice cream (my favorite) call to us, don’t they?

Have you committed to reducing your sugar intake this year? Looking for some fresh motivation to limit the sugar in your diet? Spend a few minutes with me going over some of the biggest ways 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. A 2016 study included healthy volunteers who were placed into one of two groups. One group was fed a controlled diet that limited added sugars and fats, and emphasized fiber. The 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 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. The volunteers who ate more sugar also took longer to fall asleep. And they experienced more restless sleep, with more frequent awakenings throughout the night.

Some sugary treats also contain caffeine, which will undermine your sleep, especially if you consume it in the evenings. Ever snacked on some dark chocolate and had a fitful night of sleep follow? That’s a one-two combination of sugar and caffeine interfering with your rest.

Sugar stimulates appetite and cravings

Eating sugar activates the brain’s reward circuitry, and a complex web of hormones related to hunger and metabolism. (The truth is, sugar is such a powerful trigger that even catching sight of a sugary treat is enough to stimulate the brain’s reward system, studies show.) 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. (If this all sounds a lot like a drug addiction, you’re right. 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 like gambling and sex.)

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, including leptin and insulin.

What does this have to do with sleep? Cravings, and an appetite distorted by over-consumption of sugar, lead to late-night eating that will disrupt your sleep. And that poor sleep in turn 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 appetite-regulating 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

I recently wrote about the relationship between sleep and inflammation. Both sleep and inflammation are regulated by our circadian bio 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, low-grade inflammation that is a significant contributor to disease.

Systemic inflammation, in turn, can also undermine healthy sleep. How? 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. (Physical pain is a common factor in insomnia and other sleep problems.) 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

You’ve heard me talk before about the complex relationship between sleep and gut health. Our gut microbiome is the vast community of microscopic organisms living our intestines. Our gut microbiome has a nervous system, produces neurotransmitters and hormones (including the sleep hormone melatonin). Like sleep, our microbiome is regulated by circadian rhythms. We’re still just beginning to understand how gut microbiota affects our health and contributes to aging and disease. But this densely populated microbiotic community appears to have a significant influence over our metabolism, immune health, cardiovascular and circulatory function, as well as mood. We have yet to see definitive research, but there are indications that the gut microbiome also may play an important role in sleep.

The research on sugar’s effects on the gut microbiome is surprisingly limited. There’s an abundance of evidence that a standard Western diet—one that’s high in processed sugars and fats—causes unhealthful changes to the composition of our gut microbiota, and to the strength of the intestinal wall that contains this collection of microorganisms, and keeps them from entering the bloodstream, where they can cause inflammation and other damage to healthy functioning.

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 – a simple sugar found naturally in fruits and juices and also found in processed sweeteners including table sugar and high-fructose corn syrup – causes changes to the microbial make-up of the gut. There’s also a very interesting 2017 study conducted in rats which showed that consumption of added sugars in childhood and adolescence led to alterations to the gut microbiome. In this study, scientists were able to isolate and attribute the specific effects of sugar, apart from other factors such as caloric intake and body fat, which also affect gut microbiota. It’s great to see new research exploring the effects of sugars on microbiotic health—we need to see much more.

There are other ways sugar may indirectly affect our gut health. Sugar contributes to inflammation, and inflammation is harmful to the diversity and function of gut bacteria. A diet that includes frequent consumption of added sugars is likely to lead to weight gain. Studies show that dietary-induced obesity creates changes to the microbial life in our gut. People who get calories from sugary foods may also be consuming less healthful nutrients, including fiber, from whole, unprocessed, no-sugar-added food sources.

Fiber is food for the bacteria and other microbes in our intestines. Eating plenty of fiber is one way to keep our gut healthy. One recent study in mice showed the dramatic effects of switching to a low-fiber diet from a high-fiber one. A low-fiber diet produced significant changes to the diversity of bacterial life in the microbiome. The mice developed inflammation, and their blood sugar levels rose. The intestinal barrier that holds bacteria within the gut weakened. Greater intestinal permeability—sometimes called “leaky gut”—is associated with inflammation and disease.

A low-sugar, high-fiber diet that focuses on whole, unprocessed foods will help keep your gut healthy. It will also help you sleep better. A great night of restful sleep is another reward for saying no thanks to most of the sugar temptations that come our way!