The beverage aisle in your local grocery store contains a slew of unhealthy options — but some drinks can actually help improve your health and well-being. Writing for U.S. News & World Report, Julie Upton and Ruben Castaneda outline the best drinks for gut health, brain health, relaxation, and hydration.

What are functional beverages?

According to Upton, "[f]unctional beverages are drinks that contain wellness-aligned ingredients such as CBD, adaptogens and nootropics." These beverages can provide additional health benefits beyond their primary nutritional value. 

Due to their wide range of heart, GI, and brain health benefits, coffee and tea are often considered the "original functional beverages," Upton notes.

In recent years, manufacturers have created hundreds of functional beverages aimed at addressing a variety of health concerns. Over the past decade, functional beverages have become the fastest growing segment of the food industry, with drinks claiming to improve digestion, immunity, mental acuity, relaxation, sleep, and physical performance.

Best drinks to improve your health and well-being

With so many options on the market, it can be difficult to determine which functional beverages can actually help improve your health. According to Upton, these are the best drinks with the strongest evidence to support their claims:

Best beverages for GI health

For individuals suffering from GI issues like constipation, irritable bowel syndrome, gas, heartburn, bloating, or those who simply want to increase their intake of beneficial bacterial, Upton recommends drinking probiotic beverages, including:

• Fermented kefir

In published  review articles  about kefir, researchers noted that the fermented beverage may provide several health benefits. The studies found that the drink is anti-inflammatory, has anti-cancer properties, lowers cholesterol and blood pressure, improves mood, helps with muscle recovery, and offers other health benefits.

• Prebiotic soda alternatives

A popular new product in the GI health offerings is prebiotic, lower sugar soda alternatives. These are carbonated beverages that contain prebiotic fiber and botanicals to promote gut health. They mimic "the taste and experience of drinking a classic soda," Upton notes.

Best drinks for brain health

Ketone beverages are designed to provide "an alternative fuel source for the brain, muscles and all bodily functions when dietary carbohydrate and carb storage is depleted," Upton writes.

According to Richard Bloomer, dean of the  College of Health Sciences and the R. Brad Martin Student Wellness Center at the University of Memphis, ketones pass through the blood-brain barrier to supply fuel to the brain, which may aid in post-concussion recovery.

While there are still a lot of unknowns surrounding ketone beverages, experts believe that consuming a ketone beverage every three to four hours to maintain elevated blood ketone levels in the days following a concussion may aid the recovery process.

In a study in  Frontiers in Neurology, researchers found that exogenous ketones can help address the cerebral energy deficits that often occur with traumatic brain injuries. "While more research is needed to understand the exact dosage and timing, the authors believe that exogenous ketones are clinically useful," Upton writes.

Best drinks to promote sleep and relaxation

Currently, there are several functional beverages that help promote relaxation and improve sleep. Typically, these beverages contain sleep-promoting botanicals and nutrients, including ashwagandha, cherry juice, valerian, melatonin, chamomile, L-theanine, lavender, and lemon balm. Studies suggest that these ingredients help promote restful sleep.

• Infused warm milk

According to Patricia Bannan, author of "From Burnout to Balance," milk is nature's relaxation beverage. It "has numerous naturally occurring components that help people relax and promote sleep, including tryptophan, melatonin, magnesium and calcium. If you prefer a plant-based milk, almond milk or oat milk are good options as they also contain tryptophan-producing melatonin and magnesium to help you relax," Upton writes.

The best beverages for hydration

• Water

Typically, water is the best choice for optimal hydration and a strong immune system, Bannan concluded. To enhance the taste and add nutrients, Upton suggests infusing your water with citrus, mint, berries, or cucumber slices.

• Electrolyte-rich beverages

To boost hydration and maintain optimal health, experts also suggest incorporating electrolyte-rich drinks into your diet. Electrolytes are essential to brain function, healthy blood pressure, muscle health, and nerve function, Castaneda writes. It is important to replenish your electrolytes when your body loses them.

"Our bodies perform better and function optimally when we have the right balance of electrolytes in our body," said Amy Kimberlain, a registered dietitian and spokesperson for the  Academy of Nutrition and Dietetics. "It's important to note that electrolytes do not increase the amount of hydration we're getting from the beverage and sometimes the added sugars in sports drinks might negate the health benefits offered by the electrolytes."

According to Castaneda, the 10 best electrolyte-rich beverages are:

1. Coconut water

2. DIY electrolyte-rich drink recipes

3. Electrolyte-infused water

4. Pedialyte

5. Plant-based milks

6. Pickle juice

7. Smoothies

8. Sports drinks

9. V8 +Hydrate drinks

10. Watermelon Juice

(Upton, U.S. News & World Report, 4/13; Castaneda, U.S. News & World Report, 2/16)