If waves of coronavirus infections ebb and flow until a vaccine arrives and if — as some have posited — we're all likely to get it at some point, should we be preparing for a possible infection? The coronavirus is fatal for some, while others — between 25% to 50% according to the latest estimates — have no symptoms at all. Everyone else falls somewhere in between. As the medical community seeks possible explanations for that variability — viral load (how much of the virus you have in your body) and genetic susceptibility are both being studied — we are left to wonder what amount of influence, if any, we have over how our bodies will react to being infected. Age, gender and underlying health conditions can affect outcomes, but there may be many simple things people can do to boost their immunity — and some of the world's most prominent resorts, hotels and restaurants were encouraging them even before the pandemic struck.

The single easiest way to boost your immunity

The internet is replete with supposed immune-boosting supplements and recipes — a situation that long predated the arrival of Covid-19 — but the answer to an improved immune system may be far less complicated. "In my experience, the single best way people can improve their immune system is through adequate sleep," said Dr. Steven Tucker, an American oncologist and medical director of Tucker Medical, a multi-specialty medical practice that focuses on the prevention and reversal of chronic diseases.

Sleep is not a pillar of health but the bedrock foundation upon which all health, including immunity, is built. Dr. Steven Tucker

"I used to say that health was based on fitness, nutrition, mindfulness and sleep. I would tell patients that these are the four pillars of health. I no longer do that," he said. "I can't emphasize it enough if you want to improve your immunity, sleep is not a pillar of health but the bedrock foundation upon which all health, including immunity, is built." It's believed people who experience a quick, sudden decline in health from a coronavirus infection do so as a result of the immune system suddenly kicking into overdrive in a process known as a cytokine storm. The focus then turns to controlling one's immune system as well as the infection. Cytokines can rise by a single night of bad sleep.

Sleeping in — a silver lining to the shutdown

From overnight flights and peering into hand-held screens past midnight, to massive coffee intake, the modern-day lifestyle is no friend of sleep. "Whether your sleep is disrupted from jet lag or from too much training or from anxiety stress, getting more sleep and better sleep improves your resilience, lowers your adrenal and stress hormones and thus improves your immunity," said Dr. Tucker.

Drs. Steven Tucker and Brian Schwender of Tucker Medical, an integrated care health facility that focuses on disease prevention and reversal. Courtesy of Tucker Medical

Sensing a void among a sleep-deprived customer base, luxury hotel brands created a new form of customer experience. An industry that once wanted to wow you with services and activities started putting you straight to bed. Sleep programs — marketed as Rest & Renewal or Deep Sleep packages — started in hotels like the Four Seasons and Swissotel. As far back as 2016, Six Senses partnered with "sleep doctor" Michael J. Breus to develop sleep programs at select hotels that include a two-night sleep tracking analyzer, nutritional advice, yoga nidra (yogic sleep), linen that regulates body temperature, special lighting, sound therapy machines and sleep-inducing snacks.

Six Senses' sleep programs includes sleep tracking consultations, yoga nidra and nutritional advice. Courtesy of Six Senses

While you may not be able to book a sleep program at the nearest luxury hotel right now, you can set a sleep schedule, avoid blue screen devices within one hour of bedtime and exercise in the morning all from the comfort of home. One shutdown silver lining could be longer sleeping hours. With no business travel, after-hour parties to attend, kids to get ready for school and early office hours to adhere to, going to bed early and sleeping in late has never been easier.

What to know about coffee and home cocktails

Dr. Tucker said to focus on sleep you need to consume less caffeine and "ideally, no alcohol as it really destroys sleep quantity and quality. One or two cups of coffee in the morning before 12 noon is probably OK." In an interview with NPR, bestselling food author Michael Pollan said caffeine causes problems people often miss as it undermines the quality — but not necessarily the quantity — of sleep, especially "slow wave" or deep sleep. "This isn't REM sleep, where you're having dreams, or light sleep. This is a really deep place you go for not that long a part of the night, but it's really important to your mental and physical health," Pollan said. "It's like cleaning up the desktop on your computer at the end of the day."

Eighty percent of the world's population, including children, use caffeine every day. RyanJLane

When sleep is disrupted — from work, exercise or emotional stress — the hormones adrenaline and cortisol are activated. This initially stimulates the immune system but when it continuously occurs, the immune system is weakened. "This will ultimately induce daytime fatigue and nighttime insomnia creating a vicious cycle between the pituitary gland, the adrenal glands and the immune system," said Dr. Tucker. "Compounding the situation today, disrupted sleep will also increase the risk and intensity of anxiety and depression."

'Immune-boosting' drinks and supplements

Generally speaking, immune-boosting foods and drinks are not going to provide a significant effect if you are not focusing on sleep nutrition and physical activity, said Dr. Tucker. Dr. Tucker recommends nutrient-rich food over immune-boosting supplements, but doesn't rule out supplements to improve sleep, such as magnesium, melatonin, 5-HTP, L-theanine and serotonin.

There's no organic bee pollen smoothie that is going to improve your immunity compared with a good night's rest. Dr. Steven Tucker

Dr. Brian Schwender, a Singapore-based gastroenterologist at Tucker Medical, said there is a misconception around taking vitamin C to prevent the coronavirus. "There is no evidence at present to support taking vitamin C, especially in high or super doses, to prevent or treat this infection," he said. "Most of this misinformation is probably from extrapolating the use of vitamin C to reduce the risk of getting the common cold, which is modest at best." A large review by Cochrane, a U.K.-based independent medical research organization, of 29 medical trials published in 2013 did not show any benefit to routine vitamin C consumption among the general public for reducing the rate or severity of the common cold. Furthermore, high doses of vitamin C (greater than 2 grams) can have gastrointestinal side effects and are not advisable for people with kidney stones.

Turmeric, ginger and honey are popular immune-boosting foods, but they are no substitute for sleep. Seksak Kerdkanno / EyeEm

Turmeric and ginger are compounds that have been found to boost one's immune system and reduce inflammation, however there is no data to support the use of any of these supplements in the prevention or treatment of Covid-19 at this time, said Dr. Schwender. "Most of these 'immune-boosting drinks' are anecdotal at best with respect to preventing or treating Covid-19," he said. Dr. Tucker agrees. "There's no organic bee pollen smoothie that is going to improve your immunity compared with a good night's rest," he said.

Other coronavirus tips to improve immunity

When it comes to eating healthy, consuming whole foods may not sound as sexy as a hot new superfood, but they're sound advice when it comes to your immune system. Dr. Tucker recommends eating whole foods and particularly vegetables to boost immunity, especially those that grow above ground that are less starchy. Processed foods should be avoided. Geert Jan Vaarjes, the executive chef at Anantara's resort in Hoi An, Vietnam, recommends sticking to freshly-cooked food.

The turmeric tea at the Al Baleed Resort Salalah. Courtesy of Anantara