Welcome to the first 2021 edition of Research Extracts. “The Extracts” is designed to keep busy practitioners and savvy consumers up-to-date on the latest research on diet, nutrients, botanicals, the microbiome, the environment, and lifestyle approaches to good health. Our medical team, which includes NDs, MDs, PhDs, RDs, an MS, and an LAc, has summarized the essence of several of the most interesting studies.

In this issue are two studies that relate obstructive sleep apnea to COVID-19 risk, a study on the effect of matcha tea on cognitive function, and, to spice things up a bit – two studies on the health benefits of chili peppers.

COVID-19 outcomes correlate with sleep apnea risk 

Sleep apnea is the disorder that involves prolonged pauses in breathing during sleep. Many individuals with sleep apnea are not aware they have it, making it a hidden risk factor for those who are facing surgery or who contract a respiratory disease. A screening test called the symptomless multi-variable apnea prediction index (sMVAP) uses commonly available information – sex, age, and body mass index (BMI) – to evaluate an individual’s risk for having obstructive sleep apnea, a type of sleep apnea where the airway becomes blocked by the tissues in the throat. Males, older people, and individuals with higher BMIs are more likely to develop obstructive sleep apnea.

To investigate a possible connection between sleep apnea risk and COVID-19 outcomes, an observational study was conducted in which 97 patients requiring hospitalization for COVID-19 were screened for sleep apnea using sMVAP. The sMVAP results were compared with COVID-19 disease outcomes – discharge from hospital or death. Participants were divided into four groups based on their risk scores, with Group 1 being those individuals with the lowest sMVAP scores and Group 4 being those with the highest sMVAP scores and, thus, the highest risk.

Significantly more participants in Group 4 required mechanical ventilation and significantly more had to be transferred to the ICU compared to Group 1; likewise, the incidence of complications was higher for Group 4. Group 4 had eight times the mortality of Group 1. The authors propose the use of sMVAP as a simple screening tool – one that does not require the collection of non-standard information – might be a simple way to improve management of high-risk patients with COVID-19.

Contributed by Sheena Smith, MS MA 

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  • Zhang S, Xu Y, Li J, et al. Symptomless multi-variable apnea prediction index assesses adverse outcomes in patients with Corona Virus Disease 2019. Sleep Med 2020;75:294-300. doi:10.1016/j.sleep.2020.08.031

Sleep apnea associated with hospitalization from COVID

In a second study, conducted at a Finnish hospital, a disproportionate number of patients admitted with COVID-19 were found to have obstructive sleep apnea.1 In this review of patients admitted to Turku University Hospital, the prevalence of sleep apnea in COVID-admitted patients was 29 percent, compared to only 3.1-percent prevalence among general hospital admissions. There was a high degree of obesity among the COVID admissions as well. C-reactive protein, a marker of inflammation, and procalcitonin levels (which can be a sign of a bacterial co-infection) were also significantly higher in the patients who required critical care. These results are in line with findings from other studies.2 

The connections are fairly clear – obesity increases the risk of having obstructive sleep apnea and is also associated with chronic, low-level inflammation,3 because inflammatory cytokines are secreted from fat cells – all of which increase risk for poor COVID outcomes.

Contributed by Kathi Head, ND

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  1. Feuth T, Saaresranta T, Karlsson A, et al. Is sleep apnea a risk factor for Covid-19? Findings from a retrospective cohort study. Sleep Med Dis Int J 2020;4(3):61-65. DOI: 10.15406/smdij.2020.04.00075
  2. Hu R, Han C, Pei S, et al. Procalcitonin levels in COVID-19 patients. Int J Antimicrob Agents 2020;56(2):106051. doi:10.1016/j.ijantimicag.2020.106051
  3. Wisse B. The inflammatory syndrome: The role of adipose tissue cytokines in metabolic disorders linked to obesity. J Am Soc Nephrol 2004;15 (11):2792-800.

For more information on the connection between obesity, inflammation, and COVID-19, check out this recently posted Take 5 Daily post from our friends at Mayo. 

Does matcha green tea affect cognitive function in elderly individuals?

A randomized, double-blind, placebo-controlled trial investigated the effects of matcha green tea on cognitive function and impulsivity in healthy participants over age 60 with no diagnosis of dementia or mild cognitive impairment. Participants were given matcha green tea or black tea to drink twice daily over 12 weeks. At baseline and after 12 weeks, cognitive function was measured using the Montreal Cognitive Assessment (MoCA) and the Mini-Mental Status Exam (MMSE), while impulsivity was measured with the Barrett Impulsiveness Scale-11 (BIS-11).

When the participants were considered as a whole, there was no change in MoCA, MMSE, or BIS-11 at 12 weeks versus placebo. However, the female treatment subgroup showed significant improvements in MoCA compared to the female placebo group (p=0.0103). Of the MoCA subcategories, language showed the most significant change with matcha use (p=0.0008). The male treatment group did not report significant changes compared to placebo. The authors note this female-specific improvement with matcha green tea use was consistent with previous studies on matcha green tea supplementation and memory enhancement in elderly women.

Contributed by Jennifer Greer, ND, MEd

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  • Sakurai K, Shen C, Ezaki Y, et al. Effects of matcha green tea powder on cognitive functions of community-dwelling elderly individuals. Nutrients 2020; 12(12):3639. 

Spice up your diet – it might help you live longer

Spicy food lovers can rejoice a little extra this holiday season based on new findings presented in a scientific session of the American Heart Association’s annual meeting. A large scale review of more than 4,000 studies containing a half-million participants strongly supports regular consumption of chili pepper for significantly reducing the chances of dying from cardiovascular disease or cancer. The study, conducted at the Cleveland Clinic, included dietary and health data from individuals from the United States, Italy, China, and Iran, and compared regular chili pepper consumers to non-consumers.

The conclusions were very favorable for chili eaters, showing a 26-percent relative reduction in cardiovascular mortality, a 23-percent relative reduction in cancer mortality, and a 25-percent relative reduction in all-cause mortality. The researchers speculate that the benefits could be due to anti-inflammatory, antioxidant, anti-cancer, and blood glucose regulation effects of compounds found in chilis. The researchers, however, made the point that more research needs to be done, especially randomized controlled studies, to confirm these benefits. So, while we can’t say for sure that if you eat more spicy food you will live a longer, healthier life, there’s no harm in trying. If you are new to eating chili peppers, it’s best to start with something relatively mild like an Anaheim, banana, or shishito pepper, and work your way up to the hotter jalapeño, aji, and habanero peppers. Most people build tolerance to the “heat” over time and enjoy even spicier foods as they do.

Contributed by Jacqueline Jacques, ND


  • Impact of chili-pepper intake on all-cause and cardiovascular mortality – a systematic review and meta-analysis.   https://www.abstractsonline.com/pp8/?&_ga=2.241603266.1992222014.1602856798-1601912555.1597336667#!/9144/presentation/39489  [Accessed December 10, 2020.]

Can chili peppers help you lose weight or lower your cholesterol?

The above-cited Cleveland Clinic study is not the only recent research to look at the potential health benefits of peppers. A recent meta-analysis evaluated intervention trials that compared consumption of Capsicum annuum to placebo for its effect on various aspects of metabolic syndrome. The analysis included various subspecies of C. annuum – cayenne, jalapeno, sweet pepper, bell pepper, and others; i.e., any pepper besides black pepper. Twelve studies fit the inclusion criteria, including five from the United States, three from Korea, two from Japan, and one each from Australia and China. Ten studies were parallel-arm studies, while the other two were crossover studies.

Active constituents in Capsicum annuum include capsaicin (responsible for the hot spiciness of peppers) and capsinoids (non-pungent, non-spicy constituents) – and are typically responsible for their anti-inflammatory, antioxidant, thermogenic, and lipid-lowering effects. The Capsicum groups had significantly reduced LDL cholesterol (the “bad” cholesterol) and small but significant decreases in weight compared to placebo. Blood sugar, other lipids (triglycerides, HDL, and total cholesterol), and blood pressure were not affected.

Contributed by Kathi Head, ND

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  • Jang H, Lee J, Lee S, et al. Effects of Capsicum annuum supplementation on the components of metabolic syndrome: a systematic review and meta-analysis. Sci Rep 2020;10:20912 https://doi.org/10.1038/s41598-020-77983-2