Welcome to the March 2023 issue 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, summarizes the essence of several interesting recent studies.

In this issue: (1) Mental Health Moment: sunshine, anxiety, and low vitamin D, (2) black tea and mortality, (3) tea consumption and ovarian cancer risk, and (4) healthy lifestyle and long-COVID risk.

Mental Health Moment: Vitamin D, Sun Exposure, and Anxiety among College Women

A low vitamin D level is often found in individuals living in Middle Eastern countries due to sun avoidance during hot-weather months, traditional clothing covering the majority of skin surfaces, and limited vitamin D-rich food sources. A low vitamin D level is known to adversely affect bone health, immune function, and neurological health, with some studies also evaluating the adverse effects of a low vitamin D level on psychiatric and mental disorders. Sunlight exposure increases the release of serotonin and melatonin that are both related to sleep and mood regulation. Sunlight also promotes nitric oxide production, which aids in reducing inflammation and oxidative stress, while also upregulating serotonin and melatonin. In the present study, the researchers investigated the correlation between anxiety, vitamin D levels, and sun exposure in college-aged females living in the United Arab Emirates.

Dietary data was collected to assess the average intake of vitamin D-rich foods or supplements over a 4-week period. A sun-avoidance inventory assessed sun avoidance attitudes and behaviors to determine whether participants aimed to minimize or maximize sun exposure. Anxiety severity was also measured. The results were as follows: 

  • 65 percent of participants reported a vitamin D deficiency
  • 58 percent of participants reported taking a vitamin D supplement
  • The majority of participants had an inadequate intake of vitamin D-rich foods
  • The majority of participants reported high sun-avoidance scores
  • 67 percent of participants had high levels of anxiety

Looking further into the correlations between vitamin D levels and anxiety, the results showed that the participants who reported a history of vitamin D deficiency, greater sun avoidance, and lower vitamin D-rich food intake had a higher risk for anxiety.

Contributed by Carly Duffy, MPH, RD

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Note: How is your vitamin D level? You can test it at home with Thorne’s Vitamin D Test.

Black Tea Consumption is Associated with Lower Mortality Risk

Tea is a beverage of choice worldwide; and green tea, in particular, is frequently researched for its health-promoting properties. Less well-studied, but more frequently consumed in Western countries, black tea might also have health benefits. Both forms of tea contain antioxidants and caffeine, albeit in differing amounts.

In a study of data from the UK Biobank, self-reported tea intake was compared with the leading causes of death, including cancer, cardiovascular disease, ischemic heart disease, stroke, and respiratory disease. The study analyzed the data from almost half a million men and women ages 40-69. Participants reported how many cups of tea they drank daily, fruit and vegetable intake, servings of red meat and processed meat, coffee consumption, and tobacco use.

For all causes of death, drinking two or more cups of tea daily was associated with a lower mortality risk. There was also an inverse relationship between tea consumption and risk of cardiovascular disease, ischemic heart disease, and stroke – indicating higher tea consumption is associated with lower disease risk.

Contributed by Jennifer L. Greer, ND, MEd

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Drinking Tea is Associated with a Lower Risk of Ovarian Cancer

Consumption of non-herbal teas from the Camellia sinensis plant, mainly green, black, white, oolong, and Pu-erh teas, is linked with various health benefits, including a decreased incidence of cancer. Previous research linking tea intake and gynecological cancer has had conflicting results – some studies show no impact of tea consumption on cancer development, while others indicate a protective effect. 

A meta-analysis of 19 studies, including more than two million participants, found the following:

  • There was no significant correlation between tea consumption and morbidity of gynecologic cancers; in other words, drinking tea did not increase or decrease death from gynecological cancer.
  • Consumption of black tea especially, but non-herbal tea in general, might help prevent ovarian cancer.
  • Tea consumption of 1.4-3.12 cups per day was associated with a trend toward decreasing risk of ovarian cancer, but higher tea consumption was not associated with greater protective effects.
  • Tea consumption was not significantly associated with other gynecological cancers.

Contributed by Jennifer L. Greer, ND, MEd

Reference

Healthy Lifestyle Factors Can Decrease the Risk for Long COVID

Now that the acute nature of the COVID pandemic is winding down, many individuals have lingering health issues, often referred to as long COVID or, as it’s referred to in the medical literature: post-COVID-19 condition (PCC). A recent study in JAMA Internal Medicine examined the effects of lifestyle on risk for PCC. In this prospective study, 32,249 women from the Nurses’ Health Study II cohort reported their lifestyle habits between 2015 and 2017. Factors identified were body mass index (BMI), smoking history, alcohol intake, exercise, sleep, and diet. The participants completed seven surveys between April 2020 and November 2021, and of those who tested positive for COVID, 1,981 participated in 19 months of follow-up. Of those, 871 (44%) experienced at least four weeks of symptoms following COVID diagnosis.

Healthy lifestyle factors were defined as: BMI of 18-24.5 (compared to higher or lower BMI); never a smoker (compared to quit smoking or current smoker); moderate alcohol intake of 5-15 grams/daily (equivalent to 1/3-1 glass of wine, compared to no or more alcohol consumption); moderate-to-vigorous exercise of at least 150 minutes a week; 7-9 hours of sleep nightly (compared to less or more sleep); and high-quality diet (upper 40% of an Alternate Healthy Eating Index-2010 score). Each healthy lifestyle factor was assigned a score of one point. A healthy lifestyle was associated with a dose-dependent decreased risk for PCC – the greater the number of healthy lifestyle points, the lower the risk. Women with 5-6 of the factors had 49-percent decreased PCC risk compared to women who had none – which translates to prevention of 36 percent of PCC cases. Two factors – BMI and sleep – independently decreased PCC risk (15% decreased risk with normal BMI compared to all other BMIs; 17% decreased risk with 7-9 hours of sleep compared to less or more sleep). The results were maintained when looking at symptoms lasting at least two months or that were still ongoing.

Bottom line: Adherence to a healthy lifestyle in the years prior to a COVID diagnosis decreased the risk of PCC.

Contributed by Kathi Head, ND

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