Nav: Home

Are you sticking to your diet? Scientists may be able to tell from a blood sample

June 19, 2018

An analysis of small molecules called "metabolites" in a blood sample may be used to determine whether a person is following a prescribed diet, scientists at Johns Hopkins Bloomberg School of Public Health have shown.

Clinical trials of diets and their health impacts are often plagued by participants' poor adherence to assigned diets, which can make it difficult or even impossible to detect the true effects of those diets. The new approach, described in a paper in the American Journal of Clinical Nutrition published on June 18, could provide an objective and relatively easy-to-obtain measure of dietary adherence, potentially greatly reducing the uncertainty of dietary intake estimates.

The Bloomberg School scientists demonstrated their approach by showing that the levels of dozens of metabolites in the blood differed significantly between treatment and control groups enrolled in a clinical trial of the blood pressure-lowering DASH (Dietary Approaches to Stop Hypertension) diet. The DASH diet emphasizes fruits and vegetables and restricts red meat, sodium and sweets.

"We can now consider these metabolites as candidate biomarkers for assessing adherence to the DASH diet in future nutrition research studies, and one day clinicians might use these markers to monitor what their patients eat," says study lead author Casey M. Rebholz, PhD, an assistant professor in the Department of Epidemiology at the Bloomberg School.

Dietary adherence in clinical trials and even in ordinary clinical practice traditionally has been assessed by asking participants to keep track of what they eat. Human nature being what it is, such self-reports are not always accurate.

Some researchers have sought an objective measure of dietary adherence by testing urine samples from participants, but the requirement for each participant to collect samples over one or more days for testing is burdensome, and urine analysis covers a very limited set of nutrients.

Rebholz and colleagues decided to evaluate a potentially more informative and patient-friendly method based on blood samples. They demonstrated their approach using frozen stored blood samples that had been drawn from participants during the landmark 1997 study of the DASH diet. That study found that the DASH diet, compared to a control diet reflective of what the average American eats, significantly reduced blood pressure. The trial design, in which participants were provided with all study meals, ensured that dietary adherence was measured accurately--meaning that the trial data could be used later to test new measures such as blood metabolites.

The Bloomberg School scientists analyzed blood samples from 329 DASH trial participants for levels of metabolites--lipids, amino acids and other small-molecule byproducts of the body's biochemical activity that exist in everyone's blood and reflect food consumption. Using an advanced "untargeted metabolomics" approach, in which they looked at all known metabolites, the researchers found 97 metabolites whose levels differed significantly between the DASH diet-assigned participants and the control group.

"There was a clear differentiation in metabolite profiles between the DASH diet and the control diet," Rebholz says.

The researchers also identified 67 metabolites whose average levels differed significantly between the DASH diet group and a third study arm, the "fruits and vegetables" group. The latter was assigned to eat a diet richer than average in fruit and vegetables but not as rich in low-fat dairy as the DASH diet.

Rebholz and colleagues found evidence that for each dietary comparison a set of 10 metabolites with the sharpest diet-related differences was sufficient to collectively distinguish the two groups. "We don't think a single metabolite will be enough to detect a dietary pattern," Rebholz says. "It really needs to be a combination of metabolites."

For the DASH vs. control comparison, the top 10 discriminator metabolites were N-methylproline, stachydrine, tryptophan betaine, theobromine, 7-methylurate, chiro-inositol, 3-methylxanthine, methyl glucopyranoside, β-cryptoxanthin, and 7-methylxanthine.

In principle, according to Rebholz and colleagues, a panel consisting of these metabolites could be used in future studies and even in an ordinary clinical setting to assess patients' adherence to the DASH diet. And the same basic metabolomics strategy could be applied to differentiate non-DASH diets. "This approach certainly could be adapted for other dietary patterns, and I hope it will be," she says.
-end-
"Serum untargeted metabolomic profile of the Dietary Approaches to Stop Hypertension (DASH) dietary pattern" was written by Casey M. Rebholz, Alice H. Lichtenstein, Zihe Zheng, Lawrence J. Appel and Josef Coresh.

Funding was provided by the National Institute of Diabetes and Digestive and Kidney Diseases (K01 DK107782, P30 DK072488, U01 DK085689), and the National Center for Advancing Translational Sciences (UL1 TR001079).

Johns Hopkins University Bloomberg School of Public Health

Related Public Health Articles:

The Lancet Public Health: US modelling study estimates impact of school closures for COVID-19 on US health-care workforce and associated mortality
US policymakers considering physical distancing measures to slow the spread of COVID-19 face a difficult trade-off between closing schools to reduce transmission and new cases, and potential health-care worker absenteeism due to additional childcare needs that could ultimately increase mortality from COVID-19, according to new modelling research published in The Lancet Public Health journal.
The Lancet Public Health: Access to identification documents reflecting gender identity may improve trans mental health
Results from a survey of over 20,000 American trans adults suggest that having access to identification documents which reflect their identified gender helps to improve their mental health and may reduce suicidal thoughts, according to a study published in The Lancet Public Health journal.
The Lancet Public Health: Study estimates mental health impact of welfare reform, Universal Credit, in Great Britain
The 2013 Universal Credit welfare reform appears to have led to an increase in the prevalence of psychological distress among unemployed recipients, according to a nationally representative study following more than 52,000 working-age individuals from England, Wales, and Scotland over nine years between 2009-2018, published as part of an issue of The Lancet Public Health journal on income and health.
BU researchers: Pornography is not a 'public health crisis'
Researchers from the Boston University School of Public Health (BUSPH) have written an editorial in the American Journal of Public Health special February issue arguing against the claim that pornography is a public health crisis, and explaining why such a claim actually endangers the health of the public.
The Lancet Public Health: Ageism linked to poorer health in older people in England
Ageism may be linked with poorer health in older people in England, according to an observational study of over 7,500 people aged over 50 published in The Lancet Public Health journal.
Study: Public transportation use linked to better public health
Promoting robust public transportation systems may come with a bonus for public health -- lower obesity rates.
Bloomberg American Health Initiative releases special public health reports supplement
With US life expectancy now on the decline for two consecutive years, the Bloomberg American Health Initiative is releasing a supplement to Public Health Reports, the scholarly journal of the US Surgeon General.
Data does the heavy lifting: Encouraging new public health approaches to promote the health benefits of muscle-strengthening exercise (MSE)
According to a new study in the American Journal of Preventive Medicine, almost 75 percent of US adults do not comply with public health guidelines recommending two or more muscle-strengthening exercise (MSE) sessions a week, with nearly 60 percent of the population doing no MSE at all.
The Lancet Public Health: Moderate carbohydrate intake may be best for health
Low-carb diets that replace carbohydrates with proteins and fats from plant sources associated with lower risk of mortality compared to those that replace carbohydrates with proteins and fat from animal sources.
Mass. public safety, public health agencies collaborate to address the opioid epidemic
A new study shows that public health and public safety agencies established local, collaborative programs in Massachusetts to connect overdose survivors and their personal networks with addiction treatment, harm reduction, and other community support services following a non-fatal overdose.
More Public Health News and Public Health Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.