Pauline Anderson
February 28, 2018
A diet previously shown to reduce hypertension and stroke risk may also help ward off depression, new research suggests.
Participants who most closely adhered to the low-sodium Dietary Approaches to Stop Hypertension (DASH) diet were 11% less likely to become depressed over time than those least adherent to the diet, the study found.
The results suggest that the DASH diet may have the “dual benefit” of protecting against cardiovascular disease and helping to boost mood, lead author, Laurel J. Cherian, MD, assistant professor, vascular neurology, Rush University Medical Center, Chicago, Illinois, told Medscape Medical News.
“I think that’s a valuable tool for us as neurologists.”
Late life-depression is a “major issue,” not only for patients aging normally but also for those with cognitive issues and those who have had a stroke, said Cherian. “For me, as a stroke doctor, I know that post-stroke depression is a major issue that is undertreated, and contributes to morbidity.”
The study will be presented April 23 at the upcoming American Academy of Neurology (AAN) 2018 Annual Meeting in Los Angeles, California.
Food Frequency
The analysis included 964 participants in the Memory and Aging Project (MAP), a cohort of Chicagoans aged 60 years and older who are followed annually and evaluated over time for development of Alzheimer’s disease. In addition to having regular cognitive assessments, MAP participants are screened for depression by using the 10-item version of the Center for Epidemiology Studies-Depression scale.
They also complete a 144-item food-frequency questionnaire. Participants are asked how often and how much they ate of various items over the past year.
On the basis of this self-reported intake, researchers then looked at how closely participants adhered to the DASH diet. In addition to emphasizing low sodium, this diet encourages consumption of foods rich in nutrients, such as potassium, calcium, and magnesium, that help lower blood pressure.
The diet scoring system used in the study has been validated in previous research. The DASH score ranges from 0 to 10, with more points given for eating healthier foods daily.
Researchers divided participants into tertiles based on their diet scores. “For example, the highest tertile would be people who were scoring 8, 9, or 10 on the DASH diet and the people who were scoring 1, 2, or 3 would be in the lowest tertile, which is probably closer to the typical Western diet,” said Cherian.
The typical Western or American diet is generally low in whole grains, fruits, and vegetables and high in sweets, saturated fats, and processed foods.
Those in the middle tertile might have some good dietary habits but might be eating too many unhealthy saturated fats and salty foods, said Cherian.
High-Risk Population
The mean age of study participants was 81.32 years. Cherian pointed out that their age made them a high-risk population for depression.
For this study, depression was defined as the presence of four or more depressive symptoms, for example, feeling hopeless about the future and being troubled by things that aren’t usually bothersome.
Participants were followed for an average of 6.53 years. The researchers controlled for factors known to affect depression, including age, education level, sex, caloric intake, and cognitive function.
The analysis showed that participants who were most adherent to the DASH diet were less likely to become depressed. Those in the second (β = – 0.0786; P = .0319) and third (β = – 0.1109; P = .0061) tertiles of the DASH diet had lower rates of depression over time than those in the first tertile (β = –0.03; P = .004).
On the other hand, the analysis showed that eating more of a Western diet was positively associated with depression over time (β = 0.0195; P = .0346).
Depression symptoms can come and go, but because depression was assessed annually, and not just once, the study was less likely to have captured a depression episode by chance, said Cherian.
This study did not separate out stroke survivors, but Cherian and her colleagues aim to do so in another analysis.
MIND, Mediterranean Diets
The researchers also looked at the Mediterranean diet. This diet emphasizes fish, fruits, and vegetables, with olive oil as the main source of fat.
As well, they examined the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet, a kind of hybrid of these two diets. But the MIND diet also emphasizes brain-healthy foods, such as green leafy vegetables, berries that are loaded with antioxidants, and olive oil.
In previous studies, both the Mediterranean and MIND diets protected cognition, and recent research has suggested that the Mediterranean diet can improve mental health in patients with depression (for example, the SMIILES study and the HELFIMED study).
The scoring patterns for the Mediterranean and MIND diets are different from that of the DASH diet, but in this current study they were standardized in tertiles so the diets could be compared to each other, said Cherian.
The new study did not find a statistically significant association between depression and the Mediterranean or the MIND diet. It’s not clear why these other healthy diets didn’t have a significant effect on depression, but a larger study might have found that they also affect mood, said Cherian.
In the meantime, she’s keen to learn what it is about the DASH diet that seems to boost mood. “We need to do some additional studies to try to figure out what is it about the DASH diet that may be helpful,” said Cherian.
It could be that the DASH diet focuses on low sodium. However, Cherian emphasized the difficulty of quantitatively measuring sodium in the diet, especially when some people aren’t even aware they’re taking it in.
Food as Medicine
The bottom line, though, is that all three diets — DASH, Mediterranean, and MIND — “are substantially better for people than the typical Western diet,” she said.
This new study and others highlight the power of food as medicine, said Cherian.
“As a neurologist, I realize that medicines are wonderful tools; they’re very powerful and something we definitely want to utilize. But medicines have side effects and for some people, it’s challenging to be on psychiatric medications.”
Cherian said she hopes this research will draw attention to this area.
“We know that our elderly population is at increased risk of developing depression. I think a healthy lifestyle, and in particular including a healthy diet, can be a way to ward off depression.”
Commenting on the study, Helmi Lutsep, MD, vice chair and Dixon Term Professor, Department of Neurology, Oregon Health & Science University (OHSU), associate director, OHSU Stroke Center, and a fellow of the AAN, said it’s “very valid.”
“We always love randomized trials, but it can be very difficult to answer some of these questions that way,” she told Medscape Medical News.
The approach the researchers took was commendable, added Lutsep. “They’ve got a large patient population; they seem to have followed them for a long period of time; and assessed them quite frequently, so from what I can tell from the abstract, it looks well done.”
It’s possible that the DASH diet is a little more “prescribed” than the other diets so people may be more likely to stick to it, said Lutsep. “Maybe they were just a little more careful or compulsive about food intake compared to those following other diets.”
She agreed that having “that extra element of watching your sodium intake” might have affected depression among adherents to the DASH diet.
Lutsep noted that of all the diets, the DASH diet emphasizes alcohol the least. Alcohol can be a depressant and drinking more than the recommended amount can increase blood pressure, she said.
Red wine is part of the Mediterranean lifestyle, and the MIND diet also includes some alcohol.
“So very theoretically, if people are trying to control their blood pressure, maybe that would also be the group that is drinking less than the other groups,” said Lutsep.
She also pointed out that the economic status of the different groups wasn’t clear and that eating a healthy diet can be expensive.
“There are potential constraints, or things we can’t always tease out in a study like this.”
The study was funded by grants from the National Institute on Aging. Cherian and Lutsep have disclosed no relevant financial relationships.
American Academy of Neurology (AAN) 2018 Annual Meeting. Abstract 3569 (P2.179). To be presented April 23, 2018.
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