Science Spotlight

Take a load off: lower glycemic load for a good mood

Scores on The Center for Epidemiological Studies Depression Scale (CES-D) in overweight and healthy weight participants at baseline, at the end of the high glycemic load diet (High GL), and at the end of the low glycemic load diet (Low GL).
Scores on The Center for Epidemiological Studies Depression Scale (CES-D) in overweight and healthy weight participants at baseline, at the end of the high glycemic load diet (High GL), and at the end of the low glycemic load diet (Low GL). Kara L. Breymeyer

Depression is one of the most common mental disorders in the United States. According to the World Health Organization, depression also carries the heaviest burden of disability among mental and behavioral disorders. Preventing depression remains a critical health challenge.

Emerging evidence suggests diet and obesity associate with depression. One specific area of research focuses on how carbohydrate quality relates to neurological function and mood. Glycemic load (GL) is a measure that simultaneously describes the blood glucose-raising potential (glycemic index) and the quantity of the carbohydrate in a food, both of which have subsequent effects on brain function. The glycemic load is determined by multiplying the grams of a carbohydrate in a serving by the glycemic index, then dividing by 100. A glycemic load of 10 or below is considered low; 20 or above is considered high. For example, watermelon has a high glycemic index (80), but since a serving of watermelon has so little carbohydrate (6 grams), its glycemic load is only 5.  In contrast, jellybeans have a high glycemic index (76) and a large amount of carbohydrate in a serving (28 grams), thus its glycemic load is 21. 

There is little research on the influence of GL diet patterns on mood among healthy individuals. This gap in the literature motivated Kara Breymeyer MPH, Marian Neuhouser PhD, and colleagues (Public Health Sciences Division) to investigate the subjective mood and energy levels of healthy participants in a randomized crossover, controlled dietary intervention testing the effects of high glycemic load (HGL) and low glycemic load (LGL) diets. In addition, the researchers sought to understand whether the associations of these diets with mood varied by obesity status. The results from this trial were recently published in Appetite.

Study participants include healthy individuals, both normal weight and overweight/obese, from the Carbohydrates and Related Biomarkers (CARB) study. Participants (n = 82) were randomized into either a HGL or LGL diet arm for 28 days, followed by a 28-day washout period, and then placed on the opposing diet for another 28 days. Mood assessments, using the Profile of Mood States (POMS) subscales and The Center for Epidemiological Studies Depression Scale (CES-D), were taken at baseline and at the end of both 28-day diet periods. The investigators used linear mixed models to test the intervention of the diet on mood, controlling for baseline factors and diet sequence.

Compared to the LGL diet, the HGL diet resulted in a 38% higher score for depressive symptoms (P = 0.002), as well as 55% higher score for total mood disturbance (P = 0.05), and a 26% higher score for fatigue/inertia (P  = 0.04). In subgroup analyses, the overweight/obese participants had 40% higher scores on the depressive scale compared to healthy weight participants (P = 0.05).

Kara Breymeyer expands on the impact of this study, "Our study contributes to the emerging research examining possible relationships between diet patterns, obesity, and mood disorders such as depression. A major strength of this study compared to other studies asking similar questions is that we had both healthy weight and overweight/obese but otherwise healthy participants that experienced both the HGL and LGL diet patterns on a rigorously controlled diet intervention. Our participants remained weight stable over the course of the two months they received their specified meals which eliminates a plausible change in mood based on weight loss or gain. In addition to our statistically significant findings that showed higher scores of vigor and activity on the LGL diet and higher scores of fatigue and inertia on the HGL diet, many participants anecdotally reported much higher levels of energy on the LGL diet and 'brain-fuzz' and overall tiredness on the HGL."

Next on the frontier, Breymeyer notes, "It would be very interesting to further investigate our findings based on subjective mood questionnaires by comparing them with the objective measures of the inflammation milieu often indicated in the dysregulation of healthy metabolism such as biomarkers, metabolites, and gut microbiome profiles collected from our participants and analyzed by colleagues here at Fred Hutch."

Funding for this study was provided by the National Cancer Institute, the National Institutes of Health, and the Fred Hutch.

Breymeyer KL, Lampe JW, McGregor BA, Neuhouser ML. 2016. Subjective mood and energy levels of healthy weight and overweight/obese healthy adults on high-and low-glycemic load experimental diets. Appetite. 107: 253-259.