People who drink most of their coffee in the morning show a lower likelihood of having metabolic syndrome than those who spread their intake across the day, according to a new study.
The study, published recently in the British Journal of Nutrition, was led by Maoqi Shen and colleagues in the department of cardiovascular medicine at the Second Xiangya Hospital of Central South University in China. The team analyzed dietary data from 11,632 adults aged 20 and older who took part in the U.S. National Health and Nutrition Examination Survey between 2003 and 2018.
Participants were sorted by when they drank coffee — a "morning-concentrated" group that drank mainly in the morning hours and an "all-day" group that spread intake across multiple times of day — and each group's rate of metabolic syndrome was compared with that of people who did not drink coffee.
Morning Coffee Drinkers 20% Lower; No Difference for All-Day Drinkers
The morning-concentrated group was 20% less likely to have metabolic syndrome than non-drinkers, the analysis found.
The association held after adjusting for factors that could affect the outcome, including sex, age, income level, smoking and drinking, exercise habits, sleep quality, diet quality and total daily calorie intake.
The amount of coffee made little difference. Whether morning intake was small or large, the likelihood of having metabolic syndrome was consistently lower.
Among the all-day group, which drank coffee several times from morning through evening, no clear difference in metabolic syndrome rates was found compared with non-drinkers.
Metabolic syndrome is a condition in which several metabolic abnormalities occur together, including abdominal obesity, high blood pressure, high blood sugar, high triglycerides and low HDL cholesterol. It is considered a leading risk factor for cardiovascular disease and type 2 diabetes.
Link Stronger in Women and Those Under 40; Cut Late-Day Coffee
The link between morning-concentrated coffee intake and a lower likelihood of metabolic syndrome was relatively stronger among women and participants aged 40 and under, the study found. The pattern was also more pronounced among people of normal weight, underweight or overweight.
The researchers pointed to the possibility that caffeine, polyphenols and other antioxidant and bioactive compounds in coffee interact with the body's circadian rhythms and affect metabolic processes. Because caffeine consumed late in the day can affect sleep and the body clock, they said, it is worth considering not only how much coffee people drink but also when they drink it.
Experts advised against adding excessive sugar, syrup or cream to coffee and said it is better to cut back on the habit of drinking coffee in the late afternoon or evening, when it can disrupt sleep. "Even with morning coffee, a moderate amount is recommended alongside a breakfast that includes vegetables, fruit, whole grains and protein foods," they said.
The study alone cannot establish that morning coffee directly prevents metabolic syndrome. It is a cross-sectional observational study that compared participants' coffee habits and health status at a single point in time. Nor can it be said to prove a causal link between afternoon or evening coffee and poorer metabolic health.
