▎ WuXi AppTec content team editor
Coke, sausages, fries, chicken nuggets, spicy strips, biscuits, ice cream... Eating these "delicious" ultra-processed foods makes us happy.
However, there have also been many previous studies reporting that the consumption of a large number of ultra-processed foods is related to the incidence and mortality of obesity, hypertension, cardiovascular disease, type 2 diabetes, cancer and other chronic diseases. Does consuming ultra-processed foods have an impact on liver health?
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A recent study published in Liver International found that eating large amounts of ultra-processed foods was associated with an 88% increased risk of metabolic syndrome in the general population, and that in patients with non-alcoholic fatty liver disease (NAFLD), high consumption of hyperprocessed foods was associated with markers of nonalcoholic steatohepatitis (NASH). In addition, long-term smoking may have synergistic effects with ultra-processed foods, thereby increasing the risk of liver fibrosis.
In the study, ultra-processed foods included many types of confectionery, snacks, packaged bread, cereals, margarine, sauces, processed meats, soft drinks, "energy" drinks, alcoholic beverages, sugar-sweetened yogurt (including "fruit" yogurt), spreads, and prepackaged pizzas and pastries.
Screenshot source: Liver International
In this cross-sectional study, a total of 789 participants with an average age of 59 years and an average body mass index (BMI) of 28.6 kg/m2 were included. None of the participants had health problems with hepatitis B antibodies, hepatitis C antibodies, fatty liver secondary to hepatotoxic drugs, and unreasonable caloric intake.
Unreasonable caloric intake, defined in the study as:
Men's daily energy intake is less than 800 kcal or higher than 4000 kcal;
Women's daily energy intake is less than 500 kcal or higher than 3500 kcal;
Men drink ≥ 30 grams per day or women drink ≥ 20 grams per day.
All participants were required to undergo fasting blood collection and an ultrasound of the lower abdomen at the hospital, which included noninvasive testing for NASH and liver fibrosis. In addition, the researchers also counted the participants' eating habits, drinking and smoking, exercise habits and health conditions.
The results found that among all participants:
44.2% (n=349) of people were diagnosed with metabolic syndrome;
38.7% (n=305) were diagnosed with NAFLD;
31.5% (n=225) of people may have NASH (elevated markers);
19.7% (n=141) of people experienced significant fibrosis.
Metabolic syndrome is defined by the American Heart Association and is present in at least 3 of the following 5 criteria:
Impaired fasting blood glucose: fasting blood glucose ≥ 100 mg/dL;
Hypertension: systolic blood pressure ≥ 130 mmHg, diastolic blood pressure ≥ 80 mmHg and / or taking medication;
Low levels of high-density lipoprotein cholesterol (HDL): men
Hypertriglyceridemia (TG): TG≥ 150 mg/dL or taking medication;
Abdominal obesity: female waist circumference ≥ 88cm, male waist circumference ≥ 102cm.
In the study, the average daily intake of ultra-processed foods for all participants was 28.84 kcal. The researchers found that participants whose intake of ultra-processed foods was higher than the median had the following characteristics:
Males are the majority;
Low HDL levels, may also have hypertriglyceridemia, hypertension, metabolic syndrome, and high serum ferritin levels and liver fibrosis scores;
More likely to eat high-calorie, high-saturated fatty acids (SFA), high-carbohydrate, low-protein diet;
These participants drank coffee significantly less often and consumed relatively less dietary fiber.
Similarly, in participants with NAFLD, the same pattern was also observed.
After adjusting for factors such as age, sex, BMI, and other nutritional and lifestyle factors, the researchers found that people who ate large amounts of ultra-processed foods:
The risk of developing metabolic syndrome increased by 88% (OR=1.88, P=0.001); the risk of developing hypertension increased by 53% (OR=1.53, P=0.026);
The risk of hypertriglyceridemia increased by 51% (OR=1.51, P=0.017);
The risk of low HDL increased by 55% (OR=1.55, P=0.028).
In participants with NAFLD, although there was no significant association between ultra-processed food intake and metabolic syndrome, patients with high intake of ultra-processed foods with NAFLD:
The risk of NASH developing increased by 89% (OR=1.89, P=0.03);
The risk of developing hypertension increased by 126% (OR=2.26, P=0.012);
The high TGs/HDL ratio increases by 101% (OR = 2.01, P = 0.016).
The analysis also showed that smoking was an independent factor in increasing the risk of liver fibrosis.
Among all smokers, high intake of ultra-processed foods was associated with an 89% increased risk of liver fibrosis (OR=1.89, P=0.039); in patients with NAFLD, high intake of ultra-processed foods was associated with an increased risk of liver fibrosis by 185% (OR=2.85, P=0.026).
Significant hepatic fibrosis dose-response relationships were observed in smokers, regardless of whether NAFLD was diagnosed or not, for every 10% increase in ultra-processed food intake (energy share).
The researchers explained that the characteristics of ultra-processed foods are high energy density, high saturated fatty acids, high sodium and high sugar, but low nutrient density and low dietary fiber content, which are inseparable from NAFLD and NASH.
But the study also has certain limitations. First of all, cross-sectional studies cannot make causal inferences, and the results need to be verified in prospective studies. Second, participants' eating habits were dependent on recall and may be biased, so the relevance of the outcomes may be weakened. Finally, the diagnosis of the associated disease is determined by blood test markers and is not determined by liver biopsy, so the results may be biased.
The paper concludes: The findings suggest that ultra-processed foods can harm the liver and metabolic health of the general population and NAFLD patients. Patients with NAFLD should especially avoid the intake of ultra-processed foods to prevent more severe liver damage and cardiovascular disease, especially in people who smoke for a long time.