Fiber and Cardiometabolic Health in Children
What was the question? To what extent is dietary fiber intake during childhood associated with cardiovascular health markers?
Who does this study apply to? European children below the age of 8.
What was the intervention? The diet of the same children was recorded at the ages of 3, 4, 5, 6, and 8. At 8 years old, their physical measurements, blood pressure and blood samples were taken and analyzed, and linear associations were generated.
What was the main take-away? In this longitudinal observational study, a diet rich in fiber from fruits, vegetables, pulses and nuts was associated to a healthier cardiovascular profile in 8-year-old children, regardless of weight.
What was the question?
To what extent is dietary fiber intake during childhood associated with cardiovascular health markers?
Why was the question worth asking?
The two main functions of diet in childhood are to support normal growth and development and to reduce the risk of chronic disease during adulthood. The physiological benefits of increasing dietary fiber intake are frequently related to both digestive and cardiovascular health in the adult population.
These health benefits are largely due to gut microbes that ferment the ingested fiber into short-chain-fatty-acids (SCFAs). SCFAs are responsible for initiating several signaling pathways that result in anti-inflammatory action, protection against colonic cancer, reduction of insulin resistance, and control of cholesterol and glucose synthesis. These functions are related to optimal cardiovascular health and decreased risk of chronic disease.
In adults, low fiber intake has been associated with increased risk of cardiovascular diseases (CVDs) such as hypercholesterolemia, diabetes mellitus, high blood pressure and obesity. Additionally, metabolic syndrome (MetS), a cluster of conditions that increase the risk of CVD and type II diabetes, is only well defined in adults despite, nowadays being considered a pediatric condition (Fulgoni, 2020). Studies analyzing the association between dietary fiber intake and cardiovascular health in children are rare and have mostly been performed in adolescents. Previous studies have also not analyzed the relationship between fiber intake and blood sugar regulation. Therefore, the authors aimed to analyze the relationship between dietary intake and cardiovascular health markers in children including blood sugar control.
There are very few studies analyzing the association between dietary fiber intake and cardiovascular health in children. This will be one of the first that does this and takes glycemic control into account.
How was the question answered?
This study is a secondary analysis of data collected by the EU Childhood Obesity Project (EU-CHOP) carried out in Germany, Belgium, Italy, Poland and Spain. EU-CHOP was a double-blind, randomized dietary intervention trial that recruited infants from birth and followed their dietary intake until the age of 8 years.
In this secondary analysis, research nutritionists recorded the dietary intake of the same individuals using 3-day diet diaries at 3, 4, 5, 6 and 8 years old as part of an observational longitudinal analysis. A longitudinal analysis is where the same individuals are studied primarily via observation over a certain period.
When the children turned 8years old, the following standardized measurements were taken:
Anthropometry: weight, height, body mass index and, waist circumference
Blood Pressure: systolic and diastolic
Blood Sample Parameters: total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides, glucose and, insulin
These measurements were then used to calculate the cardiometabolic risk factor as a score using different equations according to sex. A higher score is indicative of higher cardiometabolic risk and signals worse cardiovascular health. Linear regression models were used to assess the relationship between the cardiometabolic risk factor score and dietary fiber intake. The models were adjusted according to country, average calorie intake, sex, maternal education and breastfeeding duration. The cohort decreased from 534 children at 3 years old to 400 children at 8 years old.
An observational longitudinal analysis where diet at the ages of 3, 4, 5, 6, and 8 years old was recorded. At 8 years old, their physical measurements, blood pressure and blood samples were taken and analyzed, and linear associations were generated.
What was the answer?
From the cardiometabolic risk factor scores and recorded fiber intakes, the authors made 4 principal findings.
Increasing fiber dietary intake can improve cardiovascular health risk markers independently of weight.
Children who consumed more fiber had a higher BMI without reaching concerning levels. This association was independent of the dietary fiber source and total energy intake. This means that increasing dietary fiber intake can decrease the cardiometabolic risk factor and therefore, improve cardiovascular health in the long and short term in children independently of weight. This finding supports data from other publications demonstrating that high fiber intakes do not cause growth problems in healthy children (Ruottinen, 2010)
A sustained low fiber intake from childhood could be associated with poorer glucose tolerance.
In adults, increased dietary soluble fiber improves glucose homeostasis by improving insulin resistance. The evidence from this study demonstrated that in 8-year-old children, a diet with a higher amount of soluble fiber from fruits and vegetables could reduce insulin resistance. Other studies have shown that this is also true in adults (Chandalia, 2000).
Higher fiber intakes from childhood results in improved lipid profiles.
Lipoprotein composition is a key marker of cardiovascular health as increased LDL concentrations may lead to plaque formation, atherosclerosis and coronary heart disease whereas higher HDL levels are associated with a reduction of cholesterol absorption and better cardiovascular health. Similar to previous studies on adults, adolescents and children, the results demonstrated that higher fiber intake was associated with lower LDL cholesterol in 8-year-old children (Fulgoni, 2020).
Children with sustained lower fiber intake demonstrated higher figures for systolic blood pressure.
This finding contradicts the associations found in adults, as in adults, higher fiber intakes are related to a decrease in both systolic and diastolic blood pressure. The authors suggest that this contradiction may be due to the dietary sources of fiber. Fiber-rich fruits and vegetables may be poorer in sodium and rich in potassium depending on the preparation. Also, while nuts contain high levels of unsaturated fatty acids and other bioactive compounds that may improve blood pressure, pulses are high in potassium, vegetable protein and fiber which have reducing effects on blood pressure. Intake of resistant starches in the form of potatoes as fries and chips is normally accompanied by a high salt intake that may cause an increase in systolic blood pressure.
How much should you trust the answer?
The authors highlighted that a major limitation to this study is that it did not account for physical activity which is considered an accurate indicator of health outcomes. The authors also noted that salt intake could not be quantified, this is especially important for the association between higher fiber intake and blood pressure. Previous studies have clearly shown that higher salt intake is associated with higher blood pressure in adults and children (He and Marrero, 2007) (Domingo, 2010). Hence, the association between fiber intake and blood pressure may be subject to variation and therefore cannot be truly considered trustworthy until future studies where salt intake is considered are conducted.
Other dietary factors such as the proportion of sugars and fats were not included in the analyses despite being indicative of cardiometabolic risk. This especially influences the association found between high fiber and glycemic control as well as that of high fiber and lipid profile. Although all the analyses were adjusted by overall energy intake, previous literature has shown that lower sugar intake and lower fat intake improve glycemic control and lipid profile (Tarino, 2010). Hence, as these variables are not controlled it is difficult to evaluate the extent to which the associations found are true.
This study was one of the first to associate higher fiber intake with blood pressure and glucose tolerance respectively. Therefore, these associations may only be considered as preliminary as scientific consensus cannot be made until the findings of future studies are available. Nonetheless, the associations made between higher fiber intake and improved lipoprotein compositions reinforces previous studies and therefore, adds to scientific consensus.
Also, despite the large initial cohort, there was a decrease in the number of participants with increasing age especially those who completed all dietary data. However, it should be noted that as this was a long-term longitudinal observation it is effective in monitoring variable patterns overtime. Although the mechanisms for how fiber intake affects cardiometabolic control have been proposed for adults, the results of this study are also all based on linear regression models and thus, there are no proposed mechanisms for them in children.
Despite the several associations found in this study, as it was one of the first to make them in children, the results of this study should be considered preliminary. Future studies where other factors such as salt intake, sugar and fat proportion and physical activity will have to be carried out to confirm the associations between cardiovascular health and fiber intake in children.
The results may be considered as primary. Future studies with more controlled variables need to be conducted for greater consensus.
What’s the take-home?
In this longitudinal observational study, a diet rich in fiber from fruits, vegetables, pulses and nuts was associated with a healthier cardiovascular profile in 8-year-old children, regardless of weight.
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