Consumers who eat more vegetables have higher salt intake – Japanese survey analysis
Researchers in Japan conducted a survey analysis on participants from the 2016 National Health and Nutrition Survey (NHNSJ). They found that those who consumed more vegetables might have a more favourable intake of food groups and nutrients in general, but they also tend to take in more sodium.
“Participants with vegetable intake ≥350 g/day might have a more favourable intake of food groups and nutrients,” wrote the researchers in Journal of Nutritional Science. “However, our findings revealed that sodium may be a concern when promoting vegetable intake. Compared to a previous study, sodium intake was higher in our participants with vegetable intake of ≥350 g/day, which may reflect a higher intake of condiments and seasonings.”
A diet low in vegetables ranks fifth among the leading dietary factors associated with the risk of developing and dying from lifestyle-related diseases. A recent trend analysis based on NHNSJ data from 1990 to 2016 estimated that vegetable intake in the Japanese population will decrease to 238 g/day in 2040. Studies on dietary patterns in Japanese populations have suggested that high vegetable intake is not only related to a higher intake of some healthy foods (e.g., seafood and fruits) but also sodium intake. However, no recent study has examined the intake of food groups and nutrients in relation to the recommended vegetable intake in Japan.
Therefore, the researchers wanted to compare the differences in the intake of food groups and nutrients between participants who met and those who did not meet the recommended vegetable intake.
Researchers in Japan conducted a survey analysis on participants from the 2016 NHNSJ, a cross-sectional household interview and examination survey that represents populations across 47 prefectures in Japan. For this survey analysis, 21,606 individuals aged 20 years old and above were included.
The dietary assessment was a one-day semi-weighed household-based dietary record. For each meal, meal preparers weighed the components for preparation (or consumption) when possible.
Seventeen primary food groups were classified based on the NHNSG categories: Vegetables, potatoes and other tubers; mushrooms; seaweeds; cereals; sugar and sweeteners; legumes; nuts; fruits; seafood; meats; eggs; milk and dairy products; fats and oils; savoury snacks and confectionaries; beverages; and condiments and spices.
Diet quality was tentatively assessed as one’s intake of the total number of nutrients that met the Dietary Reference Intakes (DRIs) for the Japanese according to sex and age groups.
The intakes of protein, total fat, saturated fatty acids (SFA), and carbohydrates were calculated as a percentage of total energy intake for comparison with the DRIs. For a more accurate comparison, for the other nutrient intakes, the researchers used energy-adjusted values (values adjusted according to sex- and age-specific estimated energy requirements).
Participants were then classified into two groups: those who consumed <350 g/day of vegetables (excluding potatoes and other tubers, mushrooms, and seaweeds) and those who consumed ≥350 g/day of vegetables.
Given the low fibre content of vegetable juice and high sodium content of fermented (or pickled) vegetables, the analysis was repeated by excluding them.
The researchers found that less than one-third (28.8%) of the participants had a vegetable intake of ≥350 g/day. Also, the energy-adjusted intake was significantly higher in the ≥350 g/day group for all nutrients, including sodium, than in the <350 g/day group, except for carbohydrates (which was significantly lower in the ≥350 g/d group) and vitamin B12.
In line with the energy-adjusted intake, the ≥350 g/day group had a higher percentage of participants who met the DRIs (median of 63.1%) than those in the < 350 g/day group (median of 50.6%) for almost all nutrients. However, significantly lower rates were observed for SFA and sodium in the ≥350 g/day group (52.3% and 6.4%, respectively) than in the <350 g/day group (52.9% and 10.3%, respectively.
“Our results revealed that participants with vegetable intake ≥350 g/day also had a larger percentage of consumers for all vegetable subgroups and other food groups (except for cereals, eggs, and condiments and seasonings) than those who consumed <350 g/day vegetables. Additionally, the energy-adjusted intake for all vegetable subgroups was higher in the ≥350 g/day group than in the <350 g/day group,” said the researchers.
“For other food groups, the ≥350 g/day group had a lower energy-adjusted intake of cereals (with all subgroups), fruit juices, eggs, and beverages (with all subgroups), but a higher intake of condiments and seasonings than the <350 g/day group. Although the ≥350 g/day group had a higher intake of most nutrients and a higher percentage of participants who met the DRIs, the opposite was observed for sodium.”
On average, the participants in the ≥350 g/day group consumed a greater variety of vegetables with a higher amount of each type than those in the <350 g/day group. Therefore, promoting the consumption of various vegetables in abundance may be necessary to meet the recommended vegetable intake.
The researchers also observed that vegetable juice intake was high in the <350 g/day and ≥350 g/day groups, which suggests that vegetable juice may be an important source to meet the recommended vegetable intake.
Participants who met the vegetable intake recommendation also had a greater variety of food groups in their diet, higher nutrient intake, and were more likely to meet the DRIs.
Unlike findings from Western countries, where higher vegetable intake has been reported to have a negative or null relationship with sodium intake, dietary patterns with higher vegetable intake in Japan were often positively associated with higher sodium intake. This may be related to Japanese cooking practices, where salt-containing condiments and seasonings are often added when preparing and preserving foods.
“Higher vegetable intake in the Japanese population may indicate a diverse and generally healthy diet. It is also necessary to explore ways to increase vegetable intake without increasing the sodium intake. Future studies may need to explore individual behavioural factors related to the meeting of the recommended vegetable intake for developing more targeted plans for promoting vegetable intake,” concluded the researchers.
Source: Journal of Nutritional Science
“Analysing food groups and nutrient intake in adults who met and did not meet the daily recommended vegetable intake of 350 g: the 2016 National Health and Nutrition Survey in Japan”
Authors: Xiaoyi Yuan, Ryoko Tajima et al.
