Tuesday August 2 2011
Babies and toddlers have much lower salt limits than adults
“Seven in 10 babies fed too much salt,” read the Daily Express headline. The newspaper’s report said that “giving babies cow’s milk is a risk because it contains nearly four times as much salt as breast or formula milk”. The Express also highlighted that according to NHS guidelines babies under the age of one should not not be given cow’s milk to drink.
The research behind this news looked at the diet and salt intake of more than 1,000 eight-month old babies in 1993. The study found that 70% of these babies consumed over 0.4g sodium (1g salt) per day, which is the current recommended daily limit for babies. Researchers found that the quarter of babies with the highest sodium intakes were more likely to consume cow’s milk as a main drink rather than breast or formula milk. Their salt also tended to come from bread, cereals, tinned pasta and gravy.
The researchers point out that the measurement of salt in baby foods was done in 1993 and there have been reductions in the salt content of these products since that time. However, this study does highlight that there are some household foods which may contain more salt than the baby’s parent or carer realises, and it is important to check the labels to see whether the salt content is appropriate to keep within the 0.4g sodium (1g of salt) that is the recommended daily limit for babies.
Where did the story come from?
The study was carried out by researchers from Bristol University and Nutricia Ltd, a division of the Danone food company. The study was funded by Nutricia Ltd and published in the peer-reviewed European Journal of Clinical Nutrition.
The study was funded by Danone and tested products made by Cow & Gate, a subsidiary company of Danone. The research paper features a conflict of interest statement, which said that the research work was carried out independently from Danone, despite Danone funding the research.
Some newspapers mentioned that the study’s data was collected in the UK 18 years ago, but generally failed to discuss how health awareness among parents and the salt content of packaged foods may have changed since then.
What kind of research was this?
This was a cross-sectional study that looked at the salt intake of eight-month old babies in the Avon area over a three-day period. The children and parents were part of an ongoing longitudinal study, the Avon Longitudinal Study of Parents and Children (ALSPAC), which was designed to investigate various aspects of the health and development of children. The ALSPAC project is also known as the “Children of the 90s” study.
The researchers looked at data on more than 1,100 babies, including dietary records recorded by their mothers. These records were then used to estimate the babies’ sodium and energy intakes.
In the UK, it is recommended that babies up to the age of 12 months consume no more than 1g of salt (sodium chloride) per day. One gram of salt contains 0.4g of the element sodium, the substance responsible for the harmful effects of excessive salt intake. The researchers were interested to see whether infants were exceeding recommended sodium levels during the weaning period when babies would be receiving solids as well as breast milk or formula. They also wanted to see what types of additional foods babies were being given, and whether these foods were appropriately low in salt.
What did the research involve?
The researchers used participants from the Avon Longitudinal Study of Parents and Children (ALSPAC). This study had recruited pregnant women living in the former Avon Health Authority in South West England with an expected delivery date between April 1991 and December 1992. In total, the diets of 1,178 infants from this project were assessed in this study.
Data on diet was collected from the infant’s main caregiver at an eight-month clinic visit in 1993. The caregivers were asked to use a structured diary to record all food and drink consumed by the infant over three days (two weekdays and one weekend day). Quantities of food and drink consumed were recorded using household measures. If women were breastfeeding they were asked to record the duration of each feed.
The completed dietary records were used to to create coded records of the food and drink consumed and to estimate portion size (usually based on the number of spoonfuls consumed). An analysis programme was used to calculate the nutrients in each food the child ate, as well as average energy and nutrient intakes, weights consumed and sodium content of each food.
At the eight-month check-up, body measures such as the babies’ length and weight were taken, and a BMI calculated. The researchers also had information on the mother’s educational level and the age at which solid foods had been introduced.
What were the basic results?
The researchers found that 70% of the babies consumed more than the recommended 0.4g of sodium per day. The range of sodium intakes was used to divide the babies into four groups of increasing sodium consumption (quartiles). The whole sample included 644 boys and 534 girls, but there were more boys than girls in the top quarter. Boys were also heavier and of longer body length than girls at this age.
The majority of babies (925, or 79%) had first had solids introduced between the ages of three and four months. Most infants were receiving either breast or formula milk; however, 13% received only cow’s milk. Cow’s milk has higher sodium content (55 mg/100g ) than formula (15 to 30 mg/100 g depending on type) and breast milk (15 mg/100 g). The 25% of babies with the highest sodium intake were more likely to be taking cow’s milk than babies with lower sodium intakes. Twenty-nine per cent of babies in the highest sodium intake group were receiving only cow’s milk, which made a large contribution to the sodium intake in this group.
The researchers then looked at the salt content of specific foods consumed by the babies. They found at the time of data collection (1993) baby foods contained:
- 71 mg/100 g for dry baby cereal (once made up)
- 72 mg/100 g for jars of savoury food
- 26 mg/100 mg for jars of sweet food
The researchers said that the levels of salt have been reduced in baby food over the intervening years since the sample was taken. In 2010, values for foods from Cow & Gate (a subsidiary of the Danone company that funded the research) were:
- 41 mg/100g for dry baby cereal
- 51 mg/100g for jars of savoury food
- 15 mg/100g for jars of sweet food
The sodium content of non-ready-made foods were:
- bread: 180mg/slice
- weetabix: 54mg/biscuit
- ready brek: 2mg/portion
- cornflakes/rice krispies: 222mg/portion
- gravy granules: 153mg from one tablespoon of made-up gravy
- cheese: 67mg for 10 g of chedder
- pasta/rice: canned spaghetti contained 420 mg/100g
- marmite: 45mg from one gram
The researchers found that in all babies, the highest contributor to sodium from this list was bread. The quartile of infants with the highest sodium intake had higher intakes of bread and breakfast cereals, gravy and marmite than babies in the lower sodium-intake group.
Sodium intake was not related to maternal educational status.
How did the researchers interpret the results?
The researchers said that “poor complementary feeding practices in eight-month-old infants were associated with higher sodium intakes from the diet”. Babies with the highest sodium consumption were consuming “inappropriate” food such as cow’s milk as a main drink, salty flavourings and canned pasta during complementary feeding. The researchers said that these foods contributed to very high sodium levels in their diet.
This study highlights that 18 years ago a high proportion of babies were consuming over the recommended 0.4g of sodium (1g salt) per day. While it did highlight foods and drinks that might contribute towards parents inadvertently giving their baby too much salt, the study’s data on salt intake was collected in 1993, and since then advances have been made in reducing the salt content of baby foods, cereals and some tinned products. Health awareness and education among parents have generally improved.
However, the researchers say that further salt reduction, particularly of processed food, is still required, and that parents should be aware that such foods may not be appropriate for young children. In particular, the researchers highlighted that drinking cow’s milk as a main drink may make a large contribution to daily salt intake and that some household foods may not be appropriate for babies, such as canned spaghetti, owing to the high salt content.
This study does highlight the potential problem of salt levels in food as an overall issue, but this does not necessarily mean that the foodstuffs identified in 1993 are still problematic now. Instead it provides a useful reminder that parents of children under 12 months old should be aware of the salt content of food, and should use resources such as food labels to ensure that their babies have a salt intake within the 1g limit. Current NHS advice is that babies under 12 months should not be given cow’s milk to drink.