Lower levels of vitamin B12, riboflavin and iodine in UK milk

A new survey of cows’ milk on sale in UK supermarkets has found that it contains lower levels of vitamin B12, riboflavin and iodine now compared to 1996. Lower levels of these important micronutrients in milk products could increase the risk of deficiencies for individuals and the population.

Dairy products are the largest contributors to the UK population’s intake of vitamin B12, riboflavin (vitamin B2) and iodine, according to the National Diet and Nutrition Survey, which will be updated with this information to estimate the population’s current intake of these nutrients.

The survey was carried out by the Quadram Institute’s Food and Nutrition National Bioscience Research Infrastructure (FN-NBRI) and funded by the Department of Health and Social Care and the Biotechnology and Biological Sciences Research Council, part of UK Research & Innovation.

To find out the up-to-date nutrient levels, the team examined skimmed, semi-skimmed and whole fat milk, both pasteurised and UHT. Samples from the most popular brands of cows’ milk from 10 different supermarket chains were combined and analysed to provide representative average nutrient levels for each type of milk. The survey was carried out in 2022 and 2023, was repeated in summer and winter to examine seasonal differences in the amount of nutrients.

Vitamin B12

Vitamin B12 helps make blood cells, DNA and maintains the health of nerve cells. It is primarily found in animal-based foods, such as meat, seafood, and dairy, so it’s essential for individuals following a vegan diet to supplement their intake.

In the survey, vitamin B12 levels in milk were 50% lower on average compared to 1996.

For all pasteurised milk samples, the results for the 2023 analysis (between 0.3 to 0.5μg per 100g) were lower than in the 1996 survey (between 0.7 to 0.9μg per 100g) in both seasons. The UHT milk samples showed lower average levels of vitamin B12 compared to pasteurised milk in both the 1996 and 2023 analyses.

Previously, a small glass of milk (200ml) provided about half of the Reference Nutrient Intake of 1.5 µg of vitamin B12 for adults. However, with the updated values, it now supplies only around a quarter of that daily requirement.

It’s important to note that this change in values does not necessarily reflect a decrease in the actual vitamin B12 content but rather may be due to adjustments in the analytical methods used. Additionally, less than 10% of the adult population is currently considered vitamin B12 deficient, based on serum vitamin B12 levels as reported by the National Diet and Nutrition Survey.

Riboflavin

Riboflavin, also known as vitamin B2, helps the body derive energy from food and helps keep our skin, eyes and nervous system healthy. It’s not stored by the body, so our daily diet needs to include riboflavin-rich foods, such as eggs, dairy and fortified breakfast cereals.

The survey found that riboflavin levels in pasteurised milk samples were an average 22% lower, decreasing from 0.21-0.24mg per 100g, to 0.14-0.21mg per 100g.

However, the opposite was found in UHT milk, where the new averages for all UHT milk samples (between 0.18 to 0.20mg per 100g) were slightly higher than those of the 1996 survey (between 0.17 to 0.18mg per 100g).

Iodine

Iodine is a key nutrient for making thyroid hormones that keep our cells and metabolism healthy. Good sources of iodine include seafood, dairy products, eggs, and meat.

Iodine levels in milk were found to be 21% lower on average in 2023, compared to 1996 except for pasteurised skimmed milk.

Compared to the 1996 survey (between 31 to 41μg per 100g), results for 2023 were between 23 to 34μg per 100g. A similar trend was found in UHT milks, where 2023 average values were lower than those in the 1996 survey, with the exception of skimmed milk.

While the most recent data in the National Diet and Nutrition Data survey indicate that the average daily iodine intake of the general UK population meets recommended levels, women of childbearing age have been identified as a subgroup at risk of insufficient intake. 21% of this group had median urinary iodine concentration levels below 50 μg/L, indicating moderate iodine deficiency.

With the decline in iodine content in dairy milk, and limited alternative dietary sources, there is a risk that more people may not meet the recommended intake.

There are a number of potential factors that might have contributed to the changes:

For example, cows’ diet has a major impact on the nutrients that are found in the milk, so the changing levels may be down to differences in feed, grazing practices or supplementation.

Most of the samples taken in summer had lower riboflavin, vitamin B12 and iodine contents than their winter equivalents, which may be due to the increased supplementation of minerals in cows’ feed during the winter months.

Other factors may include changes in the cows’ genetics, environmental conditions, or processing techniques.

When comparing nutrition data over time, it’s also important to consider how advances in analytical methods may have improved in the intervening years.

The Food & Nutrition NBRI team at the Quadram Institute maintain and update the UK’s Food Composition data as a national resource for researchers, dietetics, healthcare professionals and clinicians, as well as the food industry, policy makers, government and consumers.

This survey is part of their ongoing work to ensure that the UK national food composition data is an up-to-date reflection of the foods that UK consumers are eating.

“This update to the data on key nutrients in milk has implications for understanding and interpreting how what we eat affects health, for individuals and at the population level,” said Dr Maria Traka from the Food & Nutrition NBRI. “The updated nutrient levels will affect estimates of population intake of these micronutrients in the National Diet and Nutrition Survey, which is the basis for dietary recommendations and food policies.”

The National Diet and Nutrition Survey collects detailed information about the type and quantity of foods eaten by adults and children across the UK, to assess nutrient intake of the population.

Milk and dairy products are a staple for 89% of the UK population and so are one of their most vital sources of these important micronutrients. If a significant proportion of the population aren’t getting enough of these nutrients to support their health, this supports the need for other ways to boost intake through, for example, supplementation or biofortification.

Reference: Nutrient analysis of cows’ milk: sampling and analytical report is available to read via the Office for Health Improvement and Disparities (OHID), part of the Department of Health and Social Care (DHSC). The updated values for milk have been incorporated into the National Diet and Nutrition Survey 2019-2023 to estimate the population’s intake of these nutrients. These values will be published in the McCance and Widdowson’s The Composition of Foods integrated dataset in due course, accessible through the Food & Nutrition NBRI website.

Related content