Effect of low B12 on lipogenesis in human Chub-S7 cell line and primary Sc adipocytes. Credit: BMC Medicine (2025). DOI: 10.1186/s12916-025-04056-4

People rely on animal products such as meat, fish, eggs and dairy for vitamin B12, or supplements and fortified foods.

Researchers at Nottingham Trent University and the University of Warwick argue that a major contributing factor to vitamin B12 deficiency is an increasing dependence on ultra-processed foods. Their work is published in the journal BMC Medicine.

In today's world, these modern diets are high in calories but often lack essential micronutrients, such as vitamins, which are crucial for good health.

Vitamin B12 is also not naturally present in plant-based foods, which puts vegetarians and vegans at a higher risk of deficiency. While the effects of excess calories on body fat are well understood, the researchers argue that the deficit in micronutrient—particularly vitamin B12—accompanied by modern lifestyle is often overlooked.

They wanted to better understand why B12 deficiency—particularly during pregnancy—is often linked to higher body fat, unhealthy blood fat levels and a greater risk of developing type 2 diabetes.

Globally, more than half (60%) of pregnant women are overweight or obese, leading to well-known risks for adverse pregnancies and other metabolic health issues.

The study involved examining fat samples from the belly area of 115 pregnant women with low vitamin B12 levels, as well as fat cells of those with a range of different body weights.

Human fat cells grown in the laboratory were also studied to see how they responded to normal or deficient levels of B12.

The research involved measuring vitamin and fat levels in the blood, proteins that signal the body's health and how the cells functioned.

The scientists also studied the activity of specific genes involved in fat production and breakdown, fat storage inside cells and how well the cells produced energy.

Finally, to understand how B12 affected the body, they investigated whether it caused fat tissue to release chemicals that cause inflammation.

The findings revealed that women with low B12 had higher body weight and unhealthy fat levels in their blood, while their "good" cholesterol—high density lipoprotein—which helps to remove other forms of cholesterol from the bloodstream, was lower.

Fat tissue in these women also showed signs of making more fat and breaking down less and the energy-producing parts of their cells—mitochondria—were not working properly.

Their fat tissue also released more inflammatory substances that can act throughout the body to impact health.

"In these pregnant women, the changes we observed in fat composition, gene expression and inflammatory markers are well-established risk factors for metabolic disorders, including type 2 diabetes and heart problems, " said lead researcher Dr. Adaikala Antonysunil, a scientist in Nottingham Trent University's School of Science and Technology.

She said, "Our findings highlight the importance of monitoring and improving vitamin B12 levels before and during pregnancy to protect long-term health.

"We recommend maintaining a balanced diet rich in fruits, vegetables, and other whole foods, while limiting ultra-processed foods. This can help to maintain adequate B12 levels and reduce future health risks."

Professor Ponnusamy Saravanan, from the University of Warwick, added, "Our research provides crucial evidence for the need for planning and commissioning future clinical studies in this area to further assess the impact on metabolic health of young women in pregnancy and any potential consequences for the next generation."

The study, was also co-authored by Professor Philip McTernan, from De Montfort University, who has worked with the team over several years examining adipose tissue metabolism and metabolic health.

More information: Jinous Samavat et al, Maternal B12 deficiency during pregnancy dysregulates fatty acid metabolism and induces inflammation in human adipose tissue, BMC Medicine (2025). DOI: 10.1186/s12916-025-04056-4  Journal information: BMC Medicine