Over the past couple of years, many people suffering from long Covid reported suffering symptoms that are often grouped together as “brain fog”.
Problems with memory loss, difficulty in concentrating and a lack of mental focus have all been cited as lingering effects of infection with the coronavirus.
But there are other causes of these symptoms, including a deficiency of a nutrient that, experts say, is sometimes not given the attention it deserves.
Cobalamin, better known as vitamin B12, plays a key role in many essential processes in the body, and shortages can cause everything from tiredness to mood changes and brain fog.
“It affects some of the ability of the brain to function properly,” says Prof Martin Warren, who leads a group researching vitamin B12 at the Quadram Institute, a centre for food and health research in Norwich in the UK.
“A lot of the symptoms associated with B12 deficiency are similar to those that are observed with long Covid. They’re obviously not identical, but they are similar.”
B12 deficiencies have been highlighted by the Medicines and Healthcare products Regulatory Agency, a UK government organisation, which said last month that they were common in patients receiving metformin, a treatment for type 2 diabetes.
The organisation has advised that B12 levels should be tested in patients on metformin if they show symptoms that suggest they may have a deficiency.
Symptoms can be gradual
When it comes to the “brain fog” sometimes seen with B12 deficiency, symptoms can include confusion and memory problems, while depression may also result.
“Vitamin B12 plays two key roles in metabolism, and one of those roles is to help produce agents in the brain that we use as neurotransmitters, and it also affects the nerve endings and the way that those are put together,” Prof Warren says.
“The effect there is that if you don’t have enough B12, some of those things don’t work properly, and that’s what gives rise to the neurological issues.”
The vitamin’s essential roles in many processes ― from making amino acids, the building blocks of proteins, to synthesising DNA, the genetic material ― mean that the effects of deficiencies are widespread.
Anaemia is one other consequence, with shortages of B12 leading to the production of larger than normal red blood cells, which are unable to function properly.
But despite being potentially serious, symptoms do not show up quickly, so are often not recognised.
“It’s not like you suddenly go down with a fever,” Prof Warren says. “You gradually feel more lethargic or your brain just doesn’t think in the way you used to, but it’s a gradual process.”
Healthy, balanced diet
Ruminant mammals, such as cattle, sheep and goats, obtain B12 from micro-organisms present in their digestive tract. Humans, however, do not absorb B12 from their gut bacteria, so we have no option but to consume it in our diet.
B12 is more common in meat, fish and dairy products and, as a result, vegetarians and especially vegans have to be more careful to ensure that they consume enough.
The increased availability of plant-based alternatives to dairy products, such as almond or soya milks fortified with B12 and other important nutrients, have made this easier.
“With good planning and an understanding of what makes up a healthy, balanced vegan diet, you can get all the nutrients your body needs,” the UK’s National Health Service states in an online briefing document.
For example, 250ml of an unsweetened almond milk substitute sold by a major supermarket chain in the UK contains 0.95 micrograms of B12, which is 38 per cent of the recommended daily intake.
Supplements are an alternative source and are considered safe because, unlike with some other nutrients, consuming significantly more B12 than is necessary is not considered harmful.
But it is important to take in small amounts regularly, because when large amounts are ingested, only a fraction is absorbed.
Another group of people advised to pay particular attention to B12 are the elderly, because about 20 per cent of over 60s are deficient.
“Their bodies lose the ability to absorb the nutrient,” Prof Warren says.
People at particular risk are those with a condition called pernicious anaemia, caused by the immune system attacking cells that produce a protein, an intrinsic factor that is essential for the absorption of B12.
Deficiency in children
Deficiencies of vitamin B12 are also found in the developing world, including in children, whose healthy growth may be impaired.
Among the researchers to have looked at this is Prof Henrik Friis, of the University of Copenhagen’s Department of Nutrition, Exercise and Sports.
Earlier this year he and his co-researchers released a study, carried out with Medecins Sans Frontieres, which found that B12 deficiency in infants was a major problem in the West African country of Burkina Faso.
Looking at more than 1,000 children with acute malnutrition aged between six and 23 months, they found B12 deficiencies were widespread and were linked to anaemia and hampered motor development, meaning the growth of the child’s bones, muscles and ability to move.
“In children in a low-income situation we found very high prevalence of deficiencies,” Prof Friis says. “We found two thirds of these children had low or marginal B12 status.”
While cautioning that he is not a neurologist, Prof Friis says that because cobalamin is important for the brain development, deficiencies in children may have long-lasting effects.
“It’s very likely it will have some detrimental effects on the development of these children, and they may eventually grow up and have impaired intellectual capacity,” he says.
Aside from consuming animal-based products, people in developing countries could benefit if B12 was added to foodstuffs available to poorer people, something Prof Friis said might need to be made mandatory.
While the production of many nutrients is relatively straightforward using chemical processes, with B12 about 70 steps are needed and yields are “incredibly low”, Prof Warren says, making it uneconomic.
“We’ve looked at ways to enhance B12 production,” Prof Warren says. “It’s the most structurally complex of all the nutrients, consequently it’s not one of the nutrients you can make through chemical synthesis.”
Instead, it is made by bacteria that are cultured industrially, and Prof Warren and other researchers are looking at ways to improve this synthesis.
While B12’s production is not as easy as it might be, the vitamin is available in many foodstuffs ― and people at particular risk are advised to make sure they take in enough of these products to ensure they do not suffer deficiencies of this vital nutrient.