Vitamins for vegans made from algae could soon prove to be the most effective solution to replacing an important nutrient missing from plant-based diets, thanks to recent research by scientists at Cambridge University.

The popularity of meat- and dairy-free foods in western diets is leaving many people potentially exposed to vitamin deficiency. In particular, they can suffer from a lack of the vitamin B12, a key nutrient involved in blood and nerve cell manufacture.

Research by Cambridge University scientists has highlighted an unusual solution to the problem. Their experiments have shown that many types of algae – largely aquatic organisms that lack roots or stems – show a remarkable ability to accumulate B12. These could soon be exploited by manufacturers to provide effective supplements of the vitamin, they say.

“Diets based purely on plant products are great on many levels but they have certain deficiencies, and one of the most important of these is their lack of the vitamin B12,” said Prof Alison Smith, head of the plant metabolism group at the university.

Supplements based on vitamin B12 are already available but some are effective and others are not because there are different forms of B12, added her colleague, Dr Payam Mehrshahi. “If you are on a vegan diet, you are at risk of being vitamin B12 deficient. You can buy supplements but if you pick up the wrong tablet, the wrong supplement, then you you can end up not getting enough B12 and might become ill. Some tablets or ingredients, particularly those from Spirulina, contain a form of B12 that humans cannot take up efficiently.”

In addition, there is a problem in that vegans and vegetarians – once they have been made aware of the issues involved in B12 deficiency – want to take supplements that are naturally sourced. “Many vegans would prefer not to have chemical supplements and they would like to get their B12 as a natural part of their diet,” added Smith. “You cannot get it from plants but we have found that certain algae are rich sources of the vitamin.”

Vitamin B12 is an essential micronutrient. Lack of it triggers muscle weakness, numbness, nausea, weight loss, fatigue and increased heart rate while continued deficiency will eventually leave people susceptible to ailments that include pernicious anaemia, heart disease and diabetes.

“The crucial point is that B12 is made by bacteria such as those that grow in the digestive systems of cows and sheep,” said Mehrshahi. “You cannot get it directly from plants. Meat has been the main traditional source along with dairy products and eggs.

“However, if you adopt a vegetarian diet, or more noticeably a vegan diet, your B12 intake can be drastically reduced, and that is now having noticeable consequences for the nation’s health.”

It is estimated that the total number of vegans in the UK has grown to more than one million, almost 1.5% of the country’s population. This rise is reflected in sales of plant-based foods, which increased by 49% since 2018 but have now levelled off.

However, vegan diets supply only 10% of the B12 that is provided by a standard UK diet. This typically works out at about 0.5 micrograms of B12 a day, a figure that is well below the level considered to be a healthy dose, according to a recent paper in the European Journal of Nutrition. The study also pinpointed pregnant and lactating women, as well as older people, as now being at particular risk.

“This highlights an urgent demand for fortification of plant-based dairy and meat alternative foods in the UK, in particular to combat deficits in vitamin B12,” states the study, whose authors include members of CluB12, a group that was recently set up to highlight the growing danger of B12 deficiency in the west. Adopting a vegan or vegetarian diet requires careful planning and continuous monitoring, its members have warned.

As part of their research, Smith’s group has demonstrated how algae accumulate B12. “They don’t make it themselves, they take it up from their surroundings, where it is made by bacteria,” she told the Observer.

“We have identified that there are different forms of B12 and pinpointed which algae accumulate the varieties that work in humans. That means we can help industry start making effective algal supplements that should allow us to start tackle the serious problem that we are now facing over B12 deficiency.”

• This article was amended on 14 August 2023. An earlier version incorrectly said that taking some forms of B12 could cause harm. In fact, some tablets or ingredients contain a form of B12 that humans cannot take up efficiently and so do not deliver the amount of B12 needed to help with deficiency.