When it comes to vitamin B12, red meat tops the charts.

Author, Dr Anneline Padayachee

Scurvy, a deficiency of vitamin C, was a major issue for sailors during the middle-ages causing bleeding gum and weak bones; iron deficiency and anaemia is often considered a problem for women, particularly those of child-bearing age; calcium deficiency and osteoporosis is generally a focal problem for menopausal women and the elderly. When it comes to vitamin B12, everyone regardless of age, gender, or job type is at risk.

Given that humans are unable to produce vitamin B12 (our gut bacteria produce very little during fermentation), vitamin B12 is considered an essential nutrient we need to obtain from our dietary intake. Deficiencies, while easy to prevent, can have seriously detrimental impact on health and quality of life. Vitamin B12, as the name suggests, is a B-group vitamin and is the generic name used to describe a group of vitamins that have cobalt (a mineral) as part of the chemistry. This group of vitamins are known as cobalamins, are water soluble (1, 2). Although easily absorbed into the blood stream, water-soluble vitamins are also lost in urine and perspiration. Thus, it’s not easy to accumulate toxic levels of water-soluble vitamins. Conversely, it is easy to have a deficiency, especially with restrictive diets. Red meat is often touted as the best source of vitamin B12. But how true is this? And more importantly, why does vitamin B12 matter? Today we are going to delve into this relatively common, albeit extremely important vitamin and investigate what it does, populations at risk of a B12 deficiency, and check out how true the meat “vitamin B12 health claim” really is. Regardless of whether you are an omnivore or a plant-exclusive consumer, we’ll also look at ways you can ensure vitamin B12 is a regular part of dietary intake.

Functions in the body

Vitamin B12 has several key functions in the human body including (2):

Red Blood Cell Formation: working with folate (vitamin B9), vitamin B12 is essential in producing healthy red blood cells responsible for carrying oxygen from the lungs to the rest of the body’s tissues. Vitamin B12 deficiency can result in either less red blood cells or deformed red blood cells being formed which will lead to a range of health problems including anaemia.

Neurological Function and maintaining the health of the Nervous System: Vitamin B12 is involved in the formation of the myelin sheath, a protective covering that surrounds and insulates nerve fibers needed to facilitate proper nerve transmission. Vitamin B12 deficiency can lead to neurological symptoms such as numbness, tingling, and weakness in the extremities, as well as cognitive impairment and mood disturbances.

DNA Synthesis: Vitamin B12 is essential in the production of nucleotides, the building blocks of DNA, and is thus critical for normal cell growth, replication, and repair. A lack of vitamin B12 could lead to DNA mutations or impaired cell division.

Energy Metabolism: Vitamin B12 participates in the metabolism of carbohydrates, fats, and proteins, which are essential for energy production. Essentially the energy trapped in carbohydrate-, fat- and protein-containing foods we consume is released from the food matrix during digestion. It then needs to be converted to glucose, the body’s primary source of energy. Glucose is essentially further processed by the body via various metabolic pathways that generate ATP (adenosine triphosphate), the energy currency of cells. Vitamin B12 is involved in all these steps, particularly the glucose and ATP pathways, converting energy in food into energy the body can use.

Methylation Reactions: Methylation is a biochemical process essential for various physiological functions, including neurotransmitter synthesis, hormone regulation, and DNA repair. Vitamin B12 serves as a cofactor for methionine synthase, an enzyme involved in methylation reactions.

For a water-soluble vitamin, excreted in sweat and perspiration daily, adequate intake of vitamin B12 is crucial for maintaining overall health and preventing deficiency-related complications. Water solubility also has a direct impact on nutritional quality of food sources of vitamin B12.

What does water solubility mean?

When it comes to vitamins, we have two groups: fat soluble and water soluble (3). Solubility is based on chemistry and refers to the substance (i.e. fat or water) needed to absorb a particular vitamin, the absorption pathways in the body (fat soluble vitamins follow fat absorption pathways, while water-soluble follow different pathways) as well as how the body stores the vitamin: fat-soluble vitamins are stored in fat, while water-soluble vitamins are excreted in excess water in the body. Fat soluble vitamins are A, D, E and K while water-soluble vitamins are C and the B-group vitamins (B1, B2, B3, B5, B6, B7 ,B9, and B12) (3). Being able to dissolve readily in water allows B-group vitamins including vitamin B12 to be easily absorbed into the bloodstream primarily from the small intestine (4)) and transported throughout the body to muscles, tissues, organs, developing foetus, etc, wherever they are needed. Unlike fat-soluble vitamins, water soluble vitamins are not stored in the body to a significant extent and are excreted in urine and perspiration (3). It’s essential to consume water soluble vitamins to maintain optimal health especially if one is doing a lot of manual work or exercise, or lives in humid environment where there is a higher body water loss via sweating, or if they have a disease that may cause excessive urination (e.g. diabetes insipidu, a disease that causes the body to produce higher than normal amounts of urine; it is not the same a diabetes mellitus (5)). Although the lack of storage of in the body means water-soluble vitamins have a lower risk of toxicity than fat-soluble vitamins, excess consumption of water-soluble vitamins can still lead to toxic outcomes in some cases. The major issue that affects water-soluble vitamins from fat-vitamins is their sensitivity to being exposed to heat and light leading to degradation during cooking and food processing while fat soluble vitamins are relatively stable. It’s important to handle and prepare foods containing water-soluble vitamins properly, to preserve their nutritional content.

Dietary Sources of Vitamin B12

Although plant foods like algae and mushrooms, or foods that have been exposed to bacteria like tempeh and kimchi may contain vitamin B12, it’s relatively low (6). Furthermore, the form of vitamin B12 in plant foods has a lower bioavailability than animal derived vitamin B12, and is easily degraded during cooking and food preparation (6). The best dietary sources of Vitamin B12 are animal-derived foods particularly red meat (including organ meats). Although approximately 30% of vitamin B12 is lost during cooking, red meat derived B12 has both the highest quantity in food AND the highest bioavailability (amount absorbed) with up to 90% absorbed in the small intestine (7, 8). Other foods that contain vitamin B12 include fish (particularly oily fish like salmon, trout, mackeral) and seafood (like oysters, clams), and dairy products (milk, yoghurt, cheese) are good sources of vitamin B12, but it is important to note that content can vary based on degree of processing and fortification (or lack of fortification) (7-9). Likewise while eggs and poultry contain lower levels of vitamin B12, the bioavailability is comparatively low (about 8%) compared to red meat (varies between 55-90% depending on the individual).

When it comes to vitamin B12, there are several issues with plant-derived foods that do not allow them to be a significant source of vitamin B12. Firstly, vitamin B12 is synthesized (produced) by certain microorganisms, such as bacteria and archaea, rather than by plants or animals themselves. Essentially vitamin B12 is a by-product of fermentation by certain bacteria commonly found in soil or the digestive tract of animals (10). Animals obtain vitamin B12 by consuming these microorganisms directly when they eat grass (growing in soil containing these bacteria), by eating plants that have been contaminated with them, or via their bacterial fermentation process. Given that cattle do all these things and have a rumen responsible for fermentation, beef is an exceptionally high source of vitamin B12 (10).

Red meat, particularly beef, is considered an excellent source of Vitamin B12 for several reasons (10, 11):

High concentration compared to many other food sources.

Highly bioavailable form meaning it is easily absorbed and utilized by the body than the synthetic form found in supplements or fortified foods.

Red meat is a complete protein source, meaning it contains all the essential amino acids required by the body. This completeness aids in the absorption and utilization of Vitamin B12 and other nutrients present in the meat.

Vitamin B12 in red meat exists in the form of methylcobalamin. This form is easily metabolized by the body, contributing to its effectiveness in fulfilling vitamin B12 requirements. The other forms of vitamin B12, while still absorbable, are not as easily metabolized as the form in red meat.

Red meat can be stored for longer periods without significant loss of vitamin B12 content, making it a reliable and convenient source of this essential nutrient.

Red meat encompasses various cuts and types, offering consumers a range of options to include in their diet. Whether it is lean cuts like sirloin or fattier cuts like ribeye, individuals can choose based on their preferences and nutritional needs while still obtaining ample amounts of vitamin B12.

Throughout history, red meat has been a staple in many diets around the world. Its inclusion in traditional diets reflects its importance as a source of essential nutrients, including vitamin B12.

The combination of high concentration, bioavailability, completeness, natural form, storage stability, variety, and historical significance makes red meat an exceptional source of vitamin B12 in the diet. You don’t need a lot of red meat to get sufficient vitamin B12. According to the National Health and Medical Research Council (NHMRC), the recommended dietary intake of vitamin B12 for men and women above 18 years is 2.4 ug/day. Due to the rapid rates of growth and development during pregnancy, pregnant women require 2.6 ug/day, while lactating women require 2.8 ug/day (12).

The vitamin B12 content in different animal-derived foods varies (table 1).

Conversely, plants do not require Vitamin B12 for their own growth and metabolism, and therefore do not actively synthesize (produce) or store Vitamin B12 (11). As a result, plant-based foods do not naturally contain Vitamin B12 unless they have been fortified or contaminated with Vitamin B12-producing microorganisms. Although rare, plant-based foods can become contaminated with Vitamin B12-producing microorganisms from the environment, such as soil or water. For example, unwashed vegetables, fruits or mushrooms grown in soil containing these microorganisms may contain trace amounts of Vitamin B12 (9). Some plant-based foods, such as fortified breakfast cereals, plant-based milk alternatives (e.g., soy milk, almond milk), and nutritional yeast, are fortified with Vitamin B12 (11). These fortified foods can be a suitable source of Vitamin B12 for individuals following vegetarian or vegan diets.

At risk groups

It is important to realise that even if red meat or plant-based foods fortified or naturally containing small amounts of Vitamin B12 are consumed regularly, the vitamin may not be efficiently absorbed by the human body (13, 14). Vitamin B12 requires intrinsic factor, a protein produced by the stomach lining, for absorption in the small intestine. Intrinsic factor binds to vitamin B12 and facilitates its absorption into the bloodstream. Without intrinsic factor, vitamin B12 absorption is significantly impaired, which is why vitamin B12 deficiency is more common in individuals with gastrointestinal disorders that affect intrinsic factor production or absorption. Other causes of vitamin B12 malabsorption include Addison’s pernicious anaemia, bariatric surgery, coeliac disease, bacterial overgrowth and parasitic infections and inflammatory bowel diseases (13, 14).

In truth, all age groups are susceptible to vitamin B12 deficiency if they have underlying digestive issues. Risk factors for vitamin B12 include (13, 14):

Plant exclusive dietary intake: As animal-derived foods are the primary source of vitamin B12, those following a plant-exclusive diet have a higher risk of vitamin B12 deficiency.

Age: As we get older, we may produce less stomach acid which is needed for the absorption of vitamin B12 from food.

Gastrointestinal Disorders: Certain gastrointestinal conditions, such as pernicious anemia, celiac disease, Crohn’s disease, and atrophic gastritis, can impair the absorption of vitamin B12 from food, leading to deficiency.

Medications: Some medications, such as proton pump inhibitors (PPIs), histamine-2 receptor antagonists (H2 blockers), and certain diabetes medications, can interfere with vitamin B12 absorption or increase the risk of deficiency over time.

Alcohol Consumption: Excessive alcohol consumption can interfere with the absorption and metabolism of vitamin B12, increasing the risk of deficiency.

Pregnancy and Breastfeeding: Pregnant and breastfeeding women have increased vitamin B12 requirements to support the growth and development of the fetus or infant. If their dietary intake is inadequate, they may be at risk of deficiency (12).

Other Factors: Certain genetic factors, such as mutations in genes involved in vitamin B12 metabolism, can predispose individuals to vitamin B12 deficiency.

While vitamin B12 deficiency is more common in certain populations, it is generally preventable and treatable with dietary changes, supplements, consuming fortified plant-based foods (especially important for vegans) or injections of vitamin B12. It’s important to be aware of the risk factors and to maintain a balanced diet rich in vitamin B12-containing foods or supplements if necessary, especially for individuals at higher risk of deficiency. Regular monitoring and consultation with a healthcare provider can help prevent and manage vitamin B12 deficiency effectively.

Vitamin B12 deficiency health issues

A vitamin B12 deficiency can lead to various symptoms and health complications due to its essential roles in body. Potential consequences of vitamin B12 can vary and requires diagnosis by a medical health care provider and include (11, 13, 14):

Fatigue and weakness: Vitamin B12 is essential for energy metabolism, and deficiency can result in fatigue, weakness, and lethargy due to impaired production of red blood cells and energy.

Megaloblastic anaemia: One of the most common consequences of vitamin B12 deficiency is megaloblastic anaemia. In this condition, the bone marrow produces abnormally large and immature red blood cells, which are unable to function properly. Anaemia can result in symptoms such as fatigue, weakness, pale skin, shortness of breath, and dizziness. This is further exacerbated by a plant-exclusive diet that is low in haem iron as well.

Neurological Symptoms: vitamin B12 deficiency can lead to neurological complications due to its role in maintaining the health of the nervous system. Symptoms may include numbness or tingling in the hands and feet (peripheral neuropathy), difficulty walking, balance problems, muscle weakness, memory loss, cognitive impairment, and mood disturbances.

Neurological Damage: Prolonged vitamin B12 deficiency, especially if left untreated, can lead to irreversible neurological damage, including demyelination of nerve fibers in the brain and irreversible neurological deficits.

Gastrointestinal Issues: Vitamin B12 deficiency can affect the gastrointestinal tract, leading to symptoms such as diarrhea, constipation, loss of appetite, and weight loss. In severe cases, deficiency may result in glossitis (inflammation of the tongue) or mouth ulcers.

Pregnancy Complications: Vitamin B12 deficiency during pregnancy can increase the risk of complications such as neural tube defects in the developing fetus and preterm birth.

Increased Risk of Cardiovascular Disease: Some studies suggest that vitamin B12 deficiency may be associated with an increased risk of cardiovascular disease due to its role in regulating homocysteine levels. Elevated homocysteine levels are a risk factor for cardiovascular disease.

Vitamin B12 is an essential water-soluble vitamin in the body, and affects various physiological processes in the body, including energy metabolism, cell metabolism, and plays various important roles in maintaining overall health. Vitamin B12 deficiency can have significant implications for overall health and well-being, affecting multiple bodily systems including the hematologic, neurological, gastrointestinal, and cardiovascular systems. Early detection and appropriate treatment of vitamin B12 deficiency are essential to prevent or alleviate symptoms and reduce the risk of complications. While plant foods may contain trace amounts of vitamin B12 due to contamination or fortification, they are not reliable sources for most individuals. If you can eat red meat, eggs, fish, poultry, and dairy products, these foods remain the primary high quality dietary sources of vitamin B12. Otherwise, fortified plant-foods and supplements may be needed. It’s important to consult with a healthcare professional for proper evaluation and management, especially if you’re one of the higher risk groups.

References

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