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Vitamin B12: Foods, Why We Need It And Deficiency Symptoms

Plus the difference between B12 and iron.
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Nutrients in foods are often the last thing we think of when we're enjoying a tasty meal. In reality it's the huge range of nutrients -- from iron and calcium to vitamin C -- which help our bodies to run most effectively.

Vitamin B12 is a topic of confusion for many. Why do our bodies need it? In which foods is B12 found? What happens when we're B12 deficient? To answer your questions, HuffPost Australia spoke to accredited practising dietitians of The Biting Truth, Alexandra Parker and Anna Debenham.

What is B12 and why do we need it?

"Vitamin B12 is a crucial B vitamin that our bodies cannot synthesise -- hence we rely on receiving it via either food or supplementation," Debenham told HuffPost Australia.

"B12 plays a crucial role in our nervous system, the production of red blood cells, digestion and brain function. It helps to prevent anaemia and helps to enhance mood and energy levels."

As you can see, having adequate levels of vitamin B12 is important not only for our physical health but also our mental health.


Where is B12 found?

"Vitamin B12 is found naturally in foods of animal origin," Parker said. "Meat and meat products are the major source of vitamin B12 in our diets, but we can also receive vitamin B12 from dairy products and eggs."

Due to vitamin B12 predominately being found in animals products, vegans are at risk of developing vitamin B12 deficiency. However, eating B12-fortified foods and taking B12 supplements can help.

"Vitamin B12 can also be found in some fortified cereals and grains, as well as nutritional yeast," Parker said.

"Foods such as mushrooms and fermented soy products may have traces of vitamin B12 but this is not sufficient to meet requirements."

List of vitamin B12-rich foods:

  • Beef, particularly beef liver
  • Chicken
  • Lamb
  • Ham
  • Sardines
  • Mackerel
  • Wild salmon
  • Trout
  • Tuna
  • Nutritional yeast
  • Milk
  • Cheese
  • Natural Greek yoghurt
  • Eggs
  • Fortified cereals and grains

Vitamin B12 deficiency symptoms

"Because of the relatively large stores of B12 in our livers (there is enough for to last several years) the onset of B12 deficiency is usually quite gradual," Debenham explained.

Low levels of B12 in our blood occurs first and can lead to megaloblastic anemia (larger than normal red blood cells) or neuropathy.

"If you're not getting enough B12, you might experience 'brain fog' which will make you feel like your memory is hazy and you'll find it difficult to concentrate," Debenham said.

"People with a B12 deficiency can also feel weak, fatigued, constipated, anaemic and even depressed."

If you're constantly tired for no reason, check in with your GP for some blood tests.
Stacey Rozells / Unsplash
If you're constantly tired for no reason, check in with your GP for some blood tests.

What's the difference between vitamin B12 and iron?


"Iron is an essential mineral needed by our bodies to form new red blood cells, transport oxygen to our muscles and keep our immune systems strong," Parker said.

"Iron is not made by our bodies so we need to get it from the food we eat. There are two main types of iron: haem iron that comes from animal sources and non-haem iron that comes from plant-based sources. Deficiencies in iron are quite common (especially in women) and pregnant women have higher requirements."

Vitamin B12

"Vitamin B12 is also involved in the production of red blood cells but is also required for healthy brain function and DNA synthesis. Unlike iron, it is only found in animal products and fortified foods," Parker said.

So, while iron and B12 are interrelated, the body requires both independently for different reasons and without either, this can result in health complications.

Seafood is a rich source of B12.
Getty Images/iStockphoto
Seafood is a rich source of B12.

What's the best way to make sure we're getting enough B12?

"The recommended dietary intake of vitamin B12 is 2.8 micrograms (ug) -- keep in mind women who are breastfeeding or pregnant will require more," Parker said. "When those suffering from vitamin B12 deficiency experience DNA damage, the recommended intake increases dramatically."

To get an idea of how much vitamin B12 is in common foods:

  • 100g sardines: 8.9ug
  • 100g salmon: 4.3ug
  • 100g tuna: 3.0ug
  • 100g lamb: 2.6ug
  • 100g chicken: 0.4ug
  • 1 large egg: 0.8ug
  • 1 cup milk: 1.4ug
  • 100g mushrooms: 0.04ug

The list above shows that if you are consuming animal products as part of a healthy diet, it is relatively easy to reach the recommended daily intake of vitamin B12, which is why B12 deficiencies are more rare, Debenham explained.

"For those who are vegetarian or vegan, it is a good idea to speak to your doctor and if you're worried, a blood test can determine your B12 levels. People who are vegetarian or vegan may need to take a vitamin B12 supplement."

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