B12 deficiency and diet

B12 deficiency can make you feel very unwell as it is a co-factor in most cellular processes. Deficiency often manifests first as fatigue, then neurological symptoms (such as pins and needles) and then as anaemia.

There are many other symptoms of B12 deficiency.

There are many causes of B12 deficiency. Some are caused by lack of absorption in the stomach or intestines. These include:

  • Pernicious Anaemia – the body produces antibodies against B12 binding proteins.
  • Gastric atrophy – the body doesn’t produce the binding proteins. Very common in the elderly
  • Drug interference – some medications can impair absorption.
  • Terminal Ileum problems – the body can’t absorb the B12 in the lower gut.
  • Malnutrition – you aren’t eating enough B12 in the diet.

However many people are B12 deficient because our modern diet doesn’t contain enough. B12 is made by microbes that live in the soil next to plant roots. We get it by eating dirt still on our root vegetables or by eating animals that have done so. In these modern times, we tend to prefer to wash our vegetables, so eat very little soil and our animals are also kept in farmed conditions, often being fed “clean” food. This means most farmed animals are given B12 supplements to ensure they get enough.

Unless we are living a self-sufficient lifestyle with all our own, home-grown veggies and we choose not to wash them very well, then we will need to take a B12 supplement. We can either do this by eating an animal that has been supplemented with B12, or we can take the supplements ourselves.

In New Zealand there are a few animals which still contain a lot of B12 and these are seafood – especially mussels and other bivalves, oily shore fish such as kahawai and wild game. However, the increased B12 in consumption of these animals has to be offset by the bad health effects seen in eating animal protein. If you do wish to eat animal protein – stick to these animals and see below for quantity.

The recommended dietary intake of B12 is fairly low at 2.4mcg per day, but there are some scientists who think this is too low and there are few risks seen from taking a higher dose (up to 1000mcg per day). Once we have saturated the B12 receptors any extra B12 is excreted.

How to replace B12 is variable. Very occasionally injections are needed especially in the beginning. However, most people can use oral supplements and there is good evidence that they can be absorbed through the lining of the mouth. This means even people who have a gut problem, preventing absorbtion, can still use oral supplements.

Supplements are cheap and come as 50 micrograms (mcg) or 1000 mcg, and the price is about the same. I recommend taking a 1000mcg supplement once or twice a week for people eating no animal protein. Those eating a little fish could supplement less. This means a bottle of 90 tabs will last almost 2 years. Let them dissolve in the mouth as much as possible before swallowing.

However, ensuring you have enough B12 isn’t the whole story. For B12 to be used effectively in the body, you also need a good supply of the other cellular co-factors.

In general these will be supplied by eating a varied, plant-based diet, but if you have B12 deficiency it is also helpful to concentrate on getting enough of the other B vitamins, potassium, magnesium, iron and folate as these seem to be particularly important.

Sometimes you may need to take supplements of these other cofactors for the first 3-12 months, but long term it is best to get all your micronutrients from your food. (They work better this way).

Foods you need to eat:

Leafy green vegetables – Folate, B1 (thiamine), B2 (riboflavin), B6 (pyridoxine) potassium, magnesium and iron. 2-3 large portions every day. All the brassicas (cabbage family), spinach, silverbeet, cauliflower, broccoli, Brussels sprouts, watercress, bok choy, beet and turnip tops, radishes.

Wholegrains – B Vitamins especially B3 (niacin), B6, B7 (biotin), magnesium, potassium. Eat 1-2 portions each day. Whole wheat, brown or black rice, barley, rye, quinoa, buckwheat, oats. (If gluten free, this list will reduce).

Legumes – B vitamins esp B1, B3, pantothenic acid, folate, iron, magnesium eat 1-2 portions every day. Lentils (all types), beans (all types), chickpeas, peas (all types), peanuts.

Avocados, mushrooms, bananas, capsicum, asparagus – pantothenic acid, biotin, folate, magnesium, potassium. Eat a range across the week.

Other sources of magnesium and potassium include cocoa – ideally as it comes, or as dark chocolate. Not more than 40g per day.

Meat, dairy, eggs and fish contain many B vitamins but can lead to other health problems.

If you choose to continue to eat the animal protein then oily fish (kahawai, mackerel, sardines, pilchards, salmon) or bivalve seafood (mussels, oysters, pipi, scallops) have the highest amount and can be consumed at 100g up to twice weekly.


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