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Why you can't always rely on soy milk for vitamin B12

People relying on plant-based milks and foods risk a deficiency that causes more than just fatigue.

QUESTION: Is there any vitamin B12 in soy milk and soy products? A lot of us are on a dairy-free diet for one reason or another and it would be helpful to know.

ANSWER: Whether vitamin B12 is found in non-dairy milks depends on whether it is added by the manufacturer, because the vitamin isn’t naturally present.

Humans need a regular supply of vitamin B12 to make healthy red blood cells, to synthesise DNA, and for the proper functioning and development of the brain and nerve cells.

The major problem with a vitamin B12 deficiency is that it causes progressive and irreversible damage. What starts as a bit of numbness and tingling in the hands and feet can cause permanent injury to the spinal cord and nerves outside the brain. Other side effects include anaemia, fatigue, poor memory and stomach problems such as constipation, which result in weight and appetite loss.

So, it’s crucial that a vitamin B12 deficiency is promptly diagnosed, or, better still, prevented in the first place.

Fortunately, foods derived from animals, such as meat, milk, eggs, fish and shellfish, are major sources of vitamin B12. It’s estimated that about a quarter of our vitamin B12 needs come from red meats, with a further 30% met by milk and dairy products.

However, as you’ve pointed out, people are increasingly turning to non-dairy milks as an alternative for health or environmental reasons.  Vitamin B12 is synthesised only by certain bacteria and other single-cell organisms, but not by plants, so non-dairy milks don’t naturally contain it.

 The vitamin is synthesised in the gut of cows and sheep, for example, and accumulates in their body tissues. Hence the meat and milk of herbivorous ruminants are good sources of vitamin B12 for humans.

In the sea, phytoplankton acquire vitamin B12 through a symbiotic relationship with bacteria, and they then become food for larval fish and bivalves such as oysters, mussels and scallops.

With plant-derived products such as soy, oat, rice and almond milk, it’s up to the manufacturarbitraryer whether to add vitamin B12 during production. A simple check of the ingredients list should reveal whether it has been added. I checked So Good and Vitasoy’s standard soy milks and both contained added B12.

 

Soy products do not naturally contain appreciable amounts of B12. However, the exception is tempeh, a fermented soybean-based food that contains about 0.21mcg per cup, a reasonable amount of B12. This is probably a result of bacterial contamination during the production and fermentation of tempeh.

However, it’s worth noting that some non-dairy milk products don’t have added B12. For instance, Vitasoy’s Almond Milky does not contain vitamin B12, whereas Sanitarium’s So Good Original Almond Milk does.

Adults require about 2.4mcg of vitamin B12 a day to remain healthy. If you’re eating a good variety of meat, fish, eggs and a suitable non-dairy milk fortified with vitamin B12, you should be able to meet these requirements.

This article was first published in the October 5, 2019 issue of the New Zealand Listener.