The previous vitamin B6 blog went into what this vitamin does, and that is to act principally as a catalyst to many happenings in the body. B6 is a water soluble vitamin and is present in most foods – and yet we can be very short of it and this blog explores why. Overall there are three main reasons: the fragility of the vitamin; the plant form of the vitamin can be antagonistic to B6; and shortage of vitamin B2 and zinc, both of which are needed to activate vitamin B6.
First off, the fragility of this vitamin. Nine things destroy vitamin B6: exposure to light and/or oxygen; cooking at high temperature; prolonged cooking; processing; canning; freezing; pressure cooking; sterilisation. For instance, liver is one of the best dietary sources of B6, but in order to get the benefits of eating liver we first need to actually eat liver! – but we also have to eat fresh liver that has been gently cooked and is still pink in the middle. At one time raw liver was recommended as a health tonic – and if we bear in mind the fragility and importance of vitamin B6 alone, it becomes clear as to why this cure worked. These days it is important to buy organic liver, since the liver in all animals is the detoxification unit, and where ever possible we need to reduce our intake of toxins.
Second reason: the plant form of vitamin B6. The dietary form of B6 the body prefers comes from animals/birds or fish. It can convert the plant form of B6, provided that form is free. And thereby hangs this part of the tale: all plants come in the collective family called carbohydrates, which are sugars. And each plant contains variable amounts of sugar and fibre. Vitamin B6 can be bound to the plant sugars and this is the form that causes us problems. The term is glycosylation, and the full name of plant bound vitamin B6 is pyridoxine glucosides or PNG. When B6 becomes glycosylated it not only becomes unavailable to our digestive system, it also lowers existing levels of B6 in the body – although no one knows quite why. And cooking or freezing vegetables seems to make the glycosylation worse – the heat/ice encourages those sugars to bind to the B6. Overall grains (wheat, rice, oats etc) and legumes(kidney beans, lentils, chick peas etc) have the highest binding, from 6 – 57% followed by raw carrots at 51%, then comes orange juice at 47% with broccoli and cauliflower worse when cooked or frozen than when raw.1 Here is a chart with the percentage of B6 in the food that is glycosylated.2
|Cauliflower, frozen||66-82||Peanut butter||18|
|Carrots, raw||51-75||Whole wheat bread||17|
|Fresh orange juice||37-69||Bananas||3 –16|
|Soy beans, cooked||57-67||Peas, frozen||15|
|Broccoli, frozen||65||Apricots, dried||14|
|Raisins||65||White rice, cooked||14|
|Canned green beans||28-58||Whole wheat flour||11|
|Broccoli, raw||35-57||Green beans, raw||10|
|Orange juice, concentrate||47-53||Frozen corn||6|
|Wheat bran||27-36||Wheat flakes cereal||5|
|Shredded Wheat cereal||28-31|
Sorry about the pickle that is this chart. Much fiddling and sighing has gone on, but this will have to do now. The difference between raw and frozen cauliflower is particularly spectacular. Actually, there is quite a heated debate going on about raw vs cooked veggies, and certainly where this vitamin is concerned, raw is generally better. Do remember that these above percentages are the percentage of total vitamin B6 in the vegetable; the chart is not saying that 75% of a raw carrot is made of PNG! So as usual it is all rather complex as to which vegetables and fruits are better and which worse. Elsewhere I found that walnuts, almonds and avocado pears contain little or no PNG, so we can enjoy those at least. And finally, it is important to remember that no meat/fish source of B6 has this problem, so provided the meat is fresh and cooked with care, we should be getting B6 from there.
The third reason for low B6 levels is low levels of zinc and vitamin B2/riboflavin. Both are needed by the body to convert dietary sources of B6 into the version of B6 that the body uses. As said in many previous blogs, we are all short of zinc because of the use of chemical fertilisers, which consist of nitrogen, phosphorus and potassium, with little or no other minerals added. This means that the plants take up the zinc – and other nutrients they need, but these nutrients are not being replaced in the soil, so as time goes on, the soil gets steadily more and more depleted – so do the plants and so do the animals that eat the plants and so do we. Also a diet high in phytates drags any zinc we can find in the food out of our body: phytates are found in whole grains, nuts and pulses. Riboflavin is more available in the diet, with the best sources being yeast extract, liver and kidneys. Although present in plants, again processing tends to reduce levels – hence why flour and cereals may be fortified with riboflavin. Exposure to light also reduces B2 levels. The other thing that reduces B2 – and zinc -is poor uptake in the guts. To finish, quoting from Pam Schoenfeld, writing for the Weston A Price foundation
Diets that restrict meat, seafood, poultry, dairy or eggs – or diets that rely on improperly prepared grains, legumes and nuts that are high in phytates present three fold problems: low in B2, low in zinc and the B6 is in a form that is hard fo the body to absorb and utilize.3
So there we have it. Three very different reasons why we can be short of vitamin B6. The bottom line is to vary what we eat each and every day, every time we eat and cook it lovingly ourselves.
- Measurement of glycosylated vitamin B-6 in foods. Kbir H, leklem J Miller LT, Jour of Food Sci. vol 48. Issue 5 Pg 1422-1425. Sept 1983 [↩]
- Bioavailability of vitamin B-6 from plant foods. Reynolds R D. Am J Clin Nutr 1988; 48:863-7 [↩]
- Vitamin B-6, the under-appreciated vitamin. Pam Schoenfeld, Weston A Price Foundation, April 01, 2011 [↩]