Nutrition
To B12 or not to B12
by Jennifer Bowden
When you’re over 50, a vitamin supplement can do what your body can’t.
Question: An elderly friend has been prescribed a course of 3 x 3 monthly injections of Vitamin B12, possibly followed by a further course depending on the results of a blood test. Most GPs seem to pooh-pooh vitamin supplements provided one adheres to a diet containing (in the case of vitamin B12) lean red meat, fish, milk and cheese, and said friend and I do. Has modern science made any new discoveries? (B Wright, Ellerslie)
Answer:
What could be more confusing? First you hear doctors and nutritionists telling you to improve your diet rather than take dietary supplements; the next you hear a story like this.
But although it may seem that health professionals are, by their very nature, confusing, there is some method in this madness.
The crucial issue is that a vitamin B12 deficiency can cause progressive and irreversible damage to the nervous system. What starts as a bit of numbness and tingling in the hands and feet can end up as permanent damage to the spinal cord and nerves outside the brain, such as the optic nerve, not to mention the potential for anaemia, irritability, memory impairment and depression. Treatment must be prompt, as the longer it’s delayed the smaller the chances of reversing the neurological complications – the first very good reason for GPs’ hasty recommendation of vitamin B12 supplements.
Older New Zealanders have another good reason to take supplements – vitamin B12 deficiency is more common in older people. Worryingly, a 2005 study published in the European Journal of Clinical Nutrition suggests that there is a particularly high prevalence of vitamin B12 deficiency among older New Zealanders: 12 percent aged 65 and over are B12 deficient and 28 percent are marginally deficient.
It is widely thought that the reason for this is the increased rate of atrophic gastritis in older people, as atrophic gastritis reduces vitamin B12 absorption from the gut. However, the New Zealand study found that the condition, although a risk factor, didn’t explain most B12 deficiencies in that age group.
Poor dietary intake is not often a cause of deficiency in older adults. Rather, it seems that the problem is typically inadequate absorption or utilisation of food-bound vitamin B12 as a result of other gastric or pancreatic problems, inflammatory bowel diseases, stomach or intestinal surgery, overgrowth of certain intestinal organisms, chronic alcoholism or the prolonged use of medications. For example, ulcer and reflux medications such as Losec, Pepsidine and Zantac can interfere with absorption of B12.
If malabsorption is the cause, eating more vitamin B12-rich foods won’t help. Supplements play an important role in treatment, as their vitamin B12 is more readily absorbed if taken orally. It can also be administered by injection, bypassing the gut altogether.
Health professionals still recommend a widely varied diet to obtain all the vitamins, minerals and other nutrients your body needs. But the prompt treatment necessary to prevent permanent neurological damage caused by vitamin B12 deficiency justifies supplementation, especially if the cause is unidentified and presumed to be malabsorption.
Wondering if regular preventative oral supplements are a good idea for older adults?
The 2005 study found that regular vitamin B12 supplementation reduced the risk of deficiency in older New Zealanders.
US studies have made similar findings; health authorities there recommend that adults aged 50 years and over get most of their vitamin B12 from supplements or fortified food because of their high rate of impaired absorption.
In New Zealand, where few foods are fortified with vitamin B12, the Ministry of Health recommends that only vegans use supplements to meet the recommended dietary intake of 2.4 micrograms per day
Still, I know what I’d be doing.
Email: nutrition@listener.co.nz, or write to “Nutrition”, c/o Listener, PO Box 90783, Auckland.
