We are now coming to the end of the B vitamins and I hope that you will have found them an interesting group of nutrients that are so essential to our health both physically and mentally. B12 is no exception and certainly for those of us in our 60s it is one of the vitamins we need to make sure we are taking in sufficient amounts in our food. Since B12 is primarily in eggs, dairy products and offal it is restrictive, especially as so many ‘experts’ tell you to stop eating them because of the impact on your cholesterol levels and waistline. I disabused that myth in the series on cholesterol which is a naturally occurring substance in our bodies and necessary for some pretty major operations such as brain function.
This week I am going to be posting the series on stress as I have had a number of questions on the B vitamins role in this response to our lives. That starts tomorrow and through the rest of the week.
Vitamin B12 (Cyanocolbalamin) is an essential water-soluble vitamin but unlike other water soluble vitamins that are normally excreted in urine very quickly, B12 accumulates and gets stored in the liver (around 80%), kidney and body tissues. B12 is vital for the efficient working of every cell in the body especially those with a rapid turnover as it prevents cell degeneration. It functions as a methyl donor and works with folic acid in the manufacture of DNA and red blood cells and also is necessary to maintain the health of the insulating sheath (myelin sheath) that surrounds all nerve cells. It is involved in the production of melatonin, the hormone responsible for resetting our biological clock’s rhythm when we change to new time zones, and also helps us sleep.
The most common disease associated with B12 deficiency is pernicious anaemia, which is characterised by large, immature red blood cells. But other diseases and medical conditions associated with a lack of this vitamin are allergies, Alzheimer’s disease, asthma, cancer depression, AIDS, low blood pressure, multiple sclerosis, tinnitus and low sperm counts.
HOW DO WE BECOME DEFICIENT IN B12?
We actually do not need a huge amount of the vitamin per day, around 2 micrograms or 2millionth of a gram. The problem is that it is not particularly well absorbed by the body so larger amounts are needed in the diet to supply the amount we need. Absorption of B12 requires the secretion from the cells lining the stomach of a glycoprotein, known as the intrinsic factor. The B12-intrinsic factor is then absorbed into the ileum (part of the small intestine) with calcium.
One of the issues regarding deficiencies is that many people have turned away from the richest sources of B12 because they believe either that they are harmful, fattening or will raise levels of cholesterol. Liver, kidneys and eggs have not enjoyed wonderful press over the last few years and many people have also reduced the amount of cheese they eat believing that it is fattening.
Plant sources of B12 are virtually non-existent and many long term and dedicated vegetarians have been found to be deficient. Over use of antacids, inflammation of the stomach lining (Helicobacter pylori infection) and pancreatic problems can also lead to deficiency as the secretion of the intrinsic factor is compromised. There is some evidence that women with breast cancer have lower levels of B12 and there are indications that women after menopause with very low levels were more likely to develop the disease. It is not clear if the deficiency is caused by the cancer in the body or the other way around.
Some drugs have inhibited the uptake of B12 such as those prescribed for diabetes and ulcers and there is a great deal of research into these interactions.
As we age our ability to process our foods becomes less effective with enzyme production reduced such as the secretion of the intrinsic factor necessary for B12 absorption. Added to the fact that many elderly people suffer from a lack of appetite and you have a higher risk of malnutrition.
An interesting piece of research proposes that it is possible that Vitamin E may protect the process of absorption of B12 by preventing oxidative damage to cell membranes. If so a deficiency in this vitamin may well affect our B12 levels.
WHAT FOOD SOURCES ARE THERE FOR B12?
B12 is present in meats apart from offal, eggs and dairy products. It is better to drink a cold glass of milk than to eat yoghurt as the fermentation process destroys most of the B12 as does boiling milk. There are very few sources, if any of B12 in plants, although some people do believe that eating fermented Soya products, sea weeds and algae will provide the vitamin. However analysis of these products shows that whilst some of them do contain B12 it is in the form of B12 analogues which are unable to be absorbed by the human body.
Eating foods containing Vitamin E may help the absorption process and the best sources for this are in nuts such as the walnuts, sunflower seeds, whole grains, eggs, spinach, apples, bananas, broccoli, brown rice, carrots, onions and oily fish.
Most cereals and breads today are fortified with B12 as are yeast extracts (marmite) and vegetarian products.
©sallycronin Just Food For Health 2007
Coming up tomorrow the start of the Stress Series…thanks for dropping by and please feel free to share. Also if you have any questions please do not hesitate to ask.