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Vitamin k and cancer

MagazineAugust 1995 (Vol. 6 Issue 5)Vitamin k and cancer

Q:I read with interest one of your reader's letters regarding vitamin K

Q:I read with interest one of your reader's letters regarding vitamin K. I'm due to have my first baby in five weeks and her letter prompted me to enquire about this vitamin while attending antenatal classes.

I was given the enclosed handout from St Thomas' Hospital in London. I don't know if I have interpreted the figures correctly, but it appears that without "treatment", the chances of developing hemorrhagic disease of the newborn (HDN) are 8.6 in 100,000, whereas, further down in the article it states that 1.4 children in 1000 (140, in 100,000) may develop cancer from taking vitamin K. Am I missing something? M d F, London......

A:Thank you for your handout. In it, the authors, a neonatologist and obstetrician, make an unabashed case for continuing with injectable vitamin K, despite new published warnings about a possible cancer risk.

As you may know, vitamin K is is a fat-soluble nutrient, which is converted into substances that allow blood to clot. Without them, cuts would not stop bleeding naturally, and the normal tiny damage which occurs in blood vessels would lead to internal bleeding. On their own, newborn babies have extremely low levels of vitamin K in their blood or maintained in their liver. If this level of vitamin K is not raised, they could be at a tiny risk of developing vitamin K deficiency bleeding, as it is now called, or, more commonly, hemorrhagic disease of the newborn (HDN). Often it can start as bleeding from the nose or umbilical stump and progress to brain or other internal hemorrhage. This can be anything from a very mild to a fatal condition (about 7 per cent die and 30 per cent suffer mental impairment). Those considered most at risk include premature babies, those born after forceps, "difficult" cesarean sections, those with liver disease or those born to mothers taking anticonvulsant or medication which inhibits blood from clotting.

The conventional wisdom is that babies are most at risk of developing vitamin K deficiency who are exclusively breastfed because breastmilk is low in vitamin A. According to active birth pioneer and primal health researcher Michel Odent, this is only half right. True breast milk is low in vitamin K, but colostrum, the early milk secreted right after birth and for several days afterward, is very rich in vitamin K. One reason that babies suffer from HDN, he suggests, is that they are improperly breastfed that is, taken away from the mother and not put to the breast immediately after being born.

In many parts of the world, hospitals still advise mothers to dispose of colostrum until the "real" milk comes in, or give babies sugar water for the first three days.

According to your handout, giving supplementary vitamin K "reduces the chances of HDN from about 8.6 cases in 100,000 births without treatment to 1.4 cases per 100,000 with oral and 0.1 case per 100,000 with intramuscular treatment."

The doctors then go on to mention the famous study by Dr Jean Golding, conducted at the Institute of Child Health in Bristol, England (and the results reproduced by Golding in a later study), showing that babies receiving intramuscular vitamin K were twice as likely to suffer cancer as those receiving none (BMJ, 1992; 305: 341-46). (Oral vitamin K did not significantly increase the risk.) As you rightly point out, the St Thomas' doctors note that this increased risk translates into 1.4 extra cases of cancer per 1000 children by age 10.

Obviously, these doctors have a problem with arithmetic in assessing the risks and benefits of treatment. To review their own numbers, all babies have a risk of HDN of 0.0086 per cent a fairly obscure percentage. However, according to Golding's research, giving your child a vitamin K shot increases his cancer risk to 0.14. In other words, by getting a vitamin K shot, your baby may be 16 times more likely to get cancer than to get HDN.

But that's if Golding's study is correct. Although she reproduced her findings in a later study, other studies in Sweden (BMJ, July 10, 1993) and the US (N Eng J Med, September 23, 1993) have not been able to.

The fact is, the medical profession seems utterly befuddled by the vitamin K business whether it is better to give it orally, by injection or at all to low-risk babies. The UK Department of Health has stated that the available facts don't offer a "clear consensus" on which form of vitamin K is the safest. Most of the "facts" to date appear to be derived by received opinion, such as the commonly held notion that breastfed infants are automatically at risk.

What appears to be the case is that HDN does not strike healthy babies at random, but seems to be an outcome of another illness or poor nutrition. In a review article about vitamin K, Dr M J Shearer, from the Hemophilia Centre, St Thomas' Hospital in London, classified HDN into early (0-24 hours), classic (1-7 days) and late (two-12 weeks). In early HDN, a frequent cause is maternal drugs (such as anticonvulsants, anti-tuberculosis drugs or warfarin), all of which interfere with metabolism of vitamin K, or any delay in the establishment of breastfeeding. In classic HDN, says Shearer, the cause is unknown in most cases, although maternal drugs again may cause the problem. In late HDN, some children are shown to have an underlying disease, which causes malabsorption, including liver disease or cystic fibrosis, which causes a defect in the absorption of fats. Furthermore, in these late cases of HDN, only rarely had the milk of mothers of affected babies been found to be particularly low in vitamin K concentrations (Eur J Pediatrics, 1988; 147:106-12) which would seem to contradict the conventional wisdom about breast milk being a risk factor.

In a recently published study in Germany polling 100 obstetric units, half the children found to have HDN had cholestasis (impairment of liver bile flow). Furthermore, the incidence of late HDN seems to vary widely between countries affecting, per 100,000 children, 4.4 in the UK, 7.2 in Germany, 10.5 in Japan and a whopping 72 in Thailand. When no vitamin K is given, the risk is three times as high in Thailand than in England again, suggesting an environmental or social cause.

There is also a great deal we don't know about how newborns utilize vitamin K. In one study of all cases of HDN occurring over two years in Britain, one surprising finding was how rare bleeding was in babies during the first week of life when no vitamin K was given the very population supposedly most at risk. However, when this population was biochemically assessed, over half the children in this group were shown to have a deficiency of vitamin K, although it had resolved by their fifth or sixth weeks of life (BMJ, November 2 , 1991). As vitamin K specialists Andrew McNinch, a pediatrician at the Royal Devon and Exeter Hospital, and John Tripp, senior lecturer in child health at the Postgraduate Medical School at the University of Exeter, wrote, "There may be a biological advantage, as yet unknown, for a relative vitamin K deficiency at that time." (BMJ, 1991; 303: 1105-9).

The current experimenting with different doses of vitamin K represents a good deal of stumbling around in the dark. Vitamin K3 was first administered to babies in the 1950s until it was discovered that K3 caused nuclear jaundice in premature babies, or brain damage resulting from high levels of blood bilirubin, causing deafness, mental retardation and involuntary movement (BMJ, November 2, 1991). It also was associated with hemolysis where red blood cells are destroyed. Medicine quickly changed to K1, which appears not to pose this risk. The American Academy of Pediatrics recommended in 1965 that vitamin K be given to all infants at birth, either as a single injection of 0.05 to 1 mg or as 2 mg given orally.

Then injectable vitamin K became the norm in the US and the UK until the Golding studies. But even here, there were problems. In the 1980s, some babies mistakenly received the injection of ergometrine-oxytocin meant for their mothers, in order to hasten clamping down of the womb after the birth of the placenta, with disastrous results.

Although the Golding results have not been reproduced anywhere else, and population studies of the US and Denmark have failed to find an increase in childhood leukemia after widespread use of injected vitamin K, there are several plausible theories as to why it may pose a risk. Golding and her colleagues pointed to several experiments showing changes in chromosomes with high concentrations of vitamin K and the role of the vitamin in causing the carcinogenic effect of benzopyrenes, which occurs in coal tar.

Animal studies have also shown chromosome breakages after vitamin K injections. Then again, the problem may not be the vitamin per se, but the phenol used in the injectable preparation, which could react with the vitamin to cause cancer. Yet another experiment they cited suggested that a slight deficiency of vitamin K could actually protect against tumour growth. Or it could be that an injection itself is the problem, because it exposes newborns to foreign substances like viruses, which may trigger cancer (BMJ, May 16, 1992).

Oral vitamin K

How safe and effective are oral vitamin K preparations? W L, Boston....

Even if they don't believe Golding's findings, Britain and Germany have rushed to embrace the oral variety of vitamin K as an acceptable alternative. The British Department of Health now recommends that doctors switch to the oral variety for low-risk infants, with a dose at birth, a further dose a week later and a third dose six weeks after birth to those babies who are breastfed (formula contains vitamin K).

However, there is now some question as to whether the oral variety works. In a recent study in Germany, of 20 babies who went on to develop HDN, only two hadn't received any vitamin K, and 13 had received the oral type according to the three-step guidelines (although in five cases, the third dose had been overlooked). In total, 10 of the 14 babies who developed HDN after the sixth week had received all three doses. However, 16 of the 20 had some physical problem most often fat absorption or liver malfunction, which may have had more to do with their problem than a missing third dose (BMJ, April 29, 1995).

Two researchers from the Clinical pharmacology division of drug company Hoffman La Roche pooled the German cases with 27 British cases of HDN reported between 1988 and 1990. They concluded that two doses were probably adequate for babies breastfed for only a month and three doses for two months, but for any longer, more doses were probably needed (The Lancet, August 13, 1994).

Doctors have assumed that the injectable variety is more effective because a "depot" is formed at the injection site, from which the vitamin is gradually released. But the evidence suggests that even with the injectable variety, protection doesn't last. In one study of exclusively breastfeeding babies, eight of the 63 given injected vitamin K at birth had evidence of concentrations of a substance in the blood considered to be a marker of bleeding risk (BMJ, 1991; 303: 1105-9).

The final difficulty is that neither the UK nor the US has licensed an oral preparation for babies. At the moment, doctors are using unlicensed preparations, one reason why worried mothers are refusing to comply with the recommended doses. A new "mixed-micelle" formulation for oral use is in the process of being reviewed for licensing to babies, but a good deal of experimentation will have to be done to find the most effective and safe dosage of the new drug (The Lancet, May 7, 1994). A number of doctors are screaming for a long-term study into the safety of vitamin K, but doctors are reluctant to pursue it because they believe it would be unethical to deprive all newborns of the vitamin.

If you are reluctant to have your baby given an injectable vitamin with such question marks surrounding it and he is low-risk of HDN, make sure to specify this before you give birth. Many babies are whisked away for a "routine" check-up and given the jab without your consent. Then make sure to feed your baby right after birth and frequently during the first days so he gets a good amount of colostrum. Thereafter, ensure that you have an adequate intake of vitamin K.

The most important thing to look for is one of a number of types of warning bleeds, such as unexplained bruising, nose bleeds or oozing of blood from the umbilical stump. This can often prefigure a brain hemorrhage, and if you act upon a warning promptly and get vitamin K, you are likely to prevent the massive bleeding. Also, if your baby is still jaundiced at two to three weeks, it may be wise to consider an underlying liver problem (BMJ, April 2, 1994). If you do wish to have the oral vitamin K, you can either follow DoH guidelines or opt to have your baby get further tiny supplements.


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