Studies have found that some B vitamins increase the risk of hip fractures and lung cancer. So are B vitamins harmful? How is it really?
Can B vitamins cause bone fractures?
On July 31, 2019, the Deutsche Apotheker Zeitung (DAZ) published an article (1) with the headline: “Do vitamins B6 and B12 provoke hip fractures?”
Actually, it was previously thought that a lack of vitamin B12 and other vitamins (e.g. folic acid) promotes fractures. Because a lack of these vitamins is associated with an increased homocysteine level – and this is not only considered a risk factor for arteriosclerosis, but also for bone fractures.
How can it be that taking these vitamins is now even more likely to contribute to fractures? In summary, the following was stated in the DAZ:
Not only fat-soluble vitamins (A, D, E, K) could be risky in case of overdose, but also water-soluble vitamins. Until now, it was thought that the latter could also be taken in generous doses since excess would be excreted without any problems, but this is apparently not the case. Because according to a study published in May 2019, the high and combined intake of vitamins B6 and B12 is associated with an increased risk of hip fractures.
Study: High vitamin B doses increase the risk of bone fractures
The Nurses’ Health Study is used in the study mentioned. Based on data from around 75,000 women, it is said to have been discovered that high doses of vitamin B6 and B12 resulted in a 30 to 50 percent higher risk of fractures compared to low doses.
High doses meant the daily intake of more than 35 mg of vitamin B6 and more than 30 µg of vitamin B12 for years.
With low doses, the daily intake of 2 mg of vitamin B6 and 5 to 10 µg of vitamin B12.
Scientists advise: only take B vitamins if you are deficient
That sounds questionable and one would now like advice on how best to proceed in the future in order to avoid the risk of fractures, especially if one wants/must take B vitamins for certain reasons, e.g. E.g. with a vegan diet, with chronic stomach or intestinal complaints (which are often associated with a vital substance and here, especially with a vitamin B12 deficiency), with a proven deficiency or with an increased homocysteine level.
B vitamins protect bones
Of course, taking vitamin supplements alone cannot provoke fractures. Of course, bone health also depends on many other factors (nutrition, the overall supply of vital substances (vitamin D, potassium, vitamin C, silicon, zinc, etc.), exercise, stress, etc.). In studies, however, only a few of these factors are taken into account.
In addition, there are interesting studies that show that taking B vitamins, in particular, can support bone health very well, e.g. B. A double-blind clinical study in patients who had had a stroke and were given B vitamins to prevent another stroke. As a pleasant side effect, this study showed that the vitamins were able to reduce the risk of hip fractures.
We also know from several (!) studies that a low vitamin B12 level combined with a high homocysteine level weakens the bones and increases the risk of fractures. The same applies to low folic acid levels combined with high homocysteine levels.
In a Japanese study, 628 patients aged 65 or older received 5000 µg of folate and 1500 µg of methylcobalamin (vitamin B12) daily or a placebo preparation. At the end of the study, there were only 6 hip fractures in the vitamin group compared to 27 in the placebo group, clearly showing that high-dose B vitamins tend to be beneficial for bones.
Can B vitamins cause lung cancer?
The DAZ also reports that B vitamins (folic acid and vitamin B12) have also been associated with an increased risk of lung cancer for years. Three studies are cited as evidence:
Study 1: Folic acid increases the risk of lung cancer
The first dates from 2009. It discovered that patients suffering from coronary artery disease had higher rates of cancer and death after taking folic acid (vitamin B9) combined with vitamin B12 (800 mcg) for an average of 3.25 years of folic acid and 400 µg vitamin B12). This was not observed when taking 40 mg of vitamin B6 daily. The harmful effect is also not due to the vitamin B12, but to the excessive dose of folic acid, it said.
A year later, however, a study was published in which an even higher and longer folic acid dose (2000 µg for more than 6 years) plus 1000 µg vitamin B12 showed no increased cancer risk compared to the placebo group. This study is not mentioned by the DAZ.
Study 2: Multivitamin supplements
In the second study, which was published 15 years ago, the people took multivitamin preparations (it is not known which ones) but no individual B vitamins, so one cannot draw any conclusions about the effect of B vitamins, especially multivitamin preparations can contain so many additives that it should be considered whether they contributed to the increased risk of cancer. For more information, read e.g. B. here: List of ingredients of a conventional vitamin preparation from the pharmacy
Study 3: High vitamin B12 levels are a risk factor for lung cancer
The third study found evidence that high levels of vitamin B12 in the blood are associated with an increased risk of lung cancer. Unfortunately, it is not specified how high a B12 level must be in order to increase the risk of lung cancer. It is only said that the risk of lung cancer increases by 8 percent for every 150 pmol/L increase in vitamin B12 concentration.
That means e.g. For example, people with a B12 level of 370 pmol/L have an 8 percent increased risk of lung cancer compared to those with 220 pmol/L. For people with 520 pmol/L, the risk would be 16 percent higher than for people with 220 pmol/L. The normal B12 level is said to be between 220 and 665 pmol/l.
This does not mean that one should level off at the lower scale and thus risk a B12 deficiency just to minimize the risk of lung cancer – especially since this per 150 pmol/l vitamin B12 is actually rather low, making it easy to take action can be compensated for by a healthy lifestyle.
Study 4: Vitamin B12 intake and lung cancer risk
The following study was not mentioned in the DAZ. We include them here for the sake of completeness. It dates from 2017 and was published in the Journal of Clinical Oncology ( 20 ). Here it is said that in men taking more than 55 µg of vitamin B12 daily almost doubles the risk of lung cancer (compared to men who did not take vitamin B12 in the form of supplements). That sounds really dangerous!
But if you then look at the data of the study participants, it shows that 92.5 percent of the lung cancer patients were smokers or ex-smokers, so that one should perhaps point out the dangers of smoking rather than laboriously investigate the intake of vitamins.
If you also look at the numbers, you’re surprised that such a study is even heard.
The total number of participants in the study was 77,118 people, 40,069 women, and 37,049 men.
359 women developed lung cancer and 449 men.
Of the 449 sick men, 28 had taken more than 55 µg of vitamin B12 daily, which corresponds to 6.28 percent of the sick men.
Of the approximately 36,600 men who did not get lung cancer, 1,238 had taken more than 55 µg of vitamin B12 daily, which corresponds to 3.4 percent of the lung cancer-free men.
And since 6.28 percent is almost double (1.85 times) 3.4 percent, it is said that the risk of lung cancer is almost doubled if you regularly take more than 55 mcg of vitamin B12. (Note: The number increased by a factor of 1.98 in the study because the researchers eliminated other risk factors (obesity, previous illnesses, alcohol consumption, etc.).)
However, the study result could also be formulated differently: Out of 1,266 men who took more than 55 µg of vitamin B12 daily, 28 men developed lung cancer – but this does not attract as much attention as the sentence: The cancer risk doubles.
How should vitamin B12 be taken?
Study 3 suggests that excessive B12 levels should be avoided. However, excessively high levels should of course be avoided for all values. You want nothing more than a healthy level of all vital substances.
So if you regularly supplement with vitamins, you could e.g. B. Have your B12 levels checked once a year during a medical check-up?
However, the study mentioned always mentions the serum level of vitamin B12. This also indicates inactive B12 forms, e.g. B. the so-called analogs, which have no B12 effect at all. Measuring the serum level is therefore not suitable for determining or excluding a vitamin B12 deficiency, which is why two tests would basically have to be carried out to determine the individually required vitamin B12 dose: The serum level (to rule out high levels for the purpose of lung cancer risk) and the holo-TC value, which only indicates the actually bioavailable vitamin B12.
Pay attention to the right vitamin B12 form!
In addition, the studies do not reveal which vitamin B12 compound was taken at all – the purely synthetic cyanocobalamin (which is usually the case) or natural compounds such as e.g. B. methylcobalamin, adenosylcobalamin, and hydroxocobalamin. Also, Study 3 does not explain whether vitamin B12 levels increased from taking supplements, from shots, or perhaps from other factors.
Since an excessively high vitamin B12 level can have serious causes, it should be clarified in any case.
Does cancer cause high vitamin B12 levels?
The website of the Memorial Sloan Kettering Cancer Center (a private cancer clinic in New York, which is part of Cornell University) also points out ( 13 ) that an increased vitamin B12 level can also be cancer-related, i.e. caused by cancer because in this case the cobalamin metabolism changes (cobalamin = vitamin B12). So it doesn’t necessarily mean that vitamin B12 supplementation causes cancer.
Although the vitamin B12 level in the above study was determined before the diagnosis of lung cancer, it could well be that cancer affects the metabolism at a stage that is not yet diagnostically conspicuous.
How much vitamin B is in vitamin B complex preparations?
The usual vitamin B complex preparations usually contain no more than 2 to 10 mg of vitamin B6, but not the high doses (35 mg and more) that are warned against. Special high-dose preparations are used therapeutically and as a cure, but not for years, as in the study on which the DAZ relies.
According to official information (DGE, German Society for Nutrition), the daily requirement of vitamin B12 is now (since 1/2019) 4 µg (previously it was 3 µg). Vitamin B12 is usually contained in vitamin B complex preparations in precisely these doses, e.g. B. in the vitamin B complex from effective nature.
However, vitamin B12 is often offered in daily doses of 1000 µg. These high doses are important for many people who cannot properly absorb vitamin B12 due to absorption problems (e.g. stomach problems, taking acid blockers or metformin, etc.) and who would develop a deficiency with lower doses.
When taking such high doses of B12, B12 can be absorbed in the intestine by passive diffusion, so it is no longer exclusively dependent on specific transporter proteins (intrinsic factor, IF), as is the case with small doses. In general, no more than around 1 percent, i.e. approx. 10 – 12 µg, are absorbed through passive diffusion.