Vitamins: Kendrick on which ones you really need and why!

Confused about which vitamins to take or if you need to take any at all? You are not alone. Just ask Scottish GP Dr Malcolm Kendrick. Kendrick is a heart specialist as well as a GP, author, speaker and sceptic. That doesn’t mean he calls himself a cardiologist.

However, he knows a lot more than most cardiologists know when it comes to the real causes of heart disease. He also knows more than many doctors about the effects of diet on heart and overall health.

In this feature, Kendrick meant to write about stress, mental health and heart health. Instead, he says that people keep asking about vitamin supplements. So he looks at which ones really are likely to make a difference to your health. And he looks at why the pharmaceutical industry is so keen to persuade you not to take vitamins. You may be in for a big surprise. – Marika Sboros

By Malcolm Kendrick

I must say that I do like vitamins, I like the idea of them. And my mother did make me take vitamin C tablets every morning. So, perhaps she is to blame for my early age mental programming.

However, there is very little good evidence that any vitamin supplement is beneficial. In large part, this is because there are not huge profits to be made from selling vitamins, as they cannot be patented.

Dr Malcolm Kendrick

If a company did a major clinical trial on vitamin K and found that it saved lives, there would be nothing to stop anyone else selling vitamin K, whilst claiming the newly discovered health benefits for themselves. The company that took the financial risk and funded the trials would be unable to recoup any research costs.

Another factor in play here is that the pharmaceutical industry is doing its level best to attack vitamins as damaging and dangerous. The industry is lobbying madly to have vitamin supplements banned.

Once they achieve this state of Nirvana, they can then invent new synthetic vitamins, patent them, and sell them back to us as hugely inflated prices, making massive profits.

I just made that bit up, but I wouldn’t put it past them. What they are more likely to do is to add vitamins to various other drugs, to extend patent life. As Merck attempted to do with statins and niacin – and failed.

Another of the problems in trying to get a handle on the potential benefits of vitamins is that it can be very unclear what the optimal dose, or blood levels, might be. This, I believe is because of the way that doctors first discovered vitamins.

Over many hundreds of years, they noticed that some diseases occurred when “something” was missing from the diet. Scurvy was the first of these diseases they documented. In 1753 a Scottish surgeon first proposed that lemons and limes could prevent and/or cure the condition.

Obviously, he had no idea what it was in the limes and lemons that did the trick.

Doctors identified other diseases such as pellagra and rickets as being due to a lack of a substance, of some sort. They coined the term for theses missing substances “vital – amines”. Shortened to vitamins.

It took some time before researchers isolated the vitamins themselves. The first was vitamin B1,in 1910, the last was vitamin B12 in 1948.

Scientists generally accept that there are 13 vitamins, many of them are B vitamins, of one sort or another. However, in my opinion there are only 12. Vitamin D is really a hormone.

I think people only classified vitamin D as a vitamin because no-one knew that the body could synthesise it in the skin, from sunlight. Whilst people lived mainly outside, there was no vitamin D deficiency. It was only when the industrial revolution started, and people began to live and work indoors that rickets, (bent malformed bones) became an epidemic. A lack of vitamin D in the diet was identified as the cause.

Thus, Vitamin D looked and acted like a dietary vitamin deficiency. But it was not actually a dietary vitamin deficiency. Or at least only in part.

Click here to read: You need 5-a-day fruit and veg? No you don’t!


To prevent rickets, parents gave their children milk. Unfortunately, we are now seeing rickets again, because darker-skinned Muslim women now fully cover up their skin, and some of them are becoming severely vitamin D depleted.

(editor’s note: Kendrick has added an addendum on the benefits of magnesium supplementation.)

The reason for this ramble is to make the general point that researchers only identified vitamins when they identified major, immediate, and potentially life-threatening illness. Which meant that the first task was the find the dose, or blood level, that prevented things like scurvy and rickets and pellagra.

At the time researchers were not looking for longer-term effects, eg, prevention of CVD (cardiovascular disease), or cancer, or suchlike. Which means that there is no recommended daily allowance that takes optimal health into account.

I sometimes think of the recommended daily intake (RDI) of vitamins as being just enough to keep you alive, but no more. A bit like having a houseplant that is small and shrivelled. But if you give it some form of plant feed, it bursts into vigorous growth and is far healthier.

Unfortunately, because we have these hallowed recommended daily intakes, the medical profession views vitamins as very simple things. You give the vitamin, make sure it gets above a baseline level in the blood, and that’s that. Nothing to see here, move along.

But if we look at just vitamin B12, the reference range (normal range), is all over the place. In the UK is set at 110 – 900ng/l (It is higher in some regions). In the US is it between 200 – 900ng/l, and in Japan 500 – 1300ng/l.

With a level of 110 in Japan and the US, doctors would immediately give you additional B12. However, in the UK they would ignore you. “Your level is fine, go away.”

I have seen many patients who strongly believe that they need additional Vitamin B12 injections, as they feel tired, depressed and suchlike. The NHS simply ignores, unless they have a level below 110.

Perhaps I should advise them to emigrate to Japan.

An additional problem with vitamin B12 is that the synthetic Vitamin B12 normally used is called hydroxocobalamin. The body then converts this into the active form, methylcobalamin.

However, some people cannot metabolise into methylcobalamin and need methylcobalamin injections. Which they cannot get on the NHS. Jolly good.

Yes, the more you look into the area, the more complicated, and frustrating, it gets.

Vitamin D is the vitamin most in the news at present. The debate and arguments about vitamin D are becoming quite vitriolic.

Some doctors refuse to believe that anyone has a true vitamin D deficiency. Others think that the entire population needs to be dosed with added vitamin D during the winter months. I am very much in the latter group.

For example, researchers have only recently discovered that vitamin D has potent anti-cancer effects and may reduce the risk of CVD. What level of vitamin D would you need to provide these benefits? Almost certainly a much higher level than that required to prevent rickets.

Have researchers ever established this level? No. What about the risk of developing thin bones in old age? No.

Even more recently, a low level of vitamin D has been associated with a much higher level of hospital admission with acute asthma. What level would you need to prevent this happening? No idea. As the potential benefits of vitamin D continue to pile up, the minimum blood level remains unchanged and, it seems, unchangeable.

Moving to folate which, despite its name, is another B vitamin. Folate is known to be essential to prevent neural tube defects in the unborn child and to produce red blood cells and suchlike. Again, researchers have established the doses to stop these things happening.

However, a recent study in Cambridge has shown that B vitamins, including folate, have significant benefits in reducing homocysteine levels. And if you give them in high doses, way above those currently recommended, they may delay, or even prevent, Alzheimer’s disease and reduce, or prevent brain shrinkage.

So, what is the correct dose of folate? Enough to stop neural tube defects, or anaemia, or enough to stop Alzheimer’s?

Can vitamin K prevent atherosclerotic plaques from becoming calcified? Who knows, they have never tested the correct formulation. Can vitamin C reduce the risk of CVD? Who knows?

It was tested once in humans, at the wrong dose – at least the wrong dose according to Linus Pauling.

We haven’t the faintest clue about the correct doses, and blood levels of vitamins, required to achieve optimal health. What I do know is that you can take far more than the recommended daily dosage with no problems whatsoever. Vitamins are almost entirely safe. In the US, in 2010, for example, not a single person died from taking a vitamin.

On the other hand, you may be interested to read about the total burden of damage and deaths due to correctly prescribed pharmaceuticals. Here, from Harvard University:

“Few know that systematic reviews of hospital charts found that even properly prescribed drugs (aside from misprescribing, overdosing, or self-prescribing) cause about 1.9 million hospitalizations a year. Another 840,000 hospitalized patients are given drugs that cause serious adverse reactions for a total of 2.74 million serious adverse drug reactions.

” About 128,000 people die from drugs prescribed to them. This makes prescription drugs a major health risk, ranking 4th with stroke as a leading cause of death. The European Commission estimates that adverse reactions from prescription drugs cause 200,000 deaths; so together, about 328,000 patients in the U.S. and Europe die from prescription drugs each year. The FDA does not acknowledge these facts and instead gathers a small fraction of the cases.

Zero deaths, versus 328,000 per year. If I were truly looking for something dangerous to ban, it sure as hell would not be vitamins.

So, which vitamins would I recommend taking? My own view is, take vitamin D in the winter, vitamin C always, along with thiamine and Vitamin K2. About five to 10 times recommended daily intake should be fine.

What of other supplements, such as magnesium, co-enzyme Q10, potassium, L-arginine, L-carnitine, Omega-3 fatty acids, and suchlike. Well, I am keen on potassium, very keen. I first noted research associating higher potassium consumption with significantly reduced mortality in the Scottish heart health study.

This was not some minor difference either. We are talking more than a 50% reduction in overall mortality in men. Lesser effect in women. This was far from an isolated finding. In study after study, potassium reduces blood pressure and, in turn, reduces the risk of CVD and overall mortality. Interestingly, the Mediterranean diet, such as it exists, tends to be high in potassium7.

As for magnesium. Experts increasingly recognise magnesium as a major health issue that can greatly increase the risk of sudden cardiac death. I now routinely test patients for magnesium levels. As does the rest of the health service, which has belatedly woken up to the importance of this chemical. Magnesium deficiency can also trigger atrial fibrillation (AF) which, in turn, vastly increases the risk of stroke.

But I feel I am running away with myself a bit. I need to stop, and take stock. The last thing I want people to do is to worry too much about the levels of this and that in the blood. I do not want you rushing to the doctor or private lab to have everything repeatedly checked.

Magnesium level deficiency for example. This is almost unknown if you do not take an acid-lowering drug such as omeprazole, or lansoprazole (both proton pump inhibitors (PPIs)). Unless you are taking one of these or any other “zoles” long term, you are extremely unlikely to be magnesium deficient.

As for potassium, get some lo-salt (a mixture of potassium and sodium chloride), or eat lots broccoli and bananas, and you will be fine. Other vegetables are available.

What of Omega-3 fatty acids, the fabled fish oil. There is some good quality evidence that they can be good for you. And they seem to have beneficial effects on the conduction of electrical impulses in the heart.

They are mildly anti-coagulant, a bit like aspirin with fewer downsides, such as causing blood loss from the stomach. They also have some benefits on brain function.

So, should you take an Omega-3 supplement? Easier, I think, to eat fish once a week. Sardines on toast is my favourite. But if you feel the need to buy Omega-3 supplements, go ahead. The only downside is cost.

A few years ago, a small company that wanted to create a combination pill to reduce the risk of CVD contacted me. They asked me to give them some medical input and support, which I did, but they ran out of money. Before going bust, they did produce a few thousand tubs of Prokardia. A tablet that contained:

  • Vitamin K2 5µg
  • Thiamine 7mg
  • Folic acid 7µg
  • Potassium 50mg
  • Magnesium 50mg
  • L-arginine 600mg
  • L-carnitine  50mg
  • L-citrulline 7mg
  • Co-enzyme Q10 3mg

The L-arginine and L-citrulline on that list are “co-factors” for the production of nitric oxide (NO) in endothelial cells. Co-enzyme Q10 is something I have talked about at some length, and L-carnitine is an amino acid that has many benefits in cardiovascular health.

I would have added vitamin D and vitamin C to this list. But you can only get so much stuff in one tablet before it becomes a meal in itself.

I would have been more than happy to promote Prokardia as a supplement. It could do no harm and everything on that list was potentially beneficial for heart health. Unfortunately, Prokardia does not now exist.

However, if you took these supplements, in these doses x4 (you were supposed to take four tablets a day) you would not go far wrong.

Having said all this, I do not want everyone to get too carried away with supplements. I have read articles supporting supplement after supplement and every single vitamin that exists in high doses.

However, it can all get a bit ridiculous.

Eat good, natural foodstuffs, and it should be possible to get everything you need in the diet. After all, that was what we were designed to do.

Our ancestors did not go around searching for potassium supplements, or L-citrulline. It was all right there, in the nearest woolly mammoth. All you needed to do was catch it.