Vitamin D supplements mostly wasted

Sales of vitamin D sky-rockets but is it a necessary expense?

Are you one of the many people taking vitamin D supplements just to be on the safe side? Wouldn’t surprise me since evidence points to an exponential growth in the use of vitamin D supplements with sales increasing more than tenfold in the USA during the period 2002—2011, from US$42 million to US$605 million. Or maybe you have even gone to your medical practitioner to test your vitamin D levels? Also increasingly popular with a six per cent increase in testing volume year on year expected. Australia alone spent about A$150 million a year on vitamin D testing, despite limited knowledge about optimal levels and the unreliability of the test.

It might be worthwhile to first ask yourself if you spend less than ten minutes out in the sun each day or are always meticulous in covering up your entire body. Because most of us are self-sufficient in the production of vitamin D with ten minutes in the sun sufficient to produce our daily need. This is a bit of an anomaly since the definition of a vitamin is that they are vital nutrients that cannot be synthesized by the body, are required in limited amounts to sustain life, and must be obtained through the diet. But vitamin D is an exception.

Vitamin D is important

Don’t get me wrong. Vitamin D is important for several bodily functions. First and foremost it is needed to maintain strong bones. It does that by regulating the absorption of calcium and phosphorus. Deficiency can lead to rickets in infants or osteoporotic fractures in the elderly. There are also non-skeletal actions of vitamin D with suggestions that deficiency might result in a higher incidence of cancer, cardiovascular diseases, diabetes, infections, neuropsychiatric disorders, and a higher risk of death.

Thus it seems to be a clear case for keeping vitamin D at adequate levels. The range of potential benefits have led to calls for widespread vitamin D supplementation. But now to some puzzling findings.

Review of existing findings

A recently published report reviewed the outcomes of a number of trials testing vitamin D supplements for the prevention of myocardial infarction, stroke, cancer, or hip fracture in seniors in general. It found that taking vitamin D did not lower the incidence of these diseases. Of skeletal endpoints, only a clear reduction in the risk of hip fracture was seen for the combination of calcium and vitamin D in elderly nursing home residents. Vitamin D supplementation without the addition of calcium did not reduce hip fracture or total fracture risk.

In terms of harm, there is uncertainty as to whether vitamin D without calcium might actually increase the risk of hip fracture.

It has also been stated that without stringent indications there is a legitimate fear that vitamin D supplementation might actually cause net harm.

So what is a common person to believe?

Elderly people in residential care might benefit from vitamin D supplements.

The take-away message seems to be that there is little justification currently for prescribing vitamin D to prevent heart attack, stroke, cancer, or fractures in otherwise healthy people living in the community. Possible exceptions could be people who truly have very low levels of vitamin D, frail elderly people living in residential care, people who actively avoid the sun, and people with deeply pigmented skin.

In an even more surprising comment, the research team claimed that the body of evidence is already sufficiently large to conclusively state that vitamin D supplementation is of no use to most people and that future trials will not change that conclusion. This is a bold statement from scientists who are often keen to emphasise remaining uncertainties and the need for more research.

Despite such clear advice, research funding bodies continue to support new studies of the effects of vitamin D supplementation. The same month that the review was published, a new five-year study was launched in Australia, the sun-drenched nation, funded by the National Health and Medical Research Council. A bit of an irony, don’t you think?

References

• Controversy in vitamin D supplement (Deccan Chronicle)
• Study of Vitamin D supplements for older people (SBS World News Australia)
• Vitamin D and its role in maintaining bone health (Nursing Times.net)
• Vitamin D for bone health and little else, says Lancet (The Age)
• Testing whether vitamin D delays onset of diabetes (MedicalXpress)
• Vitamin D: Do You REALLY Need to Supplement? (She Runs Strong)

Eat less plastic with your food

Bisphenol A can be found in soup-can linings (Photo: Robert Couse-Baker)

We have covered the issue once before in case you wonder. All the extra things you get with your food. You can read the previous blog on ink migrating from the colourful outer box into your breakfast cereal as an example. But there is also phthalates used as plasticiser in plastic wrapping that can find their way into cheese. And the topic of this blog: bisphenol A used in the protective lining of food-cans moving into canned soup. So it is obvious that we eat a lot of unintended components even if not chewing directly on the plastic cover.

Are you with me so far?

Plastic component tolerance lowered

Now the European Food Safety Authority (EFSA) has published a long anticipated further review of the potential dangers of bisphenol A. Bisphenol A is used as a component in polycarbonate plastic drink-bottles, epoxy resins used as food-can linings, and in thermal paper used as cash register receipts. There are two ways, oral (eating the soup) and dermal (holding the receipt), that we can get exposed to bisphenol A, with the oral route clearly dominating.

In reviewing past and current research literature, EFSA concluded that the tolerable daily intake (TDI) for bisphenol A should be lowered from its current level of 50 µg/kg bodyweight per day to 5 µg/kg bodyweight per day and be set on a temporary basis because of uncertain scientific results. This is a huge change, lowering the tolerable limit by a factor of ten, but of course it is not going all the way to proposing that bisphenol A should be banned from food contact materials.

Is this conclusion a good or bad thing?

EFSA experts reviewed 450 scientific reports on bisphenol A (Photo: J Brew)

Well, not that easy to say.

After diligently reviewing another 450 scientific publications on top of what they covered in a previous opinion, the EFSA experts are clearly still confused. They rightly claim that some reported adverse findings are obscure and not scientifically rigorous enough to be fully trusted. But they also note that these findings get repeated by other scientists, a sign of increasing validity. Although too early to rely on, the EFSA experts are sufficiently worried to lower by a factor of ten the levels of bisphenol A intake humans can tolerate on a daily basis without showing adverse effects. And they also claim that this is only a temporary recommendation while awaiting new scientific results in the pipeline that might require more serious action.

Industry, in its usual fashion, has been quick to interpret the new opinion as supporting the continued use of bisphenol A in food contact materials without restrictions. They base this conclusion on the fact that the new suggested tolerable limit is higher than the highest exposure levels calculated by EFSA by a factor close to five.

So the good thing is that even with the lower tolerable daily intake proposed by the EFSA experts, the safety margin to the actual levels of bisphenol A consumed is sufficiently large to not be of concern.

But the bad thing is that adverse scientific findings are accumulating using much lower doses. As a consequence, the EFSA experts only set the new tolerable level on a temporary basis and flagged that they will need to review the situation again in the near future.

What are the concerns?

This is going to be a bit technical but hang in there. You see, you have an opportunity to influence the final wording in the EFSA opinion. It is just a draft and open for consultation until 13 March 2014.

The dual mountain peak (or non-monotonic) effect (Photo: Frank Kovalchek)

The final view will depend on how to interpret findings of low dose and non-monotonic effects. So far EFSA has based its opinion on changes in male mouse kidney weight as the critical endpoint. This is a straight linear effect, that is the higher the dose of bisphenol A the more serious the results. This is the way toxicologists like to see their results as they have tools to transform such results into dose levels relevant to humans. Unfortunately, the scientific debate is currently focussed on the endocrine effects of bisphenol A, which might adversely impact physical, neurological and behavioural developments. And those effects might be seen at very low doses only or even increase again with a diminishing dose. The low dose or the non-monotonic (the dual mountain) effects.

Doesn’t make sense?

Let me explain with a hypothetical scenario.

You have your first cup of coffee of the day. The caffeine will pass the blood-brain barrier and the initial high levels will saturate your adenosine receptors in the brain. As a result you will feel alert and can get on with the job of the day. But a couple of hours later you also start to feel happy. Not because of your work accomplishments but because the lower levels of the remaining caffeine has now activated dopamine that was previously blocked by the higher levels.

This outcome will be different depending on the connections between the two reactions. It might simply be that you unmask a new effect only at low doses. Or you could see the dual mountain effect in that you actually have two dose peaks, one low and one high with a valley in between. This is difficult to test for in animal experiments but very important in case it is the low doses that have the adverse effect.

Don’t worry, it is confusing scientists too!

This is currently confusing scientists with no clear guidance so far on how to handle such situations. Should you wait and see or take immediate action even if you believe the results look a bit suspicious?

The EFSA experts selected the wait and see approach which makes sense as they believe new results will soon be available. However, there is no guarantee that the new results will be clearcut and we will be back at square one.

Experts at the French agency responsible for food safety, ANSES, took the opposite approach, suggesting immediate action. They reached the conclusion that bisphenol A exposure was associated with proven effects in animals and suspected effects in humans, also at levels of exposure below currently suggested thresholds. Specific risk situations were considered for pregnant women and their unborn children. The ANSES experts believed that there were potential links between low level bisphenol A exposure in the womb and later mammary gland tumours, dysfunctional behaviour, metabolism changes, and obesity. This also makes sense considering that bisphenol A is an endocrine disruptor and could reasonably be expected to act in this manner.

So who is right?

Don’t look at me, I have no idea. But I do believe that the dual mountain effect is real. It is not easy to break away from a consensus view among food safety agencies as the ANSES experts did. We can only hope that new scientific results will be timely and unambiguous to break the deadlock.

In the meantime you can make your own soup and avoid plastic water bottles. That’s good for the environment, if nothing else.