Supplementation in clinical practice

Part 2

NOTE and DISCLAIMER:

This article is for general interest of qualified family physicians only. It is NOT for their diagnostic or therapeutic use. It is definitely NOT for any public use whatever, nor intended in any way to be taken as advice for any medical or health condition.

To minimise nutrient interactions it is often
desirable to give supplements intermittently

In the last article , we saw that vitamin and mineral supplements must take second place to food in the treatment of nutritional disorders. But this does not mean that there is no place for them.

The proper use of nutritional supplements falls into two broad applications:
(1) Augmental : where they are used to augment dietary intake in the correction or prevention of specific nutritional deficiencies, or of more generally inadequate diet. Typically the dose of supplementation appropriate to such situations would be of the same order of magnitude as the recommended dietary intake (RDI).
(2) Pharmacological : where doses usually well above the RDI are used for a specific pharmacological effect, rather than to make up any deficit in dietary intake.

Augmental supplementation might be used to give an immediate and `dose-loading' effect, for example in a patient where the family physician was concerned about the possibility of neurological damage from B₁₂ or thiamine deficiency. Similarly in an elderly patient with probable zinc deficiency that might be contributing to his poor wound healing. A pregnant woman with low iron stores will often find it very difficult to meet maternal and foetal iron requirements from her diet alone. In fact in any patient who has iron deficiency severe enough to cause anaemia, some months of iron supplementation will most likely be an essential component of their treatment, along with dietary modification.

Patients with acute infection, trauma or burns might have increased metabolic and micronutrient needs but not be in a position to consume even a normal food intake, let alone an increased one. Some patients are simply too haphazard in their compliance, or find it too difficult to make the necessary changes to lifestyle to ensure the necessary increased nutritional intake is achieved. Patients on medication that affects nutrient levels may need some supplementation to ensure adequate tissue levels. The effect of diuretics on potassium and magnesium levels is a good case in point.

Admittedly it is easy to misuse supplements in this situation by making them the quick and easy response to a wide range of possible nutritional problems, without taking proper steps to make an accurate diagnosis or to work on lifestyle modification. The doctor who prescribes supplements without making a proper nutritional diagnosis might well observe a positive subjective response from their patient. But they can all too readily be accused of working with placebo, or worse as practising unscientific quackery. On the other hand, it must be said that there has been a small but increasing and intriguing number of well conducted scientific trials that have shown that it is possible to benefit patients by giving augmental supplements even without any obvious suggestion of nutritional disorder. Several trials in elderly subjects, for example, have shown enhanced immune function and general well-being.

Using supplements in high doses for their pharmacological effect has been even more controversial over the years. Some applications are well accepted, for example the use of niacin to treat hyperlipidaemia. However, many others remain more in the realm of possibility than scientific respectability. Does high dose vitamin C really have a role in the management of acute infection or stress? Will oral zinc shorten the duration of cold symptoms? Does vitamin B₆ assist in the management of pre-menstrual syndrome? Is fish oil good treatment for asthma? Now admittedly it is possible that many of the positive effects seen in such clinical trials could be obtained just as easily with a proper balanced diet. On the other hand, in most of these studies the supplements used were given in doses well above the RDI, and it has yet to be shown that food alone would produce the same outcomes.

A major area of recent interest has been the possible role of anti-oxidant supplementation in the prevention and treatment of degenerative diseases such as cancer and various other inflammatory conditions. There have been many studies in this area which have suggested intriguing applications for such supplements. Unfortunately it must also be said that the overall picture arising from larger scale trials on these applications remains contradictory and has sometimes produced disappointing results.

In the face of such uncertainties, what common sense approach can the family physician take?

• Firstly to ensure that when supplements are prescribed there is a clear indication and rationale in the doctor's mind. Lazy vitamin pill prescribing will not do much for your clinical nutritional acumen.
• Secondly, do not give doses higher than are reasonably necessary to achieve the desired effect and be aware of interactions and possible side-effects when prescribing supplements. For instance, it would be negligent to give high dose calcium supplementation to a woman of reproductive age without taking into account the possible negative impact on her iron balance.

  To minimise such interactions it is often desirable to give supplements intermittently - for example every second day - rather than daily or with every meal.

• Finally, use a supplement prescription as a lead in to talking about food, not as an excuse to avoid it. Educate the patient about the best dietary sources of the supplemented nutrient. If a broad spectrum supplement is being used in an elderly patient, for example, teach them at the same time about simple foods with a high overall nutrient density, such as eggs and peas.

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