One of the most common questions I am asked whenever I teach nutrition to doctors is whether there is a role for vitamin and mineral supplements. Although the question is seemingly straightforward, there is no simple answer. The more one digs into it, the more complex the issues one uncovers.
One thing which is clear is that, whatever we doctors think of it, our patients have already made up their minds. Nutritional supplements are big business, and a significant proportion of the population is taking them. A quick trip to the local health food store will reveal tablets with every imaginable combination of nutrients, doses and formulations. And not just the health store. These days the local pharmacist or even supermarket offers much the same spectacle. Even amongst dietitians - who are supposed to be bastions of nutritional orthodoxy - my anecdotal experience indicates many take supplements.
My initial response when I am asked about supplements is always to point out that the fundamental basis of all nutritional therapy is food. There can be no question about this. Firstly, food is the cheapest therapy. For your malnourished elderly widower patient, it is far better economics to improve his nutritional status by teaching him to eat a breakfast of egg, wholemeal toast and a glass of orange juice than to prescribe him a bottle of vitamin supplements.
Secondly, food is the more logical option. The formulation of most nutrient supplements appears to be based on very approximate, rough or even speculative rationale at best. Most vitamin/mineral supplements contain doses well in excess of those found in food, Even for those built around the recommended dietary intake (RDI) levels, it is sobering to realise that the basis and safety margins involved in setting these RDIs varies greatly from one nutrient to another. So even if we knew mother nature's logic in formulating food, there are few supplements which could claim to mimic it.
Even if the nutrient doses were formulated with impeccable logic, there is the question of how many important nutrients and co-factors there may be in food that we do not yet know about. Such complexity may perhaps explain some of the difficulty that researchers have had in recent times in duplicating the early epidemiological evidence of the benefits of antioxidant nutrients in cancer with controlled clinical trials of supplements.
Thirdly food is the safer option. There is much that we do not yet know about nutrition, but what we do know tells us that the totality of what nature provides in a balanced diet is incredibly complex. By giving repeated artificial doses of specific nutrients we are treading for the large part in unknown waters. This has two potentially dangerous consequences:
1. Direct toxicity: fortunately vitamins appear to be, for the most part, remarkably free of serious side effects, even when given in large doses. However, there are some definite serious hypervitaminoses, such as hypervitaminosis A and vitamin B6 toxicity. We do not know whether there might also be some more subtle toxicity syndromes as yet undiscovered. Mineral supplements have greater toxicity potential than vitamins.
2. Interactive effects: many nutrients interact, for example by competing for the same absorption mechanism. This particularly applies to minerals, whose interactive potential is legion. Giving high dose calcium for osteoporosis, for example, could put iron balance at risk.
Finally, there is the vital element of enjoyment and socialising that goes along with food. Hopefully we will never reach the stage where people sit down to an enjoyable dinner party of vitamin supplements! On a more serious note, the GP is doing their patient a disservice if they deal with any problem of undernutrition without looking closely at eating patterns, and this certainly includes the psychosocial aspects. Whether it be the widower with neither the confidence nor the knowledge to cook, or the busy executive who is burning the candle at both ends, a careful appraisal and improvement of eating lifestyle is an essential component of nutritional therapy. Of course, this may not be as quick and easy as prescribing a supplement, but it is the only truly long term solution.
Nothing that I have said so far means that nutritional supplementation does not have a place in clinical medicine. It certainly does have an important place, which we will consider in more detail in the next article in this series. But that place must be complementary to, not instead of, working with the diet.