Some are easier to swallow

DIETARY supplements date from the mid-1930s, when nutritional science was in its infancy.

Despite the wealth of research since, and notwithstanding their aggressive promotion, the question remains ‘do supplements work?’

Consideration of this question is five-fold:

1. The biological effects of the vitamin or mineral must be established.

2. The levels of intake required must be determined for different population groups (this is contentious, as the amount of a nutrient required to avoid deficiency (eg, scurvy) may be significantly less than the amount required for optimal health).

3. The prevalence of low nutrient intake needs to be determined — there’s no point taking a nutrient in tablet form if you have plenty of it in your diet.

4. Determine whether or not the nutrient can be absorbed as effectively from a supplement as from food.

5. Establish if there is a hazard in taking additional amounts of the nutrient — if there is, the case for supplementation weakens.

Using these five pointers, a few nutrients may have a plausible — if not probable — benefit taken as supplements.

Surprisingly, given the vast array of vitamin pills and potions available in our supermarkets, pharmacies and health-food shops, the number in this “potentially useful” category is vanishingly small.

Bring on the sunshine — vitamin D

One vitamin supplement that may have health benefits is vitamin D. Many Irish adults are insufficient in this nutrient, prompting the Food Safety Authority of Ireland, in 2011, to recommend a vitamin D supplement for everyone. There’s also much research to suggest that optimising vitamin D in this way may protect against serious conditions, including osteoporosis, diabetes, high blood pressure and heart disease, as well as certain cancers.

The vitamin D supplied by most supplements is not only well-absorbed and utilised by the body, but is also provided at a dosage highly unlikely to have any potential toxic effect. So, all told, the case for vitamin D supplementation appears very strong.

Brain food — Omega-3

The argument for supplementation with omega-3 fish oils also looks compelling. Omega-3 has been associated with reductions in blood pressure, inflammation, and certain types of blood fat, as well as decreased risk of several cancers. It’s also been associated with better neurological and cognitive development in children, although the evidence here is less conclusive.

While taking fish-oil supplements can be hazardous for some people (eg, those on blood-thinning agents like warfarin or aspirin), in general, they’re an innocuous way of increasing omega-3 intakes in an Irish population with demonstrably low fish consumption.

Planning for pregnancy — folate

In the case of folate, there may also be merit in raising intakes through supplementation, especially for women planning a pregnancy (folic acid supplements have been proven to lower the risk of birth defects, such as spina bifida), or for those with habitually high alcohol intakes. The latter group invariably have low folate status, which has been linked to increased risk of bowel cancer and cardiovascular disease. This suggests that many people in Ireland (where one in five women, and one in four men, exceed their recommended weekly alcohol intake) could benefit from taking a supplement containing this nutrient.

Doctor’s orders — prescribed supplements

Some nutrients are important in certain patient or population groups (eg, iron in young women, calcium and vitamin D in older women and those with coeliac disease). In these instances, prescription of specific supplements may be a pragmatic and effective means of ensuring adequate supply of these important nutrients.

For most people, though, a good quality multivitamin and multi-mineral is more than enough to meet requirements.

As ever, you should speak with your GP before commencing any supplement, especially if you’re pregnant or suffering from any pre-existing medical condition.

* Dr Daniel McCartney is lecturer in human nutrition and dietetics at DIT.