Nutritional Requirements

There is a lot of official and semi-official guidance on this question. There are Recommended Daily Allowances (RDAs), Recommended Daily Intakes (RDIs) Reference Nutrient Intakes (RNIs) and Upper Safe Limits (USL). All of these define a position on the above question. The first three are official attempts to advise everyone on the least amount of each nutrient needed to avoid deficiency. The third one (USL) seeks to answer quite a different question, which is “how much is it safe to have?” This last question is posed and answered irrespective of any estimate of how much is needed.

Usually anyone interested in using supplements to maintain or improve health wants a simple answer to the question, “How much should I have?” Unfortunately the answer is not so simple because one needs to take account of individual variation, age and sex and one needs to define what you actually mean by “deficiency”, “maintain” and “improve”. You have to take many more unknown factors into account, such as how much you smoke or drink or how much tea or coffee you consume. You may also need to consider, when dealing with one nutrient, how much you are taking of certain other nutrients. Taking one may depress or enhance the absorption or utilization of another. Then again, not only tea and coffee, but also some foods act as inhibitors of the absorption of some nutrients. The more of these foods you take the higher the intake of the nutrients needed to avoid running short of them.

You cannot have all of these factors evaluated carefully without a very detailed professional assessment. Therefore, all the attempts to evaluate “need” take a broad-brush approach that rides roughshod over the individual differences.

A very important landmark in estimating nutritional requirements in the UK was the publication by HSMO in 1991 of a report of the Panel on Dietary Reference Values. This was a sophistication of previous methods in that the Panel recognised that the average requirements across the whole population failed to meet the needs of those people whose needs were above the average. The average values were listed in the report and were called “Estimated Average Requirements” (EARs). However, the Panel produced a much more useful value called “Reference Nutrient Intake” or RNI. This was defined as “an amount of the nutrient that is enough, or more than enough, for about 97% of people in a group. Whilst this may seem reasonably fair, it really does not help if you happen to be one of the 3% whose needs are not met by this level of nutrition.

The Panel on Dietary Reference Values, in its wisdom, wrote, “If average intake of a group is at the RNI, then the risk of deficiency in the group is very small”. We do not consider that the Panel was necessarily correct here. For this to be true the distribution of intake within the group must be even or nearly so. In point of fact, where you have a population depending upon the diet for supply of nutrients, if the nutrient is very unevenly distributed among members of the population, then there will always be an “underclass” of people who can be quite markedly deficient. This certainly happens in the UK. Where the average intake of a nutrient is very close to the recommended value or just below it (as in the case of magnesium), the distribution is very uneven, depending upon the diets of different individuals or groups, and hence a whole swathe of the population receives intakes at deficiency or sub-clinical deficiency levels.

Therefore, even if we go no further than to consider the avoidance of deficiency, the RNI may not be sufficient, when applied to groups or populations. When applied to an individual, in the admission of the Panel, there is still a 3% chance of being deficient. It is hard lines if you are one of those people.

The RDA and the RDI were earlier attempts to define requirements. These recommendations would keep the majority of the population away from deficiency, but they suffered from the same limitations as RNI.

However, when we are dealing with any of these official figures we are limiting ourselves to trying to avoid deficiency. Being deficient means, to most orthodox nutritionists, having the symptoms of specific deficiency diseases that are associated with many of the individual nutrients. Thus, these recommendations, if we adhere to them, will protect the majority of people from beriberi (in the case of Vitamin B1) or scurvy (in the case of Vitamin C). Sometimes rather more sophisticated biochemical criteria have been used, like in the case of selenium, where the selenium content of a selenium-requiring enzyme has been used as a yardstick.

This is a rather cheeseparing approach to nutrition by which, it often seems, and the government body ends up recommending us as little as possible. As a result, the official recommendations have been reducing over the years. Zinc is a good example. In 1991 the Panel produced an RNI of 9.9mg/d for adult men and 7.0mg/d for adult women. Previously, the USA had arrived at a figure of 15mg/d, which had been widely followed in the UK. In the mean time the zinc content of agricultural crops in the UK had fallen markedly to values that made it hard to obtain from foods much more zinc than the Panel’s new recommendations. The Panel looks independent enough but one sometimes wonders whether the recommendations are being massaged downwards to match the amount that the average person can obtain in food. For all these reasons there is little confidence these days amongst nutritionists, especially alternative nutritionists, that these official recommendations are sufficient to provide the best protection against development of chronic illness in the long term. There is no disagreement that they do protect from deficiency symptoms in the shorter term.

Next one needs to consider a strategy for supplementation. One very common one is to take the RNI amount as a supplement. Since, you have the nutrients in your diet as well, you will be assured that your intake will then be well in excess of the RNI because you have the supplement intake plus the intake in food. That strategy will almost certainly protect against overt deficiency symptoms. But the real question is “How much protection do you want?” If you want even more certain and more thorough protection then you might consider taking twice the RNI.

Then again you can look at particular strategies for different nutrients. In the case of selenium, the UK 1991 RNI values are 60 micrograms (mcg) for a woman and 75 mcg for a man. Yet a strong case can be made for a supplement of 100mcg/d, especially with advancing years, to help to minimise the risk of cancer. Some consider that 200mcg/d should be used, and a few experts even advise 300mcg. Here we hit a very real controversy in nutritional circles between the “orthodox” and “alternative” views. There much evidence that levels of nutrients considerably higher than the RNIs can provide health benefits over and above preventing the signs and symptoms of overt nutrient deficiency syndromes. Yet the Panel on Dietary Reference Values purposely ignored all such evidence and concentrated only on the avoidance of deficiencies. So we must ask, “What is a deficiency?” Is it just enough to avoid an obvious deficiency illness (in the case of selenium this might be Keshan disease) or is it enough to provide really good health and function and relative freedom from acquired chronic illnesses as the years pass?

This inevitably brings us to the Upper Safe Limit because if we increase the intake too much we may encounter overdosing effects with a few of the nutrients. Selenium is a good example. There comes a point at which the increasing intakes cease to give any further benefit and eventually there might be adverse results. It is important to know what these levels are. In the case of selenium estimates of the start of the adverse level vary between 750mcg and 3200mcg so these levels probably should not be used. The Panel on Dietary Reference Values suggested that they did not feel confident of the safety of selenium above 450mcg/d so this is their USL. This is a reasonable figure. Other sources have arrived at different values. This is understandable because this is a matter of professional judgement rather than an absolute measurement. Sometimes these estimates come down far too close to the RNI, in which case we may think that excessive caution is being applied and that the public is then being deprived of beneficial levels of supplement. We note that, notwithstanding the 450mcg level suggested above, up to 1000mcg was used in China in reversing the selenium deficiency of Keshan disease, apparently without adverse effect.

In the case of selenium there are different chemical forms that can be used in supplements. The main difference is between inorganic sodium selenite and the organic forms such as selenocysteine, selenomethionine or selenium yeast. The evidence indicates that organic forms are both more effective per mcg used and also safer at higher intakes than the inorganic form. This should have an effect upon the RNI and the USL but this important factor is usually omitted from official recommendations.

We have said little here about the RDAs. This is because they were replaced in the UK by the RNIs in 1991. However, European recommendations still use the abbreviation RDA. Although these values are not quite the same as the UK RNIs most of what we have said here about RNI also applies to the European RDAs.

We think that when you are looking at nutritional supplements across the board it is reasonable to apply the factor 1.5 times the RNI. When you are looking at individual nutrients that may be taken for specific benefits quoted in the literature one may need higher values to gain the claimed benefits. This is true of Vitamin C, where at least 1000mg/d may be suggested in literature references but the RNI is just 40mg for both men and women. Intakes of 1000mg, being 25 x the RNI, are controversial. They are generally frowned upon by orthodoxy but favoured by alternative medicine sources. The value of the publicised USL, and the desirable chemical form of the nutrient are then important and the matter is not fully settled.

Similarly, there are a number of nutrients for which there is no RNI. Chromium is one such example. The Panel on Dietary Reference Values nonetheless suggested that 25mcg/d would be enough for adults. Yet one has noted distinct benefits from using 200mcg/d and the literature reports up to 400mcg as being necessary for weight reduction and increase in lean body mass. Again, with chromium, different chemical forms behave differently and one needs to be aware of this variable.

Finally, there are many nutrients, especially phytonutrients, that are not considered essential but which are enormously beneficial. In these cases one gets no official help or advice and no RDAs, RNIs or USLs apply. Carotenoids and flavonoids are examples of these. The intake of these is very protective of our health but one can only go on recommendations from suppliers, nutritional experts or literature suggestions.

TABLE A

TABLE B

(Ref: FLR, Schedule 6, Part II Ammend)

Food Labelling Nutrition Information, Regulations 2009, EC Directive 2008/100/EC(amending 90/496/EC)

In force from 30th October 2009; trade in products not complying prohibited from 31st October 2012

N.B. Source claims can only be made if the daily intake provides at least one-sixth of the RDA of the named vitamin or mineral.

Optimal and RNI levels for vitamins:

Optimual and RNI levels for minerals, please note that all levels are given as “elemental weights”:

Table 1:
A comparison of the current HFMA Nutrient Daily Upper Safe Levels (USL) for Supplementation with the daily levels for supplementation proposed by the Food Standards Agency Expert Group on Vitamins and Minerals (EVM) and the USLs for TOTAL DAILY INTAKE from the US Food and Nutrition Board (FNB) and the EU Scientific Committee for Food (SCF).