Countries, such as the UK and USA, have developed guidelines to give the public an idea as to the amounts required for each individual nutrient. These values are commonly known as the Recommended Daily Allowance (RDA). The most up to date guidelines in the UK are the Dietary Reference Values (DRVs), compiled in 1991, which give amounts for various sectors of the population (DoH 1991). Using statistics, different levels have been devised, the upper and most important level being the Reference Nutrient Intake (RNI). This is the level of intake that will cover 97% of the population, i.e. the majority.
The problem with the RDAs is that they differ between countries, and are out dated in respect of modern evidence. They are always under criticism by top scientists, as to what extent they protect against ill health. For most nutrients, the RNI is said to be the figure which the Board came up with to cover frank deficiency for most of the population, whilst maintaining adequate amounts of that nutrient held in body stores for an stated amount of time. Newer evidence has shown new functions and roles for many vitamins and minerals, and higher levels may protect from certain diseases. Many papers have been written looking at optimal intakes, i.e. not just avoidance of deficiency but minimising risk of diseases and, in some cases, maximising performance. RDAs are therefore a starting point and 'safety net', but not necessarily optimal levels.
A good example of controversy is with the mineral calcium. The UK RNI in adults is 700 mg per day (DoH 1991); the US RDA is 1,000 mg a day - a big difference. Calcium is needed in the bone building years to help to protect against brittle bones or osteoporosis later in life. Later studies have indicated the 'optimal' level to be nearer the US figure. This is just an example; many macro- and micronutrients are under controversy. As bodybuilders we are all well aware of the protein requirements issue (discussed in Chapter 3)!
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