If the reference adult is not you, the next question is what the percentages are actually telling you. This is the part almost everybody gets wrong, in both directions.
An RDI is a target, not a ceiling
The Recommended Dietary Intake is the amount that meets the needs of nearly everyone in a group. It is set generously on purpose, so that it covers people at the higher end of normal requirement rather than the average.
Which means it is a floor to clear, not a limit to stay under. A product showing 150% of an RDI is not overdosing you. It is giving you half as much again as a figure that was already set to cover almost everybody.
This trips people up constantly, and it is the reason the percentage column causes more anxiety than it should.
The number that actually matters
The figure that describes a ceiling is called the Upper Level of Intake, and it is a completely separate number.
It is the highest regular daily intake unlikely to cause adverse effects in most people. For most nutrients it sits a long way above the RDI. Vitamin B6 has an RDI around 1.3mg for adult women and an Upper Level of 50mg. Zinc has an RDI of 8mg for women and an Upper Level of 40mg. Iron has an RDI of 18mg for women 19 to 50 and an Upper Level of 45mg.
So there is a wide band between having enough and having too much, and most products sit comfortably inside it.
Where it stops being comfortable
Australia sets maximum permitted quantities for vitamins and minerals in formulated foods. That keeps products made here well clear of the Upper Levels without you having to think about it.
Plenty of countries do not have equivalent limits. Imported powders and greens blends are often formulated to a different rulebook, and some are sold specifically on how much they contain, which is not a virtue in itself.
The nutrients where this matters most are the ones that accumulate or interfere with something else. Zinc taken at high levels over time interferes with copper absorption. Fat soluble vitamins, A, D, E and K, are stored rather than excreted. Vitamin B6 has documented risks at sustained high intake.
The five second check
Look at the percentage column on anything in your cupboard. Anything well over 100% is not a problem in itself, so do not panic at the number.
Instead, ask two questions. Where was this made, and is the amount anywhere near the Upper Level rather than the RDI?
If you cannot answer the second one, that is a reasonable thing to take to your GP or pharmacist rather than guess at. The Upper Levels are all published on the NRV website if you want to look them up yourself.
The takeaway: An RDI is the amount that covers nearly everybody's needs, so over 100% is normal and usually fine. The Upper Level is the number that describes a ceiling, and it sits far above the RDI for most nutrients. Australian made products are held to maximum permitted quantities. Imported ones may not be, which is the case worth checking.
The science behind this post:
- National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand. Definitions of Recommended Dietary Intake and Upper Level of Intake, and values by nutrient, sex and life stage. nrv.gov.au
- National Health and Medical Research Council. Nutrient Reference Values: Upper Levels of Intake. Vitamin B6 50mg per day, zinc 40mg per day, iron 45mg per day for adults. nrv.gov.au
- Australia New Zealand Food Standards Code, Standard 2.9.4: Formulated supplementary sports foods, and associated schedules setting maximum permitted quantities for vitamins and minerals. foodstandards.gov.au
- Australia New Zealand Food Standards Code, Schedule 17: Permitted forms and maximum amounts of vitamins and minerals that may be added to food. foodstandards.gov.au