How to store supplements: a practical guide and expiry dates

The two places where supplements most often end up are also the two worst places to store them: the bathroom cabinet and the cupboard above the hob. The line you find at the bottom of the label — 'store in a cool, dry place, away from light' — is information required by law, and it is the condition that validates the date printed on the packaging.

Then there's the part that is decided beforehand, by the container. Below you will find a practical guide — where to keep them, what to avoid in summer, when the fridge is needed, how long they last — and then the three properties that made us choose amber glass, with the data.

Light, heat and humidity: why a supplement degrades

LIGHToxidation
HEATfaster reactions
MOISTUREhydrolysis and caking

Closed packaging, in a cool, dry place, protected from light

A supplement is a collection of molecules, and molecules react with the environment they are in. Three factors cause almost all the damage: light, heat and humidity.

Light carries energy. The ultraviolet and blue wavelengths are enough to initiate oxidation reactions in the most reactive molecules: carotenoids, with their long chain of double bonds, and reduced chemical forms, which by definition are ready to donate electrons. The research literature shows this well for a carotenoid, astaxanthin: in a study on natural astaxanthin powder stored for eight weeks, air and full light were found to be the two factors with the greatest effect, and the combination of light, air and 45 °C oxidised 97% of the pigment; darkness, the absence of oxygen and 25 °C were the best conditions [1]. In a second study, conducted at the University of Verona on astaxanthin extracted from the alga Haematococcus pluvialis and microencapsulated, after 52 weeks, 94% remained when protected from light and in the fridge, compared to 57% at room temperature with light and oxygen [2]. These are different matrices from our capsules, and they serve to document the principle: in the dark, these molecules last longer.

Heat speeds everything up. Every chemical reaction, including those you don't want, runs faster when the temperature rises: oils, for example, go rancid sooner in summer. Heat also acts on enzymes in another way, because an enzyme is a protein and its function depends on the three-dimensional shape it has assumed: heat it enough and that shape is lost.

Humidity is the most underestimated. Water that enters a jar that is opened and poorly resealed triggers hydrolysis reactions, causes powders to clump, softens tablets and can make capsules stick together. Tablets that dissolve in the mouth are the most sensitive of all, because they are specially made to dissolve quickly on contact with water: the Melatonina Sublinguale 1 mg and the Vitamina B12 Sublinguale should be taken from the jar, which should then be re-capped immediately and tightly.

From this, one can understand why some molecules require a better container than others: a carotenoid dissolved in oil, the reduced form of coenzyme Q10, an antioxidant vitamin, an enzyme — that is, a protein — degrade precisely because of light, heat and humidity. The answer is the same for all of them, and it is the reason why we package every product in the same way: a container that keeps all three out.

Where to store supplements at home: the right places and those to avoid

BATHROOM (humidity + heat, not recommended)
KITCHEN (humidity + heat, not recommended)
BEDROOM (jar, suitable)
PANTRY (jar, suitable)

Cool and dry, away from steam and stoves

The bathroom is the worst place, and it's the one almost everyone uses. Every shower fills the room with steam, the temperature fluctuates, and the cabinet above the sink collects moisture for hours. The kitchen comes a close second, if the jar is in the cupboard above the hob or next to the oven: there, heat rises every time you cook, and with the heat comes steam. A study that mapped temperature and humidity in 35 rooms in Saudi Arabia found that bathrooms and kitchens were indeed above 25 °C over a 24-hour period [3] — the climate is harsher than ours, but the order of the rooms doesn't change.

The right places are the most obvious ones: a drawer or a closed cabinet in a bedroom, a shelf in the hallway, a cool pantry away from appliances. Somewhere dry, without direct light and without temperature fluctuations. If keeping them in sight helps you remember to take them, bring them to the breakfast table and then put them away again.

A recommendation that applies to all supplements and is found on every label: keep out of the reach of children under three years of age. A high drawer or a cabinet with a closed door solves this issue, along with that of light.

Supplements in the fridge: when to and when not to

The fridge seems like the safest solution, but often it is not. It's cold, but it's also the most humid environment in the house, and every time you open the door, the warm air that enters forms condensation on the cold surfaces — including the container. For a powder or a tablet, that condensation is a problem, not a form of protection.

The rule is simple: only things that the label explicitly states should be kept between 2 and 8 °C should go in the fridge, typically some live lactic ferments and some liquid preparations. Oils rich in omega-3, such as fish oil and cod liver oil in bottles, also do well in there: once opened, the cold slows down their rancidification. For everything else, room temperature is fine, as long as it is stable. None of our products requires refrigeration: they are fine in a cool, dry cabinet, with the cap closed.

Supplements in summer, when travelling and in the car: how to protect them from the heat

The passenger compartment of a car parked in the sun is the most hostile place for a supplement: in the study cited above, dashboards exceeded 70 °C [3]. A container forgotten in the glove compartment or in the boot during a day at the beach will be exposed to that temperature for many hours, and no packaging is designed to withstand it.

For long journeys, a cool bag is sufficient, without ice in direct contact. On a plane, the supplement should be carried in your hand luggage, in its original packaging. On holiday, the same rule as at home applies: a drawer, never the windowsill.

The weekly pill organiser deserves a separate mention, because it is very convenient and has a specific limitation. Transferring tablets to a transparent plastic compartment means removing them from the container that protects them from light and moisture. For two or three days, keeping it closed and in the shade, it is perfectly fine; as a long-term system for weeks, no — and for orodispersible tablets, it is best to avoid it altogether.

Amber glass jar or plastic: why packaging is half the battle for preservation

So far, we've covered the part that depends on the person keeping the container at home. The other half was decided by whoever chose that container. Amber glass works on three different fronts, and its strength lies in covering all three at once.

It blocks light in the relevant band. The amber colour absorbs ultraviolet and blue light, i.e. the very wavelengths that trigger photo-oxidation. This is a codified criterion: the European Pharmacopoeia, in the chapter on glass containers for pharmaceutical use, requires coloured glass for non-parenteral preparations not to transmit more than 10% of light at any wavelength between 290 and 450 nanometres. The effect can be seen in experiments. In a study on vitamin K1, a notoriously photosensitive molecule, the solution stored in clear glass bottles on a bench illuminated by fluorescent and natural light degraded with a constant of 0.31 per day, while in the amber glass bottles, it remained stable for at least thirty days; the authors conclude that packaging and storage conditions that block light remain the most effective way to maintain photostability [4]. A group from the University of Calabria reached the same conclusion regarding linseed oil subjected to light stress according to ICH guidelines: after 18 hours, the main fatty acids had dropped to 62–67%, and the amber glass containers significantly increased stability [5].

It lets nothing through. Glass is impermeable to oxygen and water vapour. Plastics, to very different extents depending on the polymer and thickness, are permeable: they slowly let in moisture and oxygen throughout the product's life. For a tablet that must remain dry and for an oil that must remain unoxidised, this is a difference that accumulates over the months.

It leaches nothing into the contents. Glass is chemically inert: it is in contact with the product without exchanging anything with it.

There is one point that needs to be made precisely, because you often read the absolute statement that ‘glass protects against light more than any plastic’, and this is not the case. A study that compared the light transmission of clear glass, amber glass, amber PVC and semi-opaque polyethylene bottles found that semi-opaque plastic and amber PVC provided more shielding than amber glass, with differences also related to thickness [6]. The advantage of amber glass, therefore, is the sum of three properties: a plastic may shield light well, but it remains permeable to gases and moisture, and can leach components into the contents.

Our choice, in full. All NUTRALAB products are packaged in tempered amber glass jars with an aluminium lid: no plastic is in contact with the product. Inside the jar, you will find a small white cylinder: it is a desiccant canister, used to absorb residual moisture and any that enters each time the jar is opened. It should remain in the jar until the last capsule and must not be ingested. It is not an ingredient and should not be removed. The only thing we ask of our customers is to close the lid tightly after each use, because the jar can only do its job when it is closed. In the case of bromelain, this choice is part of the formulation along with the gastro-resistant capsule, and we have discussed it in full in Bromelain 5000 GDU: complete guide, common myths and gastro-resistance.

Minimum storage life: what ‘best before’ on supplements means

1

Best before — date of minimum durability — quality guaranteed if stored as indicated

2

Use by — expiry date — highly perishable foods

Supplements normally use the first wording

On supplement packaging, the date is almost always preceded by ‘best before’ or ‘best before end’, followed by the month and year, usually next to the batch number. This is the date of minimum durability, and Regulation (EU) 1169/2011 clearly distinguishes it from the ‘use by’ date, the one written as ‘use by’, which is reserved for foods that are highly perishable from a microbiological point of view.

The difference is substantial. The minimum durability date indicates how long the manufacturer guarantees that the product will retain its specific properties—for a supplement, this is essentially the content stated on the label. And this guarantee is valid on one condition: that the product has been stored as indicated. The line about storage conditions and the date are therefore two sides of the same coin: a jar left on a windowsill for three weeks has a different history from one kept in a drawer, even with the same printed date.

After that date, the product does not become dangerous: the manufacturer no longer guarantees the content, and the amount of the active ingredient may be lower than that stated. From then on, the decision is up to the consumer, and a reasonable approach takes four things into account: how much time has passed, how it was stored during those months, whether the packaging is intact and properly sealed, and what the contents look and smell like. We have written a six-step guide on where exactly to find the batch number and date, and how to read the rest of the packaging: How to read a supplement label.

Sticky capsules, darkened tablets, a different smell: the signs of poor storage

Some signs are visible to the naked eye and are more important than any date.

Capsules that stick together, soften or become misshapen indicate moisture, heat or both. Tablets that change colour, become stained or crumble more than usual indicate that a reaction has already occurred, due to light, oxygen or water. A pungent smell in an oily product is a sign of rancidity. A powder that has clumped into a solid block has absorbed moisture.

If you see a sign like this, the product should be set aside, even if the date is still a long way off: in this case, what you see is more important than what is printed. And it is worth asking yourself where it has been kept, because nine times out of ten the answer is the bathroom, the car or a shelf in the sun.

Frequently asked questions

How should supplements be stored?

In the original, tightly closed packaging, in a cool, dry place away from light and sources of heat, and out of the reach of children under three years of age. A drawer or a closed cabinet in a bedroom or a cool pantry is the right place; the lid should be closed tightly after each use.

Can supplements be kept in the bathroom?

It is best not to. Every time you have a shower, the bathroom fills with steam and the temperature fluctuates: two conditions that accelerate the very reactions the packaging is supposed to protect against. The same goes for the wall cabinet above the hob.

Should supplements be kept in the fridge?

Those that specifically require it, typically certain live lactic ferments and some liquid preparations, which should be kept between 2 and 8 °C. Oils rich in omega-3s, such as cod liver oil, also keep better in the cold once opened. For others, the fridge is a humid environment and every opening creates condensation on the jar. None of the NUTRALAB products should be stored in the fridge.

Can expired supplements be taken?

The date on the packaging is almost always a best-before date: it indicates until when the manufacturer guarantees the declared content, provided that the product has been stored correctly. After that date, the guarantee is no longer valid and the active ingredient may have diminished. The decision rests with the owner, assessing how much time has passed, how it has been kept, and the condition of the packaging and its contents.

What is the difference between ‘use by’ and ‘best before’?

‘Use by’ is the actual expiry date, intended for foods that are highly perishable from a microbiological point of view: the product must not be consumed after this date. ‘Best before’ indicates the minimum storage life and relates to the preservation of the product’s properties. Supplements normally use a best-before date.

Are supplements better in glass or plastic jars?

Amber glass combines three things: it blocks the band of light that triggers oxidation, it is impermeable to oxygen and moisture, and it is chemically inert. Opaque plastic can block light even better than amber glass [6], but it remains permeable to gases and moisture. All NUTRALAB products come in tempered amber glass with an aluminium cap, with no plastic in contact with the product.

Can I put the tablets in a weekly pill organiser?

Yes, for two or three days, keeping it closed and away from light and heat. For longer periods, the pill organiser removes the product's protection from its container, and tablets that dissolve in the mouth are the most exposed to air moisture: it is best to take those from the jar when needed.

What happens if a supplement is exposed to heat or sun?

Heat accelerates chemical reactions and light triggers others, especially on the most reactive molecules: in studies on astaxanthin, the combination of light, air and 45 °C oxidised almost all of the pigment in eight weeks [1], while in the dark and at a controlled temperature the loss is much lower [2]. Brief exposure has little effect; hours of direct sunlight or a car parked in the sun matter a lot.

What is the small white cylinder inside the jar for?

It is a desiccant canister: it absorbs residual moisture and any that enters each time the jar is opened, keeping the inside of the jar dry. It should be left inside until the container is empty; it is not an ingredient and should not be swallowed.

Regulatory references and sources

Studies

Armenta R.E., Guerrero-Legarreta I., Stability studies on astaxanthin extracted from fermented shrimp byproducts, J Agric Food Chem 2009;57(14):6095-100. PMID 19548684 — doi:10.1021/jf901083d
Vakarelova M. et al., Production of stable food-grade microencapsulated astaxanthin by vibrating nozzle technology, Food Chem 2016;221:289-95. PMID 27979204 — doi:10.1016/j.foodchem.2016.10.085 (52 weeks, four conditions of light, temperature and oxygen)
Alqurshi A., Household storage of pharmaceutical products in Saudi Arabia; A call for utilising smart packaging solutions, Saudi Pharm J 2020;28(11):1411-9. PMID 33250648 — doi:10.1016/j.jsps.2020.09.006 (mapping of 35 rooms and car interiors)
Ho P.C., Wong V.K., Influence of DL methionine and sodium metabisulphite on the photostability of vitamin k1, PDA J Pharm Sci Technol 1998;52(3):129-33. PMID 9691676
Spatari C. et al., Photo and thermal stress of linseed oil and stabilization strategies, J Food Sci Technol 2018;56(2):614-23. PMID 30906019 — doi:10.1007/s13197-018-3516-0 (light stress according to ICH rules, 18 hours)
Sabah A. et al., Light transmission properties of pharmaceutical liquid bottles and evaluation of their photoprotective efficacy, Pak J Pharm Sci 2020;33(2 Suppl):877-85. PMID 32863265

Regulatory references

Regulation (EU) No 1169/2011 — provision of food information to consumers: date of minimum durability and ‘use by’ date (Art. 24 and Annex X), special storage conditions (Art. 25).
Legislative Decree of 21 May 2004, No 169 — implementation of Directive 2002/46/EC on food supplements.
European Pharmacopoeia, chapter 3.2.1 Glass containers for pharmaceutical use — light transmission limit for coloured glass intended for non-parenteral preparations: not more than 10% at any wavelength between 290 and 450 nm.

How to store food supplements: where, how and until when