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Why do food items and medicines expire after sometime?

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  • $\begingroup$ Medicine doesn't expire so quickly, actually. Just recently, a large amount of pharma drugs were found, ones that dated back to the 1950s, and they tested their efficacy, and found that 10 of the 14 active compounds in the drugs still met FDA standards. Drugs "expiring" is a kind of lie that big pharma has in place to make more $$. I'll see if I can find some literature on this, and make a more formal response. npr.org/sections/health-shots/2017/07/18/537257884/… $\endgroup$ – Charles Aug 10 '17 at 10:16
  • $\begingroup$ en.wikipedia.org/wiki/Shelf_life#Background If you read that section, it'll most of your questions. $\endgroup$ – Charles Aug 10 '17 at 16:03
  • $\begingroup$ Because the FDA requires it. $\endgroup$ – blacksmith37 Feb 7 '18 at 16:25
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There are a number of reasons

  • bacterial infection
  • fungi infection
    • Most fungi are not toxic in themselves but they release mycotoxins in the food, which are definitely toxic
  • Maggot infection
  • Other infections
  • Growth
    • E.g. a potato will slowly attempt to develop into a plant, slowly consuming the tuber (the tuber being the potato you would like to eat).
  • Oxidation
  • Unstable chemicals
    • Mainly for medicines. Note however that (from health.harward.edu; thank you @Charles for pointing that out):

Most of what is known about drug expiration dates comes from a study conducted by the Food and Drug Administration at the request of the military. ... What they found from the study is 90% of more than 100 drugs, both prescription and over-the-counter, were perfectly good to use even 15 years after the expiration date ... So the expiration date doesn't really indicate a point at which the medication is no longer effective or has become unsafe to use.

The main reasons are probably the first two (bacterial and fungi infection). Note that the list is incomplete.

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Degradation of substances and chemicals don't happen only thru oxydation but also many other factors like light, microorganisms and othwr stuff. The chemical substance will also suffer a degradation without any external factors, and some are more likely to go thru such processes than others.

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Expiring food items is obvious: for fresh food, it's almost always due to bacterial or fungal decay (spoilage).

Oxidization and sunlight doesn't really ruin food; it might alter the taste or decrease its appeal, although it remains edible even by first-world standards. However, it might destroy vitamins and other nutrients.

Medicines are a different matter. Some chemical compounds are slightly unstable, with half-lives measured in years. Instability can cause the compounds to randomly break into subcompounds that are ineffective for treating the intended condition at best and poisonous at worst. Unlike food, it's imperative to keep medicines away from sunlight (and oxidation in some cases) as both of these can further promote instability and breakage into subcompounds.

On the comment that Charles posted about medicine shelf life being much longer than advertised: The reason why they underestimate the shelf life is that it's better to have people throwing out potentially OK medicine than to have it sitting on a shelf for 20 years, going bad and sickening people, and prompting numerous lawsuits against the manufacturer. This type of deliberate underestimation in the name of safety is common in engineering - usually with weight limits advertised below the real weight limit. For example, an elevator able to haul 6000 pounds might be advertised as only 2000 because the manufacturer knows there's always going to be a few idiots who disregard the posted limit.

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  • $\begingroup$ "Most of what is known about drug expiration dates comes from a study conducted by the Food and Drug Administration at the request of the military. ... What they found from the study is 90% of more than 100 drugs, both prescription and over-the-counter, were perfectly good to use even 15 years after the expiration date ... So the expiration date doesn't really indicate a point at which the medication is no longer effective or has become unsafe to use." -- Harvard Medical School health.harvard.edu/staying-healthy/… $\endgroup$ – Charles Aug 10 '17 at 15:36
  • $\begingroup$ With regards to your answer, it would be nice if you could provide some hard examples to support your statements. $\endgroup$ – Charles Aug 10 '17 at 15:37
  • $\begingroup$ Thanks @Charles for the link, it is helpful. I would not down vote personally. user1258361 does not make any opposing claim but mainly explain why there is a need for expiration date on medicine and what could happen to medicines. $\endgroup$ – Remi.b Aug 10 '17 at 15:42
  • $\begingroup$ I downvoted because I feel that @user1258361 doesn't answer the question fully, and only provides extremely basic information, that of which isn't supported by any external sources, for which I feel there is a lot out there. "Some chemical compounds are slightly unstable, with half-lives measured in years." IMO, that doesn't explain why, and is overly general. And regarding the food, sources for those claims would be nice. Also, the reason for which safety standards of elevators was implemented is not the same as why expiration dates for medicine was introduced. $\endgroup$ – Charles Aug 10 '17 at 15:57
  • $\begingroup$ en.wikipedia.org/wiki/Shelf_life#Background $\endgroup$ – Charles Aug 10 '17 at 16:02
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Food expires because its growing. Constantly. Every ingredient you put into making specific foods has a Date when its time has ended. Just like our bodies as we age. We are one year closer to expireing. We Grow old and Our skin starts to Wrinkle. Its just a way of life. If nothing ever expired we would over populate everything. Not to mention, if our foods didnt expire they wouldnt break down in our Bodies making it hard to gain nutrients from. Ending in a result of Death. We need the foods to break down in order to survive.

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  • $\begingroup$ Umm... What? When food is thoroughly cooked, it isn't "alive" anymore and ceases to grow. The main cause of food expiration is due to decomposers (mostly fungi and bacteria) eating the food and converting parts of it into waste products ranging from "tastes bad" to "dangerous poison" depending on the decomposer. Oxidation and radiation exposure can slightly change the chemical composition of certain foods, although food generally remains edible after oxidation and irradiation. $\endgroup$ – user1258361 Jul 18 '18 at 18:57

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