Storing a sealed bottle of vitamins in extreme temperatures can degrade the quality and effectiveness of the vitamins over time. Among the options you mentioned, keeping the vitamins at 90 degrees Fahrenheit (32 degrees Celsius) on a cabinet shelf is likely the worst choice. High temperatures can lead to accelerated degradation of the vitamins and reduce their potency.
Vitamins are sensitive to heat, light, and moisture, and exposing them to high temperatures can cause chemical reactions that break down the nutrients. This can result in a loss of potency, making the vitamins less effective when consumed.
The ideal storage conditions for most vitamins are in a cool, dry, and dark place. Therefore, the refrigerator or freezer might be better options than a cabinet shelf at 90 degrees Fahrenheit, but each option has its considerations:
Refrigerator: Storing vitamins in the refrigerator can be suitable for some types of vitamins. However, moisture can be a concern, especially if the bottle is not well-sealed or if there are temperature fluctuations when removing the bottle from the fridge. Additionally, if the fridge is very cold, it might cause condensation inside the bottle when taken out, potentially affecting the vitamins.
Freezer: Freezing vitamins is generally not necessary and may not be ideal for all types of supplements. Some vitamins and minerals can be negatively affected by freezing temperatures. For example, water-soluble vitamins like vitamin C and B-complex vitamins may be more susceptible to damage. However, if you need to store vitamins for an extended period, and the label indicates it is safe to freeze them, you can consider doing so to prolong their shelf life.
In any case, always follow the storage instructions provided on the vitamin bottle's label. If in doubt, consult with the manufacturer or a healthcare professional for specific guidance on storing your particular type of vitamins. Storing vitamins properly will help ensure that they maintain their potency and effectiveness throughout their shelf life.