Caffeine supplements can provide a short-term boost in alertness, but excessive intake can cause adverse effects, including anxiety, headaches and heart rhythm disturbances. Health authorities warn that highly concentrated caffeine products pose particular risks because small amounts can contain dangerous doses.
Caffeine is a stimulant found naturally in coffee, tea and cocoa. It is also added to some dietary supplements and medicines. Unlike beverages, caffeine tablets can deliver a concentrated dose in a single serving, making it important for consumers to check product labels and account for caffeine from other sources.
Caffeine and iron absorption
Research has shown that coffee can reduce the absorption of non-haem iron, the form found in plant-based foods and iron-fortified products. A 1983 clinical study published in the American Journal of Clinical Nutrition found that coffee consumed with a meal reduced iron absorption.
The effect is associated with compounds in coffee rather than caffeine alone. The extent to which iron absorption is affected depends on the food consumed and a person’s iron status. People at risk of iron deficiency may benefit from discussing their diet and supplement use with a healthcare professional.
Excessive intake can cause serious effects
According to the US Food and Drug Administration, an intake of up to 400 milligrams of caffeine a day is not generally associated with negative effects for most healthy adults. However, individual sensitivity varies, and this level is not a target or a guarantee of safety for everyone.
Excessive caffeine consumption can cause nervousness, nausea, headaches and a rapid heartbeat. Severe caffeine toxicity can lead to dangerous heart rhythm disturbances and seizures. The risk depends on the dose, the product’s concentration and individual factors, including age, health conditions and medication use.
The FDA has specifically warned against pure and highly concentrated caffeine powders and liquids because accurately measuring a safe serving can be difficult. Consumers should not assume that these products are safe simply because they are sold as dietary supplements.
Caffeine can also disrupt sleep, particularly when consumed later in the day. Tablets should not be used as a substitute for adequate rest, and people experiencing persistent tiredness should seek medical advice rather than repeatedly increasing their caffeine intake.
What consumers should know
People considering caffeine supplements should consult a healthcare professional, particularly if they take prescription or over-the-counter medicines or have a medical condition that could make stimulant use riskier.
The amount of caffeine in tablets varies by product, so consumers should follow the label and avoid combining multiple caffeine sources without accounting for their total intake. Anyone experiencing severe symptoms after consuming caffeine should seek urgent medical attention.
