Update: In 2019, the USDA updated database values for caffeine content in foods and beverages. You can learn more here.
Humans have a long-lasting love affair with caffeine. How we consume it continues to evolve, but we have certainly found and created ways to do so for centuries, with tea being the earliest known caffeine-containing beverage, steeped in China in the 2700s BC.
Why, after these thousands of years of consumption, do we still talk about caffeine? Perhaps it is simply a healthy dose of respect for the stimulant effect that caffeine has on the body and mind. We appreciate the pick-me-up, but know that sometimes, for some people, we can have too much of a good thing. Fortunately, extensive human health research has emerged over several decades to demonstrate the safety of caffeine, define levels of healthful consumption, and also reveal some of its health benefits.
While the 2015-2020 Dietary Guidelines for Americans is largely focused on dietary patterns and foods, caffeine is one of the individual food components that gets focused attention. The Guidelines assert that the overwhelming majority of Americans are consuming a reasonable amount of caffeine that does not carry health risks. As most of the caffeine and health research reviewed was specific to coffee, the 2015 DGAs limited its specific guidance to this popular beverage. Concern is noted for a small percentage of people in certain age groups who tend to consume large quantities of caffeine, and health professional guidance is recommended for pregnant and breastfeeding women
How much is OK?
According to the Guidelines, “Moderate coffee consumption (three to five 8-oz cups/day or providing up to 400 mg/day of caffeine) can be incorporated into healthy eating patterns.” This is based on a standard brewed cup of joe, which has about 95 mg caffeine in 8 ounces. The following figure shows the caffeine content of several popular dietary sources of caffeine.
The reality is that very few Americans consume more than 400 mg caffeine per day. According to the National Health and Nutrition Examination Survey from 2007 to 2010, fewer than 5% of female and fewer than 10% of male adults exceed the recommendations. For children and adolescents, specific moderate and safe amounts have not been set in the US, but only teens in the top 90th percentile for intake are consuming more than 100 mg caffeine daily.
Most of the caffeine that is consumed in the US is in coffee, followed by tea and soda. While chocolate candy provides small amounts of the caffeine consumed by children and teens, soda, coffee, and tea are the primary sources. How Americans drink coffee is evolving, thanks to the influence of Millennials. Daily espresso drinks have nearly tripled since 2008, and both espresso-based and other gourmet coffees are increasingly chosen by 18-39 year olds. Depending on how these beverages are prepared, some “coffee house” coffee drinks can bring around 165mg of caffeine in an 8oz cup, twice the amount you would find in a home-brewed cup. The popularity of energy drinks has also been growing, although they contribute less than 2% of caffeine intake.
While the Dietary Guidelines for Americans does not define moderate consumption for pregnant and breastfeeding women, observational studies suggest that moderate caffeine intake is safe. The American College of Obstetricians and Gynecologists recommends no more than 2 cups of home brewed coffee (which would translate in about 200mg of caffeine) daily, and the European Food Safety Authority advises that 200 mg daily during pregnancy or lactation is safe.
In 2015, The European Food Safety Authority’s Panel on Dietetic Products, Nutrition and Allergies conducted a thorough review of the available evidence for caffeine and safety. The panel concluded:
- Habitual caffeine intake up to 400 mg per day is safe for adults.
- Up to 200 mg caffeine consumed at one time is safe for adults, including within 2 hours of intense physical exercise under normal environmental conditions, and in combination with other ingredients commonly found in energy drinks.
- Habitual caffeine consumption up to 200 mg per day by pregnant women is safe for the fetus.
- Up to 200 mg caffeine consumed at one time or habitually by lactating women does not raise safety concerns for breastfed infants.
- For children and adolescents, the information available is insufficient to derive a safe caffeine intake.
What are the health benefits?
While the caffeine statement in the Dietary Guidelines for Americans focuses on the overwhelming evidence for an absence of harm from caffeine intake, the story is even more exciting with a closer look at the report of the Dietary Guidelines Advisory Committee. There we see an extensive body of quality scientific evidence for numerous health benefits of coffee and/or caffeine. While most of the research reviewed by the committee focused on coffee, some of the good news appears to be specific to caffeine from all sources:
- Cardiovascular disease (CVD) risk is lower for moderate consumers of caffeinated, but not decaffeinated, coffee.
- While older evidence found no effect on coronary heart disease (CHD) risk, more recent studies document a protective effect of coffee consumption.
- While there is no apparent effect of moderate coffee or caffeine on blood pressure in healthy individuals, 200-300 mg of isolated caffeine given to people with pre-existing hypertension may cause an increase in blood pressure in the short term.
- Coffee intake is associated with a lower risk of stroke.
- Coffee, both caffeinated and decaffeinated, is consistently associated with a reduced risk of type 2 diabetes.
- While there is evidence suggesting that 200-500 mg of caffeine may increase blood glucose and insulin and decrease insulin sensitivity, following intake of glucose, there do not appear to be long-term implications of these acute effects in the population.
- As a nervous system stimulant, the role for caffeine in cognition has long been a subject of interest. Indeed, measures of cognitive decline are lower for consumers of caffeine from all sources, as are risks of both cognitive decline and Alzheimer’s disease.
- There is promising evidence for lower risk of Parkinson’s disease in coffee drinkers, and a dose-response protective effect with increasing levels of caffeine intake from all sources.
Beyond the 2015-2020 Dietary Guidelines for Americans
Given the passionate relationship most of us have with our morning coffee, you can be sure research into the health effects of caffeine will continue. In addition to the review conducted to inform the Dietary Guidelines for Americans, other reports have been published by the European Food Safety Authority and others confirming the safety and health benefits of caffeine. Those who enjoy caffeinated beverages will likely be glad to hear that science is revealing not only safety but also benefits in their morning cup, as coffee and tea drinking clearly have deep cultural roots. At the same time that our ways of consuming caffeine are evolving, research continues to build in order to help us realize its health benefits within the context of a healthy eating pattern.
This post was written by Cheryl Toner, MS, RDN, a registered dietitan living in northern Virginia helping people make healthy food choices.