Caffeine Content

Caffeine is the most studied and consumed stimulant in the world (2Trusted Source, 3Trusted Source).

Present in many common beverages, including coffee and tea, it's known for both its beneficial and adverse effects on human health.

While the caffeine content can vary depending on brewing time, serving size, or preparation method, coffee can easily pack twice the caffeine as an equal serving of tea.

The amount of caffeine considered safe for human consumption is 400 mg per day. One 8-ounce cup (240 ml) of brewed coffee contains an average of 95 mg of caffeine, compared with 47 mg in the same serving of black tea (4Trusted Source, 5, 6).

Though scientists have primarily focused on coffee when researching the positive effects of caffeine, both drinks — despite containing differing amounts of this substance — can provide its associated health benefits.

Caffeine intake may reduce your risk of certain chronic diseases and improve athletic performance, mood, and mental alertness (7Trusted Source, 8Trusted Source, 9Trusted Source).

Caffeine works as a powerful stimulant for your central nervous system, which is why it's considered a performance-enhancing substance in sports (10Trusted Source, 11Trusted Source, 12Trusted Source).

One review of 40 studies determined that caffeine intake improved endurance exercise outcomes by 12%, compared with a placebo (13Trusted Source).

As for caffeine's effect on mental alertness, research shows that it improves performance in both simple and complex tasks (14Trusted Source, 15Trusted Source).

A study in 48 people who were given a drink containing either 75 or 150 mg of caffeine revealed improvements in reaction times, memory, and information processing, compared with the control group (16Trusted Source).

Other studies indicate that caffeine may reduce type 2 diabetes risk by improving insulin sensitivity (17Trusted Source).

A review of 9 studies in 193,473 people showed that regularly drinking coffee significantly lowered the risk of type 2 diabetes (18Trusted Source, 19Trusted Source).

What's more, moderate caffeine intake has been associated with protective effects against dementia, Alzheimer's disease, metabolic syndrome, and non-alcoholic fatty liver disease (20Trusted Source, 21Trusted Source, 22Trusted Source, 23Trusted Source, 24Trusted Source).

Summary

Caffeine is a powerful stimulant that has been associated with protective effects against some chronic diseases. Coffee contains more caffeine per serving than black tea, but both beverages may provide its associated benefits.

Rich in Antioxidants

Antioxidants protect your body against free radical damage, which may help prevent the development of certain chronic diseases (25Trusted Source).

Both tea and coffee are loaded with antioxidants, primarily polyphenols, which contribute to their characteristic flavor and health-promoting properties (26Trusted Source, 27Trusted Source, 28Trusted Source, 29Trusted Source).

Many groups of polyphenols are present in tea and coffee.

Theaflavins, thearubigins, and catechins are the primary ones in black tea, while coffee is rich in flavonoids and chlorogenic acid (CGA) (30, 31Trusted Source).

A recent test-tube study discovered that theaflavins and thearubigins inhibited the growth of lung and colon cancer cells and ultimately killed them (32Trusted Source).

Studies in leukemia cells revealed similar results, suggesting that black tea may have cancer-protective properties, though more research is needed (33Trusted Source).

On the other hand, test-tube studies on coffee's anticancer properties have found that its CGA content acts as a potent inhibitor of cancer cell growth, protecting against gastrointestinal and liver cancer (34Trusted Source, 35Trusted Source).

Long-term studies in humans and further research that has analyzed larger pools of evidence show that coffee and tea may also protect against other kinds of cancers, such as breast, colon, bladder, and rectum cancer (36Trusted Source, 37Trusted Source, 38Trusted Source, 39Trusted Source, 40Trusted Source).

Aside from their antioxidant activities, polyphenols have been linked to a reduced rate of heart disease (41Trusted Source).

They contribute to heart health via various blood-vessel-protective mechanisms, including (42Trusted Source, 43Trusted Source, 44Trusted Source):

• Vasodilating factor. They promote blood vessel relaxation, which helps in cases of high blood pressure.
• Anti-angiogenic effect. They block the formation of new blood vessels that may feed cancer cells.
• Anti-atherogenic effect. They prevent plaque formation in blood vessels, lowering heart attack and stroke risk.

A 10-year study in 74,961 healthy people determined that drinking 4 cups (960 ml) or more of black tea per day was associated with a 21% lower risk of stroke, compared with non-drinkers (45Trusted Source).

Another 10-year study in 34,670 healthy women showed that drinking 5 cups (1.2 liters) or more of coffee per day lowered the risk of stroke by 23%, compared with non-drinkers (46Trusted Source).

Summary

Both coffee and tea contain different types of polyphenols, which are powerful antioxidants that protect against heart disease and cancer.

May Increase Energy Levels

Both coffee and tea can give you an energy boost — but in different ways.

Coffee's Energy-Boosting Effect

The caffeine in coffee elevates your energy levels.

Caffeine increases alertness and reduces fatigue by increasing dopamine levels and blocking adenosine (8Trusted Source, 47Trusted Source).

Dopamine is the chemical messenger responsible for the jittery effect of coffee, as it increases your heart rate. It also affects your brain's reward system, which adds to coffee's addictive properties.

On the other hand, adenosine has a sleep-promoting effect. Thus, by blocking it, caffeine reduces your feelings of tiredness.

What's more, coffee's effect on your energy levels happens almost immediately.

Once ingested, your body absorbs 99% of its caffeine within 45 minutes, but peak blood concentrations appear as early as 15 minutes after ingestion (48Trusted Source).

This is why many people prefer a cup of coffee when they need an immediate energy boost.

Tea's Effect on Energy

Though tea is lower in caffeine, it's rich in L-theanine, a powerful antioxidant that also stimulates your brain (49Trusted Source, 50Trusted Source).

Unlike caffeine, L-theanine may provide anti-stress effects by increasing your brain's alpha waves, which help you calm down and relax (51Trusted Source).

This counteracts the arousing effect of caffeine and gives you a relaxed but alert mental state without feeling drowsy.

Studies have found that consuming L-theanine along with caffeine — as in tea — may help you maintain your alertness, focus, attention, and sharpness (52Trusted Source, 53Trusted Source).

This combination may be the reason why tea gives you a soothing and more smooth energy boost than coffee.

Summary

Both coffee and tea increase your energy levels. However, coffee gives you an instant kick, while tea offers a smooth boost.

Possible Weight Loss Benefits

Due to its high caffeine concentration, coffee may help you lose weight.

Caffeine may increase the number of calories you burn by 3–13%, and maintain this effect for 3 hours after intake, translating into an extra 79–150 calories burned (54Trusted Source, 55Trusted Source, 56Trusted Source, 57Trusted Source).

Coffee has also been associated with fat-burning properties by inhibiting the production of fat cells. Some studies have attributed this effect to its chlorogenic acid content (58Trusted Source, 59Trusted Source).

A study in 455 people reported that regular coffee intake was linked to lower body fat tissue. Similar results were obtained in a review of 12 studies, suggesting that chlorogenic acid aids weight loss and fat metabolism in mice (60Trusted Source, 61Trusted Source).

On the other hand, tea polyphenols like theaflavin also seem to contribute to weight loss.

Theaflavins reportedly inhibit pancreatic lipase, an enzyme that plays a key role in fat metabolism (62Trusted Source).

Studies in rats show that tea polyphenols may lower blood lipid concentrations and reduce weight gain — even when animals ate a high-fat diet (63Trusted Source).

Black tea polyphenols also seem to alter the diversity of your gut microbiota, or healthy bacteria in your intestines, which may impact weight management.

Again, studies in rats have observed that by changing the gut microbiota, tea polyphenols may inhibit weight and fat gain (64Trusted Source, 65Trusted Source).

However, further human research is needed to confirm these results.

Summary

The caffeine in coffee and polyphenols in tea may help you lose weight, but more human studies are needed to confirm these effects.

Is One Better Than the Other?

Though coffee has been associated with multiple side effects, such as heart failure, increased heart rate, and high blood pressure, research shows that moderate consumption is safe (66Trusted Source).

Though their antioxidant compositions differ, coffee and black tea are both excellent sources of these important compounds, which may protect against various conditions, including heart disease and some forms of cancers.

Other health claims attributed to coffee include protection against Parkinson's disease and a lowered risk of type 2 diabetes and liver cirrhosis. On the other hand, tea may protect against cavities, kidney stones, and arthritis (1Trusted Source).

Coffee has a higher caffeine content than tea, which may be good for those looking for an instant energy fix. However, it may cause anxiety and impaired sleep in sensitive people (8Trusted Source).

Also, due to caffeine's effect on your brain, high coffee intake may result in dependence or addiction (67Trusted Source).

If you're highly sensitive to caffeine, tea may be a better choice. It contains L-theanine, an amino acid with calming properties that may relax you while keeping you alert.

Moreover, you can go for a decaf option of either beverage or choose herbal tea, which is naturally caffeine-free. While they won't provide the same benefits, they may offer benefits of their own (68Trusted Source).

Summary

Coffee and tea offer similar health benefits, including weight loss, anticancer, and energy-boosting properties. Still, you may want to choose one over the other depending on your caffeine sensitivity.

The Bottom Line

Coffee and black tea may aid weight loss and protect against certain chronic diseases via various metabolic processes.

Plus, the high caffeine content of coffee may give you a quick energy boost, whereas the combination of caffeine and L-theanine in black tea offers a more gradual increase in energy.

Both beverages are healthy and safe in moderation, so it may come down to personal preference or your sensitivity to caffeine.