Tea-riffic health benefits...
We love a good cuppa here in Ireland - but are there any nutritional benefits from our favourite hot drink? Resident dietitian Orla Walsh takes a closer look at the evidence takes a closer look at the evidence
What I've noticed from clinical experience is that for many people, tea leads to biscuits. Although biscuits aren't the healthiest choice, it appears that tea is less sinful than most think. In fact, generally speaking, it's rather good for us.
Most of the tea drunk worldwide is either black tea (roughly 78pc) or green tea (20pc). Ireland is thought to be the second-largest consumer of tea in the world (after Turkey) - with more than one-in-three of us drinking more than three cups a day. So the fact that this may be a good habit is music to the ears of many.
The Nutrition of Tea
Tea comes from plants. As with all plants, the type and age of the plant as well as where it is grown will have a significant affect on the nutritional composition of the tea leaves. However, what also appears to matter is just how much processing the tea has undergone.
Most foods are superfooods, it's just that their superpowers haven't yet been discovered. For tea, its superpower lies with its polyphenolic flavonoid content, especially the catechins in green tea and the theaflavins within black and oolong teas. Tea is also a source of caffeine, with black tea containing more caffeine than green tea. However, both teas provide less caffeine than coffee.
If you were to sum up why tea is good for us, apart from the fact it's so hydrating, is that it is naturally high in antioxidants. Antioxidants help neutralise free radical molecules within the body. Free radicals are highly reactive, unstable molecules that cause oxidative stress. This stress then damages the body. As tea is rich in antioxidants, it is not surprising that scientific research suggests that tea prevents many conditions and diseases. Studies have shown that the levels of antioxidants in the blood increases after drinking tea. So what does this mean health-wise?
Green tea is regularly praised for its anti-obesity effects. These effects are often overstated. The two main components of tea to help with weight-loss are its caffeine and catechin content. But what's the evidence? A review of the research was completed and published in 2012. Analysis of the studies showed weight loss of anywhere between 0.04 kg to 3.5 kg when people regularly drank green tea preparations. The amount of weight loss is small and therefore may not be clinically relevant. However, more recent research seems more positive. Green tea extract (856.8mg) was tested on women who were carrying too much fat around their middle. The 115 women were randomly assigned to either receive the extract or a placebo for 12 weeks. They didn't know which group they were in and neither did the researchers. Significant weight loss occurred and averaged about 1.1kg.
Interestingly, cholesterol levels seemed to also improve. The good news was that the women tolerated this supplement and didn't experience any side effects or adverse events. What is also interesting is that the green tea extract changed the levels of hunger hormones.
The findings on tea and heart disease are upbeat.According to one piece of published research, black and green tea may reduce the risk of heart disease and stroke by 10pc to 20pc. In a different study following more than 37,000 people for 13 years, those that drank plenty of tea were less likely to die of heart disease than people who don't drink tea. In fact, the people who drank three to six cups of tea each day were 45pc less likely to die from heart disease than those who drank less than one cup. What's more, a systematic review in the Journal of the American Dietetic Association which assessed 20 trials reported that green tea catechins caused a significant reduction in total and LDL 'bad' cholesterol levels. This is good news for many Irish people, as we do love our brew and heart disease is our number one killer.
In an analysis of 17 high-quality controlled trials, drinking green tea was associated with decreased fasting glucose of 1.6 mg/dL and insulin by 1.16 μIU/mL, which is good news for Type 2 diabetics. It also brought down the average three-monthly blood glucose level by 0.3pc. These aren't huge results, but they are easily achieved. Again, we don't know just what the ideal dose is, as the clinical trials gave 208mg to 1,207mg each day of green tea catechins and the studies ranged in duration from two weeks to six months.
For the diabetics wishing to have better blood sugar control between meals, a study showed that when women drank 350ml of catechin-enriched green tea with breakfast, there was a 3pc reduction in their glucose levels after a meal.
Oxidative stress and inflammation play a role in neurodegenerative diseases. A dose-response meta-analysis was carried out between Parkinson's disease risk and tea. Eight studies involving approximately 345,000 people were included.
One study showed that tea consumption reduced the risk of developing Parkinson's disease. Interestingly, the protection that tea provided was even stronger in males. More research is needed.
When it comes to tea, you have to think about yourself as an individual. Your body may not tolerate caffeine, or tea, and if that's the case, you need to be mindful of how much tea you drink.
Studies have shown that around 10 to 12 cups of tea each day can produce side effects such as excess gas production, nausea, heartburn, stomach pains, and even muscular pain. Drinking about four cups of tea each day hasn't been associated with significant side effects in most people.
Green or black?
Green tea does appear to be more protective than black tea. Freshly-brewed tea is considered a safer, and cheaper, way to consume the beneficial nutrients within tea.
Health & Living