I’m afraid that I also have some bad news:
Nowhere in the study do they recommend that you increase your intake of wine and chocolate.
But fear not! Whilst the media reporting was misleading (and a diet of Mars bars and Merlot may not prevent you getting diabetes), this study is a great example of how normal amounts of surprisingly simple foods can help us along the way to better health.
This is the first large study to have looked at how different subtypes of flavonoids in the diet can reduce the risk of diabetes and inflammation.
Flavonoids are substances found in plants that, over the last few decades, have been implicated in having anti-inflammatory and anti-cancer properties, as well as potentially improving glucose control and reducing the risk of diabetes and cardiovascular disease. However, some studies have found no connection between certain flavonoids and diabetes, so the aim here was to investigate the issue further.
Flavonoids are often responsible for the colour of things like berries, and can be found in a number of herbs, citrus fruits, berries, tea and cocoa. This already sounds yummy.
In the study, the investigators analysed the food consumed by a large database of twins in the UK, using food diaries, and took some blood samples to look at the participants’ markers of inflammation and insulin resistance (how well the body handles sugar).
Insulin resistance and inflammation are increasingly associated with cancer, diabetes and heart disease. These markers are intimately related to our diet and lifestyle, and are good indicators of how much stress the body is under.
The group of twins studied has been extensively researched before, and is considered to be fairly representative of the UK population, though they do tend to weigh slightly less, and smoke less. To make sure that food intake in the study was accurate, they excluded anybody whose food diary was missing items, or contained an improbable number of calories (too many or too few). The diaries were then run through a computer programme that counted up all the flavonoids that were likely to have been in the food that they ate.
What did they find?
Two groups of flavonoids were associated with reduced insulin resistance and inflammation:
Anthocyanins: Often red or purple in colour, these tend to be found in apples, pears, plums, red cabbage and red onions, pomegranates and grapes (and therefore wine).
Flavones: These tend to be yellow, and are found in parsley, celery, citrus peel and chamomile tea.
The most significant benefit was seen when comparing people who ate the most foods containing anthocyanins with those that ate very few. Eating a total of at least 35mg of anthocyanins per day provided the best improvement, and this is a lot easier than you may think. All these foods contain enough anthocyanins to get the reported benefits:
- Around 100g of grapes, strawberries or raspberries.
- 100g of red cabbage.
- 1 red onion.
- A paltry 21g of blueberries. That’s barely a handful!
Though not mentioned in the study, a small (175ml) glass of red wine contains 5-25mg of anthocyanins, which will contribute nicely to the daily quota. However, the anthocyanin content of wine decreases as it ages because they react with other compounds in the wine, and end up in the sediment. This is a reason to think about getting most of your flavonoids elsewhere… Sorry!
It is essential, when looking at studies, to assess how we can apply any relevant findings to ourselves and to the population as a whole. Accordingly, www.nhs.uk raised a number of sensible issues with this study:
- This was a cross-sectional study, which only describes the characteristics of the people involved. It can tell you that people who eat more flavonoids have better insulin control, but not that the flavonoids were the cause of this.
- The study included only women.
- Of a potential group of over 5,000 twins, only 2,000 had accurate food diaries and the right blood samples, which may have changed the characteristics of the group as a whole.
- The study only looked at markers that may predict future diabetes rather than how diet affected the risk of actually getting diabetes.
In addition, there was actually very little mention of chocolate or wine, despite the media reports.
The study authors themselves also point out a couple of other drawbacks of the study:
- In general, people who eat more flavonoids may live healthier lifestyles. Though they took things like BMI, smoking and activity levels into account, they didn’t include other important things like sleep and stress.
- The flavonoid content of fruits and vegetables will differ depending on where they were grown. The study used foods eaten in the UK, but flavonoid content was calculated with a US database. Therefore, final flavonoid intake will never be quite what they estimated it to be.
The answer to most of these problems would be a randomised controlled trial, where standardised pills of various flavonoids are compared to a placebo in a large group of people. Trials like this are the only way that we could prove, one way or the other, which specific flavonoids are beneficial. This is what the study review by the NHS demands before large conclusions are drawn.
Though these trials may be done in the future, a far more relevant study would somehow examine the effects of real changes in diet (such as more Snickers bars and Sancerre) on diabetes risk. This is probably never going to happen.
As mentioned above, the study only looked at women. There are a number of reasons why men may not have been included in the study. Men and women tend to have rather different hormone levels, which affect how they gain weight and develop diseases like diabetes and cancer. For this reason, men and women are often studied separately.
It could be that the parallel study in men will follow shortly. Alternatively, it may be that men were studied but that the results showed no benefit at all. Sadly, negative results tend to be forgotten about, and often fail to reach the scientific journals.
In line with the last point, a recent randomised trial in which men were given 640mg of anthocyanins per day showed no effect on blood pressure or inflammation, though there was a beneficial increase in HDL (“good”) cholesterol. Conversely, just last week a trial was published showing that increasing flavonoid-rich fruits and vegetables in the diet significantly improved a number of risk factors for cardiovascular disease in men. It will clearly take some time before we have the whole picture figured out.
What about chocolate?
Despite what the news reports said, one class of flavonoids (flavan-3-ols), which predominates in cocoa, did not appear to have any effect on the diabetes risk factors studied in the twins.
The flavonols in chocolate have been studied for a long time, because in cross-sectional studies similar to the one discussed here, they appear to reduce the risk of cardiovascular disease, improve blood pressure and reduce the risk of death by all causes!
However, most of the trials that have given participants chocolate (or flavan-3-ols) to look for improvements in health have been small, poorly controlled and of a very short duration. Nonetheless, when you put them all together in a meta-analysis (a study of many trials), there does still appear to be some significant benefit:
- Improved insulin resistance.
- Reduced risk of high blood pressure.
- Improved cholesterol levels.
These same flavonoids are also particularly abundant in green tea, apples, pears, plums, peaches and red berries. However, there are considerably more of them in chocolate than almost anything else.
Now, before you rush out to buy a large tub of Quality Street, it is worth remembering that the bitter flavour of flavonoids often means that they are removed from chocolate. The popular “Dutch” method of refining cocoa to make chocolate may remove up to 98% of the beneficial compounds. So, it’s best to stick with raw chocolate and products containing real cocoa powder.
An important thing to remember here is that most of the studies looking at flavonoids in the diet have either estimated intake based on diaries, or have given people a fixed dose through berry juices or dark chocolate with extra flavonoids added. Also, most of the studies have also only lasted a relatively short period of time, often less than a month. Therefore, the reliability of these studies, in isolation, can be queried.
Despite this, research in this area has frequently shown improvements in blood pressure and the risks of cardiovascular disease, diabetes and cancer. Therefore, it is slowly becoming clear that small amounts of some flavonoid compounds can have significant health benefits.
The study in question here even suggested that the highest levels of anthocyanin intake improved insulin resistance almost as much as regular exercise. No, this is not an excuse to stop exercising.
Here are some simple ways to increase flavonoid intake and potentially reduce your risk of future disease:
Drink tea: Green tea is much better than black tea for levels of flavan-3-ols. The levels are also dramatically reduced when green tea is decaffeinated, so if you want something before bedtime, try having some flavones from chamomile tea instead.
Eat raw chocolate: As people begin to rebel against highly processed foods, it is becoming easier to find raw chocolate in health food shops. As it tends to be much richer, you will also only want to eat small amounts. However, this should be enough to give the reported benefits.
Eat berries and herbs: Berries are little flavonoid powerhouses. Just a handful or two a day could significantly reduce your risk of high blood pressure and diabetes. Adding parsley and celery to some simple salads or cooking is another easy, cheap way to get some good flavonoids in your life.
Drink red wine occasionally: However, drink wine because you enjoy it. Don’t do it for the flavonoids. The best route to health will never come through alcohol, but multiple studies show that drinking in moderation can have a number of positive effects.
Pills may not be the answer: As discussed above, many people will want to capture the beneficial components of fruits, chocolate and tea into pills in order to do trials. Whilst trials of standardised pills are considered the scientific gold standard in medicine, we should consider that deconstructing real food like blueberries in order to create pills of their constituent parts actually defeats the whole point. We could easily be missing out on the real good stuff, which only comes from eating the food whole.
We could make a pill containing all this stuff. Or we could just EAT SOME ACTUAL BLUEBERRIES!
If we all ate a few more berries, had some raw chocolate and drank some green tea, we may reduce our risk of future diabetes and heart disease. If not, the worst thing that will happen is that we’ve had some nice food.
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