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Fruit Extracts Help Exercise Recovery and Asthma

By Roger Hurst

Natural fruit compounds may balance the impacts that exercise can have on the body and help breathing in some types of asthma.

It has long been accepted that fruit, vegetables and grains are good for us, but it is only more recently that scientists have begun investigating plant bioactive compounds and the mechanisms by which they keep us healthy.

But before looking at more recent findings it is useful to consider some food science history. In the early 20th century vitamins were discovered, and it was found that small amounts of these compounds were just as important to our good health as macronutrients like proteins and carbohydrates. Some vitamins are essential for life, and without them people develop deficiency diseases like scurvy, pellagra and beriberi.

More recent research has revealed that some vitamins and other compounds in plant-based foods have further benefits to health in addition to being antioxidants.

What Are Antioxidants?
Antioxidants are substances that slow or stop the oxidation of other molecules in the human body. They act as antidotes to the body’s own poisons.

It is useful to think that within the vast majority of our cells there are chemical factories undergoing many processes that are complex and not fully understood. Oxidation is a vital part of these processes, and is important in generating energy for the growth and repair of human tissue. Oxidation takes place when we breathe, eat and exercise; if it didn’t we’d die.

But part of the oxidative process produces free-radical and oxidant poisons as waste products, and these can lead to heart disease and cataracts. By counteracting these oxidative waste products, antioxidants lead to better health and slow down the ageing process.

There is still a great deal to discover about the processes within us that keeps us healthy. Our own recent findings suggest that some natural compounds in fruit act in different ways to antioxidants to keep us well. Indeed, some fruit-based compounds may have several ways of keeping us healthy.

Exercise Recovery
My research team is looking at the effects of natural compounds in blackcurrants and how they may help to balance the impacts that exercise can have on the body. We have found that an extract derived from New Zealand-grown blackcurrants, taken in capsule form before and after exercise, has three potential effects: adjusting oxidative stress, adapting inflammation that may minimise muscle damage and aid repair, and potentially enhancing the body’s natural defences against infectious disease.

Exercise is universally considered healthy, and people who exercise moderately have fewer sick days due to a strong immune system response. However, exercise that is intense and/or carried out for long periods, like marathon running and triathlon training and competing, temporarily lowers immunity.

We wondered what the mechanisms are that offer a positive immune system response after exercise, and what role natural compounds from fruits or vegetables might play in that. What we would really like to do is find out which natural plant compounds keep us healthy, and how they do it.

To decide where to start our search we examined the scientific literature and found emerging evidence that fruits containing important flavonoids could reduce oxidative stress and improve natural and adaptive immunity. We wanted to find out if the mechanisms that keep us healthy when we eat fruit with key compounds also support the health benefits we get from exercising regularly and moderately.

We chose to experiment with blackcurrants because they are a known superfruit with several health benefits, probably the best known of which is their ability to reduce oxidative stress. We had been working with New Zealand-grown blackcurrants, and knew from feeding and cellular studies that the flavonoids and anthocyanins in them showed a range of health benefits including antioxidant properties. Other benefits included anti-inflammatory properties and enhanced immune status. There is scant knowledge of the mechanisms for these, and we wanted to find out what was going on.

We conducted a human clinical trial in which 10 healthy untrained individuals aged 37–63 years undertook moderate exercise. Participants were given two gel capsules before rowing for 30 minutes at 80% effort, and two more capsules immediately after the row. Blood samples were taken before the exercise and capsules were taken, and immediately after exercise but before the second two capsules were swallowed. Further blood samples were taken at 1, 2 and 24 hours after exercise and the samples were tested for blood measures of oxidative stress, immune function and muscle damage.

The study results showed that those who took the black­currant extract, which was high in anthocyanins and low in vitamin C, exhibited reduced markers for oxidative stress linked to muscle damage and inflammation as well as increased activity linked to immune response.

In cellular activity tests we found that when the cells were given the extract at the same time as they were stressed by bacteria there was a reduced inflammatory response. However, there was an enhanced reaction when the cells were stressed first and the extract was given later. The inflammatory response observed occurred earlier and for a shorter time than in the control.

This inflammatory response is, we think, an important initial response that must occur before important follow-on repair mechanisms kick in. We think it is also a prelude to the adaptive mechanism that must occur to enhance our immune system so that our bodies are better prepared for any similar events in future.

The finding that natural compounds in blackcurrants activate an enhanced response that promotes good health is new. To date, the thinking has been that natural compounds suppress the adverse cellular activity that occurs as the body reacts to exercise.

It’s possible that the benefits gained from moderate exercise occur because the body’s natural way of repairing and adapting to future similar events are enhanced. It looks like some natural compounds in blackcurrants complement these mechanisms.

Of course, this is preliminary research and while we now have a better idea of what and where to look, there is still a great deal to discover about the compounds and the mechanisms offering the positive outcomes. What has excellent potential is that, once we know a lot more, there’s a great opportunity to develop foods and beverages that will enhance our body’s natural activity to maintain health.

Our team is yet to determine exactly what compounds in the blackcurrant extract cause the observed effects, but we doubt that vitamin C is a factor because the extracts tested contained only very low levels of it. Instead we’re looking closely at the role of flavonoids in the fruit, as these are known antioxidants and include the anthocyanins that give blackcurrants their intense black-red colour.

Asthma Symptoms
When the lungs are exposed to allergens, the body’s natural response is to attack the perceived foreign body. In some people this results in long-term inflammation. But selective compounds found in fruit and vegetables may work with the body’s natural defence mechanism to suppress long-term inflammation in the lung.

Our team is now looking at the effects of berry-fruit compounds on inflammation and immunity processes. We have already shown that fruit consumption reduces symptoms in allergy-induced asthma, so we are now investigating the mechanisms by which this may occur. Once again, we chose blackcurrants because they are a known superfruit containing flavonoids and anthocyanins.

We are using cells obtained from lung tissue to test the effects on the immune system of a blackcurrant extract, and have already found a compound with several actions against allergy-induced asthma. This compound, called epigallocatechin, enhances the natural defence mechanisms in lung tissue by suppressing inflammation-causing reactions.

We have discovered that epigallocatechin in blackcurrants reduces inflammation in lung tissue by working with other natural immune responses that occur at the same time to reduce inflammation. Epigallocatechin is also a known antioxidant and a major component of proanthocyanidins found in blackcurrants.

While this is the first research to give insights into the mechanisms of how fruit compounds reduce symptoms in allergy-induced asthma, it must be emphasised that this research is at an early stage, and by its very nature raises as many questions as it answers. What it does do is show that fruit extracts can have a beneficial effect on human health, and scientists now know where to explore further to find out how to maximise the health potential of fruit.

Dr Roger Hurst leads the Food and Wellness Group at Plant & Food Research in New Zealand.