We speak with Professor Mirosława Krauze-Baranowska, Head of the Department of Pharmacognosy at the Faculty of Pharmacy of the Medical University of Gdańsk, about pharmacognosy, berry fruits and, in particular, red and black raspberries – their biological properties and their preventive and therapeutic potential.
Professor Krauze-Baranowska has been conducting research into black and red raspberries, as well as other berry fruits, for many years.
Professor, let us begin with the most fundamental question: what is pharmacognosy?
Pharmacognosy is a scientific discipline concerned with medicinal plants. It examines their chemical composition and evaluates their pharmacological activity.
We have met primarily to talk about raspberries – red raspberries and black raspberries. You are an expert, researcher and advocate of these fruits.
That is correct. Red raspberry is a plant material that has been used successfully in folk medicine for decades – one might even say for centuries – primarily as a remedy for colds.
Contemporary scientific research allows us to broaden the range of potential applications of raspberry fruit and to understand its biological properties in greater detail.
We know that Poland is the largest exporter of red raspberries in Europe. Black raspberry, however, remains relatively unknown in Poland, even though it is an exceptional fruit that certainly deserves greater recognition.
Why is black raspberry so little known in Poland?
Primarily because it is not a species that occurs naturally in Poland. It originates from the United States, where it is cultivated on a large scale.
We are still far from achieving such large-scale cultivation in Poland, although individual black raspberry plants can occasionally be found in home gardens.
From a scientist’s point of view, what makes black raspberry so exceptional?
Black raspberries differ from red raspberries primarily in quantitative terms. In other words, it is not that they contain entirely different active compounds, but rather that they contain higher concentrations of them.
How much higher?
It is estimated that the anthocyanin content – and anthocyanins are the compounds we are referring to – may be eight or even eleven times higher in black raspberry products than in red raspberry products.
Scientific research shows that anthocyanins are a very important group of biologically active compounds present in raspberries and are responsible for many of their properties.
Interestingly, the high anthocyanin content of black raspberries meant that their juice was used as a natural food colouring in the United States long before the nutritional value and biological activity of these fruits became widely understood.
Like red raspberries, black raspberries contain not only anthocyanins but also ellagitannins. The presence of ellagitannins alongside anthocyanins is a characteristic feature that distinguishes all raspberry species, regardless of variety, from other berry fruits.
The main advantage of black raspberries over red raspberries is therefore their higher anthocyanin content.
Ellagitannins and anthocyanins are increasingly discussed in the context of antioxidant activity. Could you explain what antioxidant activity actually means?
Antioxidant activity is associated with the presence of polyphenolic compounds, most commonly linked with bioflavonoids, a group to which anthocyanins belong.
The antioxidant properties of a particular plant material are also influenced by ellagitannins and flavan-3-ol derivatives, including catechins, which are also found in raspberries, although in lower concentrations.
These three groups of compounds are responsible for what is commonly referred to as “free-radical scavenging”. As we know, free radicals contribute to the development of many lifestyle-related diseases, including cancer, cardiovascular disease and metabolic syndrome.
The level of free radicals in the body increases in the course of many illnesses, even during a simple cold.
Free radicals damage cells. For example, they may damage pancreatic cells and the islets of Langerhans, which may contribute to the development of diabetes, although other factors are, of course, also involved.
Free radicals can also damage the vascular endothelium, facilitating the rapid formation of atherosclerotic plaque.
They are additionally responsible for various types of mutations and changes within DNA, which may in turn lead to the development of cancerous changes.
All plant materials with high antioxidant potential help to scavenge free radicals and may therefore play a major role in the prevention of lifestyle-related diseases.
Can we therefore say that red raspberries, and black raspberries in particular, can be highly beneficial in the prevention of cancer, cardiovascular disease and metabolic syndrome?
Yes, definitely.
What exactly is metabolic syndrome?
Metabolic syndrome is a group of interconnected factors that significantly increase the risk of developing atherosclerosis, type 2 diabetes and the serious cardiovascular complications associated with these conditions.
It is characterised primarily by elevated blood glucose levels, meaning diabetes or the early stages of diabetes.
It is also associated with elevated cholesterol and triglyceride levels, which may indicate the early stages of atherosclerosis.
Obesity and its consequences are another component. High blood pressure is also taken into account when diagnosing metabolic syndrome.
In brief, we are talking about hypertension, hyperlipidaemia, hyperglycaemia and excess body weight.
How can red and black raspberries help in this context?
They can help by affecting the individual components of metabolic syndrome.
I would like to emphasise that, as a scientist, I am referring to effects that have been confirmed in clinical studies.
You mentioned diabetes. We often hear that people with diabetes should avoid fruit because of its sugar content. How does this relate to the recommendation to consume raspberries?
I will refer to the results of research conducted on chokeberries. Researchers assessed whether the sugar naturally present in fruit could potentially increase blood glucose levels.
No relationship was observed between the consumption of chokeberries and an increase in blood glucose—neither postprandial glucose levels nor fasting glucose levels.
Clinical studies concerning black raspberries and metabolic syndrome similarly found no effect of black raspberry consumption on either postprandial or fasting glucose levels.
Clinical studies have also examined the influence of raspberry consumption on triglyceride and cholesterol levels.
After a sufficiently long period of daily consumption, beneficial effects were observed in relation to total cholesterol, LDL cholesterol and high blood pressure.
Research has also suggested that raspberry consumption may accelerate the reduction of body fat.
You mentioned cancer among lifestyle-related diseases. Have studies been conducted on the effects of black raspberries in relation to cancer?
A great deal of research has been conducted using a variety of models, ranging from in vitro experiments to clinical studies.
In the case of black raspberries, numerous studies have indicated beneficial effects in relation to skin cancer, oesophageal cancer and colorectal cancer.
Clinical studies have confirmed, for example, that black raspberries may inhibit the progression of precancerous lesions, as well as existing cancerous lesions, within the colon.
Scientific literature contains a considerable amount of information concerning the therapeutic significance of black raspberries and their beneficial effects in cases of colorectal cancer.
These effects are associated with the multi-directional activity of anthocyanins and ellagitannins.
Anthocyanins are not merely antioxidants. They are also chemical compounds that have a beneficial effect on capillary blood vessels.
A diet rich in anthocyanins may therefore help to reduce inflammation within the gastrointestinal mucosa, partly because of this beneficial influence on blood vessels.
Anthocyanins, as well as other flavonoids found in raspberries, increase the elasticity of blood vessel walls and reduce vascular permeability, thereby helping to limit inflammation.
For this reason, raspberries—and other fruits containing anthocyanins—are considered beneficial for patients with gastric ulcers and various inflammatory conditions affecting the gastrointestinal mucosa.
Antioxidant activity is therefore not the only relevant mechanism. Other properties are also important.
Returning to cancer prevention and the supportive role that these fruits may play during cancer treatment, considerable significance is attributed not only to anthocyanins but also to ellagitannins.
Ellagitannins are compounds derived from ellagic acid and have demonstrated anticancer properties in laboratory models.
In the human body, ellagitannins are broken down into ellagic acid, which is known for its antimicrobial and antiviral properties.
Ellagic acid is subsequently metabolised into urolithins, some of which have anti-inflammatory effects.
Red raspberry has traditionally been used to support the body during colds. Can we expect black raspberry to have similar antibacterial and antiviral properties?
There is no fundamental difference in the types of active compounds found in the various raspberry species. The difference, as I mentioned earlier, is mainly quantitative.
Black raspberries contain higher concentrations of active compounds, especially anthocyanins. It can therefore be inferred that they may be an even more effective remedy for colds.
We have been discussing therapeutic applications, but it is also worth saying more about prevention and about building good health every day, step by step.
Personally, I believe that berry fruits – particularly those rich in anthocyanins, including red raspberries and, above all, black raspberries – should be consumed regularly throughout our lives.
Why? Because they have an excellent effect on the condition of blood vessels, including capillaries.
This is relevant to matters that may appear very different but are equally important, such as visual performance, the overall health of the cardiovascular system and the prevention of atherosclerotic changes.
Does that mean everyone should eat berry fruits every day, from children to senior citizens?
Of course. We should remember that consistency is essential.
To obtain the greatest possible benefit from raspberries later in life, it is best to begin consuming them when we are young.
We should eat them every day and continue doing so throughout our lives.
Can pregnant women and breastfeeding mothers also consume berry fruits in this way?
Yes, absolutely. Everyone can and should consume them, both preventively and as dietary support during illness.
Raspberries can provide support in cases of inflammation.
Temporary infections that occur in pregnant women and mothers may be effectively addressed in their early stages by increasing the intake of berry fruits, including raspberries.
This requires no particular effort. Quite the opposite, in fact, because raspberries have a very pleasant flavour.
We are talking about eating berry fruits every day, throughout the year, but the season for fresh berries is very short.
Fortunately, we have processing methods available – specifically, two main solutions.
The first is freezing.
The second is the method offered by your company: high-quality freeze-drying without the use of microwaves.
This type of freeze-drying is undoubtedly the most advantageous method because it makes it possible to preserve active compounds at levels comparable to those found in the fresh raw material.
Other popular processing methods, particularly those involving elevated temperatures, cause active compounds to break down.
Freeze-drying without the use of microwaves makes it possible to maintain stable levels of active compounds comparable to those found in the original fresh fruit.
What about the microbiological quality of freeze-dried fruit? Is it preserved?
Freeze-drying is essentially a process of drying the raw material, although it takes place under specific conditions.
Enzymes are inactivated and, of course, water is removed. Since an aqueous environment provides highly favourable conditions for the growth of microorganisms, a properly conducted freeze-drying process provides very effective protection against microbial growth.
Drying at elevated temperatures presents certain limitations. If the temperature is too high, active compounds may break down. If it is too low, microorganisms may develop.
Freeze-dried fruits must subsequently be stored correctly, protected from moisture and light.
Critics of freeze-dried fruit sometimes claim that it does not taste good.
I must say that your products are truly exceptional, and I say that sincerely.
They have a very pleasant texture. They are crisp, slightly tart and, at the same time, have a delicate sweetness.
There is no need to force yourself to eat them – quite the opposite.
This demonstrates just how much depends on the quality of the raw material and the quality of the freeze-drying process when it comes to appreciating this form of fruit processing.
During an earlier conversation about the concentration of active substances in different fruits, you said: “In black raspberries, these substances occur as a cocktail, and it is this cocktail that makes the overall effect more powerful.”
A characteristic feature of plant-derived products – whether foods or medicinal products – is that they contain different groups of active compounds that work simultaneously and through multiple mechanisms.
This distinguishes a plant-derived product from, for example, a synthetic medicine that may have only one principal mechanism of action.
In the case of black raspberries, one mechanism involves anti-inflammatory activity, including their influence on blood vessel permeability.
Alongside this, we have the mechanism of scavenging excess free radicals produced during inflammation. These are already two separate directions of activity.
We can also add the anticancer effect I mentioned in relation to colorectal cancer and the protective effect on the gastrointestinal mucosa.
But that is not all.
Raspberries are very rich in vitamin C, which has an exceptionally beneficial effect on the immune system.
In addition, the flavonoids found in raspberries help to stabilise vitamin C.
When all these mechanisms are considered together, the overall effect is genuinely impressive.
This leads us to another question: is it possible to consume too many berry fruits, including freeze-dried fruit?
No. Berry fruits contain compounds for which no toxicity has been demonstrated, so we cannot speak of an overdose in this context.
What daily serving would you recommend?
Any amount, provided it is consumed every day, can have health-promoting and strengthening value.
Even a handful can be beneficial, while a cup certainly provides a meaningful serving.
However, when we refer to the results of clinical studies concerning specific and serious medical conditions, beneficial effects have been observed at a daily intake of 60 grams of freeze-dried fruit.
Clinical studies have been conducted in which participants received 20 grams of freeze-dried black raspberries three times a day. Researchers observed an effect involving the inhibition of the progression of cancerous lesions within the colon.
Our conversation has focused mainly on raspberries, but every berry fruit is unique in its own way in terms of its health-promoting properties.
That is correct.
Wild strawberries are recommended for people with chronic joint conditions because they contain, among other compounds, salicylic acid.
Not everyone may know that during the Second World War, British pilots were instructed to eat bilberries to improve their visual acuity at dusk.
The anthocyanins found in bilberries have a beneficial effect on the capillaries within the eye.
There is a difference between bilberries and raspberries resulting from the different chemical profiles of their anthocyanin compounds.
Bilberries contain a mixture of various anthocyanins that have a beneficial effect on the capillaries of the eye.
In raspberries, by contrast, the dominant anthocyanin is cyanidin, which exhibits particularly strong anti-inflammatory and antioxidant properties.
Red raspberry has also demonstrated anti-rheumatic properties and a capacity to support the regeneration of articular cartilage in laboratory models and animal studies.
However, clinical trials are still required before all these effects can be conclusively confirmed. Such studies involve lengthy procedures and, above all, are very expensive.
Nevertheless, I remain optimistic.
Professor, we would like to conclude with a personal question: what is your favourite fruit?
Definitely black raspberry.
I enjoy its flavour and, as a scientist, I am also aware of its therapeutic potential.
I like fresh black raspberries, but I am delighted that you freeze-dry them, because the flavour of your freeze-dried black raspberries is truly remarkable.
We are very pleased to hear that. Thank you for speaking with us.
Thank you as well.
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