There are an estimated 352,000 species of Angiosperms, the family of plants that grow fruits.1 Some are quite super, and some are merely average, but most have not been researched. For the sake of this article, lets focus on fruits that are a part of human diet and have some level of potential health benefit documented in the scientific literature.
Biologically speaking, all fruits and vegetables maintain some level of endogenous antioxidants in order to live. In the test tube, fruitsparticularly concentrated fruit extractstend to be powerful free radical scavengers. Yet, in vitro antioxidant results vary in terms of their relevance to biological functions in the body.
If the first decade of this millennium was characterized by mainly test-tube science on these fruits, the second decade may be ultimately remembered for clinical research.
For example, some fruit phytochemicals may not absorb into the body very well. Or, they may have a specific effect on biological functions that is not captured by the scientific design of test tube, animal or human experiments. Results from some large-scale trials have raised doubts about the value of antioxidants and superfruits. But at the same time, the suitability of the studies may not fit their intended purposes.
In any case, suitability of a scientific test (whether in the test tube or the medical clinic) is evolving as a central question that may define the dietary landscape for years to come: whom do we intend to benefit, and with what dietary intervention?
Cue scientific advances. In recent years, we have seen an increased focus on what actions superfruits exert on the human body. Hundreds of studies have demonstrated consumption of various fruits and vegetables tends to increase the blood's antioxidant capacity. These studies tend to focus on polyphenols (such as catechins, anthocyanins and tannins) as well as triterpenes, carotenoids and other classes of bioactive compounds from plants.
For example, in a 2013 study, some measures of antioxidant capacity and vitamin C levels were increased in healthy humans who drank one serving of juice containing blackberries, camu-camu and acai.2 Perhaps if the subjects had consumed the juice for longer than one day, a more pronounced effect would be observed, but it is interesting that a single serving of superfruit juice has a positive impact on biological function.
In another study that was just published, daily consumption of grapefruit juice for six weeks reduced isoprostanes, pro-inflammatory markers of lipid oxidation, in overweight adults who had high baseline values. However, no effect was observed in overweight adults who had normal baseline levels.3 This difference in results suggests grapefruit juice could be most effective for some types of people and not others.
It is this sharpening of clinical study design that suggests specific dietary interventions may only be effective for specific subpopulations of people. The results lead to another question: what does all of this antioxidant stuff actually mean? As we see often in the news, perhaps not all antioxidants (or superfruits) are created equal, especially after subjected to the vagaries of the human body. For example, some are more durable in stomach acid than others.
Thus, the new world of clinical science on superfruits is beginning to travel beyond antioxidant status in humans, taking full advantage of advances in technology and research budgets. As analytical and clinical techniques improve in terms of resolution and sensitivity, and clinical results are replicated with different methods, we are able to pinpoint how superfruits may work for specific health applicationsand for what types of people.
For example, a recent study on pomegranate juice found when young, healthy men consumed pomegranate juice with a high-fat meal, their postprandial systolic blood pressure was lowered versus when they had only water with the meal.4 A previous study over a longer term and in older people eating their normal diet with daily pomegranate consumption found a similar result. Together, the body of evidence suggests consumption of pomegranate may help both acutely with poor diets and over the long term with normal diets.
In a study published in 2013 by Finnish researchers, results indicated different fractions of sea buckthorn berries offer subtly different effects on blood lipids in humans, specifically low-density lipoprotein (LDL) cholesterolbut the results were seen predominantly in subjects with higher cardiometabolic risk.5 Likewise, in this study, bilberry also improved some measures of blood lipids in subjects at higher risk.
Blueberries are not necessarily considered your average exotic berry consumed by an Amazonian tribe, but the substantiation picture is evolving for their qualification as super" as well. In healthy men, intake of polyphenol-standardized blueberry extract led to an improvement in vascular function.6 The study linked this activity to the distinct mechanism of neutrophil NADPH oxidase activity key in the development of atherosclerotic plaques. Blueberries are interesting, yet there is still room for research on what blueberry composition is likely to be the best.
While we have only touched the surface, dont forget about the thousands of scientific studies on what are considered superfruits botanically speaking, such as tomatoes, pumpkins, walnuts, avocados, coffee beans and cocoa. Some of the great Ayurvedic mainstays, lest we forget, are fruits as well: amla, bitter melon, garcinia, moringa, mucuna. More science is on the horizonand there are only another 350,000 fruit species yet to be studied.
For a list of references, email [email protected]
Blake Ebersole is technical director at Verdure Sciences , where he has led botanical quality initiatives and formed collaborations with dozens of universities and research centers focused on preclinical and clinical development of botanical extracts.