Superfoods and performance: don’t go completely nuts!

Hardly a day goes by without a new ‘superfood’ appearing on shelves of health food stores and supermarkets up and down the country. But as Andrew Hamilton explains, some superfoods may not be so super for your performance…

One of the benefits of living in a modern, interconnected world is the choice of different foods on offer. Most people no longer need to rely solely on traditional dishes, and enjoy exploring more exotic and international options! The same goes for so-called ‘superfoods’ such as gogi and acai berries, chia seeds, moringa and many others. When it’s easy to fly in different foods from around the globe, it’s no surprise that new products with bold health and performance claims are regularly appearing on supermarket shelves up and down the country.

But while it’s tempting to rush out and stock up on the latest superfood, perhaps we should stop and ask ourselves just how super they really are? Can they really enhance your health or performance and (apart from the often eye-watering cost!), are there any drawbacks? With so many superfoods out there, it’s impossible to provide a comprehensive answer; indeed, some research suggests that not every superfood is that super, and that we perhaps could do with taking a more cautious approach.

Nuts about pistachios

A case in point is pistachio nuts. Pistachio nuts are very nutrient-dense, supplying high levels of vitamins, minerals, and water and in particular, fat-soluble antioxidants. It’s for this reason that some nutritionists have suggested that they could be good for sport performance. The argument put forward is that since these antioxidants are effective at reducing antioxidant damage and inflammation in the muscles during exercise, consuming pistachio nuts regularly might reduce muscle soreness and fatigue.

To test this theory and see what benefits (if any) pistachio nuts might have for endurance athletes such as cyclists, runners and swimmers, scientists studied 75km cycling time trial performance in nineteen competitive cyclists after two weeks of pistachio supplementation(1). The cyclists were randomly assigned to one of two groups:

  • A pistachio nut supplementation group, consuming 3oz of nuts per day for a period of two weeks.
  • A no-supplementation group, who ate no pistachio nuts.

During the 2-week period, all the cyclists maintained their normal training and food intake patterns; the only difference was that the pistachio group also consumed the nuts. At the end of the two weeks, all the cyclists performed a 75km time trial and their times were recorded. After a 2-week ‘washout’ period, the cyclists did an identical second trial but switched groups so that the cyclists who had taken pistachios in the first trial now took nothing and vice-versa (a so-called crossover trial). Just as in the first intervention, the cyclists performed another 75km time trial at the end of the second intervention and the times were recorded.

When the researchers analysed the data, they found that (compared to the nut-free intervention) consuming pistachio nuts significantly boosted the cyclists’ intake of carbohydrate, protein, fat and a range of vitamins and minerals including vitamin B6, folic acid, potassium, iron, copper, magnesium, zinc, and molybdenum.

That was the good news; the bad news was that consuming the pistachio nuts didn’t result in enhanced performance – quite the opposite in fact. After consuming the pistachios, the cyclists completed the 75km time trial in an average of 170.4 minutes – 7.8 minutes slower than when they hadn’t been eating the nuts (see figure 1)! Another interesting finding was that the pistachio nut intervention resulted in a slightly reduced ability to consume oxygen during the time trial, which probably explains why average power outputs fell in the pistachio time trial (from 207 watts to 201 watts).


Figure 1: Pistachio supplementation and 75km time trial performance


Obvious question

The most obvious question that follows is how could consuming something (apparently) so healthy result in worse cycling performance? The most likely explanation for this drop in performance is that pistachios are rich in a naturally-occurring sugar called ‘raffinose’. Raffinose is also found in onions and many types of beans and peas. In many ways, raffinose is thought to be beneficial for human health; in particular, it acts as a ‘prebiotic’, helping promote the growth of friendly bacteria such as bifidobacteria and lactobacilli in the gut. A healthier gut flora is known to have positive effects on bowel function and is also associated with a reduced risk of inflammatory bowel disease and bowel cancer(2).

Unfortunately, there’s a downside to eating raffinose-rich foods because high raffinose intakes increase the body’s production of a compound called ‘9,10-DiHOME’, which is known to interfere with the process of producing energy in mitochondria – the ‘energy factories’ in your muscle cells(3,4). Although no direct measurement of 9,10-DiHOME in the cyclists was made, the fact that oxygen consumption was adversely affected when the cyclists ate the pistachios led the researchers to conclude that it was the raffinose in the pistachios (and the 9,10-DiHOME produced from the raffinose) that had caused the poorer performance.

Practical implications

What do these results mean for endurance athletes? In terms of performance, they suggest that unless there’s good scientific evidence to the contrary, the term ‘superfood’ should be taken with a pinch of salt. This study also shows that a superfood claimed to offer health benefits may not tick the performance box – in this case, the pistachio nuts actually worsened performance! There’s also the issue of raffinose. Is it wise for endurance athlete to avoid other raffinose-rich food (see table 1) during the days prior to an important event or race where maximum performance matters? Although more studies are needed, the answer to that for now at least is ‘probably’ – especially as there are many other healthy foods low in raffinose that can substitute for high-raffinose foods in an athlete’s diet!


Table 1: Some high-raffinose foods

Food Raffinose (grams per 100g)
Sunflower flour 3.0
Onions (raw) 1.4
Chicory (raw) 1.2
Soybean flour (defatted) 0.8
Mung beans (raw/sprouted) 0.8
Pistachios (shelled) 0.6
Parsley (raw) 0.6
Chickpeas (cooked) 0.4
Broadbeans (cooked) 0.4
Mung beans (cooked) 0.3
Oat bran 0.3

References

  1. PLoS One. 2014 Nov 19;9(11):e113725
  2. PLoS One 2012; 7(10): e47212
  3. J Biosci 2007; 32:279–291.
  4. J Am Coll Nutr 2003; 22:502–510

See also:

Share this

Follow us