Going Nuts On Fruits: Ellagic Acid in Rasp- and Blueberries, Pecans, Walnut & Co Protects Against Visceral Obesity

Image 1: I hope you are not one of the guys who spits the tiny seeds of the raspberries out. That is not just disgusting, you would also spit away ~90% of their ellagic acid content.

Nuts and fruits, once hailed as healthy superfoods have been under serious scrutiny within the sometimes overtly "health-conscious" blogosphere. Yeah, consumed in excess both will make you fat; but I would venture the guess that it would be easier to kill yourself by drinking too much water, than by eating too many almonds and bananas... well, before I get derailed here, let's take a look at the data from a recently published study on the effects of ellagic acid, a dilactone of two gallic acid molecules that is found in a wide variety of - guess what? - nuts (pecans, walnuts, cashews, brazil nuts, etc.) and fruits (raspberries, pomegranates, grapes and blackcurrants, plums, grapes, cherries and the list goes on)!

Good for your heart, good for your gut, good for your metabolism, ... but bad for you belly fat

In previous studies ellagic acid has already been identified as a potential heart protectant (Kannan. 2011a, 2011b); it has been shown to ameliorate the progress of cancer (Losso. 2004), to protect from Staphylococcus aureus biofilm formation (Quave. 2012), to exert potent anti-inflammatory effects (Umesalma. 2010), to protect the gut (Gonzalez-Sariaz. 2010),... an open list of health benefits, on which the anti-visceral fat effect Panchal et al. observed in their 16-week rodent trial is probably not going to be the last health-benefit to be added.

Figure 1: Ingredient (g/kg) and macronutrient (% of total energy) composition of the control and the HCHF diet (diet according to Pudjal. 2010, which was used as a reference diet by Panchal. 2012).

In the study at hand Sunil K. Panchal, Leigh Ward and Lindsay Brown kept 8-9 week old male Wistar rats on regular (extreme high carbohydrate, cf. figure 1) or high carbohydrate + high fat (the scientists even state that explicitly and don't mislabel their diet as simply being "high fat"!) diets either with or without 0.8g ellagic acid per kg chow.

Figure 2: Ellagic acid (µg/g dry weight) content of methanol extract of selected nuts and fruits (based on Daniel. 1989)

In view of an average food intake of 30g and 22g in the control and HCHF diet groups and given an average weight of 400-450g per rodent, the animals thusly consumed roughly 40-60mg ellagic acid per kg body weight per day*:

• control: 60mg/kg per day - human equivalent ~ 10mg/kg
• HCHF: 40mg/kg per day - human equivalent ~ 6mg/kg
  
  *note: I calculated those myself, Panchal et al. provide an estimate of 50mg/kg, as a reference

If we take the data from a 1989 study by Daniel et al. as a reference (figure 2) and assume that you weigh ~80kg and that your stomach is about as effective in extracting the ellagic acid from the dry part of the fruit (it is interesting to note that in strawberries >90% of the ellagic acid is in the pulp, while in raspberries 87% is in the seeds) as the laboratory equipment of the scientists was, and if we further take into account that most fruit are ~90% water, you would have to eat ~3,200g of raspberries or blackberries to get your daily dose of 6mg of ellagic acid; or, due to the lower water content (most nuts have ~5% moisture; cf. Beuchat. 2006) 2,181g pecans or 1,220g walnuts.

Note: The above calculation is by no means scientifically valid. In addition to that, the ellagic acid content of fruits and nuts vary according to season, origin, storage, etc. So, don't blame me, if - despite adding a bag of walnuts and a huge basket full of raspberries to your pizza, cola, pasta, twinkies, hamburger, fries, etc - you still gain weight on your high fat high carbohydrate (=standard American diet), ok?

No matter how (in-)accurate the above calculations may be (as I noted, they are probably not very accurate), I am not as confident as Panchal et al. that the average diet with its ~1g of total polyphenols would more or less 'automatically' contain the required 480mg-800mg of ellagic acid, "if the majority of polyphenols in the diet are taken from the fruits and nuts containing ellagic acid".

A cup of blueberries and a handful of nuts a day keep the doctor away?

Although it would seem that Panchal et al. have not done their homework as far as the real-world implications are concerned (and as I will argue in the conclusion - mishaps like these are at the heart of the "superfood myths"), the results of their experiments suggest that ellagic acid could be one of the rare cases, where it may be worth helping nature along, by extracting and capping a polyphenol that is, at least in some cases - such as pomegranate, for example, where large amounts are contained in the leaves (Lei. 2003) - not even necessarily contained in the edible part of the fruit / plant.

Figure 3: Body weight gain, food intake, water intake and energy intake (left); body composition data (right) of rodents fed either a standard high carbohydrate (regular corn starch) or an energetically dense high carbohydrate high fat diet with or without 0.8mg/kg chow ellagic acid for 16-week (data adapted from Panchal. 2012).

If you take a look at the ameliorative effect the lower ellagic acid dosage ('lower' simply due to the lower intake of the energetically more dense high carbohydrate high fat chow) exerted you will see that its effects are surprisingly depot-specific: Contrary to the total body fat mass, which is (within the statistical margin) virtually identical in all groups, the allegedly dangerous abdominal fat was reduced by -33% and -36% by the treatment in both the control (remember >90% of the energy from cornstarch ;-) and the HCHF group, respectively (the reduction was similar in all visceral fat depots; data not shown).

Figure 4: Basal glucose, AUC glucose after 2 g/kg body weight glucose load, triglycerides, total cholesterol, non-esterified fatty acids, c-reactive protein, uric acid and urea levels in rodents fed the supplemented control and the unsupplemented and supplemented high carbohydrate high fat diets; data expressed relative to unsupplemented control diet (data calculated based on Panchal. 2012).

These profound reductions in the amount of inflammatory visceral body fat, stand in line with the statistically significant improvements in glucose and lipid metabolism (cf. figure 4). As you can see the diet-induced increases in glucose, NEFA, triglyceride, cholesterol, CRP and uric acid, as well as the reduction of its counterpart, urea were completely blunted in the high carbohydrate + high fat group that received the ellagic acid enriched chow, an effect, the researchers attribute to...

• an increase in fatty acid oxidation, indicated by increased CPT1 activity and
• reduced inflammation, indicated the reversal of diet-induced increases in Nrf2 and NF-kappaB 

... in heart and liver of the rodents. That the addition of ellagic acid to the diet also minimized the necrotic damage to the liver of the animals, is thusly not surprising.

"So, shall I embark on the fruit and nuts diet?"

Despite those scientifically 'proven' benefits I should yet not have to tell you that it would not be particularly wise to take this study as an opportunity to ransack Trader Joe's dried fruit and nuts warehouses... As unreasonable as the contemporary condemnation of real (not dried!) fruit and (non-rancid!) nuts may be, it did not come out of nowhere, but has its roots in the detrimental overconsumption of both, nuts and fruits in the media-driven believe that adding tons of those healthy "superfoods" to your diet would allow you to live into your late 90s without ever having to worry about any of the ailments of the Western society. Both, nuts and fruit are yet only two "superfoods" within a "superfood diet", ... ah pardon, a whole foods diet, where neither of them is a "treat" or "cheat", but simply nutrition!

On a side note: Can you imagine that your ancestors sprouted a handful of nuts after all the work they had to shell them? They must have been nuts, if they did - don't you think so?

 Contrary to the impression you may get, when you follow the discussion on certain bulletin boards, eating healthy does thus not imply that you have to restrict your dietary repertoire to meat, fish, butter, eggs and the occasional sweet potato; this is all the more true, since ellagic acid is only one example for the myriad of already known and still to be discovered micronutrients with beneficial health effects, of which you would be depriving yourself, if your list of "allowed foods" contains no more than 5-10 items.

Think about it: Just as the FDA-approved food additives are "harmless" if you consume only one of them and potential hazardous, when you eat the whole variety that is present in the fast-food laden SAD diet, it is the synergy of all those ellagic acids and whatever their names may be that makes a varied whole-foods diet so healthy - don't miss out on that!