Nutty About Nuts

Let’s say you’re trying to lose 20 pounds – or boost your immunity – or increase your ability to fight Covid – or even cancer. Well – the amazing thing is – with the right diet – you are well on your way to achieving these vital health goals. Welcome to the NutritionFacts podcast. I’m your host Dr. Michael Greger. 

Today, we can finally justify – eating nuts…with wild abandon. And we’ll start with a little-known nut called the baru nuts. 

There is a new nut on the market called baru almonds, branded as “barukas,” or just baru nuts. Technically, it isn’t a nut, but a seed native to the Brazilian Savannah, known as the Cerrado, which is sadly now among the most threatened ecosystems in the world. For the last 30 years, extensive cattle ranching and feed crop production to fatten said cattle have destroyed much of this ecosystem. So, hey, if we can make it profitable not to cut down the native trees by selling baru nuts, for example, then that could be good for the ecosystem’s health. But what about our health?

Although baru nuts are popular and widely consumed, few studies report on their biological properties. They do have a lot of polyphenol phytonutrients, presumably accounting for their high antioxidant activity; 90 percent of the phytonutrients are present in the peel. So, are they nutritious? Sure. But do they have any special health benefits (and not just for the treatment of chubby mice)?

Groups fed baru nuts showed lower cholesterol, supposedly indicating that they have a great potential for dietary use in preventing and controlling cholesterol problems. But the groups were rats, and that was compared to lard. Basically anything lowers your cholesterol compared to eating lard. Nevertheless, there haven’t been any reports about the effect of baru almond consumption on human health, until this study. A randomized, controlled study of humans found that eating less than an ounce a day for six weeks led to a 9 percent drop in LDL cholesterol. Twenty grams would be about 15 nuts or a palmful.

Like many other nut studies, even though the research subjects were told to add nuts to their regular diets, there was no weight gain, presumably because nuts are so filling you inadvertently cut down on other foods throughout the day. How good is a 9.4 percent drop in LDL? Well, that’s the kind of drop you can get from regular almonds, though macadamias and pistachios may work even better––but those were at much higher doses. So, it appeared that 20 grams of baru nuts worked as well as 73 grams of almonds, and so, on a per-serving basis, or a per-calorie basis, baru nuts really did seem to be special.

Now, there are lower dose nut studies showing similar or even better results. People were given 25 grams of almonds for just four weeks, and got about a 6 percent drop. And in this study, people were given just 10 grams of almonds a day––I mean we’re talkin’ just seven individual almonds a day––and got more like a 30 percent drop in the same time frame as the baru nuts. Three times better at half the dose with regular almonds.

But the biggest reason we’re more confident in regular almonds is that studies have been done over and over––more than a dozen randomized controlled trials, whereas in the only other cholesterol trial of baru nuts, there was no significant benefit at all for LDL cholesterol, even at the same 20-gram dose given for even longer—a period of eight weeks. That’s a bummer.

The primary reason I would suggest choosing other nuts instead, though, is that you can’t get baru nuts raw. They contain certain compounds that have to be inactivated by heat before human consumption. So, the reason raw nuts are preferable is because of advanced glycation end products (AGEs), so-called glycotoxins, which are known to contribute to increased oxidative stress and inflammation.

Glycotoxins are naturally present in uncooked animal-derived foods, but then dry-heat cooking, like grilling, can make things worse. The three highest levels recorded are bacon, broiled hot dogs, and roasted barbequed chicken skin (nothing comes close to that.) Any foods high in fat and protein can create AGEs at high enough temperatures; so, although plant foods tend to contain relatively few AGEs, even after cooking.

Now again, with most plant foods. it’s not at all a problem. I was surprised that veggie burgers were so low, even when baked or fried. But nuts and seeds are up in tofu territory, especially when roasted, which is why I would recommend raw nuts and seeds and nut and seed butters whenever you have a choice.

In our next story, we’ll look at some randomized controlled studies that put nuts, berries, and grape juice to the test for cognitive function.

When you read articles in Alzheimer’s disease journals, about how “Eating more berries may reduce cognitive decline in the elderly,” they’re talking about observational studies like this, where “berry intake appears to delay cognitive aging by up to 2.5 years” in the Harvard Nurses’ Health Study, or the “intake of nuts” appearing to delay brain aging by two years. They’re just talking about associations. Berry-eaters and nut-eaters tend to have better brain function as they age after trying to control for a bunch of other lifestyle factors, but you don’t know if it’s cause and effect…until you put it to the test. Thankfully, we now have a growing number of interventional studies that have done just that. Randomized, controlled trials where people eat berries or nuts and you can prove it—actually show improvements in cognitive performance, raising the berry nutty idea that we may be able to forestall or reverse the effects of neurodegeneration in aging with food.

For example, this study on the “effects of walnut consumption on cognitive performance.” College students split up into groups doing two months of walnuts, followed by two months of placebo or vice versa, and then they switch. How do you make a placebo nut? They baked it in. They gave people banana bread with or without nuts; same ingredients, just one with walnuts, and those on the nuts showed a significant improvement in “inference capacity,” the ability to accurately draw conclusions from a set of facts—in other words, critical thinking. And so, on a practical level, “maybe students or young professionals in…fields that involve a great deal of critical thinking or decision-making could possibly benefit and gain a slight advantage through regular consumption of walnuts.”

Or this berry study, where they randomized folks to some crazy berry smoothie with blueberries, black currants, elderberries, lingonberries, strawberries, and…a tomato. And not only did their bad cholesterol drop about 10 points, they “performed better” on short-term memory tests. So, good for heart, good for the brain. And not just better on like pencil-and-paper tests, but real-world applications. Give people Concord grape juice versus some fake grape Kool-Aid-type placebo, and you can get improved performance on everyday tasks—like quicker response times in driving tests. Why not just give people Concord grapes instead of juice? Well, then, it’s harder to create a placebo, and, of course, the study was paid for by Welch’s.

Okay, fruit and nuts; what about vegetables? “Consumers of cruciferous vegetables, (cabbage, cauliflower, kale, collards, broccoli, and Brussels sprouts) [have been found to perform] better in several cognitive tests than non-users.” And, in terms of cognitive decline with aging, “women consuming the most green leafy vegetables” did better—effectively slowing brain aging a year or two, and not just cruciferous, but other dark green leafies like spinach; so, maybe it’s the nitrates.

As we age, our cerebral blood flow drops—the amount of blood flowing through our brain, “which may be due to an age-related decrease in the production of [nitric oxide],” the open-sesame molecule that dilates our blood vessels and is boosted by the consumption of nitrate-rich vegetables. “This reduction in blood flow to the brain [may be] a major risk factor for the impairment of cognitive function and development of neurodegenerative diseases, such as dementia.”

Finally today, we’ll discover how just a few small servings of nuts a week may increase our lifespan and lower cancer risk.

We’ve known “[i]ncreased nut consumption has been associated with a reduced risk of major chronic diseases, including [heart disease and diabetes].” But do those who eat nuts actually live longer lives? “Clinical trials have shown” nuts help lower cholesterol and oxidation, and improve our arterial function, and blood sugar levels, but does this all translate into greater longevity?

Researchers at Harvard “examined the association between nut consumption and subsequent…mortality” of over a hundred thousand people, followed for decades. In that time, tens of thousands died, but those that ate nuts every day lived significantly longer. Daily nut consumers had fewer cancer deaths, heart disease deaths, and fewer deaths from respiratory disease. And, this was after controlling other lifestyle factors. So, nut consumers lived significantly longer whether they were older or younger, fat or skinny, whether they exercised more or smoked, drank, or ate other foods that may affect mortality.

But, nuts are so filled with fat. “There may be a concern that frequent nut consumption can result in weight gain.” However, that’s not what they found, and, in fact, other studies have associated nut consumption with a slimmer waist, less weight gain, and lower risk of obesity. If you look at all the studies put together, it’s pretty much a wash. Diets enriched with nuts do not seem to affect “body weight, body mass index, or waist circumference” much at all.

Hence, it appears, the incorporation of nuts—around one or two small handfuls a day—would be advisable to ensure various health benefits, without the risk of body weight gain. And, what was nice about this review is that there were no apparent ties to the nut industry.

How nuts do we have to go? Not much. Just a few servings a week may boost our lifespan and lower cancer rates. But, it appears we have to keep it up. In the PREDIMED study, when long-time nut eaters were told to cut down on eating nuts, or choose extra virgin olive oil, within five years, they apparently lost much of their longevity benefit. Only the group that started out eating nuts and continued to eat at least the same amount of nuts had the significant survival advantage.

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