bite my words

Dispelling nutrition myths, ranting, and occasionally, raving


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Why the nut study made me nuts

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A study published last week in the New England Journal of Medicine found that the consumption of nuts was tied to lower mortality rates. I love nuts but I hate studies like this.

The research was funded by the International Tree Nut Council Nutrition Research and Education Foundation. Yep, that sounds like an impartial sponsor. I’m sure that didn’t affect the results whatsoever. Yes, they may have had no influence on the design and results but if they study hadn’t found a benefit to eating nuts would it have been published? Would it still have been promoted in the press?

Even putting aside the significant issue of bias, this study wasn’t great. It used the data from the Nurses’ Health Study. Why do I see this as an issue? Well, it relied on self-reported data. We know that self-reported food intake surveys are flawed and tend to provide inaccurate information. Even if the information provided was accurate, we don’t know how generalizable the results from a survey solely of nursing staff is to the general population. These nurses may differ in some fundamental way from the general populace. There’s huge potential for confounding factors in studies like this. Lower mortality rates may be attributed to other aspects of lifestyle, diet, or socioeconomic status. The nut eaters could have been eating the nuts with something else that was the actual health promoter or they may have been eating the nuts in place of something else that was detrimental to health.

It also bothers me that people who had previously had cancer, heart disease, or stroke were excluded from the study. This means that even if eating nuts benefits healthy people (as the study claims) we still don’t know if it benefits those who are, or who have been, ill.

The study also fails to tell us if there is a limit to how many nuts we should eat in a day for maximum benefit. They found that those who eat nuts at least daily had the lowest mortality rates. However, they didn’t say how many nuts people were eating each day. Nuts are undoubtedly delicious and nutrient dense. They are also calorie dense. Having a handful of nuts on your oatmeal or a walnut pesto on your pasta may be beneficial but eating a large bag of trail mix for a snack most likely is not. Simply telling people to eat more nuts is not helpful dietary advice.


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Should you be fighting phytic acid?

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I’ve had a few people ask me about the merits of soaking grains overnight to remove phytic acid. “What is phytic acid and why would I want to get rid of it?” you might ask.

Phytic acid is an antioxidant present in nuts, seeds, grains, and legumes. Many people are adamant that it be removed from foods before consuming as it binds to minerals such as calcium, zinc, and iron, minimizing the amount that you’re able to absorb from that food. It’s been suggested that grains should be soaked or sprouted before cooking in order to remove the phytic acid.

The issue: it’s uncertain how much phytic acid is actually removed by soaking grains and beans. It seems that only about 10% of phytic acid is removed through overnight soaking (1). Also, it’s unlikely that, if you’re consuming a healthy diet including a variety of foods, you’re going to experience any malnutrition due to the presence of phytic acid in your oatmeal or bean salad.

Finally, it’s possible that there may be benefits to the consumption of phytic acid of which we’re unaware. For example, some research (admittedly not the greatest study, nonetheless) has indicated that phytic acid may actually be of benefit in Alzheimer’s disease prevention/slowing of progression. Even if this research proves to be meaningless it helps to illustrate how little we know about the individual components of food. This is one reason we dietitians are always harping on about obtaining as many nutrients as possible from whole foods. We don’t know precisely how all of these nutrients are interacting with each other in food and we don’t know how that impacts the benefits we obtain from foods.

While there’s no harm in soaking your grains, or sprouting them, there’s probably little benefit as far as phytic acid removal is concerned. And who knows, that may not be such a bad thing.


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Don’t go too nuts for walnuts

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I’ve been seeing a few news reports recently regarding nut consumption, particularly walnuts, and diabetes. The reports are based on a study Walnut Consumption Is Associated with Lower Risk of Type 2 Diabetes in Women. This study used data from the Nurses’ Health Study to determine the effect of nut consumption on diabetes risk.

The news article all proclaim that regular consumption of walnuts can reduce the risk of developing type 2 diabetes. There was a risk reduction shown with consumption of walnuts as little as once a month but the greatest risk reduction (24% in comparison to women who ate few or no nuts) was seen in the women who ate walnuts at least once a week.

Now, as much as I’m a fan of nuts, I’m always a little skeptical of reports such as this. I always wonder if the news reports accurately reflect the study’s findings and if the study is well-designed. So… I went and took a look at the journal article.

I’m immediately wary of any study that uses food frequency questionnaires to obtain data on food consumption. These questionnaires are notoriously inaccurate. Putting that issue aside and looking at the rest of the study, a couple of additional issues popped out at me. While the researchers controlled for things such as physical activity, fruit and vegetable consumption, and obesity, it is impossible to control for all variables and it’s possible that a factor common to the walnut eating group other than their walnut consumption may have reduced their risk of diabetes. Also, after controlling for BMI, the risk reduction afforded by walnut consumption dropped from the reported 24% to 15%. Perhaps if another measure, such as waist-to-hip ratio had been used this percentage would have decreased further.

Most importantly: funding for the study was provided by the California Walnut Commission.

I certainly don’t want to discourage anyone from eating walnuts. However, too much of any one thing can be bad for us and I don’t want anyone reading reports from this study erroneously thinking that they should be consuming unlimited quantities of walnuts to stave off type 2 diabetes. There are benefits to all nuts and they all contain fairly concentrated calories so it’s certainly possible to go overboard with them. Incorporate a variety of nuts in your diet to obtain the maximum health benefits from their consumption.


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Nut nutrition

I find the peanut often gets a bad rap. I’m not sure why this is, perhaps it’s seen as “common” in comparison to other more exotic nuts like macadamia nuts (yes, I know, the peanut is technically a legume and not a nut at all). Perhaps it’s because it’s the cause of anaphylactic shock in people with severe nut allergies and as a result it has been banned from many schools. What ever the reason, it’s still a great source of nutrients and doesn’t deserve to be looked down upon.

When it comes to nuts, there really is no clear winner in the nutrient department. They all have different nutrient profiles and can all play roles in a healthy diet. If you were wondering which nut has the most protein, the least saturated fat, or the most calcium, or other some other nutrient, look no further than this handy dandy little chart I’ve compiled for you:

Nut variety Protein (g) CHO (g) Fat (g) Sat. Fat (g) kCal Fibre (g) Ca (mg) Mg (mg) K (mg) Zn (mg) Se (micrograms)
Peanuts 8.8 8.0 18.4 2.6 217 3.0 20 65 244 1.2 2.8
Almonds 7.7 6.8 18.5 1.4 209 4.1 93 100 261 1.2 1.0
Cashews 5.3 11.4 16.1 3.2 199 1.0 16 90 196 2.0 4.1
Walnuts 3.9 3.5 16.5 1.6 166 1.7 25 40 112 0.8 1.2
Pecans 2.7 3.8 20.7 1.8 198 2.6 20 37 118 1.4 1.1
Pistachios 6.7 8.6 14.3 1.7 178 3.2 34 37 325 0.7 2.9
Brazil nuts 5.1 4.4 23.6 5.4 233 2.7 57 133 234 1.4 680.6

All values are based on a 60 mL/37 g serving of dry roasted nuts and rounded to one decimal place.


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Don’t go too nuts

I know that I’m frequently extolling the virtues of nuts on here but I’m a bit annoyed by all the news articles I’ve been reading about the benefits of eating nuts lately. Here’s the article that prompted this post: Tree nuts linked to lower body weight, decreased type 2 diabetes risk: study. The article states that daily nut consumption (of more than 1/4 ounce) leads to lower body weight, higher HDL (aka the “good” cholesterol), and lower risk of metabolic syndrome. Important things to note here: the differences between the nut-eaters and the non-nut-eaters were quite small (5% or less for most risk factors). Also, the study was funded by the International Tree Nut Council Nutrition Research & Education Foundation (to the news article’s credit it does point this out). It’s always a little questionable when a study shows results which are favourable to the funder. The biggest issue, as I see it, is that this study showed an association between tree nut consumption and the aforementioned health benefits. This means that these benefits may be attributable to some other fundamental difference(s) between the tree nut-eaters and the non-nut-eaters. For example, nuts are fairly expensive, perhaps nut-eaters are healthier because they have a higher socioeconomic status than non-nut-eaters. Nut-eaters may be more health conscious than non-nut-eaters. When you’re looking at an association it’s very difficult to attribute the difference between the two groups to one specific behaviour, such as nut-eating. So, while I would encourage everyone to consume a variety of foods, including nuts, I would also encourage everyone not to overdo it. Nuts are not going to compensate for an overall poor diet. Just adding nuts to a diet that’s high in calorie-dense, nutrient-poor foods is not going to protect you from developing heart disease or type two diabetes. It’s also important to note that nuts are high in calories so you can easily have too much of a good thing.