Monday, January 14, 2019

Is whole wheat any better for you than refined wheat?

The Study
Whole grains are really important to include in your diet. They are high in fiber, high in micronutrients and have an easier impact on your blood sugar than their refined counterparts. However, are they all equally beneficial? This study is a meta-analysis that compared the blood glucose response of whole wheat vs. refined wheat and whole grain rice vs. refined white rice. Twenty randomized trials were included in this investigation. Whole grain rice resulted in a significantly lower post-prandial blood sugar when compared to white rice. Unexpectedly, whole wheat did not significantly lower blood sugar in subjects when compared to refined wheat.
American Journal of Clinical Nutrition 2018;108:759-74.

Take Home Message
I have recommended whole grains in place of refined grains to my clients since day one for many reasons. In the research literature, a high consumption of whole grains has been associated with a reduced risk of heart disease, stroke, type 2 diabetes, cancer and total mortality. For those looking to lose weight, replacing refined grains with whole grains reduces the swings in blood sugar and insulin that tend to increase hunger and promote fat storage. 

However, I noticed that when my clients ate whole wheat, they were still just as hungry as if they were eating refined wheat. For this reason, I have always had my clients limit whole wheat and focus on other whole grains such as brown rice, quinoa and old fashioned oats. This study shows that whole wheat raises blood sugar in a similar fashion to refined wheat. This is the first time I have seen this in the literature but it makes total sense to me. My initial recommendations are confirmed, limit whole wheat and instead focus on brown rice, quinoa and old fashioned oats for your all-important sources of whole grains.

Drop in resting energy expenditure with weight loss

The Study
There is evidence that after weight loss, resting energy expenditure (REE) drops to levels lower than predicted. This is a major reason why so many people quickly regain lost weight. In this case-control study, three different groups of subjects had their resting energy expenditure measured. The first group included 34 subjects that had lost over 30 lbs. and kept the weight off for 1 year. The second group included 35 normal weight subjects. The third group included 33 overweight and obese subjects. Resting energy expenditure was predicted by standardized formulas and then precisely measured with indirect calorimetry. There were several interesting results:

-In the subjects that lost at least 30 lbs., there was no significant difference between predicted and measured resting energy expenditure.

-However, in the 34 subjects that had lost over 30 lbs. and kept it off for a year, there was a lot of variability. When comparing the expected to the actual resting energy expenditure, the range was -257 to +163 calories per day.

-In the weight loss maintainers, a lower than predicted REE was positively correlated with maximum weight, maximum BMI and maximum weight lost. American Journal of Clinical Nutrition 2018; 108:658-66.

Take Home Message
There are 3 really interesting things about this study:

1) The more weight that a subject had to lose, the more severe the reduction in resting energy expenditure. This supports the idea that the more weight you lose, the harder it is to keep it off.

2) Even though these subjects lost a lot of weight, their REE did not drop all that much from what would be expected given their new weight. This is somewhat surprising given previous results.

3) There was a lot of variability in resting energy expenditure after weight loss. The range was 257 calories per day lower than expected to 163 calories higher than expected. It is encouraging that even subjects who had a serious drop in REE were able to maintain their weight loss for over a year. It has been previously argued that a drop in REE makes it impossible to keep lost weight off.

The REE response to weight loss is a fascinating topic that we need to learn more about in order to increase weight loss success. The fact that it varies so much at the individual level is a new concept to me.  Is this because of exercise habits, genetics or something else? We’ll have to stay tuned as further research evolves on this topic.

Does eating organic foods reduce risk of cancer?

Organic produce is really expensive. The majority of people who purchase organic instead of conventionally grown produce believe that it is superior from a health and nutrition standpoint. However, there is surprisingly little research that tests this hypothesis. You may have heard in the news of a study on this topic recently published in JAMA Internal Medicine.

The Article
This study followed 68,946 French men and women for an average of 4½ years (Reference 1). Subjects were asked in a questionnaire how often they purchased organic foods for 16 different food groups. Subjects who reported the highest consumption of organic foods had a 25% lower risk of cancer when compared to subjects who reported the lowest consumption of organic foods.

While this research is interesting, there are some limitations that need to be mentioned before considering how these results fit into the context of prior research. 

First off, there is a strong possibility of residual confounding in this study that may account for the results. A confounder is a variable that is associated with the outcome of a study and may influence the relationship between the independent variable and the outcome. In this study, subjects reporting a higher organic food score were less likely to smoke, drank less, had a lower body weight and a much healthier diet (higher fiber, lower processed meat and less red meat). Each of these variables reduces risk of cancer. While the authors of the study attempted to measure these variables and control for them in the statistical analyses, they may not have captured them completely. If this was the case, the reduction in risk of cancer seen in these subjects may have been due to their healthier lifestyle and not the organic produce consumption.

Secondly, and more importantly, the organic food score was not validated. This was discussed in an invited commentary to the French study by Harvard nutrition researchers, including the Department Chair, Dr. Frank Hu (Reference 2). When a self-reported variable is supposed to measure something, it is critical to prove that it measures what it is supposed to. For example, you could take a subset of the cohort, measure their self-reported organic food consumption and then test their urine or serum for pesticide residues. You could then see if those who had a high self-reported organic food score had a low pesticide residue and vice versa. This was not done in the new study and is a major limitation of this research. The truth is that we don’t know what the organic food score measured, if anything. It may have just been an indicator of a healthy lifestyle, which would completely explain the reduction in cancer risk found in this investigation.

In fact, in the invited commentary, Hu cites a reference from the Environment and Reproductive Health Study showing that self-reported organic produce was not significantly related to urinary pesticide residues (Reference 3).

Other Research
There are a couple of other important studies to mention on this topic. In 2014, a study was published in the British Journal of Cancer that followed over 628,000 British women from the Million Women Study for 9 years (Reference 4). By the end of follow-up there was no relationship between self-reported organic food consumption and risk of cancer. Interestingly, there was a significant increase in breast cancer in subjects consuming the most organic produce. Keep in mind that this study had a much longer follow-up and many more subjects than the more recent French study.

Another really important study was a systematic review of the health effects of organic food published in the journal Annals of Internal Medicine in 2012 by Stanford University researchers (Reference 5). Here are some of the more important findings of this study:

-The majority of conventionally grown produce (62%) that was tested contained no detectable pesticide residues.

-7% of organic produce contained detectable pesticide residues.

-The researchers found 3 studies that tested if pesticide residues exceeded maximum limits. One of these studies found that neither the organic or conventionally grown produce exceeded maximum limits. One study found that 1% of both the organic and conventionally grown produces tested exceeded maximum limits. The other study ironically found that 6% of organic produce tested exceeded maximum limits while only 2% of conventionally grown produce exceeded maximum limits.

-Four of five studies analyzed found that organic produce had a higher risk of bacterial contamination than conventionally grown produce.

Here is the major conclusion of this well-done study:

“In summary, our comprehensive review of the published literature on the comparative health outcomes, nutrition, and safety of organic and conventional foods identified limited evidence for the superiority of organic foods. The evidence does not suggest marked health benefits from consuming organic versus conventional foods…” (Reference 5).

Conclusions And Recommendations
The jury is still out on whether or not choosing organic produce improves health in comparison to conventionally grown produce. More research is needed here. However, to date, there is not much evidence that this is the case. In fact, much of the evidence suggests that there is no difference. We’ll keep our eye out for further research in this area. 

In the meantime, conventionally grown fruits and vegetables are a wonderful addition to a healthy diet. There is no need to limit them. If you like organically grown produce and can afford the higher price tag, feel free to buy it. If your major reason for doing so is that you think you will be much healthier, keep in mind that this very likely may not be true.

While the evidence is not quite there for organic produce, there is strong evidence that you can reduce your cancer risk by not smoking, maintaining a healthy weight, exercising regularly and eating a healthy diet. These are the important areas to focus on for all of us.

1) Baudry J, et al. Association of frequency of organic food consumption with cancer risk. JAMA Internal Medicine 2018; doi:10.1001/jamainternmed.2018.4357.

2) Hemler EC, et al. Invited commentary: Organic foods for cancer prevention-Worth the investment?
JAMA Internal Medicine 2018; doi:10.1001/jamainternmed.2018.4363.

3) Chiu YH, et al. Comparison of questionnaire based estimation of pesticide residue intake from fruits and vegetables with urinary concentrations of pesticide biomarkers.  J Expo Sci Environ Epidemiol 2018; 28:31-39.

4) Bradbury KE, et al. Organic food consumption and the incidence of cancer in a large prospective study of women in the United Kingdom. British Journal of Cancer 2014; 110:2321-2326.

5) Smith-Spangler C, et al. Are organic foods safer or healthier than conventional alternatives? A systematic review. Annals of Internal Medicine 2012; 157:348-66.