Being a Savvy Auntie means being savvy about an extensive range of topics, including nutrition. After all, haven’t we all been responsible at some point for feeding our nieces and nephews? And while we occasionally look the other way when it comes to the ice cream, chocolates, and candy that kids love, we also want to ensure that our nieces and nephews develop healthy eating habits.

However, being savvy about nutrition may not be as easy as we thought, as some of our traditional assumptions about food are now being challenged. 

You’re about to make a sandwich. Do your reach for the freshly stone-milled whole-grain wheat flour, sourdough leavening, superior ingredients baked in a stone-hearth oven to create a picture-perfect, super-healthy loaf of artisanal bread? Or, white bread—the industrial kind made from white flour.

Wholesome choices vs healthy choices

Since the 1970s, white bread has had a bad name. But a new study conducted at the Weizmann Institute of Science in Israel reveals that these “wholesome” choices are not necessarily the healthiest for everyone. Weizmann Researchers investigated this decades-old assumption as part of their extensive studies on the microbiome – the bacteria that live in our guts. Their findings have already shown that our microbiome affects our health and well-being in wholly unexpected ways – and this study was no exception in terms of surprises.

The sourdough bread described earlier was prepared especially for this study, and was made to be as healthy as possible. The white version was standard store-bought white bread. The study involved 20 participants, divided into two groups of 10, who were asked to eat a great deal of bread – about a quarter of their caloric intake – for 10 days. One group had white bread for 10, took a two-week break, then ate the sourdough for 10, while the other group did the opposite. Each person was measured for several physical changes, to see if their bodies responded differently to the healthy or “junky” types of bread.

Surprisingly, the team found significant differences between groups of people in their response to bread – but perhaps not the responses you’d expect. One of the effects of bread is raising glucose levels: blood sugar, which is associated with diabetes and other metabolic conditions.

Trusting our gut bacteria

About half the participants had higher blood-sugar levels after eating white bread, as expected; however, the other half had higher blood sugar after eating sourdough bread. How is this possible? The scientists believe it is related to the gut bacteria.

As part of the study, the team had also measured levels of intestinal microbes. They found that each person had their own personal microbiome, meaning that the composition of microbes was unique to them. The scientists managed to develop an algorithm that connected the microbiome’s composition with the person’s type of bread, and were able to predict who would have high blood sugar after eating sourdough and after white.

The Weizmann Institute study shows that general dietary recommendations are not enough – our bodies are all different in their responses to foods. What works for you may not work for me – and “healthy” bread might not be so healthy after all, depending on your gut.

So, the next time that the young ones try to convince you that your PB&J sandwich tastes better on white bread, or a classic French baguette, you can put the whole grain artisanal bread aside and not feel guilty.

But not cutting off the crust like they prefer? Well, for that, you're on your own.

Want more scientific proof? Watch this!