In the last blog post in my series on Nutrition, I discussed the history of the Australian Dietary Guidelines (ADGs). I spoke about the strong emphasis on reducing fat, particularly saturated fat and that, the advice to limit saturated fat to less than 10% of daily calories simply isn’t based on the totality of the science we have available. In this post I’ll explore the alternative macronutrient we’ve been encouraged to eat for the past handful of decades – that is ‘complex carbohydrates’ from the Grains and Cereals food group. I’ll look at the history of how this advice evolved, the science (or lack thereof) to support it and the physiology of what happens in our body when we follow this advice. I’ll also discuss the confusion added into the mix, engineered by the food industry.
One of the major Food Groups we are told to include every day to achieve good health is the Bread and Cereals group. The reason for this is to obtain ‘key nutrients’ and also supposedly that these foods are associated with reduced risk of ‘cardiovascular disease, type 2 diabetes and excess weight gain’ (1).
Luise Light, a nutritionist in the US in the early ’80s describes here how the influence of food industry significantly changed the original recommendations of the Food Guide Pyramid in the US. The original version of the Pyramid recommended 3-4 serves of wholegrain bread and cereals. Dr Light was dismayed to find the modified version had bumped it to a massive 6-11 servings of a combination of white and wholegrain cereal serves (with one serve being equivalent to 2 slices of bread). The 2003 version of the Australian Dietary Guidelines still included this unfathomable recommended amount of up to 22 slices of bread per day. The most recent 2013 version of the ADGs and it’s supplementary document the Australian Guide to Healthy Eating (AGHE) had quietly backed off on this recommendation to a more modest 4-6 serves for adults, with a serve now only one slice of bread, rather than two. A significant reduction, no doubt to try and counter the rising rates of obesity and Type 2 Diabetes, but not one that was well publicised.
What are the real gains of consuming grains?
We are repeatedly told that consuming fibre and whole grains is protective against various chronic illnesses such as Type 2 diabetes, heart disease and colon cancer. Studies conducted in the 80s and 90s observed better health outcomes when white flour products are replaced with wholegrain products. Dr William Davis, a US cardiologist, highlights the flaws in this logic using the following analogy in his book, Wheat Belly: “If high tar cigarettes are bad for you and low tar cigarettes are less bad, then lots of low tar cigarettes should be good for you.” The equivalent logic in nutrition science is to substitute something like white flour products, which are detrimental to health in excess, with wholegrain products, which are less detrimental, but far from ideal for our health. Brown rice, for example, has a listed Glycemic index of 66 for a 150g serving. White rice, has a listed GI of anywhere from about 55 to 95, depending on the variety and cooking method. So not too dissimilar from the wholegrain variety. How does brown rice compare for nutrition content to white rice? Many people who follow a LCHF diet will substitute cauliflower rice for white and brown rice. In this table, I have compared the nutrient content of a serve (150g) of cauliflower rice with an equivalent serve of white and brown rice to examine the ‘key nutrients’ cited as to why we need to include cereal products in our daily diet. (I pulled the data from the Australian Food Composition Database). As you can see, the cauliflower rice outperforms the white and brown rice on nearly all nutrients, with far less of a post-meal glucose spike.
Nutrition facts and fallacies
When we consider a Low Carbohydrate High Fat (LCHF) diet as an overall ‘eating pattern’, critics express concern that by ‘cutting out a whole food group’ one might be at risk of being deficient in nutrients like B vitamins and fibre. However, Zinn and colleagues showed that well designed LCHF diets are nutritionally replete in micronutrients, including fibre. (Interestingly they showed saturated fat intake doesn’t need to be excessive even when compared to mainstream saturated fat targets) (2). Grains, even if whole grain, have a large effect on our secretion of the hormone insulin after we eat them. I explained in my previous post, this is because of their high carbohydrate content. Given that hyperinsulinaemia and insulin resistance are driving factors of many common diseases we see today (3), it makes sense for people who have these conditions or are at risk of developing them, to restrict the macronutrient that is doing the most damage. At the same time, and with some proper planning, the nutritional adequacy of their diet in terms of micronutrients will be better off. For people with diabetes or pre-diabetes, it’s even more critical to minimise the consumption of grains, despite the perceived concern that this will result in lower consumption of dietary fibre. A study published in Nutrients examined the effect different diets had on weight loss in groups with varying degrees of insulin resistance. The authors concluded, “Once the prediabetic state is more advanced, as is likely the case for subjects with pre-diabetes and high Fasting Insulin, it seems that an adverse effect of carbohydrates overrules the potential beneficial effect of dietary fiber intake, indicating a need to replace carbohydrates in the diet with proteins and fats.” (4)
Another reported reason nutrition ‘experts’ recommend we consume grains is to nurture our gut microbiome. There’s little doubt the microbiome is an interesting area of research. Evidence is continually emerging that the composition of the gut microbiome can have a strong determinant on our overall health. A review paper published in 2011 outlines some of these benefits. However, we should note that the area of the microbiome is emerging science and in reality, we’ve barely touched the tip of the iceberg on the intricacies. And there is zero evidence that attempting to manipulate the gut microbiome by adding fibre-containing grains into our diet, provides any benefit whatsoever to our overall health. Another review paper published in the European Journal of Nutrition in 2018 points out “for a clinical practice to be broadly accepted, the mode of action, the therapeutic window, and potential side effects need to thoroughly be investigated. This calls for further coordinated state-of-the art research to better understand and document the human gut microbiome’s effects on human health” (6). This statement is particularly true for people who have metabolic syndrome. But this, of course, hasn’t stopped the processed food industry from using the microbiome as a reason why we need to eat whole grains every day. Much of their marketing material supports this view.
Why are grains still so actively promoted?
The simple answer is: money and economics. Grain products have long shelf lives and can be made relatively cheaply for high-profit margins. They are billion dollar industries. This documentary about the origins of Kellogg’s cereal gives us some insight of the stakes involved. The reality is, that public health nutrition reform to significantly reduce the amount of grains recommended to a large proportion of society would cause too much economic instability.
So the message about the harmful effects of grains for a large proportion of the adult population is watered down. So what can we do? Amongst all the confusing science and political forces at play, how can you know the best diet for you and your family? I will discuss this in the next blog post of this series.
- National Health and Medical Research Council (2013) Australian Dietary Guidelines. Canberra: National Health and Medical Research Council.
- Crofts C, Zinn C, Wheldon M, Schofield G (2015) Hyperinsulinemia: a unifying theory of chronic disease? Diabesity 1:34–43