How low resistant starch diet is contributing to high blood pressure

Resistant starch diets

In 2022, the Daily Graphic reported that data available to the Ministry of Health indicates that approximately 35 percent of the adult population of the country are hypertensive, the disease described as a silent killer if not controlled, with many more affected people unaware of their condition or undiagnosed.

Hypertension has been identified as the leading cause of premature preventable deaths locally, among other implications, as uncontrolled and undiagnosed hypertension is driving huge numbers of preventable deaths and disabilities from cardiovascular diseases (CVDs) and non-communicable diseases (NCDs) locally and globally.

Due to this, the Ghanaian Society of Cardiology (GSC) has called for an urgent need to re-strategise to diagnose all hypertensive cases for effective management to avert more preventable deaths and disabilities while efforts on prevalence control continue.

But I believe the first thing to do is to educate the public on preventive mechanism available. Research also has to be conducted in our local diets and their impact on our health. This is because it appears our neglect of local diets and overreliance on the so-called modern diets are contributing to the high rise of NCDs in the country. In this article I justify why the neglect of our local diets could be the key reason why NCDs are on the rise.

Justification

Dr. Francine Marques and her colleagues made a substantial discovery at the Baker Heart and Diabetes Institute in Australia using animal study  and found  that the lack of prebiotic fibre that is found in traditional diets lead to hypertension and cardiovascular diseases (Kaye, et al. Circulation 2020). In this study, the researchers used resistant starch diets as their prebiotic fibre.

They found that a diet low in dietary fibre triggers the prevalence of high blood pressure for some time. However,  this study established that the lack of fermentable fibre is not only associated with heart diseases, it vigorously contributes to high blood pressure and heart diseases.

This breakthrough study outlines a gut-immune-heart axis. This means that foods that ferment are good for our health and our refusal to eat them are the problem in the modern era. Local foods that ferment when we eat them – such as fufu, kokonte, banku, porridge, kenkey, et al – are good for our health. As they ferment, they help impove the good bacteria in our gut. Without going into all the study details, the sequence of effects from gut fermentation to cardiovascular health can be summarised as follows:

The resistantStarchResearch.com explained that prebiotic fibres, including resistant starch, are fermented in the large intestine by the resident microbiota. This fermentation produces short-chain fatty acids (SCFAs), primarily acetate, propionate and butyrate. These SCFAs change the expression of the genes not only within the large intestine, but also all over the body. Butyrate is the primary food or fuel for the colonocytes, but the short-chain fatty acids acetate and propionate are absorbed into the blood and used as energy and biochemical messengers all over the body.

Within the gut, some genes were upregulated (i.e., tight junction protein, Tjp1), and some genes were down-regulated (pro-inflammatory cytokines interleukin 17a (Il17a), and interleukin 6 (Il6), and markers of fibrosis Tnfa and Col3a). Beyond the gut, G-protein coupled receptors GPR41, GPR43 and GPR109A were activated by resistant starch and by short-chain fatty acids, independently.

Changes in the gene expression drives changes in the immune system. The spleen contains a high concentration of GPR receptors and was shown to be involved. Within the spleen, the expression of numerous genes changed, the number of Treg cells (a well-known immune modulator) increased, and the production of L-DOPA was also significantly increased. The significance of each of these biochemical pathways is not yet clear.

The end result was that resistant starch and the SCFAs resulted in reduced blood pressure, and stronger hearts. Diets lacking the prebiotic fibre resulted in the development of hypertension, and a larger and stiffer heart (all signs of heart disease).

These cardiovascular benefits were driven by the short-chain fatty acids produced by the intestinal fermentation. The microbes themselves were not the drivers, although the study also examined the microbes. Probiotics alone are not sufficient to drive this process – they need the fermentable fibres to produce the bioactive SCFA metabolites actually doing the work. Resistant starch alone was sufficient and the SCFAs alone were sufficient.

These benefits were not limited to resistant starch. Other fermentable prebiotic fibres also produce SCFAs, and may contribute to the same cardiovascular benefits. Bulking fibres (i.e., cellulose, psyllium, soy fibre, wheat bran) are minimally fermented and will not produce the same benefits simply because they do not produce sufficient quantity of the SCFAs (if at all). Viscous fibres (i.e., beta-glucan, psyllium) may or may not be fermented but cannot be consumed in large quantity because of their viscous impact on foods and the potential for intestinal blockage. (See Gallaher 2006 for more information on these three mechanisms of fibre)

One human clinical study by Jama et al. (2023) determined if acetylated and butyrylated modified resistant starch can decrease blood pressure of hypertensive individuals via the modulation of the gut microbiota and release of high levels of short-chain fatty acids found  resistant starch supplement produced a clinically relevant reaction in 24-hour systolic blood pressure independent of age, sex and body mass index without any adverse effects. It also increased levels of acetate and butyrate, shifted the microbial ecosystem and expanded the prevalence of SCFA producers.

Fermentable, prebiotic fibres are the stars of this show. These results cannot be attributed to fibre in general, because major categories of fibre will not produce the SCFAs necessary to drive the biochemical processes. We have to differentiate between the three different categories of dietary fibre in our communications to consumers. The concept that all dietary fibres are the same is misleading and simply wrong, according to resistantStarchResearch.com.

Grabitske & Slavin (2009) noted that in the ancestral days, our forefathers consumed 35-50 grams of resistant starch per day. However, today’s consumption of resistant starch is only 5-6 grams per day in modern societies. Resistant starch is insoluble and ferments slowly, resulting in a dose tolerance of 45 grams per day.

People can eat a lot of resistant starch and get a lot of these powerful SCFAs without getting uncomfortable digestive symptoms.

Resistant starch is available in dietary supplements, but it would be more convenient for people to get their resistant starch in foods (as in olden days). In the advanced countries, knowing the importance of resistant starch diest, some technologies exist now to put resistant starch back into foods and promote them for their real benefits. It’s not about ‘generic’ dietary fibre. It’s about fermentable, prebiotic fibre and the improved metabolic benefits of the SCFAs produced by intestinal fermentation, according to the resistantstarchresearch.com.

Take home

We must go back to eating our local diets as they have more resistant starch as compared to the modern day diet we are abreast with. This is because in the ancestral days, our forefathers consumed 35-50 grams of resistant starch per day, thus improving their health as compared to our consumption of resistant starch in modern day diet that only provides only 5-6 grams per day. Resistant starch is insoluble and ferments slowly, resulting in a dose tolerance of 45 grams per day, thus improving our health. Thus, as the food ferments in the gut, it improves our heart.

NB: Prof. Nyarkotey has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations to justify his write-ups. My articles are for educational purposes and do not serve as Medical advice for Treatment. I aim to educate the public  about evidence-based scientific naturopathic therapies.

The author is a Professor of Naturopathic Healthcare and President of Nyarkotey College of Holistic Medicine & Technology (NUCHMT)/African Naturopathic Foundation.

E-mail: [email protected].