Clinical trial to focus on benefits of potato based resistant starch for healthy kidneys

An apple a day is all fine and good. But what about a potato?

Or more precisely, a raw potato to fight chronic kidney disease. That’s at the heart of a soon-to-be-launched clinical trial of a made-in-Manitoba dietary supplement consisting of what’s called a resistant starch.

Renal Health

The initiative comes out of one of the world’s leading centres for chronic kidney disease research, the Chronic Disease Innovation Centre at Seven Oaks General Hospital.

And it’s the brainchild of nutrition and lifestyle researcher, Dylan Mackay, a University of Manitoba associate professor of community health sciences.

Dylan Mackay:

“We’re testing a product that’s made in Carberry to see if it can assist with a problem that we have an over-representation of in Manitoba.”

It’s estimated that more than 130,000 Manitobans have chronic kidney disease, Manitoba’s Renal Health Program data show.

A progressive illness resulting in the kidneys losing their ability to filter toxins from the blood, among other important functions, the condition often leads to end-stage kidney disease. Again, Manitoba tops the nation with a 24 per cent higher incidence of kidney failure, which in its worst cases, requires dialysis or a kidney transplant to treat.

Dylan Mackay:

“It’s obviously not a good situation; dialysis is expensive, and people either get a transplant or they eventually die on dialysis.”

Quality and expectancy of life are often greatly reduced.

Dylan Mackay:

“So any intervention that could potentially delay the onset of dialysis is worthwhile.”

And that’s where Mackay and other researchers hope a prebiotic supplement already available in stores could be a beneficial, low-cost treatment.

MSPrebiotic

The product, called MSPrebiotic, is manufactured in Carberry and it largely consists of what’s called resistant starch, which is derived from raw potatoes.

Already another Manitoba-based study has shown the supplement offers promise in managing blood-glucose levels and reducing insulin resistance, a key cause of Type 2 diabetes — which also happens to be a key culprit in chronic kidney disease.

Jason Leibert, vice-president of business development for MSPrebiotic:

“What we also saw was an increase in... good bacteria... and a decrease in the bad bacteria. Basically it showed that it can have a positive impact on your microbiome.”

Besides its benefits for diabetics, the findings could lead to new ways to prevent and treat a host of common, serious illnesses because the bugs that live our gut are now considered linchpins of good health, says a top microbiome researcher based in Kelowna, B.C.

Natasha Haskey, registered dietitian and a PhD candidate at UBC Okanagan:

“Basically any chronic inflammatory condition you can think of — from inflammatory bowel disease to diabetes — research has shown changes to the gut microbiome are associated with their development.”

She says the gut contains an entire ecosystem of "not just bacteria, but also viruses and fungi."

Some of these organisms are good; others not so much. Generally speaking, healthy food feeds the good microbes and processed foods nourish the bad ones, Haskey adds.

This notion is central to the double-blind preliminary study seeking to determine whether the MSPrebiotic supplement can help slow kidney disease. Two groups will receive a dietary supplement powder to add to a smoothie or a glass of water with one group getting the resistant starch, and the other cornstarch.

Resistant Starch is a prebiotic

Mackay says the reason he and other researchers are investigating the supplement is because resistant starch is a proven prebiotic, meaning it is indeed beneficial for gut microbes.

Found in high levels in raw potatoes as well as unripe bananas, the carbohydrate is sometimes referred to as a fermentable fibre because it is metabolized by bacteria, creating short-chain fatty acids. Resistant starch is not digested in the upper intestines and converted into energy for the body. Instead, resistant starch passes through to the lower intestine, where it becomes food for bacteria, which create butyrate, which is known to help prevent colon cancer.

Weston Family Microbiome Initiative

The study, funded by a grant from the Weston Family Microbiome Initiative, seeks to determine if the starch will also help reduce a toxin produced by certain bacteria when they consume protein. This toxin is absorbed by the body, and that puts additional pressure on the kidneys.

Dylan Mackay:

“So if we give them resistant starch, a carbohydrate, we’re providing a different fuel for these bacteria.”

“From a kidney perspective, we think it’s a cleaner burning fuel.”

Mackay notes similar studies have been done elsewhere using other forms of resistant starch. Resistant starch is also found in oatmeal, sweet potatoes, beans and cashews.

Dylan Mackay:

“There’s been no clear breakthrough yet.”

“But no one has looked at the MSPrebiotic supplement in this way.”

“So we’re doing essentially a feasibility pilot to see if it works, and we can figure out later what’s the best time, dosages and delivery method.”

At the moment, the recommended daily dose of resistant starch is about five grams per meal, Haskey says.

Dylan Mackay:

“But people typically consume about five grams a day.”

She says this is due to changing diets. We generally eat more processed foods, whereas earlier generations ate more whole foods.

Resistant starch can be difficult to include in diets becuase it breaks down when heated. Consequently, cooked potatoes are poor sources (though the starch reforms in cooked potatoes that are left to cool.

Haskey adds the new Manitoba study marks just one more step among several toward an overarching goal of understanding the human microbiome and personalizing nutrition to promote better health.

Natasha Haskey:

“Basically this speaks to the idea there is no one diet that fits everyone.”

“While it’s been established individuals respond differently to different foods because of their specific microbiome, perhaps someday diets will be tailored to individuals’ gut microbes for more effective prevention or treatment of disease.”

But the gut microbiome is complex, she adds.

Natasha Haskey:

“To put things in perspective, there are trillions of microbes in our gut, and so we’re not there yet.”