While we think of resistant starch (RS) as protective, there’s a new paper out that says RS may cause cardiovascular disease! We’d better check this out.
Sample headline: “Marker for Cardiovascular Disease Linked to Resistant Starch in Diet.” And a quote from the Canadian Centre for Clinical Trials:
These results mean that a diet high in RS or a diet high in carbohydrates is enough to increase the levels of TMAO in the blood.
TMAO, is trimethylamine-N-oxide, a chemical that is said to predict heart disease when it’s found in the blood. Sounds bad. Time to stop eating resistant starch? Not so fast!
TMAO and Red Meat
TMAO was all over the news a couple years ago. The “Paleo” community was freaked out. TMAO was found to come from paleo staples like red meat and eggs! Everyone was talking about it:
If red meat consumption elevates TMAO, and elevated TMAO increases the risk of heart disease, we’d expect to see higher rates of heart disease in people that eat more red meat.
Choline, another important nutrient found in eggs, meat, dairy, and offal with a similar structure to carnitine, was shown a couple years ago to convert to TMAO after exposure to certain types of gut flora, causing researchers to suggest it too promotes atherosclerosis.
Something that everyone also noticed was that this TMAO was not found directly in the red meat, but was produced by gut bacteria that ate undigested bits of red meat called choline and carnitine.
And guess what the cure for all this red-meat-carnage was?
Resistant Starch, the Saviour!
There have been many studies over the last couple years showing that resistant starch has the ability to negate much of the damage caused by eating red meat.
The delivery of fermentable carbohydrate to the colon (as resistant starch) seems to switch from fermentation of protein to that of carbohydrate and a reduction in adduct formation, supporting previous observations that dietary resistant starch opposes the mutagenic effects of dietary red meat.
Significantly greater damage was seen with some protein sources, including red meat and casein, than with others, such as chicken, which is consistent with prospective population studies. Damage was dose-dependently opposed by dietary RS (resistant starch)
Or, Resistant Starch, the Cause?
Here’s where I have to play the Fake News card.
Here’s where the rumor started. In December 2016, a paper was released in a UK journal that implicates RS in TMAO production. “Diets high in resistant starch increase plasma levels of trimethylamine-N-oxide, a gut microbiome metabolite associated with CVD risk.”
While it’s true that the researchers saw more TMAO in the blood of the people on the highest RS, it was dependent completed on the amount of total carbs in the diet. The conclusion of the study:
In conclusion, our study showed that, in the context of a lower-CHO (low-carb) diet, high RS intake resulted in significantly higher plasma concentrations of TMAO, a novel CVD risk biomarker.
But also the RS, at all levels, did some good things:
RS blunted the postprandial glucose and insulin responses to meals consumed acutely…
Just like I’ve been saying. RS is good, low carb is not so good.
Flaws in the Study?
This study was not so great. As our president would say:
…approximately 50% of the high-RS maize starch was consumed raw, mixed into beverages, fruit purees and soups
In fact, all the foods used were kept frozen and reheated, changing the RS profile of all foods used, even the researchers said in the paper:
Therefore, we cannot rule out the possibility that in our study freezing and storage may have promoted retrogradation of gelatinised starch products in a manner that rendered them more resistant to digestion, thus attenuating differential metabolic effects of high- and low-RS diets.
They f*dged it all up. But at least they recognized their mistakes before they published the paper, also:
Another limitation of our study is the short-term duration of the dietary intervention.
You need to take your time when introducing RS to the diet. Takes weeks for our gut flora to fully adapt.
And an admission that maybe this paper is not worth the paper it’s printed on:
Hence, although there is strong evidence for the relation of TMAO to atherosclerotic CVD, we cannot conclude that the dietary effects on TMAO observed here would translate into changes in risk for CVD. Furthermore, whether increases in TMAO are clinically relevant in the context of a concomitant improvement in glycaemic control, as is commonly observed with RS, remains to be established.
Additionally, nowhere in the paper did it give relative comparisons between the TMAO increases they saw on a low-carb, high RS diet and the increases seen when eating red meat and eggs. My gut feeling is that it’s not even comparable, which is why they did not produce such a chart.
This study highlights the absolute need for a thorough investigation into resistant starches used in research studies. I feel they totally botched it, and then did not test, just relying on the published values of RS in Hi-Maize. Resistant starch needs to be tested at every stage of the process to ensure an accurate RS accounting.
If you enjoyed this article, and have not done so, please donate to my Resistant Starch Analysis Project ASAP. I intend to set the research world straight on how to use RS in their experiments before they scare people off of every good food.