Potatoes: Another Stupid Study

"People with type 2 diabetes need not avoid eating potatoes based on glycemic index" is the title of a recent Eurekalert news release about potatoes. Now, most people seeing that would think "I don't need to avoid potatoes" and wouldn't read the rest of the story.

Note that the study was funded by the Alliance for Potato Research and Education (APRE), and although they say APRE had no role in designing or carrying out the study, one tends to be biased toward any group that is sponsoring one's work. APRE "is a not-for-profit organization 100% dedicated to expanding and translating scientific research into evidence-based policy and education initiatives that recognize the role of all forms of the potato—a nutritious vegetable—in promoting health for all age groups." That certainly doesn't sound unbiased.

However, even more important that the funder for this study is what they actually showed. They showed that participants had a better 'nocturnal' glycemic response when they ate a mixed meal with skinless white potatoes compared to an isoenergetic and macronutrient-matched mixed meal that included a low glycemic index carbohydrate food -- basmati rice. 

Note that they didn't compare potatoes with a no-starch meal, say substituting broccoli or spinach for the potatoes. They just say potatoes aren't worse than basmati rice. But I suspect some people, even dieticians, will remember "People with type 2 diabetes need not avoid eating potatoes" and eat baked potatoes or even french fries when they would have much better control if they ate green vegetables instead. 

Participants ate about 50 grams of carbohydrate per meal, the same amount that is used to measure glycemic index.

 I agree with the authors that the glycemic index alone isn't enough to predict the glycemic impact of a mixed meal. And even with the exact same meal, different people will have different responses. Even one person may have a different response on a different day. We have to test ourselves, preferably with a continuous glucose monitor, to find out how various foods and mixed meals affect us.

However, no one with type 2 diabetes should be eating 50 grams of carbohydrate per meal. Unless money is really tight and we need to fill up on cheap starches, when potatoes would be better than cake and cookies, I think the potatoes should remain at the grocery store. And people who write research press releases should be clearer about exactly what their research shows.

The full text of the study can be found here.

Short and Long-Term Effects

While looking for something or other, I recently came across this article saying that arginine has no long-term effect on heart health. Arginine is one source of nitric oxide, which dilates blood vessels. Nitroglycerin, used by heart patients for angina, also produces nitric oxide.

 The cited article was published in 2007 and took me back. At the time, arginine was hot stuff among some people concerned with heart disease. Author and blogger David Mendosa wrote about it in 2006, and it was strongly recommended by his endocrinologist, Dr. Joe Prendergast. Sadly, both David and Dr. Joe have since died. Here is a more recent article. 

I won't discuss here the merits of arginine or the arginine-containing Heart Bars (discontinued) that Dr. Joe was so enthusiastic about. What is interesting is the fact that according to the first article, arginine does improve heart health in the short term, but just not in the long term. 

This is true for other treatments and supplements as well. One good example is caffeine. Caffeine binds to a receptor for adenosine and blocks the adenosine from binding. When you need sleep, your levels of adenosine are high, and binding to that receptor makes you sleepy. When caffeine blocks the adenosine you're less sleepy.

Sounds great if you need to stay awake past your usual bedtime, but there's one problem. When you ingest caffeine on a regular basis, your body compensates by making more adenosine receptors. So now you need even more caffeine, and more, just to stay awake during the day. You're addicted.

Thus when you try anything new, you should be aware of the possibility that the short-term benefits, or side effects, may be different from the long-term effects. Metformin is a good example of the difference in negative effects. Many people can't tolerate metformin if they start it at the full dose, because of gastrointestinal problems like diarrhea. But if they start it slowly, it's fine. The body, which is generally smarter than we are, has figured out how to adapt.

I have personal experience with metformin side effects. I'd taken it for about 20 years with no problem, when it occurred to me that instead of taking 500 mg extended release (ER) twice a day, it would be easier to take 1000 mg once a day. My endocrinologist prescribed the 1000 mg without mentioning that it wasn't ER; the 1000 mg doesn't come in ER. I didn't notice that the bottle didn't mention ER, and because the pills were so large, I just assumed that's what it was. Dumb mistake.

After a while I started getting diarrhea. As my water supply isn't perfect (a spring with some surface water), I wondered if it was Giardia. We did tests and more tests. No clues. Finally, it occurred to me that it could just be the metformin, and sure enough, when I stopped taking it, the diarrhea went away.

A dosage that worked when spread out over the day didn't work without side effects when given at one time. I then returned to the 500 mg twice a day, introduced slowly, and had no more problems. 

Sometimes, especially if you find that a drug or supplement that worked wonderfully when you started taking it seems to have lost its oomph, it might make sense to take a vacation from it for a short time. Obviously this wouldn't be a good idea for a life-saving drug like insulin or medication for high blood pressure. But it might work for less essential supplements.

We don't know a lot more than we do know about how the body works, so any treatment is a work in progress. Stay alert to the effects of the drugs and supplements (and food) that you do take. Let your doctor know if prescription drugs seem to be working differently than when they were first prescribed. Maybe, like arginine, the differences are not in your imagination.