April 09, 2015

The Health Benefits of Sweet vs. Regular Potatoes

Why do sweet potatoes get "superfood" status while regular potatoes are vilified? Here's why both tubers deserve a place on your plate.
It's time to set the record straight on spuds.

In recent years, and in certain "healthy eating" circles, the sweet potato has been crowned a "superfood" while the regular potato has been treated like the bad guy.

High carb, high glycemic index, loaded with antinutrients? Is the plain old potato really so bad?

Here's the real deal: Both regular potatoes and sweet potatoes deserve a place in your diet. You can eat both as part of a well-balanced, whole food diet and still have a lean and healthy body.

But as usual, there is a catch or two. Here's what you need to know.

In defense of starchy carbohydrates
Have you been warned by diet gurus to stay away from "starchy carbs"?

Moderating your carbohydrate intake (or timing your consumption of carbs around your exercise program) may be a good thing, depending on your goals, body type, and activity levels.

But there's a difference between high-carb processed foods and whole foods that contain resistant starch.

Resistant starch refers to complex starch molecules that we can't digest. To break these molecules down, the gut bacteria in our large intestine need to go to work. That breakdown process takes time and effort.

Both regular potatoes and sweet potatoes contain starch, some of which is resistant starch. That's one of the reasons why they're considered "slow-burning" -- they make you feel full for hours because it takes your body longer to process them. That provides energy and satiation -- a satisfied, full feeling that is especially important if you're trying to eat less.

Resistant starch is one of the reasons why you shouldn't lump potatoes together with high-carb processed foods. Because a plain baked potato is going to behave differently in your body than a bag of chips or a donut.

Don't be mislead by the glycemic index
Maybe you've heard of the glycemic index, and the benefit of eating "low glycemic" foods.

The glycemic index (GI) maps how quickly a food converts to glucose. This is often compared with how much a food converts to glucose (which is known as the glycemic load, aka GL).

The idea is to avoid foods with a high GI and/or GL, lest they cause a blood sugar spike, and contribute to fat gain. People following this approach will usually choose sweet potatoes over regular potatoes.

But there's a problem with ranking food this way. 

For one thing, GI changes with food type. And potatoes vary by variety, so floury potatoes will wind up somewhere different on the glycemic scale than waxy potatoes.

For another, GI changes when other foods are introduced. We don't usually grab a plain baked potato and start gnawing on it. We generally eat both potatoes and sweet potatoes as part of meals.

Finally, and perhaps most striking, GI changes with food preparation. Boiling usually results in a lower GI, since starch can bind with water. The dry heat of baking, on the other hand, lowers moisture and concentrates sugars. Cutting up potatoes and sweet potatoes helps preserve their starchiness, while cooking them whole results in more sugariness.

So, for example, a baked sweet potato actually has a higher GI than a boiled white potato.
Bottom line: The glycemic index misses a lot of important information. If you take into consideration all the variables, it's also incredibly complicated. Good luck trying to hack your way through that potato matrix. 

Antinutrients aren't so scary

What about antinutrients? Don't worry, they're not as scary as they sound.

Antinutrients are substances that either interfere with nutrient absorption, or act as toxins in the body. Almost all plant foods contain antinutrients as natural defensesagainst pests, diseases, and environmental threats. Tubers are no exception.

For instance, most tubers are relatively toxic when uncooked. In fact, green potatoes are poisonous (so cut off the green bits or toss green potatoes altogether).

Potatoes contain proteins such as patatins and lectins, which can be allergenic, particularly if if eaten raw. However, most of these are problems only for people with existing allergies, intolerances, and autoimmune disorders. If you eat potatoes and feel fine, don't worry about it.

Sweet potatoes also contain some antinutrients. But as with regular potatoes, cooking decreases or removes most of them. And sweet potato allergy or intolerance is quite rare.

In the end, both potatoes and sweet potatoes -- like nearly all other plant foods -- have some antinutrients. But these occur in very low levels, and most of the time our bodies are perfectly able to process them.

The good stuff

Now that I've debunked some nasty myths about potatoes, here are some feel-good reasons you should eat them.

Sometimes we get so caught up in talking about macronutrients (proteins, fats and carbs) we forget about the small-but-mighty micronutrients (aka our vitamins and minerals). So let's get micro for a minute.

Sweet potatoes and potatoes of various varieties contain antioxidants, substances that help control oxidative damage in the body. They also offer other nutrients like carotenoids (vitamin A precursors), ascorbic acid (vitamin C), and tocopherols (vitamin E). Plus, they're packed with potentially helpful phytonutrients, including polyphenols, alpha-lipoic acid, selenium, lycopene, and many more.
All these great vitamins, minerals and powerful little plant chemicals may offer some great health benefits. On that basis, sweet potatoes or colored potatoes (e.g., yellow, orange, and purple-fleshed varieties) do offer some extra benefit. In fact, red-fleshed or purple-fleshed potatoes are comparable to Brussels sprouts, blueberries or spinach!

Eat potatoes, not "potatoes"

The most important question you should really be asking about potatoes is: "How am I eating them?"

Is that a plain baked potato on your plate, next to a serving of grassfed steak or wild salmon and some steamed kale?

Or is it a pile of French fries, slathered in ketchup, accompanying your fast food burger?

Did your potato come from the ground... or out of a bag or box?

The reality is, most people in the western world consume potatoes in some processed form -- as French fries, tater tots, or potato chips.

Then we layer all kinds of stuff on top of those treats. Fries get ketchup or gravy. Chips get dip. Even baked potatoes get "loaded" with sour cream and bacon.

The sweet potato doesn't get a free pass either. In North America -- especially in the Southern U.S. -- the phrase "sweet potato" is often followed by "pie." (Cue the mini-marshmallows.)
Let's get real with ourselves. Something that ends in the word "pie" probably doesn't count as a vegetable.

Here's how to get the best from your regular and sweet potatoes:

Prepare them properly. First, make sure they're cooked. Baking, boiling, or roasting potatoes and sweet potatoes is generally healthier than frying them. When fried, the starch can create harmful acrylamides

Eat them as part of a healthy meal. Next to your lean protein and some other veggies, potatoes have their place. Just go easy on the condiments or toppings. A little bit of healthy fat (like a small pat of butter or a drizzle of olive oil) can help your potatoes taste great, and it will even help you absorb the vitamin A in your sweet potatoes.

Mind your portions. In general, a baseline of 1 to 2 cupped handfuls of starchy carbs per meal is reasonable. Potatoes and sweet potatoes count, but so do beans and lentils, fruit, and whole minimally processed grains. You can adjust your carb choices based on your goals and your body's needs -- and have some fun with variety, too. 

Potatoes are great... in their natural form, properly cooked, and as part of a healthy meal.
So if you want to eat potatoes, eat potatoes.
Hold the fries.

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