Greater potato consumption was once associated with a greater risk of developing diabetes. This first came from the Harvard Nurses' Health Study, where the science was confounded with a lack of control as to whether potatoes were consumed boiled, baked or in French fry form. Regardless, when potato intake was studied in boiled or baked form, the same conclusions were met. Perhaps then, one should ask: what are these people consuming potatoes with? Meat and potatoes? Shepherd's pie? Spanish omelette? Jacket potatoes with butter and/or cream? Unfortunately, even when animal products were removed from the equation, it still resulted in that same pesky link: potato consumption carried a small risk for the future development of diabetes.

The thought that potatoes may increase one's chances of developing diabetes came as a surprise, considering how countries with long-living populations (such as Ikaria, Greece) consider the white potato as a staple food. Additionally, in countries like Iran, where consumption of boiled potatoes was quite high, Iranians' odds of developing diabetes was cut in half, notwithstanding that the rest of their diet was heavy on whole-foods and plants. Swedish and Italian studies then showed that boiled potatoes had no correlation with diabetes or hypertension, but the opposite was consistently shown in studies coming out of the USA.

• In 2015, the University of Harvard confirmed this association and found that potato intake by way of French fries increased your risk for developing type 2 diabetes five-fold. French fries also increased the risk of dying from cancer, even with a mere twice per week consumption.
• In 2018, a meta-analysis (the best study you can ask for), found a 20% increase in diabetes' risk in those having one serving/day of white potatoes. But this study, again, failed to control for potatoes consumed as French fries.

We know that potassium tends to decrease one's blood pressure and potassium is found plentiful in white potatoes, which surprisingly have been shown to increase blood pressure too. Though once again, such studies did not account for the ways potatoes were cooked (fried/boiled), what was added (salt/pepper) and what they were served with (meat/salads). Boiled, baked and even mashed potatoes were not linked with hypertension but were still linked to a future diagnosis of diabetes.

What is the silver-lining in all this? These were observational studies and observational studies do not prove cause and effect, even though a link may be established.

The good news - It seemed that when researchers controlled, rigorously, for all confounding factors (even smoking), potatoes and the risk for premature death in humans disappeared.

---

Nutritional Value

As far as the nutrient profile goes - 100g of white potatoes (94 kcal) gives us about 21g of carbohydrates, 2g of protein and 0.2g of fat. Within such macros we find fibre, Vitamin C and Potassium too, but the positive effect they might have on the body may be counterbalanced by the high glycaemic index of the potato (that is, how badly they spike our blood sugars). Why? Because of the rapidly-absorbed starch within the potato.

Conversely, 100g of sweet potatoes (86 kcal), gives us about 20g carbohydrate, 2g of protein and 0.1g of fat. Similar carbohydrate content - with the only difference that sweet potatoes are high in "resistant starch", which does not spike one's blood sugar as badly as white potatoes. To compare the glycaemic indexes of both potatoes when boiled for 30 minutes:

1. Boiled potato = 85 (high)
2. Boiled sweet potato = 46 (low)

But what if we prefer eating white potatoes? Well you'd be happy to know that there are techniques one could use to blunt or decrease the blood sugar spikes:

1. Boil them, chill them and (optional) re-heat them. This method slows the rate the starch is absorbed because it causes the starch to crystallize and resist breakdown in the gut. It was found that this method decreased the GI from 85 to 56!
2. Add vinegar. Vinegar tends to blunt large blood sugar spikes. Simply adding 1 tbsp can drop GI levels by 30-40%. 1-2 tbsp. of vinegar per day are important for blood sugar control, particularly in patients with diabetes.
3. Add cooked broccoli. Adding two servings of cooked broccoli could decrease the glycaemic spike. Conversely, adding animal protein can increase it.
4. Add lemon juice. Lemon juice has a starch-blocking effect in the body.

So potato consumption was not, therefore, associated with mortality. Potato-eaters could, technically, live as long as non-potato-eaters. Thus, we have three tiers of foods:

1. Those, which potentially shorten your life - like hot dogs and cold cuts (processed meats)
2. Those, which potentially prolong your life - like walnuts and vegetables
3. Those, which have a neutral effect on your lifespan - case in point, white potatoes

Regardless of all prejudice, the best potatoes are the ones with the brightest colour. Throughout nature, foods with bright colours normally contain some kind of pigments. Blueberries, for example, are blue because they contain anthocyanin.

Pigments act as starch-blockers and therefore blunt the glycaemic response in foods. Thus, the best kind of potato would be the purple sweet potato (which is high in anthocyanin). It has been shown that purple sweet potatoes have the best ability to reduce glycaemic response and reduce inflammation - owing to the fact that the purple sweet potato had 20 times more polyphenols than yellow potatoes. So much so that they are the single greatest food out there able to reduce arterial stiffness and lower your blood pressure. It just goes to show how Okinawans once had the greatest lifespan in the world (before they became westernised that is) when 80% of their diet comprised of purple sweet potatoes.

So when shopping for potatoes remember to go for the brightest colour:

Purple sweet potatoes > Orange sweet potatoes > Yellow potatoes > White potatoes (for treatment of inflammation and oxidative stress).

 

So what can we conclude?

1. Do not consume French fries
2. Consume sweet potatoes over white potatoes
3. The occasional consumption of white potatoes won't hurt you, particularly if your diet is high in whole-foods and plants
4. Boil your potatoes for at least 30 minutes and chill prior to consuming. You may re-heat with a microwave (this is optional) but the crucial step is the "chilling phase"
5. Consider adding vinegar, lemon juice and at least 2 servings of broccoli