Diet Myths: Surprises from my Food Research

Debunking some common food beliefs

Dessert with caramel topping
If the snack also has a topping, does that count as one serving?


Most of my research on the effects of various types of food on premature death matches most common sense. A modest amount of fruits and vegetables is a good thingProcessed meat is quite unhealthy.Eggs and milk are OK in moderation. Some research, though, surprised me and made me rethink my daily food choices. In this blog post, I’ll share the unexpected outcomes from my research on the longevity effects of good. So let’s dive in and uncover the truth about sugar, canned fruit, processed foods, and potatoes!

1. Sugar is not Evil

Sugar has been vilified recently, with many experts blaming it for the rise in obesity, diabetes, and heart disease. However, while excessive sugar consumption can lead to weight gain, it’s essential to recognize that not all sugar is created equal.

I previously included sugary beverages in my list of “Things that Will Kill You.” This time, let’s talk about sugar not in liquid form — desserts and sweet toppings. When excluding sugary beverages, the 2019 Swedish study found adding sugar to the diet from snacks (cake, cookies, candy, chocolate, etc.) or toppings (jam, syrup, honey, etc.) reduced premature death by 20% or 10%, respectively, for about one serving per day. After that serving, there was no further harm or benefit for consuming more.1 I’ll admit it’s unlikely that myself or readers of this blog are getting less than one daily sweetness serving (about 60 g [2 oz.] for desserts or 10-20g [1 oz.] for toppings), but the critical point is that over that amount wasn’t harmful.

Even fructose, the allegedly most evil of sugars featured in high fructose corn syrup (HFCS), does not seem to affect longevity when not in liquid form. A study of reduced-calorie diets featuring moderate fructose vs. low fructose found more weight loss from the moderate fructose diet,2 and a study that added 30-60g of fructose to a daily diet found no change in lipid or glucose biomarkers.3

2. Canned Fruit Is Bad For You

Canned fruit is still fruit, but its health benefits are reversed into harm when the fruit is packaged in a tin or can. Canned fruit might seem like a convenient and healthy option, but it often contains added sugars and preservatives that negate the benefits of consuming fresh fruit. While one 100g (3 oz.) fruit serving will reduce premature death by about 10%, the same sized serving of fruit from a can will increase the chance of early death by 13%.4

Canned fruit on shelves in a grocery store
Canned fruit: a life-shortening sneak attack snack

If you’re looking for a way to save fruit, frozen is the way to go. Frozen fruit maintains the healthy nutrients of fresh foods without the sugary and chemical effects of canning.5

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3. Preserved Meat or Smoked Foods Are Unhealthy, Not “Processed Foods”

The media often focuses on “processed foods” as bad for you. After reviewing the studies, it’s not clear that there is anything about processing that significantly affects health or longevity. Indeed, many processed foods are healthy, such as whole grain breakfast cereals or breads, nut bars, or hummus.

In 2015, the World Health Organisation (WHO) announced that “processed meats” are bad for you, which they defined as “meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavor or improve preservation.”6 Note this excludes things like hamburger, which I would consider processed since it’s minced meat, but doesn’t seem to have adverse effects over regular beef, but does include things like ham, pastrami, sausage, and salami. Deli meats, like turkey or chicken slices, would fall into this category.

I prefer to call these preserved meats to clarify that minced meats are no worse than the unminced versions. It seems the chemicals added to meats increase their shelf-life (salts, nitrates, etc.), which cause additional health harm over red meat.

The World Health Organisation (WHO) listed these preserved meats as Class 1 carcinogens, along with tobacco or asbestos.7 Processed meats also increase cardiovascular disease and diabetes risk.8

Since smoked meats also appear in the list, I suspect that smoking food has the same adverse effects on non-meat foods as on meats. Smoking something adds carcinogens and probably other inflammatory chemicals.9 Accordingly, it’s probably wise to avoid smoked nuts, fish, or other smoked foods when seeking longevity and health.

4. Potatoes Are The Healthiest Vegetable

For years, potatoes have been demonized as unhealthy due to their high carbohydrate content and association with fried foods like French fries and potato chips. As a result, many health studies exclude them when talking about how much vegetables people consume. However, when consumed in their natural form, potatoes are a nutrient-dense vegetable packed with vitamins, minerals, and fiber. They are an excellent source of potassium, vitamin C, and B vitamins, which support heart health, immunity, and energy production.

However, all-cause mortality studies show white potatoes are healthier than other vegetables. A 2017 meta-analysis of vegetables found that a serving of potatoes reduced the chance of premature death by 22%, compared with 13% for vegetables overall.10

One way that potatoes are exceptional is how filling they are. A 1995 study reviewed 38 foods to see how filling they were compared with white bread, and potatoes landed at the top of the chart–over three times as filling as white bread. That’s almost twice as much satiety as any other carbohydrate-rich food.11 It’s not fully understood why this is, but one suspect is a protein in potatoes (potato protease inhibitor II) that suppresses appetite.12

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Chart showing high satiety of potatoes
The Great White Potato laughs at your feeble attempts to predict its satiety index!

Unfortunately, that doesn’t hold for french fries or potato chips. The health benefits of potatoes do seem strong enough to make frying them overall neutral for health and longevity; they’re no longer as positive as other vegetables. I guess it’s better than other foods, like chicken, which shift from a neutral food to statistically harmful food when fried.13


As we’ve seen, many commonly-held beliefs about nutrition may not be as clear-cut as they seem. Nevertheless, we can support our health and longevity goals by staying informed and making thoughtful food choices. So, go ahead and enjoy that baked potato, prioritize fresh fruits, avoid preserved foods, and remember that sugar, when consumed as a dessert or topping, isn’t all bad!


1. Is all sugar equally harmful for longevity?

No, not all sugar is equally harmful. While excessive sugar consumption can lead to health issues, a 2019 14 study debunked one of the diet myths by stating that adding sugar to the diet from snacks or toppings, excluding sugary beverages, actually reduced premature death by 20% or 10%, respectively, for about one serving per day. After that serving, there was no further harm or benefit for consuming more.

2. Is fructose, found in high fructose corn syrup (HFCS), bad for longevity?

Contrary to diet myths, fructose does not seem to affect longevity when not in liquid form. Studies comparing diets with moderate fructose vs. low fructose found that moderate fructose diets led to more weight loss, and adding 30-60g of fructose to a daily diet did not change lipid or glucose biomarkers.

3. Is canned fruit a healthy option?

Canned fruit, despite being fruit, can be unhealthy due to added sugars and preservatives. While fresh fruit reduces premature death by about 10% for a 100g serving, the same-sized serving of canned fruit can increase the chance of early death by 13%. Frozen fruit is a better alternative as it retains healthy nutrients without the negative effects of canning.

4. Are all processed foods unhealthy?

Not all processed foods are unhealthy. The term “processed foods” can be misleading. Many processed foods, such as whole grain cereals, nut bars, or hummus, can be healthy. The concern lies with preserved meats, like ham, pastrami, sausage, and salami, which are associated with health risks due to added chemicals and processes that enhance flavor and preservation.

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5. Are potatoes a victim of diet myths, and can they be a healthy vegetable choice?

Potatoes, often misunderstood due to diet myths, can actually be a healthy vegetable choice when consumed in their natural form. They are nutrient-dense and packed with vitamins, minerals, and fiber. All-cause mortality studies even show that a serving of potatoes reduces the chance of premature death more than other vegetables, by 22% compared to 13% for vegetables overall.


  1. Association between added sugar intake and mortality is nonlinear and dependent on sugar source in 2 Swedish population–based prospective cohorts
  2. The effect of two energy-restricted diets, a low-fructose diet versus a moderate natural fructose diet, on weight loss and metabolic syndrome parameters: a randomized controlled trial
  3. Dietary Fructose and Glucose Differentially Affect Lipid and Glucose Homeostasis
  4. Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality—a systematic review and dose-response meta-analysis of prospective studies
  5. Nutritional comparison of fresh, frozen, and canned fruits and vegetables II. Vitamin A and carotenoids, vitamin E, minerals and fiber
  6. IARC Monographs evaluate consumption of red meat and processed meat
  7. The Cancer Atlas
  8. Unprocessed Red and Processed Meats and Risk of Coronary Artery Disease and Type 2 Diabetes – An Updated Review of the Evidence
  9. Chemical hazards in smoked meat and fish
  10. Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality—a systematic review and dose-response meta-analysis of prospective studies
  11. The Satiety Index
  12. Potato protease inhibitor II suppresses postprandial appetite in healthy women: a randomized double-blind placebo-controlled trial
  13. Association of fried food consumption with all-cause, cardiovascular, and cancer mortality: prospective cohort study
  14. Swedish study

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