#242 Is There a Sugar Cancer Link?

Is There a Sugar Cancer Link?

If you follow the news you undoubtedly saw the headlines this past week–sugar causes cancer.  In this article, I discuss the possible sugar cancer link and share my struggles with sugar.

The Latest Sugar Cancer Study

This past week Belgian researchers published their latest findings on the sugar cancer link.  In a press release, one of the authors of this study, Dr. Johan Thevelein, even went so far as to make the following bold statement in a press release:

“Our research reveals how the hyperactive sugar consumption of cancerous cells leads to a vicious cycle of continued stimulation of cancer development and growth. Thus, it is able to explain the correlation between the strength of the Warburg effect and tumor aggressiveness. This link between sugar and cancer has sweeping consequences.

What Dr. Thevelein is saying here is that their study shows that sugar feeds cancer cells.  Almost the second this research was published, the media ran wild with the story.  

What the Media Didn’t Tell You About This Study

While sugar feeds cancer makes for a great media story, the real findings of this study aren’t that exciting.  First of all, this study wasn’t even done in humans but instead examined yeast cells growing in a laboratory petri dish.

What this study did show is that sugar at high concentrations in a laboratory environment can activate a gene called Ras in yeast.  And once this Ras gene in yeast is turned on, cancer cells start growing fast.

This study says nothing about human cancer.  You just can’t give dietary advice based on what yeast cancer cells do in a petri dish.

Does Sugar Feed Cancer Cells?

The real question this study raises is whether or not sugar feeds cancer cells.  While cancer cells love glucose scientists still don’t know if dietary sugar feeds cancer cells.  It is for this reason that for the last 80 years cancer specialists have been debating the Warburg effect.

The Warburg effect was named after the nobel prize winning, German biochemist Dr. Otto Warburg.  More than 80 years ago Dr. Warburg observed that cancer cells must consume glucose to survive.  What remains unknown is whether cancer requires sugar from the diet or whether it can just make it on its own.

Is There a Sugar Cancer Link?

While a direct sugar cancer link remains unproven, sugar may increase your risk of cancer indirectly.  For example, sugar and obesity go hand-in-hand.  And countless studies show that obesity is a significant risk factor for cancer.

Another possible sugar cancer link comes from insulin.  When glucose levels in the blood are high, insulin is released.  High insulin levels can in turn trigger insulin-like growth factor (IGF-1).  IGF-1 is a potent cancer stimulant.

Indeed, there is a rare group of people living in Equador who have an unusual mutation which doesn’t allow their bodies to make IGF-1.  To this day, cancer isn’t known to exist in this group of people who can’t make IGF-1.

My Struggles with Sugar

Long before this study ever hit the media, I have struggled with sugar.  In fact, I had such a sweet tooth that I had collected more than 20 dental fillings and two crowns by age 18!

The ironic thing is that our studies of the centenarians living in China’s Longevity Village showed that most centenarians still had all of their teeth at age 100 despite not ever brushing, flossing, or drinking fluoridated water.  This finding alone hammered home to me that the human body was not designed to eat so much sugar!

In addition to a lifetime of extensive dental work, sugar also caused me to be overweight through most of my adult life.  The reason for this is because I have found that even the slightest amount of sugar revs up my appetite.

Indeed, through careful tracking, I have found that if I consume zero sugar, including no flour which is still just sugar, I need about 2,500 calories to feel full.  In contrast, even eating a few grams of sugar or having something with flour, I need approximately 3,000 calories to feel full.

Sugar: To Moderate or Abstain?

I am not a moderator.  For me, I either eat the entire bag or cookies, or I don’t eat any at all.  Once I have a taste of sugar or something with flour, I obsess about it until it is 100% consumed.

Thus, the only way for me to maintain a healthy weight is to abstain from all sugar and flour.  While I would love to say that I am a 100% abstainer, that is just not the case.  Sometimes my willpower is overcome by temptations.

The key for me has been to eliminate the temptations.  When sugar or foods with flour are not around me, I find that I don’t even think about them.

One of the health secrets of our book, The Longevity Plan, is not to face temptations.  These people living in China’s Longevity Village didn’t have to face the temptations we face every day.  Because they were geographically isolated, they never struggled with food temptations.  They were abstainers without ever having to use any willpower at all.

In contrast, some people possess the gift of being able to eat in moderation.  While many people claim to be moderators, in my experience of working with thousands of patients, few can do so.

Practical Tips

The latest study trying to make a sugar cancer link didn’t prove anything new.  Dr. Warburg taught us more than 80 years ago that cancer loves sugar in any form.

Regardless of your personal views on sugar, the 150 pounds of it that the typical American eats each year is just too much for optimal health.  Either you should consider moderating sugar by keeping it under the 25 grams daily that the World Health Organization recommends or abstain entirely.

Personally, I lack the willpower to moderate sugar and foods, like flour, that behave like sugar in the body.  Because I know I will slip if I go somewhere slippery, I try to avoid the slippery places in life.

Are you a moderator or abstainer when it comes to sugar and flour?  Please leave your thoughts and questions below.  If you like what you are reading, please be sure to subscribe to our free weekly newsletter, read The Longevity Plan, or listen to my podcast.


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  1. Dr. Day, I have the following questions for you:

    1. I thought in the past you said you do eat some sweetened dark chocolate. Or do you eat 100% cacao dark chocolate only?

    2. Are fruits OK? I like pomegranates, citrus fruits (mainly grapefruit), berries. Fortunately I don’t like fruit juices.

    3. What about milk and yoghurt? I heard lactose is a sugar that isn’t sweet. I don’t drink much milk but do eat plain greek yoghurt.

    For me to give up sugar (and bread and chips) would be a huge sacrifice. But this article convinces me I should do it. I wish there were support groups to help with this kind of thing (e.g. alcoholics have AA which is very effective). But it’s just me trying to give up something that helps get me through the day, and no-one in my life really cares what I eat or not and there’s no-one to discuss it with.

    • Hi Diane,

      Thanks for your questions!

      You are correct, I used to eat minimally sweetened dark chocolate. However, I have found that I don’t do well with sugar. Sugar makes me hungry, makes me crave other sweets, and I just don’t feel my best on sugar. Thus, the dark chocolate I now eat has zero sugar and is stevia sweetened. I realize that stevia and other alternative sweeteners are not without their controversy, however, this is what I have found works the best for me.

      Yes, fruit is great. While some people may have blood sugar challenges with the sweet fruit like pineapple or watermelon, there is nothing wrong at all with berries, apples, pears, or citrus fruits. I agree, fruit juice is really just sugar.

      You are also correct in that there is a lot of natural sugar in dairy. When you look at the studies, dairy seems to be neutral when it comes to health outcomes. If you like yogurt then always buy the unsweetened variety.

      Sugar is indeed an addiction. I suffer from this as well. It is also something that 99% of the population is probably addicted to as well. Some people do well on a low sugar diet while others, like me, need to avoid it all. The only way to know is to test yourself. See how you feel on a low sugar versus a zero sugar diet.

      Hope this helps!


  2. Your experiences and stance on moderating use and abstaining from sugar exactly match mine. It was an odd consolation to learn most people CANNOT moderate. I thought it was my own personal weakness. Now that I think about it, the only people I know who control their consumption of sugar and “near-sugars” are those who keep it out of their homes and don’t beat themselves up when they fall prey to it away from home (like at the unavoidable birthday parties). It seems those who opt for “all or nothing” end up in the “all” grouping…wondering why they have a diagnosis of Type II Diabetes. Those who think they have totally abstained have probably slipped up somewhere…like breathing in someone’s stray wisp of cotton candy. JK…we all know what the #1 food additive is…and we could organize and object to its omnipresence if we wanted to. It would take quite the inspiring leader to launch that protest. Dr. Day?

    • Hi Eileen,

      Thanks for reading and commenting! Your comments are spot on. From a mindfulness stand point, whether someone is on a low-sugar or zero-sugar diet you can’t beat yourself up for occasionally indulging.

      Fortunately, there is a growing awareness of the harms of sugar. And, fortunately, people are starting to vote with their purchases. As more and more health conscientious people are trying to minimize or eliminate added sugar, there are becoming increasingly more options for us at the grocery store!



  3. I really needed this message. I can usually avoid sugary products when shopping, and after abstaining for a few weeks/days, I don’t have major cravings. A single piece of hard candy can usually be satisfying for a few days. I have lost 8 lbs in 3 weeks just by watching it. Thanks.

    • Hi Betty,

      Congratulations! Weight loss really can be as simple as you described.

      If a single piece of hard candy can satisfy you for days then keep doing what works for you! Be thankful that you have the rare gift of being able to moderate your sugar intake.



  4. Hi Dr. Day, I have noticed from your book and from the recipes your wife shares that fruit, and it would seem even dried fruit, are included. Does this mean that the naturally occurring sugars in fruits are OK? How about sweet potatoes? Thanks for sharing your work! Peace and best wishes, Marvin

    • Hi Marvin,

      Fruit is incredibly healthy. Dried fruit can also be healthy provided it is eaten in moderation.

      The challenge with dried fruit is that it lacks all of the water. The water in fruit is what helps us to feel full. Thus, it is incredibly easy to overeat dried fruit and get an excessive amount of sugar…

      Sweet potatoes are incredibly healthy.

      Thanks for reading!


  5. I read you are an abstained of flour, does that mean you don’t eat bread?
    If you don’t eat bread then what do you eat instead?

    I am an afibber and know bread can be a trigger, I have cut back and eat low carb bread and find some improvement but not a cure.

    My cure seems to be taking kefir (100mgs each morning) no afib for three months now. Will know for sure after six months. Fingers crossed.

    • Hi Colin,

      I am so happy to hear that you have found dietary interventions that help your Afib!

      Yes, it is true that I try my best to avoid bread with flour. Flour is really just sugar. The reason for this is that in the process of turning it into fine powder the body can then instantly convert it to sugar. This is why you will see that even whole wheat bread is much higher on the glycemic index than even a Snicker’s bar.

      I need to point out that I do in fact eat bread on most days. My favorite is Ezekiel Bread which can be purchased at most health food stores in the frozen section. Ezekiel Bread has no sugar and no flour. Thus, I don’t get the sugar rush or the bread cravings with Ezekiel Bread.

      Other “flourless” breads include Trader Joe’s flourless bread or Paleo Bread at Whole Foods.

      Hope this helps!


    • I would really like to see Dr. Day’s reply to Colin…I believe that bread may be a trigger for my afib too…I also notice that when I eat too much sugar I experience leg cramps at night…Does this mean my magnesium level is being affected or too low?

      • Hi Jackie,

        I have had many patients share with me that sugar, as well as bread, are Afib triggers. Indeed, if you look at the glycemic effect of even whole wheat bread you will see that it is much higher than a snicker’s bar.

        Leg cramps can be due to many different causes. However, top on the list is a low potassium or magnesium. While potassium levels can be easily measured, magnesium cannot. Fortunately, as long as people aren’t taking acid blocking medications like Prilosec, Prevacid, or Nexium, most people can get enough magnesium from eating nuts, seeds, or green vegetables.

        Hope this helps!


  6. Hi Dr Day,

    Your comments about your personal experience with sugar accurately mirror my own.

    I too now abstain from all/any added sugar (including avoiding all pre-prepared foods that have ANY added sugar) and I minimise other carbohydrates by eating only very modest amounts of whole grain products and a few pulses. I also eat some fresh fruit (but not bananas, pineapples or oranges and never any fruit juices).

    Even this diet contains some sugar (in milk and fruit eg) but not enough to trigger cravings/inflammation.

    I get more calories from fat and protein than the official dietary guides recommend but this diet has led to a stable, healthy weight and the absence of food cravings.

    I expect you have come across Nina Teicholz …. best wishes

    • Hi Terry,

      Thanks for reading and commenting! I, too, get more calories from fat than the official dietary guidelines (from dark chocolate, nuts, and seeds).



  7. I don’t know what I feel about the over abundance of diet information that is available today. My father lived to be 94 and my mother 87. My father’s sister lived to be 101, and probably could have lived longer if she had been willing to take medications, but at 101 she said she wanted to die. My mother’s two sisters are still living, both in nursing homes (if you can call that living). One is 99 years old and the other 97. My husband’s day also lived to 94 and was not particularly active once he retired in his early 60’s… he didn’t even play golf. NONE of these people ever followed any special diet or exercise programs. My dad was always pretty active… did his own yard work until he was quite elderly and played golf when he could. My mother did house work, but lived a pretty sedentary life as she aged. My aunt’s were not particularly active either. I read all this information about diet and exercise (I am now 68 years old) and it does nothing but make me anxious and paranoid about everything I eat, and, frankly, I think that is more detrimental to my health than anything else. I think that we do have the worst possible foodstuffs available to us in the United States, which is a humiliating fact given what this country should be, but capitalism is what is most important here, not the people. If we do not collectively demand better, well, I guess we get what we deserve.

    • Hi Donna,

      You bring up some great points. Health is really simple. Just eat real foods, maintain a healthy weight, stay physically active, don’t short change your sleep, and embrace the stress in your life.

      All too often we try to make eating so complex. This is something that previous generations never had to struggle with. As they were never bombarded with “fake foods” (i.e. processed foods) by conspiring food manufacturers trying to make money at the cost of our health, eating came much more natural to them.

      Thanks for reading and commenting!


    • Donna, I agree with you. Sugar is a major comfort food for me, and in recent years I have cut back, but I doubt I can eliminate it entirely. I read this site for advice on things I can actually do to preserve my health that aren’t too difficult, but giving up sugar is probably more than I can do.

  8. hi dr. day. saint augustine thought that abstinence was easier than a perfect moderation. thank you i enjoy your blog. steve