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Benefits of Polyphenols and a Low Fructose Diet

Benefits of Polyphenols and a Low Fructose Diet

As a follow-up to our recent webinar on June 8th, 2022 titled “The Benefits of Polyphenols and a Low Fructose Diet”, we wanted to take a minute to provide a brief summary and answer some questions we were unable to get to during the webinar. If you were unable to attend our webinar and are interested in learning more about polyphenols and fructose, please check out our Continuing Education Center for a recorded version of the webinar. If this is your first time accessing our Continuing Education Center, you will need to create a new registration account.

What’s All This Hype about Polyphenols?

Polyphenols are phytochemicals only found in plants and play a very important role in human health due in part to their high antioxidant value. They can help preserve cellular health through protecting the mitochondrial and cell membrane as well as DNA within cells. In addition, polyphenols can inhibit cyclo-oxygenase series II (Cox-2) activity which in turn helps reduce inflammation. A lesser-known ability of polyphenols is their ability to foster a healthy microbiome by feeding beneficial bacteria and reducing pathogenic populations.

All Things Turmeric

During the webinar Dr. Bagnulo talked in detail about turmeric and curcumin, which is a more isolated form of the most potent polyphenol found in turmeric. Curcumin is unique in that it becomes more bioavailable with heat and when combined with a fat source such as olive oil or coconut oil. Curcumin has limited bioavailability because it has low solubility in water – curcuminoids want to attach to fat for better gut absorption. This remains true regardless of if you are using turmeric in the spice form or a supplemental form. We aren’t talking high heat- simply 185°F does the trick – so not necessarily boiling. Even just simmering turmeric/curcumin with a small amount of oil for 5 minutes will increase the absorption rate significantly. Cooking with turmeric in a curry dish is another great option – short cooking times (under 15 minutes) will not destroy the turmeric and will give a bioavailability boost. The bioavailability change with heat and oil may be one reason why studies evaluating the benefits of turmeric/curcumin are mixed as not all studies heated the herb/supplement and/or included a fat source.

Another commonly asked question is surrounding the relationship between black pepper and turmeric/curcumin. Piperine, a compound in black pepper, has been shown to make curcumin more bioavailable by protecting curcumin from the digestive enzymes that are actively trying to remove it from the blood stream; therefore, boosting the absorption. A great cooking combination that is not only tasty but also healthy is turmeric, black pepper and oil!

The discussion of heat to increase the bioavailability of turmeric/curcumin then leads to the question – do all polyphenols need to be heated to achieve optimal absorption? Unfortunately, the answer is not clean-cut. Some polyphenols such as curcumin found in turmeric and lycopene found in tomatoes are better absorbed with heat while other polyphenols such as anthocyanins found in berries are not heat tolerant and are best consumed frozen or fresh. Check out the articles in the reference section from Perez-Jimenez et al. and Oszmianski et al. to learn more details of heat-tolerant versus non-heat tolerant polyphenols!

Here at Functional Formularies, we encourage getting as many nutrients from whole, real foods as possible. While turmeric and curcumin supplements are in abundance in health food stores and on-line, focusing on using the whole turmeric root in cooking is ideal. Keep in mind that turmeric is more than just curcumin – there are over 100 compounds in the turmeric root which have potential health benefits. If getting in turmeric in its most natural state is not possible, then certainly choosing a quality supplement from a reputable company is another option.

Optimizing Polyphenol Intake Summary

  • Try to incorporate 4 major families of plants daily – root-derived spices, herbs, dark berries and dark green leafy vegetables for example.
  • Choose whole, minimally processed brightly colored vegetables and fruits.
  • Use extra virgin olive oil for most cooking and flaxseed oil for salad dressings and non-heated meals.
  • Choose organically grown sources when possible.

So What About Fructose?

Fructose is a monosaccharide; often referred to us as a “simple” sugar. It’s important to consider that not all sugars are created equal. While they may all provide the same calories per gram, they are metabolized differently in the human body. Human physiology has the most difficult time metabolizing fructose in a safe and healthy fashion compared to other sugars. The reason being is that fructose, before it can be used by our bodies, has to be phosphorylated for liver metabolism. During this process uric acid is generated leading to an increased level of serum uric acid and excretion in the urine. Uric acid has been tied to inflammation and hepatic burden. In addition, fructose generates significantly higher levels of triglycerides and small dense LDLs (a cardiovascular risk factor) in comparison to glucose. We often think of fructose and simply avoid high fructose corn syrup, fruit juice and concentrated fructose as a sweetener, but ultimately there is a wide variability of fructose in whole fruits as well.

High Fructose Fruits

  • Peach: 8 grams
  • Banana: 10 grams
  • Apple: 10 grams
  • Pear: 12 grams
  • Grapes: 12.5 grams
  • Mango: 32 grams
  • Raisins: 42 grams

Note: Fructose grams are per 1 cup. 

Low Fructose Fruits

  • Limes & Lemons: 0 grams
  • Cranberries: 0.5 grams
  • Raspberries: 3 grams
  • Clementine: 3 grams
  • Blackberries: 3.5 grams
  • Strawberries: 4 grams
  • Nectarine: 5 grams
  • Blueberries: 6.5 grams

Note: Fructose grams are per 1 cup. 


A good resource to use to identify high and low fructose fruits would be the USDA FoodData Central database. You may see some slight variations between the different varieties of fruit- for example 100 grams of a Gala apple contains 8 grams fructose while a Granny Smith variety has 6 grams in the same portion.

 Fructose Recommendations

  • Overall try and avoid the use of sweeteners including honey and agave syrup.
  • Choose whole, lower fructose containing fruits such as berries and citrus fruits and limit high fructose containing fruits including fruit juice and dried fruits.
  • Read labels and avoid foods and condiments that contain high fructose corn syrup – looking at you ketchup.

Research suggests that most adults should limit their fructose to no more than 10 grams per meal and 25 grams per day. The 2020-2025 Dietary Guidelines for Americans recommends 1 ½ to 2 cups of fruit/day for adult women and 2 to 2 ½ cups a day for men. So how do we meet our daily fruit goal but not exceed the fructose goal suggested?

Start your day by eating 1 banana for breakfast which provides a 1 cup serving of fruit and 10 grams of fructose. While this may be considered a high fructose fruit- you can balance out the fructose by choosing lower fructose fruits for the rest of your daily fruit servings. Top a salad with 1 cup of cut strawberries at lunch and then snack on a ½ cup of blueberries before bed.  This still only brings your total amount of fructose to 17 grams for the day but provides 2 1/2 cups of fruits and still leaves you with 8 extra grams of fructose for those hidden fructose containing foods such as bread and other grains or condiments such as ketchup.


Oszmianski J, et al. Dietary Plant Polyphenols: Effects of Food Processing on Their Content and Bioavailability. Molecules. 2021 May:26(1);2959.

Perez-Jimenez J, et al. Identification of the 100 richest dietary sources of polyphenols: an application of the Phenol-Explorer Database. Eur J Clin Nutr. 2010. Nov 3;2010:S112-S120.

Serafini M, et al. Functional Foods for Health: The Interrelated Antioxidant and Anti-Inflammatory Role of Fruits, Vegetables, Herbs, Spices and Cocoa in Humans. Curr Pharm Des. 2016:22(44):6701-6715.

Softic S, et al. Fructose and Hepatic Insulin Resistance. Crit Rev Clin Lab Sci. 2020 Aug;57(5):308-322.

Taskinen MR, et al. Dietary Fructose and the Metabolic Syndrome. Nutrients. 2019 Aug 22;11(9):1987.

Tizabi Y, et al. Relevance of the anti-inflammatory properties of curcumin in neurodegenerative disease and depression. Molecules. 2014. Dec 12:19(12):20864-79.

Wang J, et al. Connection between Systemic Inflammation and Neuroinflammation Underlies Neuroprotective Mechanism of Several Phytochemicals in Neurodegenerative Diseases. Oxid Med Cell Longev. 2018. Oct 8;2018:1972714.