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Yes, you should chew thoroughly – here’s why

May 02, 2022 by Joel Fuhrman, MD

Health Concerns: Weight Loss

Your mother was right: It’s important to chew your food thoroughly before swallowing it.  Chewing is the first step in the digestion of the food we eat – it breaks down food into smaller particles, which increases the surface area so that digestive enzymes can more readily extract the nutrients from it. If we rush through our meals, we don't get the full phytochemical benefit of the foods we're eating. Slowing down and chewing thoroughly allows us to absorb more nutrients, helps us maintain a healthy weight, and even brings dental health benefits.  

 


Summary
The digestive process begins in your mouth as soon as you start chewing. When you break your food down into smaller particles, the digestive enzymes can cover a larger surface area and start to extract the nutrients. For some foods, particularly cruciferous and Allium vegetables, breaking down the structure of the food matrix drives chemical reactions that provide beneficial phytochemicals. 

Related: 
The cancer-fighting power of cruciferous vegetables
How garlic and onions promote cardiovascular health
Eat healthfully, and abundantly, for weight loss
 


 

Phytochemical benefits of chewing thoroughly

The carotenoids in raw carrots are made more accessible when the plant cell walls are ruptured by thorough chewing. Carotenoids are embedded in the matrix of the food, and the structure needs to be broken down to allow the digestive system to extract and absorb them.1,2 For some foods – specifically cruciferous vegetables and onion and garlic family members – breaking down the structure of the food matrix drives chemical reactions that produce beneficial phytochemicals. 

Glucosinolates in cruciferous vegetables (such as broccoli, cauliflower, kale, collards, and bok choy) are converted by the enzyme myrosinase into breakdown products including indole-3-carbinol and isothiocyanates (ITCs), which are compounds with beneficial anti-cancer activity. The extent of formation of ITCs depends on a number of factors, such as the food’s glucosinolate content, temperature, pH, the presence of vitamin C (which accelerates the production of ITCs), and importantly, how much the food is broken down by chopping, crushing, or chewing. 

Glucosinolates and myrosinase are physically separated in the intact vegetable, and damage to the cellular structure is necessary to bring them into contact and start the chemical reaction. Heat inactivates myrosinase, and also degrades vitamin C, which slows or stops the reaction. To maximize the health benefits, cruciferous vegetables should be eaten raw or chopped finely before cooking. 

Similarly, onions, garlic, leeks, scallions, and shallots contain an enzyme called alliinase that is damaged by heat, and physically separated from the sulfur compounds it metabolizes. Physically disrupting the plant cell structure by chopping or chewing well starts the chemical reaction that produces allicin and other beneficial compounds with antioxidant, anti-inflammatory, and anti-cancer effects.3

Related: How garlic and onions promote cardiovascular health

Chewing thoroughly also enhances the conversion of dietary nitrate to nitric oxide by oral bacteria. The body needs nitric oxide a variety of functions, including cell signaling and blood pressure regulation. One of the two major sources of nitric oxide is dietary nitrate, which is converted to nitric oxide by oral bacteria on the surface of the tongue. Green vegetables are the richest sources of nitrate, and the production of nitric oxide by oral bacteria increases when we chew more thoroughly. Note that this process only occurs in the presence of oral bacteria.4-6 For example, when we blend cruciferous greens into a smoothie, we will achieve good conversion of glucosinolates to ITCs, but we won’t get as much nitric oxide production in the mouth than if we had chewed the greens instead.
 

Sources:

Dietary factors that affect the bioavailability of carotenoids
Garlic and onions: their cancer prevention properties
From Nitrate to Nitric Oxide: The Role of Salivary Glands and Oral Bacteria

Chewing thoroughly and weight maintenance 

In addition to extracting more phytochemicals from vegetables, studies suggest that chewing thoroughly and eating more slowly helps maintain a healthy weight. Observational studies have found that participants who reported eating more slowly had lower body weight or gained less weight over time, compared to faster eaters.7,8 In another study, a greater number of chews and longer chewing time were associated with lower body mass index (BMI).9 

Chewing more thoroughly may promote a healthy weight by affecting hunger and satiety signals, which could reduce calorie intake in the current meal, and delaying or reducing calorie intake in the next meal. A meta-analysis of studies on chewing time found that participants reported feeling lower levels of hunger after a meal of longer vs shorter chewing time.10 

Related: Eat healthfully, and abundantly, for weight loss

Several studies have also found that prolonged chewing reduced calorie intake either at that meal or the next meal.10-12 For example, one study had participants eat as much as they liked of a meal while chewing either 15 or 50 chews per bite, and those who chewed 50 times per bite consumed fewer calories.13 A similar study comparing 15 and 40 chews had similar results.14 A smaller bite size is also linked lower food intake.15 

Diet-induced thermogenesis, also called the thermic effect of food, is the energy burned to digest, absorb, and metabolize food. It is a significant contribution to our daily calorie burn, making up as much as 10-15% of the calories we expend in a day.16 There is evidence that chewing more thoroughly increases diet-induced thermogenesis.16,17

Sources:

Faster self-reported speed of eating is related to higher body mass index in a nationwide survey of middle-aged women
Relationship between chewing behavior and body weight status in fully dentate healthy adults
Effects of chewing on appetite, food intake and gut hormones: A systematic review and meta-analysis
Increasing the number of chews before swallowing reduces meal size in normal-weight, overweight, and obese adults.
Chewing increases postprandial diet-induced thermogenesis

Better chewing protects our teeth

Chewing thoroughly stimulates more saliva production, which is a key factor in preventing dental erosion and dental caries (cavities). First, the extra saliva helps remove small food particles and sugars from the teeth. Increasing saliva production helps restore proper pH in the mouth after a meal by diluting and buffering acid; an acidic environment promotes erosion of tooth enamel. Plus, saliva contains minerals, specifically calcium and phosphate, which help to re-mineralize teeth.18

Source:

Saliva and dental erosion

Take action

  • Chew food to a liquid consistency before swallowing
  • Take smaller bites, and don’t overfill your fork or spoon
  • Slow down by putting your fork or spoon down between bites 
  • Avoid distractions, such as watching television, during meals
     

 

 
References
  1. Lemmens L, Van Buggenhout S, Van Loey AM, Hendrickx ME. Particle size reduction leading to cell wall rupture is more important for the beta-carotene bioaccessibility of raw compared to thermally processed carrots. J Agric Food Chem 2010, 58:12769-12776.
  2. van Het Hof KH, West CE, Weststrate JA, Hautvast JG. Dietary factors that affect the bioavailability of carotenoids. J Nutr 2000, 130:503-506.
  3. Nicastro HL, Ross SA, Milner JA. Garlic and onions: their cancer prevention properties. Cancer Prev Res (Phila) 2015, 8:181-189.
  4. Kobayashi J. Chewing Well During Meals May Benefit Health Via the Enterosalivary Nitrate–Nitrite–Nitric Oxide Pathway. J Gastroenterol Hepatol Res 2019, 8.
  5. Hezel MP, Weitzberg E. The oral microbiome and nitric oxide homoeostasis. Oral Dis 2015, 21:7-16.
  6. Qu XM, Wu ZF, Pang BX, et al. From Nitrate to Nitric Oxide: The Role of Salivary Glands and Oral Bacteria. J Dent Res 2016, 95:1452-1456.
  7. Leong SL, Madden C, Gray A, et al. Faster self-reported speed of eating is related to higher body mass index in a nationwide survey of middle-aged women. J Am Diet Assoc 2011, 111:1192-1197.
  8. Tanihara S, Imatoh T, Miyazaki M, et al. Retrospective longitudinal study on the relationship between 8-year weight change and current eating speed. Appetite 2011, 57:179-183.
  9. Zhu Y, Hollis JH. Relationship between chewing behavior and body weight status in fully dentate healthy adults. Int J Food Sci Nutr 2015, 66:135-139.
  10. Miquel-Kergoat S, Azais-Braesco V, Burton-Freeman B, Hetherington MM. Effects of chewing on appetite, food intake and gut hormones: A systematic review and meta-analysis. Physiol Behav 2015, 151:88-96.
  11. Zhu Y, Hollis JH. Increasing the number of chews before swallowing reduces meal size in normal-weight, overweight, and obese adults. J Acad Nutr Diet 2014, 114:926-931.
  12. Higgs S, Jones A. Prolonged chewing at lunch decreases later snack intake. Appetite 2013, 62:91-95.
  13. Borvornparadorn M, Sapampai V, Champakerdsap C, et al. Increased chewing reduces energy intake, but not postprandial glucose and insulin, in healthy weight and overweight young adults. Nutr Diet 2019, 76:89-94.
  14. Li J, Zhang N, Hu L, et al. Improvement in chewing activity reduces energy intake in one meal and modulates plasma gut hormone concentrations in obese and lean young Chinese men. Am J Clin Nutr 2011, 94:709-716.
  15. Zijlstra N, de Wijk RA, Mars M, et al. Effect of bite size and oral processing time of a semisolid food on satiation. Am J Clin Nutr 2009, 90:269-275.
  16. Hamada Y, Kashima H, Hayashi N. The number of chews and meal duration affect diet-induced thermogenesis and splanchnic circulation. Obesity (Silver Spring) 2014, 22:E62-69.
  17. Hamada Y, Hayashi N. Chewing increases postprandial diet-induced thermogenesis. Sci Rep 2021, 11:23714.
  18. Buzalaf MA, Hannas AR, Kato MT. Saliva and dental erosion. J Appl Oral Sci 2012, 20:493-502.

Joel Fuhrman, M.D. is a board-certified family physician, seven-time New York Times bestselling author and internationally recognized expert on nutrition and natural healing, who specializes in preventing and reversing disease through nutritional methods. Dr. Fuhrman coined the term “Nutritarian” to describe his longevity-promoting, nutrient dense, plant-rich eating style.
 
For over 25 years, Dr. Fuhrman has shown that it is possible to achieve sustainable weight loss and reverse heart disease, diabetes and many other illnesses using smart nutrition. In his medical practice, and through his books and PBS television specials, he continues to bring this life-saving message to hundreds of thousands of people around the world.

 

Comments (0):

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kwarya

05/06/2022 02:30 PM

A less often talked about subject. Badly needed reminder for those of us who just don't take time to eat in a relaxed manner. Thank you for the interesting science and reminder.

hhnelson58

05/06/2022 03:49 PM

I have TMJ disease and have to chew carefully so this is good to know. I often blend my food so I don't have to chew as much. Am I missing nutrients by doing this? I also have gut issues and cook most of my vegetables; does this mean I am missing nutrients?

Dr. Ferreri replies:

05/18/2022 01:41 PM

Some nutrients are more bioavailable when the vegetables are raw, and others when they are cooked. A combination of raw (which can be blended) and cooked is recommended.

hhnelson58 replies:

05/19/2022 01:13 PM

Thank you for replying!

IngaB14

05/06/2022 05:25 PM

IngaB14

05/06/2022 05:36 PM

Great article.

I was lucky to have a doctor as a father and one who qualified in the days when nutrition was an important part of doctors' training (he studied at Edinburgh University in the late 1920s/30s.

Thanks to him, my sister and I have pretty strong immune systems and even though I'm about a stone heavier than I was when I was younger (now being 70), I'm in pretty good shape compared with most of my contemporaries.  I put this down to the principles mentioned in the headline of this article that also tell me when I've eaten enough.

Most allopathic doctors nowadays - especially in the States - would rather prescribe some horrible pharmaceutical preparation than look into their patient's lifestyle and dietary habits.  

Although my late father frowned upon missing meals, I'd rather forego one than have to bolt it (and thus not savour the food) and then suffer indigestion - or worse - later on.

Thank you, Dr Fuhrman.

Redrunner62

05/07/2022 08:00 AM

This is the link I have missed forever! My husband is a thin healthy man and he eats so slowly. I eat very fast! So simple but so important. I have been following your book and eating so well for 2 and a half years. I  just haven't lost that last bit of weight that makes me feel not healthy. The belly fat. New habit starting today! Thank you for all you do to help us take our health into our own hands! 

mstish

05/07/2022 08:43 AM

Loved this indepth information. I always like to get the details. 

The comment about dental erosion interests me. I love grapefruit  and all  citrus as well as vinegars.  At 82 I want to maintain my enamel.

Thank you for always adding more information to my understanding. 

 

LinMercer

05/07/2022 09:09 AM

I follow Dr. Goldberg on reversing my Lupus. I believe and combine both of your wealth of knowledge and do both hypernourishing smoothies and eat raw vegan foods cruciferous. Thanks for all you do and share to help others.