HEALTH – Fad diets – are we biting off more than we can chew?

Posted by Editor on October 24, 2025 in Health | 1 Comment

From ‘Skinny Jabs’ to Intermittent Fasting (IF) the pros and cons for each can be debated, but the longer-lasting effects on oral health can be wide-ranging, as dentist James Goolnik (optimaldentalhealth.co.uk) explains:

A healthy body weight is just one of the pieces of a larger puzzle that makes up a healthy person, and yet our collective obsession with weight loss and fad diets doesn’t show any signs of waning.

“In my practice I see many patients who admit to being on one diet or another. Most recently I’ve seen an increase in patients on GLP-1 medications like Mounjaro, Wegovy and Ozempic, which is unsurprising given their popularity. As weight loss trends go, these so-called ‘Skinny Jabs’, are relatively new and so it’s difficult to determine at this stage whether they’re here to stay, but the recent rollout by the NHS, suggests they might be. 

Whilst the benefits for health are widely reported – weight loss, diabetes control, potential cardiovascular improvements, as a dentist I have three main concerns and these are dry mouth (xerostomia), nausea and vomiting and changes in taste (dysgeusia).

Dry mouth occurs when your salivary glands don’t produce enough saliva. This can be a side effect of GLP-1 medications, particularly because they may reduce appetite and fluid intake. Saliva plays a vital role in neutralising acids, washing away food particles, and protecting enamel. Without enough saliva, there’s an increased risk of tooth decay, gum disease, mouth sores, and bad breath. A simple trick to keep saliva levels healthy, is to make sure you are breathing through your nose as much as possible, and at night, mouth-taping can help encourage this.

Dysgeusia is when your sense of taste changes; foods may taste metallic, bitter, or just “off.” This can discourage proper eating and oral hygiene habits, and in some cases, people may avoid brushing their teeth or using certain products because of the altered taste sensations. They can also crave sugary foods, which of course affects oral health.

But GLP-1s are not the only weight loss trend to have a negative effect on oral health. 

Intermittent Fasting, which involves cycling between periods of fasting and eating, popular variations include the 16/8 method (fasting for 16 hours and eating during an eight-hour window) and the 5/2 approach (eating normally for five days and consuming 500-600 calories on two days), can reduce inflammation and lead to improved glucose response, but it also decreases salivary flow, which increases the risk of caries, dry mouth and halitosis. 

Halitosis is a key characteristic of the Keto Diet. The ketogenic diet induces ketosis, where the body uses fat for energy instead of carbohydrates, and this can lead to “keto breath,” due to the production of ketones during ketosis. This can smell like acetone, chemicals, or have a sweet, fruity odour. Ensuring hydration and reducing protein intake can help to mitigate keto breath. It’s also worth bearing in mind that any lack of dietary variety, in this instance carbohydrates in the form of wholegrains and fresh fruit and vegetables, can also result in deficiencies in vitamins and minerals that are crucial for oral health, such as vitamin C, which is essential for gum health.

Even veganism can be problematic for oral health. Whilst vegans benefit from an increased intake of dietary fibre, vitamins C and E, and minerals such as magnesium, animal products contain beneficial vitamins and minerals such as vitamin B12, iron, and omega-3 fatty acids, which are not readily available through a plant-based diet. 

Vitamin B12 for example, is essential for healthy gums, with B12 deficiency resulting in possible glossitis, inflammation of the tongue, and mouth ulcers.

Some studies also suggest that vegans may be prone to dental erosion due to high ingestion of acidic fruits and vegetables, whilst a lack of dairy intake increases the potential for calcium and vitamin D deficiencies; both of these nutrients are needed for healthy teeth.

So, what should you be doing?

What you eat has a huge impact on your teeth and oral hygiene, and it’s not just sugar you need to be mindful of. Moderation is key, as well as snacking. Too much of a good thing, as with the acidic fruits in the vegan diet, can have a longer-lasting, detrimental effect on your teeth. A balanced diet, healthy snacks and staying hydrated can all help to protect teeth and prevent tooth decay.

My top five foodie tips?

1. Do eat lots of crunchy and green leafy vegetables. Crunchy vegetables, like raw carrots and broccoli, will help to remove plaque from the surface of your teeth, and leafy veg, like spinach and kale, contain iron, which helps to strengthen enamel and guard against gum disease.

2. Top up on dairy or (sugar-free) dairy alternatives. Milk, yoghurt and cheese are great for strengthening tooth enamel and fighting against cavities, as they are high in calcium and protein. Almost all calcium in the body is stored in bones and teeth, and calcium deficiency has been shown to increase the risk of tooth loss. 

3. Go nutty for nuts. Raw, unsalted nuts are great for teeth. They are low in carbohydrates (which can activate the acid-producing bacteria that can lead to tooth decay). Their high fibre content also means you have to chew them, which naturally stimulates the production of saliva, helping to reduce the risk of tooth decay.

4. Do include low acid fruits such as strawberries and apples. Both contain malic acid, which can help to naturally whiten teeth. And with apples, as with nuts, you have to spend a little more time chewing, which again, helps to stimulate gums and increase saliva production.

5. Finally, chew sugar-free gum with xylitol after meals. Not strictly a food, but chewing sugar-free gum with xylitol, after meals, is scientifically proven to reduce cavities, neutralise harmful acids, and keep your breath fresh – and my go-to gum is Peppersmith Gum (Peppersmith.co.uk). Why xylitol? It’s a natural sugar alternative that bacteria cannot digest, meaning it actively fights against tooth decay. It stops bacteria from sticking to your teeth, lowering plaque build-up and reducing the risk of cavities and bad breath. Chewing gum also increases saliva flow, which helps wash away acid and protect your enamel. 

Dr James Goolnik BDS MSc, is a dentist with a passion for nutrition. Previously President of the British Academy of Cosmetic Dentistry, he is now head judge of the Private Dentistry Awards and he lectures internationally on the mouth-body connection. Twice voted ‘the most influential person in dentistry in the UK’, James is the Founder of Optimal Dental Health in London (www.optimaldentalhealth.co.uk), an accredited member of The International Academy of Oral Medicine and Toxicology and fully SMART certified.