But what were their diets like? Typically, due to being hunter-gatherers, they survived off meats, fish, nuts, and other wild-gathered foods, like purslane leaves.¹ These eating habits, which have become commonly known as the paleo diet, have gained popularity over recent times with some studies linking this way of eating to greater overall health, in addition to aiding weight loss, type 2 diabetes, and cardiovascular disease. But if the paleo diet isn’t undertaken properly it can quickly lead to nutritional and digestive system deficiencies.^{2, 3} Here we’ll take you through what the paleo diet is and how it can benefit your health as well as the potential health pitfalls of the diet and what you can do to protect your gut health along the way.

Paleo diet philosophy

Is your body designed to cope with the diet of our distant ancestors? Paleo diet adherents who argue yes typically reason that, because the human race existed for a long time hunting and gathering for food — 35,000 years compared to 10,000 years in the agricultural era — our bodies have evolved based on the foods our paleolithic ancestors ate.⁴ These foods include:

• Wild game
• Lean, and preferably free-range, grass-fed meats
• All seafood
• Free range eggs
• Moderate amounts of olive, flaxseed and coconut oils
• All fruits
• Vegetables, including root vegetables
• Seeds and nuts
• Herbs and spices
• Honey

Whereas, the foods that our ancestors didn’t have access to (as a result of a lack of modern agricultural practices), and thus those on the paleo diet should avoid, include:

• All grains: wheat, oats, rice, rye, corn, barley, spelt and amaranth
• Dairy products
• Some high-starch vegetables, such as potatoes
• Legumes
• Processed meat
• Packaged and canned foods
• Sugar and artificial sweeteners
• Added salt

The benefits

A well-planned paleo diet can be highly beneficial for your overall health. It is high in fibre, antioxidants, mono- and polyunsaturated fats, and protein. It also supplies potassium, which is typically deficient in people consuming a Western diet. The diet also boasts a low glycemic index, in contrast with the Western diet which typically includes carbohydrates that spike blood sugar.⁵ A recent study revealed that the low glycemic index of the carbohydrates sources in the paleo diet, which includes beets, sweet potatoes and squash, promoted a reduction in overall glucose levels by 36% and reduced insulin secretion by 30% in comparison with a conventional diet.⁶

Nutritional challenges of the paleo diet

The paleo diet notably eliminates dairy products, which for many people are reliable sources of Vitamin D and calcium — two important nutrients for developing and maintaining strong bones. If you don’t get enough calcium and vitamin D you might be at increased risk of bone mineral loss and cardiovascular disease.^{7, 8} If you adopt the paleo diet, it’s important that you make sure you get these from other food sources, like broccoli, kale, and spinach for calcium and seafood for vitamin D.

Another potential challenge you could face on the paleo diet is not getting enough fibre. Though a well-planned diet can provide ample fibre, due to the elimination of foods like wheat and oats, it is easy to become deficient. This could result in a number of distressing gastrointestinal symptoms, chiefly constipation, in the short term and even longer-term chronic health issues.⁹ It’s important therefore that on a paleo diet you make sure to eat enough fibre-rich foods, like sweet potatoes, kale and nuts.

The importance of a thriving gut microbiome

The human digestive tract — leading from the mouth down to the anus — is home to roughly 35,000 types of bacteria and other microorganisms with a total population of trillions.¹⁰ This population of microbes is known as the gut microbiome that works around the clock to help ferment and digest your food, and to protect against invading pathogenic bacteria that can cause illness. Many chronic illnesses have been linked to alterations in the gut microbiome: type 2 diabetes, cardiovascular disease, inflammatory bowel disease and irritable bowel syndrome.¹¹

In recent times, scientists have identified diet as one of the primary factors that affect the gut microbiome. When someone undertakes a dramatic dietary shift it can change the gut microbial population in a matter of 24 hours. ¹² Gut microorganisms rapidly adapt to different food substrates and a recent study has shown that a diet with a high amount of animal protein rapidly led to an increase in Alistipes, Bilophila and Bacteroides species in the gut, while a vegetarian diet led to higher amounts of plant-digesting Firmicutes.¹³

Protecting the gut microbiome on the paleo diet

A dramatic dietary switch to a paleo diet likely creates a significant alteration in the gut microbiome — and depending on the makeup of the paleo diet plan this could be bad news. The sudden changes in your diet might lead to changes in how your bowel functions, leading to a number of symptoms, such as constipation and diarrhoea.¹⁴

You might be able to buffer the gut microbiome against these changes through regular consumption of prebiotics. These are sources of fibre that modulate the gut microbiome to benefit general health and one common prebiotic is inulin. Inulin can be added to functional foods, or consumed in natural sources like onions, leeks, asparagus, bananas, and artichoke. If you do begin the paleo diet, prebiotics can increase your daily fibre intake and as such are a good way to help keep your gut healthy in those initial stages of diet change. You can increase your prebiotic intake by including the foods above into your diet, or by taking a daily prebiotic supplement.

The bottom line: paleo with care

The paleo diet has become increasingly popular, but it needs to be undertaken carefully so you don’t end up suffering from nutritional deficiencies or gastrointestinal distress. It’s important to watch your vitamin D and calcium intake as well as making sure you get enough fibre to support your gut — whether this is from adding inulin to your foods or consuming a daily prebiotic supplement. If you’re interested in learning more about how you can keep your gut healthy, head over to our advice page for more information.

If you'd like to read more about the benefits of keeping a healthy gut, as well as find more information on how you can promote good gut health, then head over to our Gut Health advice centre.