Potential Risks and Side Effects of the Paleo Diet: What to Know Before Starting

Overview of Potential Risks from Restricting Food Groups

The paleo diet is often described as a return to the eating patterns of pre-agricultural ancestors, focusing on meat, fish, eggs, vegetables, fruits, nuts, and seeds while excluding dairy, grains, legumes, and processed foods. This restrictive approach can lead to significant benefits for some, such as improved blood sugar control and weight loss, but it also carries potential risks.

By eliminating entire food groups, the paleo diet can make it challenging to meet certain nutritional needs. Clinical evidence suggests that the risks may be similar in some ways to those associated with vegan diets, particularly regarding reduced intake of calcium and vitamin D, because dairy products are excluded and common fortified plant-based substitutes are also avoided.

• Restricting food groups can lead to inadequate intake of essential nutrients if not carefully planned.
• The exclusion of dairy and grains can reduce sources of calcium, vitamin D, and fiber.
• Without careful substitution, followers may miss out on iodine and B vitamins found in fortified foods.

Sources: StatPearls Publishing, Harvard T.H. Chan School of Public Health

Risk of Nutrient Deficiencies: Calcium, Vitamin D, Iodine, and Fiber

The paleo diet’s exclusion of dairy products is a primary cause for concern regarding calcium intake. Short-term studies show that calcium consumption on the paleo diet is well below the recommended daily intake for healthy adults. Furthermore, the high protein intake typical of this diet may increase urinary calcium loss, potentially raising the risk for bone demineralization and osteoporosis over time, although this effect is debated and not confirmed in long-term studies.

Vitamin D is another nutrient that is nearly absent from paleo food sources. Since dairy is often fortified with vitamin D and fatty fish, egg yolks, and sunlight are other sources, paleo dieters may not get enough, especially in winter or with limited sun exposure. Adequate vitamin D is crucial for calcium absorption and bone health, so its deficiency can compound calcium shortfalls.

Iodine deficiency is also a possible risk. By eliminating dairy and often reducing salt intake, paleo followers may not consume enough iodine, a mineral essential for thyroid function. This concern is especially relevant during pregnancy, when iodine needs increase, and deficiency can lead to thyroid problems in both the mother and the fetus.

Another common nutrient gap is fiber. Whole grains and legumes, which are staples in many diets, are excluded from paleo, and if not enough vegetables, fruits, and nuts are consumed instead, fiber intake may fall below recommended levels, potentially affecting digestive health and regularity.

• Calcium intake on paleo is often well below recommendations, possibly harming bone health.
• Vitamin D is not provided by dairy on this diet; supplementation may be necessary.
• Iodine can be low, especially if salt intake is reduced; this is a particular concern for pregnant women.
• Fiber may be lower if whole grains and legumes are not replaced with enough high-fiber vegetables and fruits.

Sources: University of California, Davis

Effects on Kidney Function and Protein Intake

The paleo diet typically provides a high amount of protein, sometimes exceeding 2.5 grams per kilogram of body weight per day—about one-third of calories from protein. Studies suggest that such high protein intake may increase the risk of kidney stones and could potentially worsen kidney function, though this has not been confirmed in rigorous randomized trials.

For individuals with healthy kidneys, there is no conclusive evidence that a high-protein paleo diet is harmful. However, those with pre-existing kidney disease should be cautious, as high protein loads can strain the kidneys. It is generally advised that anyone with kidney conditions consult a healthcare provider before making significant dietary changes.

The effects of high protein on kidney function are considered debatable, with some experts noting that the risk might be overstated for healthy individuals, but the potential for harm is real for those with compromised kidney function. More research is needed to clarify these effects.

• Extreme protein intake (over 2.5 g/kg/day) may increase the risk of kidney stones and dysfunction, but evidence is not definitive.
• For healthy kidneys, no conclusive harm has been shown, but caution is advised for those with kidney disease.
• Anyone with kidney issues should talk to a doctor before starting a paleo diet.

Sources: University of California, Davis, Examine.com

Interaction with Medical Conditions and Medications

The paleo diet can affect individuals with certain medical conditions, and it may interact with medications. For example, people with diabetes may find that the diet alters blood sugar levels, potentially requiring adjustments to insulin or oral hypoglycemic agents. But because the diet is not widely endorsed by mainstream health organizations, close medical supervision is important.

For those on blood-thinning medications, sudden large changes in intake of vitamin K-rich foods—such as leafy green vegetables—can affect the stability of anticoagulation. Patients on warfarin are advised to keep their vitamin K intake consistent, and this is a relevant consideration when starting or altering a paleo diet, which may emphasize these foods.

The diet’s high protein content could also exacerbate gout, a form of arthritis triggered by high uric acid levels, which can increase with meat consumption. Individuals with a history of gout should be particularly cautious.

• Blood sugar changes may require medication adjustment for diabetics.
• Sudden large changes in vitamin K-rich foods can affect anticoagulation stability.
• High meat intake may worsen gout symptoms.

Sources: StatPearls Publishing, Harvard T.H. Chan School of Public Health, Medicine (Baltimore), PubMed Central

Challenges for Specific Populations: Pregnant, Elderly, and Athletes

Pregnant women face particular concerns with the paleo diet. One study found that following a paleo-style diet during pregnancy was associated with lower mean birth weights compared to non-paleo diets, although no adverse neonatal outcomes were observed. The same study showed improved glucose tolerance test results, suggesting a potential benefit for blood sugar control. However, the diet may also lead to inadequate intake of iodine, calcium, and vitamin D, all critical for fetal development. Because of these risks, it is essential for pregnant women to ensure they are meeting all nutrient needs, likely with supplementation, and to consult their obstetrician.

Elderly individuals may also be at higher risk for nutrient deficiencies on a paleo diet. Reduced calcium and vitamin D intake, combined with a higher protein load, could accelerate bone density loss, increasing the risk of fractures. Additionally, older adults often have decreased kidney function, making the high protein content of the diet a concern. They should work with a dietitian to ensure nutritional adequacy and safety.

Athletes and highly active individuals might struggle with the low carbohydrate aspect of a paleo diet. Since carbohydrates are the body’s primary fuel source during high-intensity exercise, restricting them can impair exercise performance and lead to muscle breakdown for energy, causing fatigue. While some athletes adapt to lower carb intakes, it requires careful planning to maintain performance.

• Pregnancy: risk of low birth weight, iodine and calcium deficiencies.
• Elderly: increased risk of bone loss and kidney strain.
• Athletes: carbohydrate restriction may impair exercise performance and cause fatigue.

Sources: InfantRisk Center, Monte Nido

Potential for Disordered Eating or Nutritionism

Any diet that strictly categorizes foods as “good” or “bad” can increase the risk of developing a disordered relationship with food. The paleo diet, with its emphasis on what is “ancestral” and “natural,” may lead to an unhealthy fixation on food purity, potentially triggering or exacerbating eating disorders. Foods excluded from the diet, such as dairy and grains, may be viewed as “bad,” leading to guilt or anxiety when consumed.

This pattern, sometimes referred to as “nutritionism,” focuses on individual nutrients and may lead to restrictive behaviors that go beyond the paleo guidelines. For individuals with a history of eating disorders, diets like paleo can be particularly dangerous, as they provide a socially acceptable framework for restrictive eating. It is important to note that this perspective comes from a clinical eating disorder treatment center and is not based on large epidemiological studies.

• A “good/bad” food mindset can increase the risk of disordered eating.
• Food restrictions may lead to social isolation or anxiety around eating.
• People with a history of eating disorders should avoid restrictive diets or proceed only with professional support.

Sources: Monte Nido

How to Minimize Risks with Planning and Supplementation

If you choose to follow a paleo diet, careful planning can help mitigate many of the potential risks. It is essential to focus on nutrient density and ensure you are meeting your needs for calcium, vitamin D, iodine, and fiber.

To increase calcium, include canned fish with bones, leafy greens like kale and bok choy, and consider fortified dairy alternatives if your version of paleo allows them. For vitamin D, prioritize fatty fish like salmon and sardines, and discuss with your doctor whether a vitamin D supplement is appropriate, particularly if you have limited sun exposure.

Iodine can be obtained from iodized salt, sea vegetables like kelp, and seafood. If you are avoiding salt, you may need to consider a supplement, especially during pregnancy. Fiber can be added through plenty of non-starchy vegetables, fruits, nuts, and seeds.

Working with a registered dietitian can help you design a paleo meal plan that avoids nutrient shortfalls. They can also advise on supplementation based on your individual needs and health status.

Additionally, if you have a medical condition such as kidney disease, diabetes, or high blood pressure, or if you are taking medication, it is vital to consult a healthcare professional before starting a paleo diet. Monitoring your health markers periodically can also help catch any negative effects early.

For pregnant women, it is particularly important to ensure adequate iodine intake, and supplementation may be necessary. Vitamin D supplements may also be recommended, especially since paleo provides no dietary vitamin D. Always discuss supplementation with your obstetrician or healthcare provider during pregnancy.

For people with kidney disease or at risk for bone loss, monitoring kidney function and bone density may be advisable, but this should be done under medical supervision. Regular check-ups can help detect and address any issues early.

• Consume canned fish with bones, leafy greens, and fortified alternatives to boost calcium.
• Include fatty fish and consider vitamin D supplements with your doctor’s guidance.
• Use iodized salt or sea vegetables to maintain iodine levels.
• Ensure adequate fiber by eating a variety of vegetables, fruits, nuts, and seeds.
• During pregnancy, pay special attention to iodine and vitamin D supplementation.
• If you have kidney issues or are at risk for bone loss, discuss monitoring with your healthcare provider.
• Seek professional guidance to personalize your plan and adjust for any health conditions.

Sources: University of California, Davis, InfantRisk Center