Merck Manual

Please confirm that you are a health care professional

honeypot link

Diet Therapy


Denise Millstine

, MD, Mayo Clinic

Last full review/revision Sep 2018| Content last modified Sep 2018
Click here for Patient Education

Diet therapy, a biologically based practice, uses specialized dietary regimens (eg, Gerson therapy, macrobiotic diets, Pritikin diet) to

  • Treat or prevent a specific disorder (eg, cancer, cardiovascular disorders)

  • Generally promote wellness

  • Detoxify the body (ie, neutralize or eliminate toxins from the body)

Some diets (eg, Mediterranean diet) are widely accepted and encouraged in conventional and integrative medicine.

Diet therapy effects may occur slowly and are inherently difficult to study.

Ornish Diet

This very low-fat vegetarian diet aims to help reverse arterial blockages that cause coronary artery disease and may help prevent or slow the progression of prostate and other cancers. As a component of an intensive lifestyle program for participants with symptomatic coronary artery disease, the Ornish diet is effective and cost saving (1).

Gerson Diet

The Gerson diet involves consuming the equivalent of 15 to 20 lb of fruits and vegetables (in solid food and juices) each day, plus taking supplements and using coffee enemas. Proponents claim that this protocol is effective for treating cancer, heart disease, arthritis, autoimmune disorders, and diabetes; however, there are no rigorous clinical trials to support any of these claims (2). Also, claims of detoxification are not based on identification and measurement of any specific toxin.

One risk with this therapy is that its unsubstantiated claims for efficacy (eg, against cancer) can delay treatment with efficacious conventional therapies and worsen outcome. In addition, participation in the diet and therapy is quite costly.

Macrobiotic Diet

This diet consists mainly of vegetables, whole grains, fruits, and cereals. Some proponents claim that this diet can prevent and treat cancer and other chronic disorders; however, no evidence supports efficacy of a macrobiotic diet for treatment of cancer.

Risks of following this diet, other than lack of efficacy in disease prevention or therapy, are very few (3).

Paleo Diet

This diet consists of types of food allegedly consumed during the Paleolithic era, when food was hunted or gathered (ie, animals and wild plants). Thus, the diet includes

  • Increased protein intake

  • Decreased carbohydrate intake (with intake consisting mainly of nonstarchy fresh fruits and vegetables)

  • A moderate to higher fat intake (with intake mainly of monounsaturated and polyunsaturated fats)

Foods thought not to be available during the Paleolithic era (eg, dairy products, grains, legumes, processed oils, refined sugar, salt, coffee) are avoided. Proponents claim that human metabolism has not adapted to handle many of these foods.

Paleo diet is thought to treat or reduce the risk of coronary artery disease, metabolic syndrome, type 2 diabetes, and many chronic degenerative disorders (4, 5). The paleo diet also potentially promotes weight loss, improves athletic performance, enhances sleep, and improves mental function. However, there is limited evidence concerning the efficacy of this diet.

Risks include inadequate nutrition (due to decreased intake of whole grains and dairy).

Knowledge of what was eaten in the Paleolithic era is limited; however, some evidence suggests that the diet of the Paleolithic era was not as limited as the modern Paleo diet.


  • 1. Zeng W, Stason WB, Fournier S, et al: Benefits and costs of intensive lifestyle modification programs for symptomatic coronary disease in Medicare beneficiaries. Am Heart J 165(5):785-92, 2013. doi: 10.1016/j.ahj.2013.01.018.

  • 2. Cassileth B: Gerson regimen. Oncology (Williston Park) 24(2):201, 2010.

  • 3. Harmon BE, Carter M, Hurley TG, et al: Nutrient composition and anti-inflammatory potential of a prescribed macrobiotic diet. Nutr Cancer. 67(6):933-40, 2015. doi: 10.1080/01635581.2015.1055369.

  • 4. Manheimer EW, van Zuuren EJ, Fedorowicz Z, et al: Paleolithic nutrition for metabolic syndrome: systematic review and meta-analysis. Am J Clin Nutr102(4):922-32, 2015. doi: 10.3945/ajcn.115.113613. 

  • 5. Whalen KA, Judd S, McCullough ML, et al: Paleolithic and Mediterranean Diet Pattern Scores Are Inversely Associated with All-Cause and Cause-Specific Mortality in Adults. J Nutr 147(4):612-620, 2017. doi: 10.3945/jn.116.241919. 

Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Professionals also read

Test your knowledge

Limb Prosthetics
An adolescent patient recently sustained a traumatic above-knee amputation. In order to provide this patient with good limb control and a natural gait, it is most appropriate to use a knee prosthesis with which of the following characteristics? 
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest