Raw vs. Cooked Food Diets

A raw food diet (RFD) is comprised primarily of plant-based foods, including fruits, vegetables, nuts, seeds and sprouted grains that are unheated and minimally processed.[i] Some fermented or pickled fruits and vegetables, as well as cold-smoked meat and fish, can sometimes be included. Consequently, RFDs can be further sub-categorized as vegetarian and non-vegetarian, however, the emphasis of either form of the RFD is on plant-based foods. RFDs are based on the premise that the micronutrient profile of foods are retained if they are not heated too high, as well as inadvertently containing no additives, like salt and sugar.

The increased bioavailability of certain nutrients and enzymes include the following:

● Cooking vegetables decreases water-soluble/heat-sensitive nutrients, such as vitamin C.[ii] However, although cooking tomatoes can decrease their vitamin C content, it can also increase the bioavailability of lycopene (a plant-based chemical and powerful antioxidant)

● Heating some vegetables decreases the activity of particular enzymes involved in activating certain phytonutrients (i.e. cruciferous vegetables and myrosinase - a family of enzymes)[iii]

● Heating alters the structure of food and may impact its digestibility (i.e. an increase in soluble fiber and decrease in insoluble fiber)[iv] as well as producing Maillard reaction products, which can be carcinogenic[v]

Research supports that some uncooked foods are better sources for many vitamins and nutrients.[vi] One study showed that cooking leafy greens longer than fifteen minutes reduced the amount of vitamin C, crude fiber and level of minerals the greens contained.[vii] Additionally, heating methods including steaming, baking and stir-frying reduces beneficial antioxidant activity in purple sweet potatoes.[viii] However, steaming or boiling foods, such as cruciferous vegetables, may actually increase their antioxidant bioavailability.[ix]

A RFD eliminates one’s exposure to inflammatory compounds produced during the cooking process. Research shows frying, roasting, searing or grilling certain foods produces compounds called advanced glycation end products, which are linked to diabetes, cardiovascular, liver and Alzheimer’s disease. However, these compounds can be reduced by cooking with moist heat, shorter cooking times, lower temperatures and by using an acidic ingredient.[x]

Eating a RFD may be of interest for certain individuals, as research suggests that it can increase serum β-carotene[xi], consequently boosting your immune system, decreasing blood pressure[xii] and LDL cholesterol[xiii] and helping to fight certain types of cancer.[xiv]

On the contrary, individuals who consume a strict RFD for the long-term can be misinformed and at risk for health issues including nutrient deficiencies, high loss of body weight, and amenorrhea in women.[xv] Additionally, exposure to high levels of harmful bacteria is cause for concern.

It appears that the main benefit of the RFD is its avoidance of the harmful cooking processes and inadvertent consequence of avoiding additives such as salt and sugar, more than the claim that uncooked foods are in and of themselves “healthier”. Furthermore, there appears to be a health benefit for a combination of raw and cooked vegetables, depending on the cooking method and the specific vegetable being considered.[xvi]

Both diets, depending on a number of factors, can be healthy or unhealthy. However, a RFD does seem to come with greater health concerns, particularly with long-term use.

ENDNOTES

[i] Koebnick, C., Strassner, C., Hoffmann, I., & Leitzmann, C. (1999). Consequences of a long-term raw food diet on body weight and menstruation: results of a questionnaire survey. Annals Of Nutrition & Metabolism, 43(2), 69-79.

[ii] Dewanto, V., Wu, X., Adom, K. K., & Liu, R. H. (2002). Thermal processing enhances the nutritional value of tomatoes by increasing total antioxidant activity. Journal Of Agricultural And Food Chemistry, 50(10), 3010-3014.

[iii] Tiwari, U., Sheehy, E., Rai, D., Gaffney, M., Evans, P., & Cummins, E. (2015). Quantitative human exposure model to assess the level of glucosinolates upon thermal processing of cruciferous vegetables. LWT - Food Science And Technology, 63253-261. doi:10.1016/j.lwt.2015.03.088

[iv] Khanum, F., Siddalinga Swamy, M., Sudarshana Krishna, K., Santhanam, K., & Viswanathan, K. (2000). Dietary fiber content of commonly fresh and cooked vegetables consumed in India. Plant Foods For Human Nutrition, (3), 207.

[v] O'Brien, J., & Morrissey, P. A. (1989). Nutritional and toxicological aspects of the Maillard browning reaction in foods. Critical Reviews In Food Science And Nutrition, 28(3), 211-248.

[vi] Joshua, Z., Timothy, A., Suleiman, M. (2012). The effect of cooking time on the vitamin C, dietary fiber and mineral compositions of some local vegetables. Science World Journal, 7 (1) 29-30

Severi, S., Bedogni, G., Zoboli, G. P., Manzieri, A. M., Poli, M., Gatti, G., & Battistini, N. (1998). Effects of home-based food preparation practices on the micronutrient content of foods. European Journal Of Cancer Prevention: The Official Journal Of The European Cancer Prevention Organisation (ECP), 7(4), 331-335.

Somsub, W., Kongkachuichai, R., Sungpuag, P., & Charoensiri, R. (2008). Original Article: Effects of three conventional cooking methods on vitamin C, tannin, myo-inositol phosphates contents in selected Thai vegetables. Journal Of Food Composition And Analysis, 21187-197.

[vii] Joshua, Z., Timothy, A., Suleiman, M. (2012). The effect of cooking time on the vitamin C, dietary fiber and mineral compositions of some local vegetables. Science World Journal, 7 (1) 29-30

[viii] Tian, J., Chen, J., Lv, F., Chen, S., Chen, J., Liu, D., & Ye, X. (2016). Domestic cooking methods affect the phytochemical composition and antioxidant activity of purple-fleshed potatoes//doiorg.uws.idm.oclc.org/10.1016/j.foodchem.2015.11.049

[ix] Hwang, E., & Kim, G. (2013). Effects of various heating methods on glucosinolate, carotenoid and tocopherol concentrations in broccoli. International Journal of Food Sciences & Nutrition, 64(1), 103-111.

[x] Uribarri, J., Woodruff, S., Goodman, S., Cai, W., Chen, X., Pyzik, R., Young, A., Striker, G., Vlassara, H. (2010). Advanced Glycation End Products in Foods and a Practical Guide to Their Reduction in the Diet. J Am Diet Association. 110(6), 911-916.

[xi] Garcia, A. L., Koebnick, C., Dagnelie, P. C., Strassner, C., Elmadfa, I., Katz, N., & ... Hoffmann, I. (2008). Long-term strict raw food diet is associated with favourable plasma β-carotene and low plasma lycopene concentrations in Germans. British Journal Of Nutrition, 99(6), 1293. doi:10.1017/S0007114507868486

[xii] Koebnick, C., Garcia, A. L., Dagnelie, P. C., Strassner, C., Lindemans, J., Katz, N., & ... Hoffmann, I. (2005). Long-term consumption of a raw food diet is associated with favorable serum LDL cholesterol and triglycerides but also with elevated plasma homocysteine and low serum HDL cholesterol in humans. The Journal Of Nutrition, 135(10), 2372-2378.

[xiii] Chan, Q., Stamler, J., Brown, I. J., Daviglus, M. L., Van Horn, L., Dyer, A. R., & ... Elliott, P. (2014). Relation of raw and cooked vegetable consumption to blood pressure: the INTERMAP Study. Journal Of Human Hypertension, 28(6), 353-359. doi:10.1038/jhh.2013.115

[xiv] Link, L. B., & Potter, J. D. (2004). Raw versus cooked vegetables and cancer risk. Cancer Epidemiology, Biomarkers & Prevention: A Publication Of The American Association For Cancer Research, Cosponsored By The American Society Of Preventive Oncology, 13(9), 1422-1435.

[xv] Koebnick, C., Strassner, C., Hoffmann, I., & Leitzmann, C. (1999). Consequences of a long-term raw food diet on body weight and menstruation: results of a questionnaire survey. Annals Of Nutrition & Metabolism, 43(2), 69-79.

[xvi] Chan, Q., Stamler, J., Brown, I. J., Daviglus, M. L., Van Horn, L., Dyer, A. R., & ... Elliott, P. (2014). Relation of raw and cooked vegetable consumption to blood pressure: the INTERMAP Study. Journal Of Human Hypertension, 28(6), 353-359. doi:10.1038/jhh.2013.115

Dewanto, V., Wu, X., Adom, K. K., & Liu, R. H. (2002). Thermal processing enhances the nutritional value of tomatoes by increasing total antioxidant activity. Journal Of Agricultural And Food Chemistry, 50(10), 3010-3014.

Link, L. B., & Potter, J. D. (2004). Raw versus cooked vegetables and cancer risk. Cancer Epidemiology, Biomarkers & Prevention: A Publication Of The American Association For Cancer Research, Cosponsored By The American Society Of Preventive Oncology, 13(9), 1422-1435.

Travis Cox