In a previous article I wrote about how vegans have been shown to have decreased risk of heart disease, cancer, and all-cause mortality. In addition, in 3 separate articles I’ve written about how cooking food at high temperature (above boiling, 212ºF), whether it is roasting, baking, frying or grilling produces molecules that have been shown to shorten lifespan (AGE products), and, that cause cancer in rodents (both acrylamide and furan). Collectively these data indicate that a vegan diet without cooking any of the food at high temperature is optimal for health. However, within the confines of a vegan diet, which is best for health, raw, or raw plus boiled? In this article, I will discuss why a purely raw food diet is not optimal for health.
In short, the reason is because of fructose. Fructose isn’t only found in HFCS, it’s also the main sugar found in fruit. On a 80-10-10 diet, almost all of the calories will come from fruit. For example, bananas contain 27% fructose (http://ndb.nal.usda.gov/ndb/foods/list). In other words, if you eat nothing but bananas in a single day, this would be equivalent to a 27% fructose diet. And, on the fructose scale, bananas are relatively low in fructose. For example, strawberries, cherries, blueberries, oranges, peaches, pears, grapes, watermelon and apples contain 34%, 35%, 35%, 36%, 40%, 46%, 48%, 53%, 53% fructose, respectively. If you ate nothing but watermelon all day you would be on a 46% fructose diet. So, are there any adverse health effects of this amount of dietary fructose?
The answer is yes: both high and low fructose diets have been shown to elevate blood levels of triglycerides, which are a well documented risk factor for cardiovascular disease (Austin et al. 1998). On a 20% fructose diet for 5 weeks, triglycerides (20%), LDL (12%) and total cholesterol (10%) each increased (Reiser et al. 1989). In contrast, although triglycerides were not found to elevated after 4 weeks of a 20% fructose diet in a separate study, both LDL and total cholesterol were significantly elevated (Swanson et. al 1992). However, evidence from 2 additional studies in humans clearly show the positive association between increased fructose intake and elevated triglycerides. Le et. al (2006) found that fructose supplemented at 1.5g/kg body weight for only 1 month was sufficient to raise blood levels of triglycerides by 36% and VLDL-triglycerides by 72%. The amount of fructose supplemented is the Le study is equivalent to 75g and 105g fructose for a 50kg woman and a70 kg man, respectively, and can easily be obtained by eating 11-15 bananas. In addition, Faeh et. al (2005) showed that fructose supplemented at 3 grams/kg body weight increased triglycerides by 79%. This amount of supplemented fructose is equivalent to eating 22-30 bananas. In addition, these are relatively low-fructose containing diets.
In contrast, rats fed a 67% fructose diet (the control diet contained only starch) more than doubled plasma triglycerides, increased the concentration of triglycerides in liver, increased liver size, and, decreased liver copper content. The importance of copper depletion is illustrated by its role as a cofactor in the antioxidant enzyme Copper-Zinc superoxide dismutase (CuZnSOD), the first line of defense against superoxide radicals located in the cytosol of all cells. Depletion of liver copper would be expected to reduce CuZnSOD activity, thereby increasing liver oxidative stress. Indeed, the concentration of lipid peroxidation products was shown to be higher in plasma, heart and urine in rats fed the high fructose diet (Busserolles et al. 2003). The good news is that an all fruit diet would never reach the 67% fructose found in the Busserolle study, but, evidence from relatively low fructose diets (20%) still show elevations in triglycerides.
What should be substituted then, if too much fructose is bad for health? As mentioned earlier, there is no risk of forming AGE products, acrylamide or furan when boiling food. Therefore, substitution of some amount of fruit on a raw food diet, perhaps one third to half of the total calories should come from whole grains. Boiled whole grains (with vegetables, for the added flavor) is a great way to keep your total fructose intake relatively low. To ensure no loss of nutrients during the boiling process, don’t dump the soup, drink it, it’s delicious! Furthermore, the tocotrienols found almost exclusively in whole grains have been shown to reduce cholesterol (Zaiden et. al 2010), to reduce inflammation (Wu et al. 2008), to reduce DNA damage (Chin et al. 2008), to reduce cancer progression (Wada et al. 2005), and are neuroprotective (Khana et al. 2003). Therefore, when substituting some amount of fruit for whole grains, you won’t be sacrificing nutrition!
Austin MA, Holkanson JE, Edwards KL. Hypertriglyceridemia as a cardiovascular risk factor. Am J Cardiol 1998;81:7B-12B.
Busserolles J, Gueux E, Rock E, Demigné C, Mazur A, Rayssiguier Y. Oligofructose protects against the hypertriglyceridemic and pro-oxidative effects of a high fructose diet in rats.
J Nutr. 2003 Jun;133(6):1903-8.
Chin SF, Hamid NA, Latiff AA, Zakaria Z, Mazlan M, Yusof YA, Karim AA, Ibahim J, Hamid Z, Ngah WZ. Reduction of DNA damage in older healthy adults by Tri E Tocotrienol supplementation. Nutrition. 2008 Jan;24(1):1-10.
Faeh D, Minehira K, Schwarz J, Periasami R, Seongus P, Tappy L. Effect of fructose overfeeding and fish oil administration on hepatic de novo lipogenesis and insulin sensitivity in healthy males. Diabetes 2005;54: 1907-13.
Khanna S, Roy S, Ryu H, Bahadduri P, Swaan PW, Ratan RR, Sen CK. Molecular basis of vitamin E action: tocotrienol modulates 12-lipoxygenase, a key mediator of glutamate-induced neurodegeneration J Biol Chem. 2003 Oct 31;278(44):43508-15.
Lê KA, Faeh D, Stettler R, Ith M, Kreis R, Vermathen P, Boesch C, Ravussin E, Tappy L. A 4-wk high-fructose diet alters lipid metabolism without affecting insulin sensitivity or ectopic lipids in healthy humans. Am J Clin Nutr. 2006 Dec;84(6):1374-9.
Fructose data in foods provided by http://ndb.nal.usda.gov/ndb/foods/list
Reiser S, Powell AS, Scholfield DJ, Panda P, Ellwood KC, Canary JJ. Blood lipids, lipoproteins, apoproteins, and uric acid in men fed diets containing fructose or high-amylose cornstarch. Am J Clin Nutr. 1989 May;49(5):832-9.
Swanson JE, Laine DC, Thomas W, Bantle JP. Metabolic effects of dietary fructose in healthy subjects. Am J Clin Nutr. 1992 Apr;55(4):851-6.
Wada S, Satomi Y, Murakoshi M, Noguchi N, Yoshikawa T, Nishino H. Tumor suppressive effects of tocotrienol in vivo and in vitro. Cancer Lett. 2005;229:181-91.
Wu SJ, Liu PL, Ng LT. Tocotrienol-rich fraction of palm oil exhibits anti-inflammatory property by suppressing the expression of inflammatory mediators in human monocytic cells. Mol Nutr Food Res. 2008 Aug;52(8):921-9.
Zaiden N, Yap WN, Ong S, Xu CH, Teo VH, Chang CP, Zhang XW, Nesaretnam K, Shiba S, Yap YL. Gamma delta tocotrienols reduce hepatic triglyceride synthesis and VLDL secretion. J Atheroscler Thromb. 2010 Oct 27;17(10):1019-32.