Dietary advanced glycation end products (AGEs) are formed as a result of the heat-induced (greater than 100C) binding of sugar to protein, fat or nucleic acids (DNA or RNA). The common way to identify AGE products in food is the browning effect: deep-frying, broiling, roasting, and grilling each produce a temperature that is sufficient to greatly increase AGE product formation, relative to either raw or boiled food.
The importance of dietary AGE products is that they shorten lifespan! Cai et al. (2007) quantified the amount of one particular type of AGE product, CML (carboxy-methyl-lysine) found in the mouse diet, and then fed mice half of this amount. The low-CML diet was sufficient to significantly extend median and maximal lifespan by 15% and 6%, respectively:
As shown below (inset), no difference in food intake was observed when comparing the 2 groups-from this it can be concluded that the lifespan extending effect of the low-CML diet was not related to a reduction in calorie intake. Also, mice on the low-CML diet had significantly decreased body weight, evidence that shows that it isn’t just calories that we should be worried about in terms of body weight maintenance.
Dietary AGE products also shorten lifespan on a calorie-restricted diet. Calorie restriction is the gold standard in terms of minimizing disease risk and extending longevity in a variety of organisms, including worms, flies, mice, dogs, and monkeys. Because CR mice eat less food than controls, the possibility existed that CR-fed animals also ate less AGE products. To address this possibility, Cai et al. (2008) quantified the amount of AGE products that CR-fed mice consumed, and then increased this amount to either equal to or greater than what mice on a regular diet ate. In terms of lifespan, mice on a low AGE, low calorie diet had increased average and maximal lifespan, relative to mice on a regular, ad libitum diet. However, lifespan was significantly reduced for CR-fed mice whose food was supplemented an AGE product amount that was equal to the regular diet!
These data suggest that if you eat less calories than normal, you will live longer, but, if your lower-calorie diet is poor in quality (i.e. high in AGE products), you will lose the lifespan extending effect of CR.
In support of the hypothesis that AGE products are bad for lifespan, dietary supplementation with glycated albumin (left) and fructosylated albumin (right) also shorten lifespan, in flies (Tsakiri et al. 2013):
To illustrate how cooking food at a high temperature impacts AGE formation, shown below is the AGE product (CML) content for a variety of foods (Goldberg et al. 2004):
For example, boiling beef (as in a chili recipe), compared with roasting it results in ~3-fold less AGE products. Boiling egg yolks results in about half as much CML when compared with frying. Interestingly, olive oil has more than double the amount of CML, when compared to broiled chicken or beef! Finally, fruits and vegetables such as bananas, apples, carrots, and green beans have almost negligible amounts of CML.
This post is now in video form!
References:
Cai W, He JC, Zhu L, Chen X, Wallenstein S, Striker GE, Vlassara H. Reduced oxidant stress and extended lifespan in mice exposed to a low glycotoxin diet: association with increased AGER1 expression.Am J Pathol. 2007 Jun;170(6):1893-902.
Cai W, He JC, Zhu L, Chen X, Zheng F, Striker GE, Vlassara H. Oral glycotoxins determine the effects of calorie restriction on oxidant stress, age-related diseases, and lifespan. Am J Pathol. 2008 Aug;173(2):327-36.
Goldberg T, Cai W, Peppa M, Dardaine V, Baliga BS, Uribarri J, Vlassara H. Advanced glycoxidation end products in commonly consumed foods. J Am Diet Assoc. 2004 Aug;104(8):1287-91.
Tsakiri EN, Iliaki KK, Höhn A, Grimm S, Papassideri IS, Grune T, Trougakos IP. Diet-derived advanced glycation end products or lipofuscin disrupts proteostasis and reduces life span in Drosophila melanogaster. Free Radic Biol Med. 2013 Dec;65:1155-63.
If you’re interested, please have a look at my book!
How much protein is optimal for health? In this article I’ll explain how to use a simple blood test to answer that question.
Blood urea nitrogen (BUN) is a blood test that you can get at a yearly checkup. It measures the amount of nitrogen, as contained in urea, in your blood. Independent of poor kidney function (where BUN levels are elevated because of an inability to excrete it), urea production is almost perfectly correlated (r = 0.98) to dietary protein intake (Young et al. 2000):
The main source of dietary nitrogen is protein, so if you eat a lot of protein, you’ll make a lot of urea. Circulating levels of urea can be easily calculated by measuring BUN, via:
Urea [mg/dL]= BUN [mg/dL] * 2.14). Therefore, measuring BUN can then be used to determine if your protein intake is too high or too low.
How much should BUN levels be, with the goal of optimizing health? The reference range for BUN is 5-20 mg/dL. Are BUN values of 5 equal to 20 in terms of mortality risk? What’s optimal? As shown below, BUN levels less than 15 mg/dL are associated with maximally reduced risk of death from all causes. As BUN increases above 15 mg/dL, mortality risk increases. For example, a person with a BUN of 20 would have ~50% higher mortality risk than someone with a value of 15 mg/dL:
Why would elevated circulating urea be associated with reduced health? Urea (42 mg/dL, light grey bars; 72 mg/dL, dark grey bars below) can diffuse into the gastrointestinal tract, where it’s involved in decreasing expression of the tight junction proteins, zonulin-1 (ZO-1), occludin, and claudin-1 (Vaziri et al. 2013):
Decreased levels of ZO-1, occludin, and claudin-1 would be expected to increase gut leakiness, the process where bacteria and/or their metabolic products (i.e. lipopolysaccharide; LPS) move from the intestine into the blood. In support of this, tight junction protein expression decreases during aging (Tran and Greenwood-Van Meerveld, 2013) in parallel with increased circulating LPS (Ghosh et al. 2015). Elevated circulating LPS increases oxidative stress, inflammation, and insulin resistance (for more details see: https://www.amazon.com/dp/B01G48A88A), three major theories of aging!
It’s important to mention that the data of Vaziri et al. (2013) showed decreased tight junction protein expression at urea concentrations of 42 and 72 mg/dL. How does that translate into BUN values? Urea concentrations of 42 and 72 mg/dL correspond to BUN values of 19.6 and 33.6 mg/dL, respectively (42/2.14, 72/2.14). Interestingly, from the all-cause mortality data, a BUN value of 20 is associated with increased risk, compared with values less than 15, and this suggests that the effect of urea on gut leakiness may be one reason why!
What’s my BUN? As shown below, I’ve measured BUN 10 times since 2006. At that time (and before), my diet was protein heavy, consuming 150+ grams of protein per day. This is reflected in my relatively high (greater than 15) BUN values until 2008, which is when I started to reduce my protein intake. In 2012, I tried a fruititarian diet for 1 year-the corresponding low protein intake (~40g protein/day) resulted in my lowest BUN value of 4. In 2013, I tried a vegan diet rich in whole grains for 1 year (~60g protein/day), and that small increase in protein compared with the fruititarian diet increased my BUN to 6. Since then, I’ve settled on a vegetable dominant, pesco-vegetarian dietary pattern that yields an average of ~85 grams of protein per day. Using that approach, my BUN is 8, well under the 15 threshold.
If you’re interested, please have a look at my book!
References
Ghosh S, Lertwattanarak R, Garduño Jde J, Galeana JJ, Li J, Zamarripa F, Lancaster JL, Mohan S, Hussey S, Musi N. Elevated muscle TLR4 expression and metabolic endotoxemia in human aging. J Gerontol A Biol Sci Med Sci. 2015 Feb;70(2):232-46.
Lustgarten M. Infectious Burden: The Cause Of Aging And Age-Related Disease. 2016. https://www.amazon.com/dp/B01G48A88A
Solinger AB, Rothman SI. Risks of mortality associated with common laboratory tests: a novel, simple and meaningful way to set decision limits from data available in the Electronic Medical Record. Clin Chem Lab Med. 2013 Sep;51(9):1803-13.
Tran L, Greenwood-Van Meerveld B. Age-associated remodeling of the intestinal epithelial barrier. J Gerontol A Biol Sci Med Sci. 2013 Sep;68(9):1045-56.
Vaziri ND, Yuan J, Norris K. Role of urea in intestinal barrier dysfunction and disruption of epithelial tight junction in chronic kidney disease. Am J Nephrol. 2013;37(1):1-6.
Young VR, El-Khoury AE, Raguso CA, Forslund AH, Hambraeus L. Rates of urea production and hydrolysis and leucine oxidation change linearly over widely varying protein intakes in healthy adults. J Nutr. 2000 Apr;130(4):761-6.
Usually, my focus on optimal health involves proper diet and exercise. But, are there other factors that can reduce mortality risk? More specifically, does how often I brush my teeth or floss have an impact on cancer and all-cause mortality?
Tooth brushing at night before bed and using dental floss every day were found to be significant risk factors for reducing mortality risk in 5611 older adults (median age 81, Paganini-Hill et al. 2011). Tooth brushing at night was found to be the most important time for reducing mortality risk, compared with the morning and during the day, as those who never brushed at night had a 20–35% (men and women, respectively) increased mortality risk. In addition, not brushing your teeth at all was associated with a 41–91% (men and women, respectively) increased mortality risk compared with those who brushed three times daily.
What about flossing? Never flossing increased mortality risk by 30%, compared with those who flossed everyday. And, to illustrate the importance of both tooth brushing and flossing at night, people who brushed their teeth at night every day but never flossed had an increased mortality risk of ~25% , when compared with those who flossed everyday.
One possible explanation for the decreased mortality risk found in those who floss daily is a reduced risk of cancer. For example, those who never floss were found to have ~3-fold more gastric precancerous lesions, when compared with controls (Salazar et al. 2012).
So, if you’re interested in optimal health and lifespan, flossing and tooth brushing every day, especially at night seems to be a must!
If you’re interested, please have a look at my book!
References
Paganini-Hill A, White SC, Atchison KA. Dental Health Behaviors, Dentition, and Mortality in the Elderly: The Leisure World Cohort Study. J Aging Res. 2011;2011:156061.
Salazar CR, Francois F, Li Y, Corby P, Hays R, Leung C, Bedi S, Segers S, Queiroz E, Sun J, Wang B, Ho H, Craig R, Cruz GD, Blaser MJ, Perez-Perez G, Hayes RB, Dasanayake A, Pei Z, Chen Y. Association between oral health and gastric precancerous lesions. Carcinogenesis. 2012 Feb;33(2):399-403.
Our story begins with Michael Rose, who used an experimental evolution approach to breed flies that live more than 2-fold longer than controls (Rose 1999). In contrast with the one gene at a time knockout or overexpression strategy that is ubiquitous in modern biology, Rose separated initially genetically homogeneous flies into two groups-one with delayed and the other with normal reproduction. As shown below, after 80 generations, the group with continually delayed reproduction had ~2-fold increased average and maximal lifespan.
While this suggests that continually delaying reproduction may extend lifespan in people, the time it would take to do that makes it an unreasonable strategy. In 2010, the average age at first reproduction in the US was 25.4 years (http://www.cdc.gov/nchs/data/nvsr/nvsr61/nvsr61_01.pdf). Therefore, to replicate the doubling of lifespan found in Drosophila, 80 generations * 25.4y would take more than 2000 years! In contrast, a more reasonable approach towards extending life in people may involve stimulation of some of the pathways involved in the extended fly lifespan.
What genetic mechanisms underlie this 2-fold increase in Drosophila lifespan? Kurapati et al. 2000) found that levels of the mitochondrially located heat shock protein 22 (Hsp22) were between two and ten-fold higher in long-lived Drospohila, relative to the shorter-lived controls. In 2004 Morrow et al. identified the causative role of Hsp22 overexpression, as average lifespan increased by ~30%, thereby implicating mechanisms related to upregulation of Hsp22 on increasing lifespan.
Unfortunately, the role of Hsp22 on influencing lifespan in mammals is unknown. But, can we learn something about the underlying mechanism of the Hsp22-induced increase in lifespan and apply that to mammalian aging?
Hsp22 expression is regulated by histone deacetylase (HDAC) inhibitors (Zhou et al. 2005). In other words, when certain HDAC’s are inhibited, histone acetylation increases, resulting in elevated Hsp22 expression. Interestingly, histone acetylation has also been shown to be involved in lifespan determination in yeast and worms (Kaeberlein et al. 1999, Kang et al. 2002, Kim et al. 1999, Tissenbaum and Guarente, 2001). In contrast, the HDAC’s that have been popularized by the resveratrol-sirtuin story results in histone deacetylation, or the removal of acetyl groups from histones.
Identification of compounds that inhibit the HDAC’s that control Hsp22 expression would seem to be a good method for potentially increasing mammalian lifespan. Supplementation with sodium butyrate increases Hsp22 expression in Drosophila (Zhao et al. 2005), resulting in increased Drosophila lifespan (McDonald et al. 2013). Interestingly, sodium butyrate is a class I, II, IV HDAC inhibitor, whereas the sirtuins are class III inhibitors (Witt et al. 2009), evidence that suggests differing roles for the HDACs on lifespan extension.
Unfortunately, the causative role of butyrate-producing bacteria on mammalian lifespan has yet to be directly tested. However, butyrate stimulates expression of fibroblast growth factor 21 (Li et al. 2012), a protein whose overexpression extends both average and maximal lifespan in mice (shown below; Zhang et al. 2012).
Furthermore, acarbose supplementation extends median and maximal lifespan in genetically heterogeneous mice (Harrison et al. 2013), an important finding because acarbose supplementation has been shown to elevate serum butyrate in human subjects (Wolever and Chiasson 2000).
How can we get butyrate into our diet? Although butter contains small amounts of butyrate, a butter-rich diet has been shown to be obesogenic (Hariri et al. 2010). Fortunately, there is another way we can increase levels of butyrate, and that’s by stimulating our intestinal bacteria to produce it! The most abundant butyrate-producing gut bacterial species are Faecalibacterium prausnitzii, Eubacterium rectale, Eubacterium hallii and Anaerostipes hadrus (Tap et al. 2009, Walker et al. 2011).
Interestingly, butyrate-producing bacteria decrease during aging, which, in my opinion makes colonizing our intestines with these beneficial bacteria all the more important. For example, Faecalibacterium prausnitzii, Eubacterium hallii and Eubacterium rectale are significantly reduced in centenarians when compared with elderly and young subjects (Biagi et al. 2010). Several other gut bacterial butyrate producers are also reduced in centenarians when compared with the other age groups, including Ruminococcus obeum, Roseburia intestinalis, E. ventriosum, and, Papillibacter cinnamovorans.
Collectively, these data suggest that increasing gut bacterial species that produce butyrate may be important for increasing lifespan in both lower organisms and, in mammals. How can we boost butyrate-producing bacteria? Prebiotics, food ingredients that stimulate the growth and/or activity of bacteria in the digestive system may be the best option. Two such food components are inulin and fructooligosaccharides (FOS), which in vitro, stimulate growth of the butyrate producers F. prausnitzii, E.rectale, E. hallii and R. intestinalis 4-15 fold above basal levels (Scott et al. 2014). In vivo, consumption of 10g/day of inulin for 16 days in healthy, middle aged humans (BMI 25 kg*m-2, avg. age 38) significantly stimulated growth of F. prausnitzii (Ramirez-Farias et al. 2009). Therefore, consumption of foods rich in inulin and FOS may be a valid strategy for boosting levels of butyrate-producing bacteria in our intestines.
Foods containing inulin and fructoligosaccharides are shown in Table 1.
First, it’s important to mention that average intake for inulin and FOS is only ~2.5 grams/day (5g total) (Moshfegh et al. 1999). This is because relatively few foods contain high amounts of these prebiotic fibers. For example, whereas 100g of bananas (equivalent to 1 small banana) contains 1 gram total of combined inulin and FOS, in contrast, chicory root and Jerusalem artichoke contain 64.5 and 31.5 grams, respectively. In addition, although not shown in the table, most fruits contain limited amounts of FOS. Bananas contain more FOS/g than apple, blackberry, blueberry, cantaloupe, grapes, orange, peach, pear, raspberry, rhubarb, strawberry and watermelon (Dumitiriu 2005). This is an important finding because one would expect fruits to be rich in inulin and FOS, as both of these fibers contain long chain fructose polymers. Furthermore, based on values for asparagus, chicory, onion, loss of inulin and FOS upon boiling is ~30%, so eating these foods raw is not the only strategy for increasing dietary amounts of FOS and inulin.
Can increasing consumption of FOS and inulin improve health and lifespan? To date, dietary supplementation with inulin has been shown to improve cognitive performance (Messaoudi et al. 2005), and, to reduce cholesterol, triglycerides and body weight, and, improved survival in rats (Rozan et al. 2008). Although randomized controlled trials examining the effect of increasing butyrate-producing bacteria on health and mortality risk in older adults has yet to be performed, collectively, the evidence presented here suggests that if you’re interested in a low risk, potentially high reward approach towards improving health and lifespan, consuming more foods containing FOS and inulin may be a valid strategy!
If you’re interested, please have a look at my book!
References
Biagi E, Nylund L, Candela M, Ostan R, Bucci L, Pini E, Nikkïla J, Monti D, Satokari R, Franceschi C, Brigidi P, De Vos W. Through ageing, and beyond: gut microbiota and inflammatory status in seniors and centenarians. PLoS One. 2010 May 17;5(5):e10667.
Dumitiriu S. Polysaccharides: Structural Diversity and Functional Versatility. 2005. CRC Press. p854-855.
Hariri N, Gougeon R, Thibault L. A highly saturated fat-rich diet is more obesogenic than diets with lower saturated fat content. Nutr Res. 2010 Sep;30(9):632-43.
Harrison DE, Strong R, Allison DB, Ames BN, Astle CM, Atamna H, Fernandez E, Flurkey K, Javors MA, Nadon NL, Nelson JF, Pletcher S, Simpkins JW, Smith D, Wilkinson JE, Miller RA. Acarbose, 17-α-estradiol, and nordihydroguaiaretic acid extend mouse lifespan preferentially in males. Aging Cell. 2013 Oct 26.
Kaeberlein, M., McVey, M. and Guarente, L. (1999). The SIR2/3/4 complex and SIR2 alone promote longevity in Saccharomyces cerevisiae by two different mechanisms. Genes Dev. 13, 2570-2580.
Kang, H. L., Benzer, S. and Min, K. T. (2002). Life extension in Drosophila by feeding a drug. Genetics 99, 838-843. Kim, S., Benguria, A., Lai, C. and Jazwinski, S. M. (1999). Modulation of lifespan by histone deacetylase genes in Saccharomyces cerevisiae. Mol. Biol. Cell 10, 3125-3156.
Kurapati R, Passananti HB, Rose MR, Tower J. Increased hsp22 RNA levels in Drosophila lines genetically selected for increased longevity. J Gerontol A Biol Sci Med Sci. 2000 Nov;55(11):B552-9.
Li H, Gao Z, Zhang J, Ye X, Xu A, Ye J, Jia W. Sodium butyrate stimulates expression of fibroblast growth factor 21 in liver by inhibition of histone deacetylase 3. Diabetes. 2012 Apr;61(4):797-806.
McDonald P, Maizi BM, Arking R. Chemical regulation of mid- and late-life longevities in Drosophila. Exp Gerontol. 2013 Feb;48(2):240-9.
Messaoudi M, Rozan P, Nejdi A, Hidalgo S, Desor D. Behavioural and cognitive effects of oligofructose-enriched inulin in rats. Br J Nutr. 2005 Apr;93 Suppl 1:S27-30.
Moshfegh AJ, Friday JE, Goldman JP, Ahuja JK. Presence of inulin and oligofructose in the diets of Americans. J Nutr. 1999 Jul;129(7 Suppl):1407S-11S.
Morrow G, Samson M, Michaud S, Tanguay RM. Overexpression of the small mitochondrial Hsp22 extends Drosophila life span and increases resistance to oxidative stress. FASEB J. 2004 Mar;18(3):598-9.
Ramirez-Farias C, Slezak K, Fuller Z, Duncan A, Holtrop G & Louis P (2009) Effect of inulin on the human gut microbiota: stimulation of Bifidobacterium adolescentis and Faecalibacterium prausnitzii. Brit J Nutr 101: 533-542.
Rose MR. Can human aging be postponed? Sci Am. 1999 Dec;281(6):106-11.
Rozan P, Nejdi A, Hidalgo S, Bisson JF, Desor D, Messaoudi M. Effects of lifelong intervention with an oligofructose-enriched inulin in rats on general health and lifespan. Br J Nutr. 2008 Dec;100(6):1192-9.
Scott KP, Martin JC, Duncan SH, Flint HJ. Prebiotic stimulation of human colonic butyrate-producing bacteria and bifidobacteria, in vitro. FEMS Microbiol Ecol. 2014 Jan;87(1):30-40.
Tap J, Mondot S, Levenez F et al. (2009) Towards the human intestinal microbiota phylogenetic core. Environ Microbiol 11: 2574-2584.
Tissenbaum, H. A. and Guarente, L. (2001). Increased dosage of a sir2 gene extends lifespan in Caenorhabditis elegans. Nature 410, 227-230
Walker AW, Ince J, Duncan SH et al. (2011) Dominant and diet-responsive groups of bacteria within the human colonic microbiota. ISME J 5: 220-230.
Wolever TM, Chiasson JL. Acarbose raises serum butyrate in human subjects with impaired glucose tolerance. Br J Nutr. 2000 Jul;84(1):57-61.
Witt O, Deubzer HE, Milde T, Oehme I. HDAC family: What are the cancer relevant targets? Cancer Lett. 2009 May 8;277(1):8-21.
Zhang Y, Xie Y, Berglund ED, Coate KC, He TT, Katafuchi T, Xiao G, Potthoff MJ, Wei W, Wan Y, Yu RT, Evans RM, Kliewer SA, Mangelsdorf DJ. The starvation hormone, fibroblast growth factor-21, extends lifespan in mice. Elife. 2012;1:e00065.
Zhao Y, Sun H, Lu J, Li X, Chen X, Tao D, Huang W, Huang B. Lifespan extension and elevated hsp gene expression in Drosophila caused by histone deacetylase inhibitors. J Exp Biol. 2005 Feb;208(Pt 4):697-705.
Michael Lustgarten 