Tag: Quantified Self

Dietary Cholesterol Vs. Plasma Cholesterol: My n=1 Data

With use of a food scale,  I’ve been tracking my daily macro- and micronutrient intake every day since April 2015. In addition, I have 15 blood test measurements during that period, and accordingly, I’m able to examine correlations between my dietary intake with my circulating biomarkers. In this post, I’ll address the question, is my dietary cholesterol intake significantly correlated with plasma levels of cholesterol?

1. Plasma levels of total cholesterol vs. dietary cholesterol:

tc.png

In the plot we see a borderline significant (p = 0.06), moderate correlation (r = 0.5) between my plasma total cholesterol with my dietary cholesterol intake. However, note that total cholesterol is comprised of “good” and “bad” parts, with HDL as the “good”, and with non-HDL cholesterol, including LDL and VLDL, as the “bad”. What does that data look like?

2. Plasma levels of non-HDL (LDL+VLDL) cholesterol vs. dietary cholesterol:

nonhdl.png

In the plot we see a highly significant (p = 0.006), strong correlation (r = 0.67) between my non-HDL cholesterol levels with my dietary cholesterol intake. It’s not possible to show causation via correlation, but this data suggests that my dietary cholesterol intake may be driving increased levels of non-HDL cholesterol.

3. Plasma levels of HDL cholesterol vs. dietary cholesterol:

hdl.png

In the plot, first note that in contrast with the positive correlations between total and non-HDL cholesterol with my dietary cholesterol intake, the correlation between HDL with my dietary cholesterol intake is negative (i.e., going in the opposite direction; r = 0.51), and borderline significant (p = 0.054).

Cumulatively, it looks like my dietary cholesterol intake may be related to increased “bad” cholesterol and decreased “good” cholesterol. As a limitation of this approach, although I’ve shown blood test data for 15 measurements (which is a decent sample size), I only have 4 measurements with an average daily cholesterol intake around 200 mg or greater. In the near future, I expect to average 200 mg of daily cholesterol (or more) per day, so let’s see if these correlations hold up!

 

If you’re interested, please have a look at my book!

 

Reducing Homocysteine? Updates.

In an earlier post I wrote about the association between elevated circulating levels of homocysteine with an increased risk of death from all causes (https://michaellustgarten.com/2017/11/22/homocysteine-and-all-cause-mortality-risk/). I started to post updates in that link, but I’ve decided to move them to here.

As of 6/2018, I now have tracked dietary data (I weigh all my food and record the values in cronometer.com) that corresponds to 7 homocysteine measurements:
Picture1

12/5/2017: Despite 42 days of 800 micrograms of supplemental folic acid, bringing my average daily folate intake to 2026 micrograms/day, my plasma homocysteine was essentially unchanged at 11.7 uMoL, when compared with my baseline value of 11.8 uMol.What’s next on the list to reduce it? Trimethylglycine, also known as betaine. I’m a proponent of using diet as a first strategy,  and to increase my dietary betaine levels, I’ll eat beets and quinoa, bringing my daily betaine levels to ~500 mg/day. Let’s see how it turns out on my next blood test!

1/2/2018: ~500 mg/day of betaine from beets and quinoa did absolutely nothing to my homecysteine levels. In fact, it got worse (15.3 uMoL)! To test the hypothesis that it wasn’t enough betaine, next I tried 4 grams/day of betaine (also known as trimethylglycine, TMG).

2/20/18: Supplemental TMG did absolutely nothing in terms of reducing my homocysteine to values below baseline! Also note that there is evidence that TMG increases blood lipids, including LDL and triglycerides (TG; Olthof et al. 2005), and that’s exactly what it did to me. My average LDL and TG values since 2015 (11 measurements) are 77 and 50 mg/dL, respectively. On TMG, these values increased to 92 and 72 mg/dL, respectively, making them my highest values over 11 individual blood tests (with the exception of 1 day with an LDL of 93 mg/dL). Next, I tried a stack that included 50 mg of B6, 1000 mcg of B12, and 400 mcg of methylfolate, as supplementation with these B-vitamins has been shown to lower homocystine (Lewerin et al. 2003).

3/20/18: Finally, some progress! My homocysteine levels were reduced during the B-vitamin supplementation period. I’ve written it like that because I’m not sure if it was the B-vitamins that caused it. For example, in the image below, we see the correlation between my dietary B6 intake with homocysteine. The trendline is down, which I would expect if B6 supplementation actually is playing a role in reducing my homocysteine levels. However, note that the correlation between my dietary B6 levels with homocysteine is not very strong (r = .48), resulting in a moderate R2 of 0.23 (similar data was obtained for B12 and folate). With 5 blood test measurements corresponding to 5 dietary periods, if B6 is playing a role, I would expect a stronger correlation. Nonetheless, with more data, the correlation may strengthen, so stay tuned for that!

b6hcy.png

5/14/2018: I changed B6-B12-methylfolate supplements so that I’d only have to take pills from 1 bottle instead of from 3. That supplement, however, had 1.5 mg of B6 instead of the 50 mg that was in my original supplement. Less B6 didn’t result in a higher homocysteine value-in fact, it went down (slightly), from 10.8 to 10.6. If an increased amount of B6 was causing lower levels of homocysteine, I would’ve expected higher, not (barely) lower homocysteine levels. This suggests that maybe my B6 intake has nothing to do with my homocysteine levels.

6/4/2018: Despite no changes to my supplements, my homocysteine came down a little more, to 10.2. Interestingly, the correlation (r) between homocysteine with my total dietary (diet + supplements) intake of B6, B12, and methylfolate is 0.39, 0.68, 0.29, respectively. The correlation between my B12 intake with homocysteine looks moderately strong, whereas the correlations for B6 and folate are weak. Based on this data, it’s possible I had a mild B12 deficiency that was causing elevated homocysteine. Note that my average B12 intake, without supplements is ~8 mcg/day, which is more than 3-fold higher than the RDA.

In looking at the association between my dietary data with homocysteine, a stronger correlation (r = 0.91; R2 = 0.83) has emerged…for my protein intake! In other words, a higher protein intake is more strongly correlated with lower homocysteine than B12:

Picture2

7/11/2018: To explore the strong association between my protein intake with homocysteine, I increased my protein intake from an average value of 104 g/day for the period that preceded my June measurement (5/15/2018 – 6/4/2018) to 136 g/day for the period up to my 7/11/2018 measurement (6/5/2018 – 7/10/2018). The result? Lower homocysteine, to 8.2 uMol/L! Interestingly, the correlation between my dietary protein intake with homocysteine remained strong (r = 0.86, R2 = 0.73, n = 7 measurements).

What about my B6, methyl-B12, methyl-folate stack? I’m still taking it, although it looks like methyl-B12 may be the only factor that is associated with my homocysteine levels. In support of that, the correlation between each with homocysteine is r = 0.02, 0.73, 0.36, respectively.

Because I now have my homocysteine < 9 umol/L, it may be time to optimize other variables (in addition to the metabolic panel and CBC). Stay tuned!

 

If you’re interested, please have a look at my book:

 

References

Lewerin C, Nilsson-Ehle H, Matousek M, Lindstedt G, Steen B. Reduction of plasma homocysteine and serum methylmalonate concentrations in apparently healthy elderly subjects after treatment with folic acid, vitamin B12 and vitamin B6: a randomised trial.vEur J Clin Nutr. 2003 Nov;57(11):1426-36.

Olthof MR, van Vliet T, Verhoef P, Zock PL, Katan MB. Effect of homocysteine-lowering nutrients on blood lipids: results from four randomised, placebo-controlled studies in healthy humans. PLoS Med. 2005 May;2(5):e135.

Platelets and All-Cause Mortality Risk

Have you had a blood test and aren’t sure what values for platelets may be optimal for health? The reference range is 150-400 platelets per nanoliter (*10^9/L). Within that range, what’s optimal?

In a study of 21,635 adults older than 35y (average age wasn’t reported) with a 7.6-year follow-up, platelets between 230-270 was associated with maximally reduced risk of death from all causes (Bonaccio et al. 2016):

platets acm

In a study of 21, 252 adults (average age 53y) with an average follow-up of 3.5y, values ~250 were associated with maximally reduced risk of death from all causes Vinholt et al. (2017) :

plat2 acm

What about in older adults? In a study of 159, 746 postmenopausal women (average age, 63y) with a 16-year follow up, maximally reduced risk of death from all causes was associated with platelet values between 200-256 (Kabat et al. 2017).

In a study of 36, 262 older adults (average age, 71y) with an 11-year follow-up, platelet values ~250 were associated with maximally reduced risk for all-cause mortality. Interestingly, even at platelet values ~250, mortality risk was highest for non-Hispanic whites, when compared with non-Hispanic blacks and Hispanics (Msaouel et al. 2014):

plat ethnicity

In 5,766 older adults (average age, 73y) that were followed for 12-15 years, values higher than 200-300 had an increased risk of death from all causes (van der Bom et al 2009). Risk for values between 100-199 was not different when compared against 200-299, but there was a non-significant trend towards increased risk (1.05, 95% CI: 0.97, 1.14).

In 131,308 older adults (~73y) with a 6-yr follow-up, maximally reduced risk of death from all causes was associated with values between 200-300, whereas risk significantly increased below and above that range, respectively Tsai et al. (2015):

plat eld

In sum, the data suggests that platelet values ~250 may be optimal for heath, with 200-300 as the “optimal range” within the 150-400 reference range. What are your values?

 

If you’re interested, please have a look at my book!

 

References

Bonaccio M, Di Castelnuovo A, Costanzo S, De Curtis A, Donati MB, Cerletti C, de Gaetano G, Iacoviello L; MOLI-SANI Investigators. Age-sex-specific ranges of platelet count and all-cause mortality: prospective findings from the MOLI-SANI study. Blood. 2016 Mar 24;127(12):1614-6.

Kabat GC, Kim MY, Verma AK, Manson JE, Lin J, Lessin L, Wassertheil-Smoller S, Rohan TE. Platelet count and total and cause-specific mortality in the Women’sHealth Initiative. Ann Epidemiol. 2017 Apr;27(4):274-280.

Msaouel P, Lam AP, Gundabolu K, Chrysofakis G, Yu Y, Mantzaris I, Friedman E, Verma A. Abnormal platelet count is an independent predictor of mortality in the elderly and is influenced by ethnicity. Haematologica. 2014 May;99(5):930-6.

Tsai MT, Chen YT, Lin CH, Huang TP, Tarng DC; Taiwan Geriatric Kidney Disease Research Group. U-shaped mortality curve associated with platelet count among older people: a community-based cohort study. Blood. 2015 Sep 24;126(13):1633-5.

van der Bom JG, Heckbert SR, Lumley T, Holmes CE, Cushman M, Folsom AR, Rosendaal FR, Psaty BM. Platelet count and the risk for thrombosis and death in the elderly. J Thromb Haemost. 2009 Mar;7(3):399-405.

Vinholt PJ, Hvas AM, Frederiksen H, Bathum L, Jørgensen MK, Nybo M. Thromb Res.Platelet count is associated with cardiovascular disease, cancer and mortality: A population-based cohort study. 2016 Dec;148:136-142.

Total Cholesterol: What’s Optimal For Longevity?

On my latest blood test (August 2015), my total cholesterol was 127 mg/dL-is that value optimal for health and longevity?

Based on data for 1,104,294 men younger than 60y (median age, 40y) that were followed for up to 14 years (Fulks et al. 2009), my 127 mg/dL value (1 – 2.4%) puts me relatively close to maximally reduced all-cause mortality risk, which occurs at 146-158 mg/dL (5-9% on the graph below):

c hdl mort

But what about the data for men older than 60?

In a 10-year study of 2,277 older adults (average age, ~77y), total cholesterol levels less than 175 mg/dL were associated with ~2-fold higher risk of all-cause mortality, compared with values greater than 226 mg/dL (Schupf et al. 2005):

tc less 175 acm

Similarly, in a 10-year study of even older adults (median age, 89y; 724 subjects), all-cause mortality risk was significantly increased in subjects with total cholesterol values less than 193 mg/dL (dark black line below), compared with values greater than 251 mg/dL (dashed line; Weverling-Rijnsburger et al. 1997). In addition, subjects with cholesterol values greater than 251 mg/dL lived ~2 years longer than those with values less than 191 mg/dL. So higher cholesterol in very old adults…increased lifespan! Does that mean I should alter my dietary approach to increase my circulating cholesterol levels after I reach 60?

chol 89y mort.png

To address that issue, it’s important to understand why cholesterol increases during aging. One possible mechanism involves the role of cholesterol in immune defense against infectious agents (bacteria, viruses, parasites, etc.). Obviously, our immune system is supposed to eliminate these pathogens, but immune function decreases with age (Targonski et al. 2007). As a compensatory mechanism, cholesterol can protect against infectious agents. For example, LDL cholesterol binds to and partially inactivates Staphylococcus aureus (Bhakdi et al. 1983). Staphylococcus aureus infection increases during aging, as its incidence rate is ~3-fold higher in adults older than 60y, when compared with younger subjects (Laupland et al. 2008). In addition, LDL cholesterol inhibits bacterial endotoxin (Weinstock et al. 1992), whose presence in the blood increases during aging (Ghosh et al. 2015). In support of the link between circulating cholesterol with infectious agents, in the older adults of Weverling-Rijnsburger et al. (1997), cholesterol values greater than 251 mg/dL (solid black line) were associated with significantly decreased infectious disease-related mortality, when compared with values less than 193 mg/dL:

infect mort

So if we’re better able to keep infectious agents out of our blood, that would be expected to reduce the need for elevated circulating cholesterol during aging. How can we do that?

One approach involves increased dietary fiber. Fermentation of dietary fiber by gut bacteria produces short-chain fatty acids, which improve gut barrier function (Chen et al. 2013), and decrease cholesterol synthesis (Wright et al. 1990). However, older adults do not eat high-fiber diets, as values of only ~19g/day have been reported (Lustgarten et al. 2014). In contrast, dietary fiber intakes greater than only 29g/day are associated with less infectious disease (and all-cause mortality) risk (Park et al. 2011). So definitely eating at least 29g fiber/day is important, but is that amount optimal to minimize the need for elevated cholesterol during aging?

In a 2-week study of the role of dietary fiber on circulating cholesterol, subjects that ate only 10g fiber/1000 calories did not significantly reduce their baseline total cholesterol values from ~182 mg/dL (Jenkins et al. 2001). In contrast, a dietary fiber intake of 19g/1000 calories reduced baseline total cholesterol from 185 to 150 mg/dL, and subjects that ate even more fiber than that, 55g/1000 calories reduced their total cholesterol values from ~182 to 142 mg/dL, a drop that was also significantly different compared with the 19g fiber/1000 calorie group.

Collectively, these data suggest that to maximally boost gut barrier function, thereby minimizing circulating infectious agents and the need for elevated circulating cholesterol during aging, a very-high fiber-diet may be important. Accordingly, my average daily fiber intake is ~100 g/day on a 2300 calorie diet, resulting in ~43g fiber/1000 calories. Based on this, I don’t expect for my total cholesterol values to change during aging, as my gut barrier function will be optimal, and infectious agents in my blood will be minimized.

To add some specificity to this approach, 2 additional measurements may be important: serum albumin and HDL cholesterol. In agreement with the studies of Weverling-Rijnsburger et al. and Schupf et al., in a 5-year study of 4,128 older adults (average age, ~79y), those with total cholesterol values less than 160 mg/dL had significantly higher all-cause mortality risk, compared with values greater than 240 mg/dL (Volpato et al. 2001):

low tc mortl

However, when considering subjects’ albumin and HDL cholesterol levels, the differential mortality risk was abolished. Subjects that had low total cholesterol but also high (within-range) albumin and HDL had improved survival compared to the higher cholesterol groups:

adj tc mort for alb hdl

If your total cholesterol values are less than 160 mg/dL, what serum albumin and HDL values should you shoot for? As shown below, albumin levels greater than 38 g/L and HDL values greater than 47 mg/dL were associated with maximally reduced all-cause mortality risk in subjects with total cholesterol values less than 160 mg/dL (Volpato et al. 2001):

volpato

My albumin values are consistently between 46-48 g/L, but during recent measurements my HDL levels have been lower than optimal (35 mg/dL on 8/2015). The good news is that I was able to increase my HDL from 28 (7/2013 measurement) to 35 mg/dL by adding ~4 oz of fish every day! To further increase my HDL, I’ve doubled my fish oil intake (~3.3 g of combined EPA + DHA per day, from 5-9 g of cod liver oil). I’ll test the effect of this on my circulating biomarkers in a couple of months, so stay tuned!

3/23/2016 Update: Because of concerns that the pre-formed Vitamin A (that is found in cod liver oil) may negate the potential health-promoting effects of optimal Vitamin D levels (Schmutz et al. 2016), I stopped taking cod liver oil during the 3-month period that preceded my latest blood test (3/23/2016). However, I was able to increase my HDL from 35 to 53 mg/dL! I attribute this increase to the daily inclusion of ~60g/walnuts per day. In doing that, although I only replaced ~200 calories from carbohydrates with fat, lower carbohydrate diets have been shown to increase HDL (Manor et al. 2016).

Nonetheless, in terms of the all-cause mortality data that includes total cholesterol (137 mg/dL), albumin (51 g/L), and HDL (53 mg/dL), based on my latest blood test results, my risk is now maximally low!

If you’re interested, please have a look at my book!

References

Bhakdi S, Tranum-Jensen J, Utermann G, Füssle R. Binding and partial inactivation of Staphylococcus aureus alpha-toxin by human plasma low density lipoprotein. J Biol Chem. 1983 May 10;258(9):5899-904.

Chen H, Mao X, He J, Yu B, Huang Z, Yu J, Zheng P, Chen D. Dietary fibre affects intestinal mucosal barrier function and regulates intestinal bacteria in weaning piglets. Br J Nutr. 2013 Nov;110(10):1837-48.

Eaton SB, Eaton SB 3rd, Konner MJ. Paleolithic nutrition revisited: A twelve-year retrospective on its nature and implications. Eur J Clin Nutr. 1997 Apr;51(4):207-16.

Fulks M, Stout RL, Dolan VF. Association of cholesterol, LDL, HDL, cholesterol/ HDL and triglyceride with all-cause mortality in life insurance applicants. J Insur Med. 2009;41(4):244-53.

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.

Jenkins DJ, Kendall CW, Popovich DG, Vidgen E, Mehling CC, Vuksan V, Ransom TP, Rao AV, Rosenberg-Zand R, Tariq N, Corey P, Jones PJ, Raeini M, Story JA, Furumoto EJ, Illingworth DR, Pappu AS, Connelly PW. Effect of a very-high-fiber vegetable, fruit, and nut diet on serum lipids and colonic function. Metabolism. 2001 Apr;50(4):494-503.

Laupland KB, Ross T, Gregson DB. Staphylococcus aureus bloodstream infections: risk factors, outcomes, and the influence of methicillin resistance in Calgary, Canada, 2000-2006. J Infect Dis. 2008 Aug 1;198(3):336-43.

Lustgarten MS, Price LL, Chalé A, Fielding RA. Metabolites related to gut bacterial metabolism, peroxisome proliferator-activated receptor-alpha activation, and insulin sensitivity are associated with physical function in functionally-limited older adults. Aging Cell. 2014 Oct;13(5):918-25.

Mansoor N, Vinknes KJ, Veierød MB, Retterstøl K. Effects of low-carbohydrate diets v. low-fat diets on body weight and cardiovascular risk factors: a meta-analysis of randomised controlled trials. Br J Nutr. 2016 Feb;115(3):466-79.

Park Y, Subar AF, Hollenbeck A, Schatzkin A. Dietary fiber intake and mortality in the NIH-AARP diet and health study. Arch Intern Med. 2011 Jun 27;171(12):1061-8.

Schmutz EA, Zimmermann MB, Rohrmann S. The inverse association between serum 25-hydroxyvitamin D and mortality may be modified by vitamin A status and use of vitamin A supplements. Eur J Nutr. 2016 Feb;55(1):393-402.

Schupf N, Costa R, Luchsinger J, Tang MX, Lee JH, Mayeux R. Relationship Between Plasma Lipids and All-Cause Mortality in Nondemented Elderly. J Am Geriatr Soc. 2005 Feb;53(2):219-26.

Targonski PV, Jacobson RM, Poland GA. Immunosenescence: role and measurement in influenza vaccine response among the elderly. Vaccine. 2007 Apr 20;25(16):3066-9.

Vasto S, Scapagnini G, Rizzo C, Monastero R, Marchese A, Caruso C. Mediterranean diet and longevity in Sicily: survey in a Sicani Mountains population. Rejuvenation Res. 2012 Apr;15(2):184-8.

Volpato S, Leveille SG, Corti MC, Harris TB, Guralnik JM. The value of serum albumin and high-density lipoprotein cholesterol in defining mortality risk in older persons with low serum cholesterol. J Am Geriatr Soc. 2001 Sep;49(9):1142-7.

Weinstock C, Ullrich H, Hohe R, Berg A, Baumstark MW, Frey I, Northoff H, Flegel WA. Low density lipoproteins inhibit endotoxin activation of monocytes. Arterioscler Thromb. 1992 Mar;12(3):341-7.

Weverling-Rijnsburger AW, Blauw GJ, Lagaay AM, Knook DL, Meinders AE, Westendorp RG. Total cholesterol and risk of mortality in the oldest old. Lancet. 1997 Oct 18;350(9085):1119-23.

Wright RS, Anderson JW, Bridges SR. Propionate inhibits hepatocyte lipid synthesis. Proc Soc Exp Biol Med. 1990 Oct;195(1):26-9.

Blood Testing: What’s An Optimal Value For Triglycerides?

In terms of all-cause mortality risk, is the reference range for circulating triglycerides (TG, <150 mg/dL) optimal?

A meta-analysis of 38 studies in 360,556 subjects with a median age of 48y and a 12-year follow-up reported lowest all-cause mortality risk for subjects with TG values less than 90 mg/dL (equivalent to ~1 mmol; Liu et al. (2013)). As shown below, each successive 90 mg/dL increase was associated with a 12% higher all-cause mortality risk. A person with a value closer to the high end of the reference range, ~150 would have a ~7% increased mortality risk compared someone with a value ~90. In other words, there would be 7 more deaths per 100 total people at a TG value of 150, compared with the death rate for people with values less than 90.

tg mortal

Added importance for the association between TG values less than 90 with all-cause mortality risk come from studies of people who have lived longer than 100 years, centenarians. As shown below, triglyceride values less than 101 mg/dL have been reported in 9 of 11 centenarian studies:

tg mort

What’s my TG value? On my latest blood test (8/2015), it was 42. I’ve measured my TGs 11 times over the past 10 years-my average value for those measurements is 62. Based on the meta-analysis and centenarian data, that would put me in the lowest risk category for all-cause mortality.

tg mort

If you’re interested, please have a look at my book!

References

Arai Y, Hirose N, Yamamura K, Shimizu K, Takayama M, Ebihara Y, Osono Y. Serum insulin-like growth factor-1 in centenarians: implications of IGF-1 as a rapid turnover protein. J Gerontol A Biol Sci Med Sci. 2001 Feb;56(2):M79-82.

Baranowska B, Bik W, Baranowska-Bik A, Wolinska-Witort E, Szybinska A, Martynska L, Chmielowska M. Neuroendocrine control of metabolic homeostasis in Polish centenarians. J Physiol Pharmacol. 2006 Nov;57 Suppl 6:55-61.

Barbagallo CM, Averna MR, Frada G, Noto D, Cavera G, Notarbartolo A. Lipoprotein profile and high-density lipoproteins: subfractions distribution in centenarians. Gerontology 1998;44(2):106–10.

Bik W, Baranowska-Bik A, Wolinska-Witort E, Kalisz M, Broczek K, Mossakowska M, Baranowska B. Assessment of adiponectin and its isoforms in Polish centenarians. Exp Gerontol. 2013 Apr;48(4):401-7.

Chan YC, Suzuki M, Yamamoto S. Dietary, anthropometric, hematological and biochemical assessment of the nutritional status of centenarians and elderly people in Okinawa, Japan. J Am Coll Nutr. 1997 Jun;16(3):229-35.

Chan YC, Suzuki M, Yamamoto S. A comparison of anthropometry, biochemical variables and plasma amino acids among centenarians, elderly and young subjects. J Am Coll Nutr. 1999 Aug;18(4):358-65.

Liu J, Zeng FF, Liu ZM, Zhang CX, Ling WH, Chen YM. Effects of blood triglycerides on cardiovascular and all-cause mortality: a systematic review and meta-analysis of 61 prospective studies. Lipids Health Dis. 2013 Oct 29;12:159.

Magri F, Muzzoni B, Cravello L, Fioravanti M, Busconi L, Camozzi D, Vignati G, Ferrari E. Thyroid function in physiological aging and in centenarians: possible relationships with some nutritional markers. Metabolism. 2002 Jan;51(1):105-9.

Paolisso G, Ammendola S, Del Buono A, Gambardella A, Riondino M, Tagliamonte MR, Rizzo MR, Carella C, Varricchio M. Serum levels of insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 in healthy centenarians: relationship with plasma leptin and lipid concentrations, insulin action, and cognitive function. J Clin Endocrinol Metab. 1997 Jul;82(7):2204-9.

Thillet J, Doucet C, Chapman J, Herbeth B, Cohen D, Faure-Delanef L. Elevated lipoprotein(a) levels and small apo(a) isoforms are compatible with longevity: evidence from a large population of French centenarians. Atherosclerosis 1998;136:389–94.

Vasto S, Scapagnini G, Rizzo C, Monastero R, Marchese A, Caruso C. Mediterranean diet and longevity in Sicily: survey in a Sicani Mountains population. Rejuvenation Res. 2012 Apr;15(2):184-8.

Willcox DC, Willcox BJ, Wang NC, He Q, Rosenbaum M, Suzuki M. Life at the extreme limit: phenotypic characteristics of supercentenarians in Okinawa. J Gerontol A Biol Sci Med Sci. 2008 Nov;63(11):1201-8.