How a Gluten-Free Diet Can be Hazardous to Your Health · Despite such a dramatic shift in the diet...

How a Gluten-Free Diet Can be Hazardous to Your Health

2018 Latin American & Caribbean Buyers Conference

Glenn Gaesser, PhDProfessor, Arizona State University

Phoenix, AZ[[email protected]]

Challenges to Grain (Wheat) Consumption

Gluten-free diets have become immensely popular in the United States. Despite <1%

of Americans having diagnosed celiac disease, an estimated 25% of American

consumers reported consuming gluten-free food in 2015, a 67% increase from 2013.

Rubio-Tapia et al, Am J Gastroenterol, 2012;107:1538-1544Mintel Group, Ltd. August 2016

U.S. Gluten-Free Products Market Revenue by Product, 2014-2015 (USD Millions)

J Acad Nutr Diet 2012;112:1330-1333

“There is no evidence to suggest that following a gluten-free diet has any significant benefits in the general population.”

Claims Against Wheat

• Gluten levels in wheat have increased

• “Old” wheats were less toxic

• Short (dwarf) wheat is a product of genetic research in the 1960s and 1970s (there is no GMO wheat on the market)

• Height genes do not code for glutenins and gliadins

• Gliadin is an opiate that stimulates appetite

Gluten Levels in Wheat Have not Increased

• Gluten levels in various wheat varieties have changed little on averagesince the 1920s.

– Gluten addition to breads and foods has increased

Kasarda DD. J Agric Food Chem. 2013;61:1155-9

Is consumption of grain foods related to obesity and chronic

disease?

Refined Grain Intake and Body Mass IndexU. S. Cohort Studies

22.0

23.0

24.0

25.0

26.0

27.0

28.0

NHS(74,091)

IWHS(34,492)

HPFS(45,540)

FOS(2,941)

BLSA(1516)

Boston(535)

Older men& women

(434)

BM

I

Lowest Intake of Refined Grain Highest Intake of Refined Grain

Adapted from Gaesser, JADA 2007; 107:1768-1780

Refined Grain Intake and Body Mass IndexU. S. Cohort Studies

Interpretation:

Refined grain intake has very little association with body mass index (BMI)

Adapted from Gaesser, JADA 2007; 107:1768-1780

Despite the Assertion…

Grain Consumption is not associated with

high levels of Belly Fat

Grain Intake and Visceral Abdominal Fat

McKeown et al. Am J Clin Nutr 2010; 92:1165-71

Framingham

Heart Study

(n=2834)

BMJ, 2016;353:i2716

Specific analyses on bread were included in this paper

Whole-grain Bread Intake and Relative Risk of Chronic Disease

00.10.20.30.40.50.60.70.80.9

1

CHD Stroke CVD Cancer All-causeMortality

Re

lati

ve R

isk

Highest vs. Lowest intakes

Dose Response, per 90 grams/day

Aune et al, BMJ 2016;353:i2716



• People who consumed the most whole-grain bread had ~10-20% lower risk of major chronic diseases and all-cause mortality rates

• For each 90 gram per day increase in whole-grain bread intake, risk of major chronic diseases and all-cause mortality rates were ~10-20% lower

White Bread Intake and Relative Risk of CHDTotal Bread Intake and All-cause Mortality Risk

0

0.2

0.4

0.6

0.8

1

1.2

CHD All-cause Mortality

Re

lati

ve R

isk

Highest vs. Lowest Intakes

Dose Response, per 90 grams/dayWhite Bread Intake

Total Bread Intake




• White bread consumption was not associated with risk of coronary heart disease (CHD)

• Total bread consumption was associated with a ~20% reduction in all-cause mortality risk

The objective of this study was to examine the association of long-term

intake of gluten with the development of incident coronary heart disease

Lebwohl et al, BMJ 2017;357:j1892

Daily gluten intake

0

1

2

3

4

5

6

7

8

9

10

Quintile 1 Quintile 3 Quintile 5

Glu

ten

Inta

ke (

gram

s/d

ay)

Nurses' Health Study

Health Professionals Follow-up Study


Gluten and risk of coronary heart disease, by quintile of gluten intake

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Q 1 Q 2 Q 3 Q 4 Q 5

Haz

ard

Ra

tio


Compared to the group with the lowest gluten intake, higher gluten intake (Q1 – Q5) was associated with ~5-12% lower risk of coronary heart disease

[This was not statistically significant, but it is important to note that the actual hazard ratios were suggestive of reduced risk, not an increased risk.]




0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Q 1 Q 2 Q 3 Q 4 Q 5

Haz

ard

Ra

tio

CHD risk, no adjusment

CHD risk, adjustment for refined grains

CHD risk, adjustment for whole grains


• Adjustment for whole grain intake attenuated the association between gluten intake and coronary heart disease (CHD)

• Adjustment for refined grain intake improved the association between gluten intake and coronary heart disease (i.e., risk became even lower: ~15% lower risk, indicating that whole grains are more strongly associated with reduced CHD risk)



Conclusions

Long term dietary intake of gluten was not associated with risk of coronary heart

disease. However, the avoidance of gluten may result in reduced consumption of

beneficial whole grains, which may affect cardiovascular risk. The promotion of

gluten-free diets among people without celiac disease should not be encouraged.

The unintended consequences of a gluten-free diet

Recent report based on data from the National Health and Nutrition Examination Survey, 2009-2014

• 7,471 participants• 73 reported being on a gluten-free diet

Bulka et al, Epidemiol, 2017;28:e24-e25

Commercial gluten-free products primarily contain rice flour as a substitute. Emerging evidence suggests rice-based products can contain high levels of toxic metals; rice is a recognized source of arsenic and methylmercury exposure.

Despite such a dramatic shift in the diet of many Americans, little is known about how gluten-free diets might affect exposure to toxic metals found in certain foods.

Urinary Metal Concentrations by Gluten-free Diet Status

0

2

4

6

8

10

12

14

Total Arsenic Dimethylarsonic acid

Co

nce

ntr

atio

n (

µg

/L)

Gluten-free Diet

Non-gluten-free Diet*

*


Blood Metal Concentrations by Gluten-free Diet Status

0

0.2

0.4

0.6

0.8

1

1.2

1.4

Total Mercury

Co

nce

ntr

atio

n (

µg

/L) Gluten-free Diet

Non-gluten-free Diet

*


Conclusions

“Americans on gluten-free diets may be exposed to higher levels of arsenic and mercury. With the increasing popularity of gluten-free diets, these findings may have important health implications because the health effects of low-level arsenic and mercury exposure from food sources are uncertain but may increase the risk for cancer and other chronic diseases.”


• National Health and Nutrition Examination Survey, 2009-2012

• 11,354 participants• 55 diagnosed for Celiac Disease• 115 reported being on a gluten-free diet

2018 report


0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

Total Mercury Total Cadmium

Co

nce

ntr

atio

n (

µg

/L)

Gluten-free Diet


*(Trend)

Raehsler et al., Clin Gastroenterol Hepatol 2018;16:244-251

Urinary Total Arsenicby Gluten-free Diet Status

0

2

4

6

8

10

12

14

16

Urinary Total Arsenic

Co

nce

ntr

atio

n (

µg

/L)

Gluten-free Diet

Non-gluten-free Diet

*



0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

Total Lead

Co

nce

ntr

atio

n (

µg

/dL)

Gluten-free Diet



Conclusions

• Persons on a GFD had significantly higher urine levels of total cadmium and blood levels of lead, cadmium and mercury than persons not avoiding gluten

• Long-term effects of accumulation not known

• Levels were generally below toxic thresholds (except for urinary arsenic)

• People for whom a GFD is not medically warranted should be made aware of the possibility of heavy metal accumulation


Wheat and Gastrointestinal Health

• Oligifructose and inulin (naturally occurring fructan-type resistant starches) help create a healthy composition of gut bacteria

• Protection against some cancers and inflammatory conditions

• May help reduce risk of CVD

• Wheat contributes ~70-78% of oligofructoseand inulin in typical North American diet

Presence of Inulin and Oligofructosein the Diets of Americans

Moshfegh et al, J Nutr, 1999

Effects of a Gluten-free Diet on Gut Microbiota in Healthy Adult Human Subjects

• 10 healthy adults (8 women)

•Gluten-free diet for 1 month• All gluten-containing foods replaced by

certified gluten-free products

• Fecal samples collected and analyzed before and after

•Multiple analytic techniques

De Palma et al, Brit J Nutr, 2009

Effects of a Gluten-free Diet on Gut Microbiota and Healthy Adult Human Subjects

4.0

5.0

6.0

7.0

8.0

9.0

10.0

Co

nce

ntr

atio

n

Baseline After 1 Month

4.0

5.0

6.0

7.0

8.0

9.0

10.0

Co

nce

ntr

atio

n

Baseline After 1 Month

De Palma et al, Brit J Nutr, 2009

Good Bad

Removal of the major source (wheat) of fructan-type resistant

starches may have adverse consequences on gut bacterial

composition (microbiome)

Nutritional Impact of Going Gluten-Free

• Diet can be high in fat, calories and meat

• Gluten-free products may be higher in

calories

• Alternative grain foods may be higher in

sugar and fat, and of lower diet quality

➢Rice cereal and/or rice-tapioca bread, muffins,

chips, doughnuts, cookies

➢High glycemic and low in whole grains and fiber

➢Not enriched or fortified

➢Low in iron, niacin, riboflavin, thiamin, folate

43Jenkins et al 1987 AJCN 45: 946-951; Berti 2004 EJN 43: 198-204

Overall Conclusions

• There is no evidence to suggest that following a gluten-free diet has any significant benefits in the general population

• A gluten-free diet may adverse consequences for gastrointestinal health

• Avoidance of gluten may decrease whole-grain and cereal fiber intake, and this may affect cardiovascular disease risk

• A gluten-free diet may increase exposure to toxic metals

Thank You!

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