KNES 337 - Unit 26 Nutrient-Gene Interactions

nutrient-gene interactions

can turn genes on and off

single gene defects

related to hundreds of diseases - including

• PKU (phenylketonuria)

• Cystic fibrosis

• Sickle cell anemia

• Hemochromatosis

(but most diseases are a combination of multiple genes and the environment)

polygenic defects

multiple genes

include - heart disease, cancer, hypertension, obesity

heart disease

high cholesterol diets → plaques in some people (not everyone is susceptible to plaque formation), diets low in folate and vegetables increase risk (some may be at increased risk of a heart attack, others will be fine)

genetic and environmental influence

cancer

• environmental vs. genetic influence differs by site

  • Endometrial (environment influence = 90%, rest is genetic)

  • Stomach (72%)

  • Prostate (42%)

hypertension

salt sensitivity - eating too much salt usually increases blood pressure but not in everyone, salt sensitive or salt resistant people 

• High sodium → whole population should decrease their sodium intake because we don’t know who is salt sensitive vs salt resistant 

genetic and environmental influence

obesity

over 250 genes associated with development (very complex) + environmental influence

celiac disease

an autoimmune disease that damages the small intestine, immune reaction to gluten (a protein)

• Gluten is in wheat, barley, and rye

• When people with celiac disease consume gluten, the immune system attacks and destroys the villi

  • Villi are not finger-like, they look like shaved off

• Oats - often manufactured where wheat and barley are, people often buy gluten-free oats to ensure no cross-contamination 

where is gluten found

wheat, barley, rye

cross contamination can be found in oats (often manufactured where wheat and barley are, people often buy gluten-free oats to ensure no cross-contamination)

genetic link of celiac disease

• Celiac disease occurs in genetically predisposed people

• HLA genes (human leukocyte antigen)

  • risk versions = DQ2 or DQ8

• Responsible for how the immune system distinguishes between the body’s proteins and foreign proteins

DQ2/DQ8

risk versions of HLA genes

~99% of people with celiac disease have these gene variants

• Risk version, but don’t develop the disease

• Interaction of gene and environment (foods you eat, viruses, other genes)

But 30% of the general population have the risk version, so development of the disease is dependent on the combination of risk variants & other gene or environmental factors 

symptoms of celiac disease

• Hard to diagnose because there are many symptoms, and symptoms vary 

• Classic symptoms - headache, fatigue, abdominal pain and bloating after consuming products with gluten, weight loss, diarrhea, constipation, foul-smelling stools 

  • Weight loss and diarrhea usually cause people to go to the doctor - especially in children (children should always be growing)

celiac disease in Canada

1% of population is affected

genetic component of celiac

if a first degree relative has celiac disease, 1 in 10 chance family member will develop it (HLA genes)

testing for celiac

blood test, small intestine biopsy, genetic screening for DQ2 and DQ8

blood test for celiac

• tTG-IgA (tissue transglutaminase antibodies), must be on a gluten-containing diet

  • Must be experiencing symptoms on a gluten diet for 6-8 weeks before the biopsy, eat 4-6 slices of bread per day

  • Now modified gluten challenge - 2-4 weeks, eat 1 ½ slices of bread per day (enough for diagnosis) 

small intestine biopsy

most definitive for diagnosing celiac, can see histology of the small intestine villi

genetic screening for celiac

can screen for risk variants DQ2 and DQ8

celiac commonly mistaken for

• IBS (irritable bowel syndrome)

• Crohn’s disease 

why would you want an accurate diagnosis?

long term consequences (malnutrition, infertility, osteoporosis)

• Also at risk for developing more autoimmune diseases - T1 diabetes, multiple sclerosis 

  • celiac varies in people - some people are very sensitive to cross contamination

non-celiac gluten sensitivity

develop symptoms when they consume gluten-containing foods and feel better on a gluten-free diet but do NOT have celiac disease

• There are no biomarkers for diagnosis 

• Autoantibodies (TTG, EMA, DGP) are absent

• There is no villous atrophy - villi not destroyed 

higher % of people have this over celiac

Other compounds in wheat, barley, and rye may trigger symptoms (e.g. proteins called amylase/trypsin inhibitors or fermentable carbohydrates)

is eating gluten free healthy for everyone?

NO, Canadian Celiac Association - word of caution

• You shouldn’t self-diagnose yourself 

• Going on a gluten-free diet should be because of a medical diagnosis 

• If you do have celiac disease, it needs to be medically monitored, don’t go undiagnosed 

• Gluten-free foods in the market are highly processed and have many preservatives/colourants, stripped of fiber, need another source of fiber

nutrigenetics

The study of how genes and diet interact to increase or decrease someone’s risk for disease

• Gene and environment interactions

• Play a role in “personalized nutrition”

What biological sample do you need for nutrigenetics? = DNA (saliva)

genetic testing

ancestry services, some companies specialize in nutrition-related genetic traits

ancestry services

• Can purchase basic ancestry, or health + ancestry, e.g. 23andMe

• Report on global ancestry (% of countries that share DNA sequences), relatives, at risk diseases, muscle composition 

• You will have to consent to learn about more serious genes - e.g. BRCA genes for breast cancer, Celiac, Alzheimer’s, Parkinson’s 

  • Because you will have to take more serious steps once learning if you have them or not

nutrigenomix

a Canadian company that specializes in nutrition-related genetic traits 

• Specific for genetics that are linked to nutrition 

• 70 genetic markers that they look at 

• More expensive ~$350 CAD

• Registered dietitian to give report

• Health test, sport test, fertility test 

food selection

• Food preferences largely learned

• 80 genes that help taste bitter foods

• Some are highly sensitive to bitter foods, genetically determined 

• If vegetables taste bitter → will eat less

• Bitter compound paper (PTC) - taste it on the tongue for the bitter taste receptors, some may taste paper, others taste 

  • “Supertasters” - small percentage, find it disgusting 

future consideration

Moving towards individualized dietary prescriptions

Complete profile with genetic risks, gut microbiota profiles, etc.