IOM Committee on Strategies to Reduce Sodium Intake. Public Information-Gathering Workshop March 30,

Transcription

1 IOM Committee on Strategies to Reduce Sodium Intake Public Information-Gathering Workshop March 30,

2 Salty taste perception and our liking of salty taste. Paul A.S. Breslin Monell Chemical Senses Center & Rutgers University, Department of Nutritional Sciences March 30, 2009

3 How will we lower sodium in the diet? Change the food / Change the behavior

4 Overview of presentation o Salt taste: Mechanisms o The role of salt in food palatability o The human liking for salt o Taste based strategies for reducing sodium intake n Technological n Behavioral

5 Why Sodium? Unlike calcium, phosphorous, and other physiologically essential ions, we have limited capacity to store sodium in our bodies long term. Yet we lose sodium in our body fluids every day and it is necessary for life. Therefore, we have evolved a very specific taste mechanism with which to seek it in the environment and identify it.

6 Each taste papillae contains many taste buds, each of which contains many taste cells PAPILLAE TASTE BUD Breslin Current Biology 2008

7 SALT TASTE MECHANISMS o How we detect salty taste is still unknown? o Stimulus specificity: n NaCl and LiCl only mostly salty substances known. n This suggests a very specific receptor mechanism. n Anions affect salt taste quality and salty taste intensity, but many salts have a salty component. o Animal models: n Neural responses to NaCl are inhibited by the diuretic amiloride (in non-humans). n Hypothesis: The salt receptor mechanism involves an epithelial Na channel (ENaC).

8 Bhalla and Hallows J Am Soc Nephrol 2008 Epithelial Sodium Channel (ENaC)

9 Postulated Salt Taste Receptors ENaC TRPV1t (VR1) GPCR Na + Na +, Ca 2+ γ α β Amiloride Except human, some mice, pig and likely other species CPC Na + G X + + [Ca 2+ ] i depolarization action potentials rise in [Ca 2+] i Indirect release via depolarization Direct release of neurotransmitter neurotransmitter release Can we block or eliminate salty taste? Amiloride and TRPV1 KO No.

10 Taste functions of salt in food To impart a desirable saltiness to foods. To favorably modify the flavor of foods.

11 Taste functions of salt in food To impart a desirable saltiness to foods. To favorably modify the flavor of foods.

12 Favorable modifications of food flavor Provides body or mouthfeel Enhances taste Blends flavors Reduces off-tastes; blocks bitterness

13 Salt Suppresses Bitterness 90 Percent Bitterness Suppression Bitter Tasting Compounds QHCl Caffeine MgS04 KCl Urea Acetamin. Pseudoeph. Keast and Breslin Pharmaceut. Res. 2002

14 FLAVORING FUNCTIONS OF SALT IN FOOD Sucrose (S) Urea (U) S+U mixed S+U mixed and salted sweetness bitterness Breslin & Beauchamp, Nature 1997

15 The human liking for salt o Innate factors n Salt appetite n Salt preference o Importance of individual experience n Fetus, infants and children n Adults

16 The human liking for salt o Innate factors n Salt appetite: Many species of plant eating animals innately recognize and respond to the salt when they are sodium depleted by avidly consuming it. Unusual in humans. n Salt preference: Many species of plant eating animals will preferentially consume salt even when they have no need for sodium. Common for humans.

17 The human liking for salt Individual Experiences o Fetal experiences modify salt preferences n Sodium depletion in pregnant women n Salt preferences and birth weight

18 PERINATAL DEVELOPMENTAL PLASTICITY: PERSISTENCE LOWER BIRTHWEIGHT IN CHILDREN SELECTING SALTY-TASTING SNACKS 4.00 AGE 5 YEARS birthweight (kg) * 3.00 NO YES at least one salty snack Stein, Beauchamp, Faith & Stunkard, unpublished

19 The human liking for salt Individual Experiences o Early diet variation influences later salt preferences in infants and children

20 DIET-RELATED DEVELOPMENTAL PLASTICITY Age-related shift: Relationship with dietary practices 0.65 PREFERENCE STARCHY Salty table TABLE foods FOOD YES NO 0.17M 0.34M months 6 months 2 months 6 months Preference LOW SALT for low salt Preference HIGH for SALT high salt Stein, Cowart & Beauchamp, in preparation

21 The optimal level of NaCl in soup is greater for children than for adults Optimal salt (M) in soup Salt level in commercial soup Adults (n=30) Pre-school children (n=46) Individuals tested Beauchamp & Cowart Devel. Psychol. 1990

22 Summary o Children are biologically disposed to like salt o Response to salty taste may be shaped by events occurring early in development n in utero n early experiential factors o Early influences may persist for several years and possibly into young adulthood

23 The human liking for salt o Importance of individual experience n Adults o A reduction in sodium intake leads to a decrease in liking for high salt foods

24 Decreasing Na intake is followed by decreased salt preference Bertino, Beauchamp & Engelman, 1982

25 Decreasing Na intake is followed by decreased salt preference Control Experimental Liking Pre diet Low Na diet NaCl Concentration in crackers (%) Bertino, Beauchamp & Engelman, 1982

26 Decreasing Na intake is followed by decreased salt preference Control Experimental Optimal salt level before going on low salt diet Liking Pre diet Low Na diet NaCl Concentration in crackers (%) Bertino, Beauchamp & Engelman, 1982

27 Decreasing Na intake is followed by decreased salt preference Optimal salt level after being on diet Control Experimental Liking Pre diet Low Na diet NaCl Concentration in crackers (%) Bertino, Beauchamp & Engelman, 1982

28 The human liking for salt o Importance of individual experience n Adults o A reduction in sodium intake leads to a decrease in liking for high salt foods o An increase in sodium intake leads to a increase in liking for high salt foods

29 Taste based strategies for reducing sodium intake

30 Taste based strategies for reducing sodium intake o Technological n Crystal size/shape changes: Ongoing n Salt substitutes: Difficult if not impossible n Salt enhancers: Possible

31 Certain basic amino acids have the capacity to enhance the salty taste of NaCl, even though the amino acids have no salty taste of themselves. Thus, salty taste enhancers are known to exist. Breslin & Brand, unpublished

32 Taste based strategies for reducing sodium intake o Behavioral n Council consumers to reduce salt use in home; stop using salt shakers ( shake the habit )

33 Beauchamp et al., JAMA

34 Taste based strategies for reducing sodium intake o Behavioral n Council consumers to reduce salt use in home; stop using salt shakers ( shake the habit ) n Reduce salt in commercially prepared foods across the board n Reduce salt in selected commercially prepared foods

35 Taste based strategies for reducing sodium intake o Behavioral n Council consumers to reduce salt use in home; stop using salt shakers ( shake the habit ) n Reduce salt in commercially prepared foods across the board n Reduce salt in selected commercially prepared foods n Target infants and young children to limit intake of salty foods

36 Key Questions That Remain o Diet, Development, and Mechanism n Must the diet be consistent in its saltiness overall (pickles versus bread)? n Are certain foods more important than others? n Must the reduction in salt be applied to all foods? n Should liquid and solid foods be treated equally? n Will exposing children to low salt diets alter their salt preferences for life? n What will replace the positive flavor altering components of sodium when it is reduced? n Can anion mechanisms of salt taste be utilized to boost the saltiness of lower sodium levels? n What is the salty taste mechanism in humans and how do we manipulate it?