Re: How science is going sour on sugar
It constantly amazes me that in the discussion on sugar being a major cause of ‘diabesity’1, in this issue of the BMJ, and over the years elsewhere, that basic physiology moves out of the picture. Starches are polysaccharides which are easily broken down or hydrolysed to constituent simple sugars; a common starch is amylose which becomes glucose, releasing a small amount of energy, when acted on by the enzyme amylase. Interestingly, amylase is even present in human saliva, and in high amounts in some human groups2, in addition to pancreatic secretions. One can taste the increasing sweetness of glucose on chewing tasteless white bread, which is unlikely to be good for teeth3. Breads, rice and white potatoes, our so-called staple foods, provide starch with a high glycaemic index and load, which may be greater than sucrose4. The sugars (monosaccharides) are absorbed extremely quickly, raising blood glucose to high levels, and releasing large amounts of energy for use or storage. Willet and Ludwig(1136/bmj.e8077)5 acknowledge this fact about starch in their commentary in this issue.
Pre-agriculture, 10,000 years ago, starchy food was scarce; tough, stringy roots and tiny grains. Subsequently, these tubers and grains have been bred to produce greatly increased volumes and proportions of starch6, and sugars, which preserve, pack and travel well. Baked breads and crackers, even of the ‘whole grain’ type, contain much refined flour. Whilst many clinicians advise whole grain based foods as part of a ‘prudent diet’ which confers health benefits, when studied, cardiovascular risk markers did not improve on a whole grain augmented diet7 8. Non fruit sources of mono- and di- saccharides (fructose, sucrose) such as from maise, sugar cane and beet, have also been highly bred for their rich energy yield. This whole group of refined starches and sugars is highly implicated in energy dense food addiction9.
On the other hand, humans evolved from a ripe fruit-eating primate, approximately 20 million years ago, and generally apes (except gorillas) have continued to eat a high energy plant diet of seeds and fruit, probably helping to supply the enlarging, energy-demanding brain10. It appears that when fruit sugars are ingested with fibres and other complex plant chemicals, it is absorbed at a slower rate. Whilst fruits may have been cultivated to be fleshier and contain more sugar they can still be eaten whole, often with skins and seeds, which appears to contribute to their low glycaemic index. Even preserved (dried, frozen), they retain fibre and unknown types of plant nutrients. Notably, it is important that these food constituents are eaten as food. As the meta-analysis of Myung et al (1136/bmj.f10)11, also in this issue, shows, vitamins and supplements are not effective at preventing cardiovascular disease (CVD).
Yudkin’s book ‘Pure White and Deadly’ mentioned by Jackson (1136/bmj.f307)12 and Watts (1136/bmj.e7800)13 could refer to both sucrose and starch. We may have to face the fact that refined starches should be treated as refined sugars and that to decrease diabesity rates, consumption of ‘high (refined) carb’ diets needs to be severely curtailed, probably aided with addiction management in the already centrally overweight.
However, adequate dietary energy for modestly active, older or overweight and/or diabetic individuals can be replaced with plenty of low-processed fruit, vegetables, oil seeds/nuts14 and free range animal products, which are also known to confer health15 16. Rapidly, such a diet rights the wrongs of severely unbalanced micronutrient to macronutrient ratios. Micronutrient insufficiency seen in diabesity17, or rather malnubesity18, decreases. Such diets reduce the central obesity related metabolic syndrome continuum of CVD, diabetes and cancer risk.
So, appetising sugar and starch laden foods indirectly cause obesity by energy overload, as well as effectively displacing food micronutrients needed for healthy metabolism.
1. Anonymous. From the NIH: Successful diet and exercise therapy is conducted in Vermont for "diabesity". JAMA 1980;243(6):519-20.
2. Luca F, Perry GH, Di Rienzo A. Evolutionary adaptations to dietary changess. Annu. Rev. Nutr. 2010;30:291-314.
3. Garcia-Closas R, Garcia-Closas M, Serra-Majem L. A cross-sectional study of dental caries, intake of confectionery and foods rich in starch and sugars, and salivary counts of Streptococcus mutans in children in Spain. Am. J. Clin. Nutr. 1997;66(5):1257-63.
4. Atkinson FS, Foster-Powell K, Brand-Miller JC. International Tables of Glycemic Index and Glycemic Load Values: 2008. Diabetes Care 2008;31(12):2281-83.
5. Willett WC, Ludwig DS. Science souring on sugar. BMJ 2013;346.
6. Jacobs DR, Pereira MA, Meyer KA, Kushi LH. Fiber from whole grains, but not refined grains, is inversely associated with all-cause mortality in older women: the Iowa women's health study. J. Am. Coll. Nutr. 2000;19(3 Suppl):326S-30S.
7. Brownlee IA, Moore C, Chatfield M, Richardson DP, Ashby P, Kuznesof SA, et al. Markers of cardiovascular risk are not changed by increased whole-grain intake: the WHOLEheart study, a randomised, controlled dietary intervention. Br. J. Nutr. 2010;104(1):125-34.
8. Jacobs DR, Jr., Tapsell LC. Food, not nutrients, is the fundamental unit in nutrition. Nutr. Rev. 2007;65(10):439-50.
9. Avena NM, Gold JA, Kroll C, Gold MS. Further developments in the neurobiology of food and addiction: update on the state of the science. Nutrition 2012;28(4):341-3.
10. Leonard WR, Snodgrass JJ, Robertson ML. Effects of Brain Evolution on Human Nutrition and Metabolism. Annu. Rev. Nutr. 2007;27(1):311-27.
11. Myung S, Ju W, Cho B, Oh S, SM P, Koo B. Efficacy of vitamin and antioxidant supplements in prevention of cardiovascular disease: systematic review and meta-analysis of randomised controlled trials. BMJ 2013;346:f10.
12. Jackson T. How science is going sour on sugar. BMJ 2013;346.
13. Watts G. Sugar and the heart: old ideas revisited. BMJ 2013;346.
14. Jenkins DJA, Kendall CWC, Banach MS, Srichaikul K, Vidgen E, Mitchell S, et al. Nuts as a Replacement for Carbohydrates in the Diabetic Diet. Diabetes Care 2011;34(8):1706-11.
15. Azadbakht L, Mirmiran P, Esmaillzadeh A, Azizi T, Azizi F. Beneficial effects of a Dietary Approaches to Stop Hypertension eating plan on features of the metabolic syndrome. Diabetes Care 2005;28(12):2823-31.
16. Mente A, Koning Ld, Shannon H, Anand S. A Systematic Review of the Evidence Supporting a Causal Link Between Dietary Factors and Coronary Heart Disease. Arch. Intern. Med. 2009;169(7):659-69.
17. Flancbaum L, Belsley S, Drake V, Colarusso T, Tayler E. Preoperative nutritional status of patients undergoing Roux-en-Y gastric bypass for morbid obesity. J. Gastrointest. Surg. 2006;10(7):1033-7.
18. McGill A-T. Malnutritive obesity ('Malnubesity'): Is it driven by human brain evolution? Metab. Syndr. Relat. Disord. 2008;6(4):241-46. .
Competing interests: No competing interests