Sugar

Sugar
Molecular formula	C₁₂H₂₂O₁₁ (sucrose)
Type	Disaccharide (glucose + fructose)
Glycemic index	Moderate, lower than pure glucose or starch
Metabolism	Hydrolyzed to glucose and fructose in the small intestine before absorption
Food sources	Table sugar, fruit, honey, milk (as lactose, a different disaccharide)
Synonyms	Sucrose, table sugar
Ray's verdict	Generally helps Supports oxidative metabolism when thyroid, protein, and minerals are adequate; sugar craving is usually a sign of hypothyroidism, not addiction

Sucrose (table sugar) molecular structure

Sugar usually means sucrose (half Glucose, half Fructose). Mainstream nutrition often treats all sugars as metabolic villains. Ray Peat wrote that sucrose supports oxidative metabolism when thyroid, protein, and minerals are adequate, and that starch-heavy, seed-oil-rich diets did more harm to physiology and epidemiology than plain sugar.

There is a great anti-sugar cult, with even moralistic overtones, equating sugar craving with morphine addiction. Sugar craving is usually caused by the need for sugar, generally caused by hypothyroidism.

— Ray Peat

Fructose inhibits the stimulation of insulin by glucose, so this means that eating ordinary sugar, sucrose (a disaccharide, consisting of glucose and fructose), in place of starch, will reduce the tendency to store fat.

— Ray Peat

Peat cited nineteenth-century physicians P. A. Piorry and William Budd, who added large amounts of sucrose to diabetic diets, as historical counterexamples to the idea that eating sugar causes diabetes. See Fructose, Starch, Glucose, Harm reduction.

History/Etymology

Sugar refining from sugarcane dates back over 2,000 years in South Asia, but sucrose wasn't isolated and characterized as a specific chemical compound until the work of 18th and 19th century chemists, including Andreas Marggraf's 1747 identification of the same sugar in beets as in cane. "Sucrose" itself, from French sucre plus the "-ose" sugar suffix, became the standard chemical name only in the late 19th century, once glucose, fructose, and sucrose were understood as chemically distinct.

The premise that meat, not sugar, built the human brain is itself contested. A 2026 modeling study spanning 4 million years of hominin evolution found dietary sugars from fruit and honey were positioned to supply the brain's obligatory glucose demand before cooking made starch digestible, putting sugars at over 25% of dietary energy across that span and making carbohydrate foods as central to brain evolution as animal foods.

Structure/Chemical properties

Sucrose (C₁₂H₂₂O₁₁) is a disaccharide formed from one glucose and one fructose unit joined by a glycosidic bond between their anomeric carbons, a linkage that makes sucrose a "non-reducing" sugar, unlike most other disaccharides. This bond is readily hydrolyzed by the enzyme sucrase in the small intestine, releasing free glucose and fructose for absorption.

Function/Mechanism of Action

The body converts very little dietary carbohydrate to fat under normal conditions. A classic overfeeding study found that even with massive carbohydrate intake (up to 5000 kcal/day, 86% carbs), de novo lipogenesis only became substantial after glycogen stores were saturated at ~500 g; even then, fat gain from carbohydrate was far less than from dietary fat itself. Under typical mixed-diet conditions, net de novo lipogenesis accounts for <5% of daily fat storage, meaning the fear that dietary sugar is efficiently converted to body fat is not supported by the metabolic evidence.

When yeasts lack sugar they can send filaments into the intestinal wall; in very weak people Peat wrote they may reach the bloodstream. Adequate sugar with Milk, cheese, and Fruit was his preferred pattern. Meat as the main protein can skew phosphorus high relative to Calcium in his notes.

If the rest of your diet is good, the energy bursts from sugar should level off, and become a steady increased metabolic rate.

— Ray Peat

Peat rejected Robert Lustig's framing of fructose as uniquely toxic; he wrote the cited charts did not support the extreme interpretations in Lustig's presentations.

Medical uses/Effects

• Sugar is addictive: Peat equated the moral panic with misread craving from Hypothyroidism, not morphine-like addiction. Reward-system literature is often cited against the addiction label.
• Sugar makes kids hyperactive: A 1995 JAMA meta-analysis (23 experiments, 16 papers) found no consistent effect on behavior or cognition.
• Sugar causes diabetes: Peat traced the belief to pre-Bernard medicine; hyperglycemia in obesity overlaps cortisol and insulin-resistance patterns he tied more to PUFA and chronic stress than to sucrose alone.
• Avoid fruit when dieting: Peat cited inverse associations between fruit intake and diabetes versus positive associations for bread and pasta in epidemiology he reproduced.
• Sugar causes cancer: Cancer cells use amino acids and fats, not sugar alone. Some cohort data on sugar restriction and survival are weak or negative in summaries Peat's readers cite. Mouse work on ketogenic diets and metastasis has been reported in university press coverage; mechanisms remain contested.

Dosing

Two quarts of Milk plus a quart of orange juice daily supply enough Fructose and other sugars for general stress resistance in Peat's email notes; larger amounts of fruit juice, Honey, or other sugars can cover higher stress or established degenerative patterns when the rest of the diet is sound.

Peat wrote totals up to about ten ounces of sugar per day can be fine depending on metabolic rate; Budd and Piorry used up to twelve ounces therapeutically in the historical cases he cited. Appetite for sugar after stress is a reasonable guide to replenishing glycogen.

Refined granulated sugar is very pure but carries no essential nutrients, making it a temporary support or winter substitute when good fruit or tolerable honey is scarce. Brown sugar's mineral traces come with impurities he considered slightly toxic or allergenic; bleaching washes away Molasses residue, and the whitest grades were least likely to provoke reactions in his experience. Coconut sugar heated dark may be more allergenic; unheated forms suit some people. Fruit remains his first choice when quality is good.

When relying on refined sugar in poor fruit seasons, Peat emphasized Milk, cheese, eggs, fruit, and occasional liver and seafood over starchy Vegetables; cooked greens and mushrooms could replace starchy sides.

Cinnamon

Cinnamon is a bark spice used for flavor and blood-sugar marketing. Cassia cinnamon carries more coumarin than Ceylon cinnamon; food-level amounts are the practical guide.

Side/Adverse effects

Refined sugar's main real drawback isn't sugar toxicity itself but nutrient dilution: it supplies energy without the minerals, protein, or other nutrients that whole foods like fruit or milk carry alongside their sugar content, which is why it's treated here as a temporary or supplementary source rather than a dietary foundation. Impure brown or dark forms carry the added risk of allergenic/irritant residues from incomplete refining.

High-carb framing

"High carb" in this framework means ample carbohydrate from fruit, juice, sugar, honey, sucrose, and safe starches, set against modern low-carb fashion, not unlimited processed sweets. Mainstream nutrition treats sucrose and starch-heavy diets as metabolic villains without good evidence; adequate carbohydrate supports oxidative metabolism when thyroid, protein, and minerals are also adequate. He also cited 19th-century physicians who added large amounts of sucrose to diabetic patients' diets as a historical counterexample to the modern assumption that sugar intake causes diabetes. Adequate carbohydrate lowers the stress-hormone need that shows up when the body has to run on free fatty acids instead; see Keto for the contrast case. Pair carbohydrate with protein and minerals rather than eating it in isolation.

See also

• Fructose
• Glucose
• Starch
• Honey
• Milk
• Hypothyroidism
• Roadmap/03 - Diet