Alpha-GPC vs Citicoline: Which Choline Supplement Is Better?

TL;DR: Both alpha-GPC and citicoline cross the blood-brain barrier and raise brain acetylcholine levels far more effectively than choline bitartrate. Alpha-GPC is roughly 40 percent choline by weight and has additional evidence for growth hormone release and power output. Citicoline is only about 18 percent choline by weight but uniquely provides uridine, which independently supports neuronal membrane repair and synthesis. The clinical evidence base is somewhat deeper for citicoline, particularly in stroke recovery and aging populations. Alpha-GPC has a potential TMAO cardiovascular concern at high doses that citicoline does not share. For most people seeking cognitive support, citicoline is the safer and more versatile default; alpha-GPC is a reasonable alternative if physical performance or acute acetylcholine effects are a priority.

Introduction

If you have spent any time researching choline supplements for brain health, you have almost certainly encountered the same question: alpha-GPC or citicoline? Both compounds are widely available, both cross the blood-brain barrier, and both have legitimate clinical evidence behind them. Yet they are not the same molecule, they are not metabolized the same way, and they do not offer identical benefits.

The confusion is understandable. Most supplement marketing treats them as interchangeable “brain choline” options, differing only in brand name and price. That is an oversimplification. Alpha-GPC (alpha-glycerophosphocholine) and citicoline (cytidine diphosphate-choline, also known as CDP-choline) have distinct metabolic fates once they enter the body, and those differences matter for specific use cases.

This article is a detailed, evidence-based comparison. We cover how each compound is metabolized, what the clinical trials actually show, how they differ on safety, and who should choose which. If you want foundational context on why choline matters for the brain in the first place, start with our companion article on choline as a brain nutrient before diving in here.

How Each Supplement Works

Alpha-GPC: Metabolism and Mechanism

Alpha-GPC (alpha-glycerophosphocholine, also called choline alfoscerate in the European clinical literature) is a naturally occurring choline compound found in small amounts in the brain and in foods such as dairy, organ meats, and soy. It is approximately 40 percent choline by weight, making it one of the most choline-dense supplement forms available.

Upon oral ingestion, alpha-GPC is absorbed in the gut and enters systemic circulation. It crosses the blood-brain barrier efficiently, where it serves as a direct precursor for two critical pathways:

1. Acetylcholine synthesis. Alpha-GPC donates its choline moiety to choline acetyltransferase, the enzyme that combines choline with acetyl-CoA to produce acetylcholine. This is the pathway most relevant to memory, attention, and learning. Animal studies consistently show that alpha-GPC administration increases brain acetylcholine levels more effectively than equivalent doses of free choline or choline salts like choline bitartrate.

2. Phosphatidylcholine synthesis. The glycerophosphate backbone of alpha-GPC can be incorporated into phosphatidylcholine, the dominant phospholipid in neuronal cell membranes. This contributes to membrane structural integrity, though the magnitude of this effect from supplemental alpha-GPC is less well characterized than the acetylcholine pathway.

One distinctive feature of alpha-GPC is its pharmacokinetics. It raises plasma choline levels rapidly and substantially, producing a relatively sharp peak in circulating choline within one to two hours of ingestion. This rapid choline delivery is one reason alpha-GPC is sometimes preferred for acute cognitive or performance applications.

Citicoline: Metabolism and the Uridine Advantage

Citicoline (CDP-choline) follows a fundamentally different metabolic route. When taken orally, citicoline is rapidly hydrolyzed in the gut wall and liver into two components: choline and cytidine. These two metabolites enter systemic circulation separately and cross the blood-brain barrier independently.

Once in the brain:

1. Choline follows the same pathways as alpha-GPC-derived choline — it can be used for acetylcholine synthesis or incorporated into phosphatidylcholine via the Kennedy pathway (the CDP-choline pathway of phospholipid synthesis, ironically named after the same biochemical intermediate).

2. Cytidine is converted to uridine, a pyrimidine nucleoside with independent and significant neurotrophic properties. This is citicoline’s distinctive advantage. Uridine stimulates the synthesis of phosphatidylcholine and other membrane phospholipids through a separate mechanism from choline itself. It also promotes neurite outgrowth (the extension of neuronal processes), increases synaptic protein expression, and enhances dopamine release in certain brain regions.

The uridine component is not a minor footnote. Research by Wurtman and colleagues at MIT demonstrated that the combination of uridine and DHA (docosahexaenoic acid, the omega-3 fatty acid) synergistically increases synaptic membrane synthesis and dendritic spine density in animal models. This is the theoretical basis for combining citicoline with omega-3 supplementation, a stack that has mechanistic plausibility even though it has not been tested extensively in human cognitive trials.

Citicoline is approximately 18 percent choline by weight — substantially less than alpha-GPC’s 40 percent. On paper, this looks like a disadvantage. In practice, it means citicoline’s benefits are not solely attributable to choline delivery. You are getting two active compounds for the price of one.

Head-to-Head Comparison

Clinical Evidence: Alpha-GPC

Alzheimer’s Disease and Cognitive Decline

The strongest clinical evidence for alpha-GPC comes from European trials in patients with Alzheimer’s disease and age-related cognitive decline. The most cited study is De Jesus Moreno Moreno (2003), a multicenter, double-blind, randomized, placebo-controlled trial involving 261 patients with mild to moderate Alzheimer’s disease. Patients received 1200 mg/day of alpha-GPC (choline alfoscerate) or placebo for 180 days. The alpha-GPC group showed statistically significant improvements on the ADAS-Cog (Alzheimer’s Disease Assessment Scale-Cognitive Subscale), MMSE (Mini-Mental State Examination), and GDS (Global Deterioration Scale) compared to placebo.

These results are meaningful, though it is worth noting that the study was conducted in Italy, where alpha-GPC is classified as a pharmaceutical agent rather than a dietary supplement, and the trial design meets clinical standards that many supplement studies do not.

Earlier Italian studies from the 1990s, including work by Parnetti et al. (2001) and Canal and Iacono (1990), also reported positive cognitive outcomes in patients with various forms of dementia, though many of these trials had smaller sample sizes and less rigorous methodology by current standards.

Healthy Adults

The evidence for alpha-GPC in healthy, cognitively normal adults is thinner. A study by Hoffman et al. (2010) in young healthy adults found that a single dose of alpha-GPC did not significantly enhance cognitive performance, though there were non-significant trends toward faster reaction times. Parker et al. (2015) reported that 400 mg of alpha-GPC improved certain measures of reaction time and force production, but these were sports-performance studies rather than pure cognitive assessments.

The pattern that emerges is one that characterizes many nootropic compounds: the effects are most detectable when the system is compromised (aging, disease, stress) and less apparent in young, healthy, well-nourished individuals whose cholinergic systems are already functioning near capacity.

Growth Hormone and Physical Performance

Alpha-GPC has an additional evidence base that citicoline does not share: physical performance enhancement. Ziegenfuss et al. (2008) demonstrated that 600 mg of alpha-GPC taken 90 minutes before exercise significantly increased peak growth hormone secretion and peak bench press force compared to placebo. Bellar et al. (2015) found that six days of alpha-GPC supplementation (600 mg/day) increased lower-body isometric force production in college-aged men.

The growth hormone effect is particularly notable. While the acute GH spike from alpha-GPC is transient and unlikely to produce the dramatic body-composition changes associated with exogenous GH therapy, it may have modest benefits for recovery and body composition over time. This makes alpha-GPC of interest to athletes and physically active individuals in a way that citicoline is not.

Clinical Evidence: Citicoline

Stroke Recovery

Citicoline has the most robust evidence base in the context of stroke recovery and post-stroke cognitive impairment. Alvarez-Sabin et al. (2013) conducted a study in which patients who had suffered a first ischemic stroke received either citicoline (1000 mg/day) or no treatment for 12 months, followed by long-term follow-up. The citicoline group showed significantly less cognitive decline and better performance on neuropsychological testing at both 6 and 12 months compared to controls.

Davalos et al. (2002) conducted a larger pooled analysis of four randomized, double-blind, placebo-controlled trials involving 1,372 patients with acute ischemic stroke, examining oral citicoline at doses of 500 to 2000 mg/day. The pooled analysis showed an increased probability of complete recovery (global recovery at three months) in the citicoline-treated group, though the individual trials had mixed results, and a subsequent large trial (ICTUS, 2012) failed to confirm benefit in acute stroke specifically. The post-stroke cognitive recovery evidence, as distinct from acute neuroprotection, remains more consistently positive.

Aging and Cognitive Decline

The Cochrane Review by Fioravanti and Yanagi (2005) examined citicoline for cognitive and behavioral disturbances in elderly patients with chronic cerebral disorders. The review concluded that citicoline had a positive effect on memory and behavior, though the authors noted that many included studies were older and of variable quality.

More recent work has been more encouraging. A randomized controlled trial by Nakazaki et al. (2021) in healthy older adults (aged 60 and above) found that 500 mg/day of citicoline for 12 weeks significantly improved overall memory, specifically episodic memory, compared to placebo. This study is notable because it was conducted in a healthy aging population rather than in patients with diagnosed dementia.

Healthy Younger Adults

McGlade et al. (2012) published a notable study examining citicoline (as the branded ingredient Cognizin) in healthy adolescent females. Participants receiving 250 mg or 500 mg of citicoline daily for 28 days showed improved attentional performance on the Continuous Performance Test (CPT-II), a well-validated measure of sustained attention and impulsivity. The improvements were observed in both dosage groups, with the 500 mg group showing the largest effects.

A study by Bruce et al. (2014) used functional MRI to examine brain activation patterns in healthy middle-aged adults after citicoline supplementation. The citicoline group showed changes in activation patterns in frontal and temporal cortical regions during a sustained attention task, consistent with enhanced neural efficiency.

These studies collectively suggest that citicoline has cognitive effects that extend beyond clinical populations and into healthy adults seeking optimization — a claim that alpha-GPC’s evidence base in healthy populations does not support as strongly.

Dosing Guidelines

Alpha-GPC

• General cognitive support: 300–600 mg/day, taken in one or two divided doses.
• Clinical cognitive decline (based on Alzheimer’s trials): 1200 mg/day, typically divided into three doses of 400 mg.
• Physical performance / growth hormone support: 600 mg taken 60–90 minutes before exercise.
• Choline delivery: At 40 percent choline by weight, a 600 mg dose of alpha-GPC provides approximately 240 mg of choline.

Citicoline

• General cognitive support: 250–500 mg/day, taken once daily or in two divided doses.
• Clinical populations (stroke recovery, dementia): 1000–2000 mg/day, divided into two doses.
• Choline delivery: At 18 percent choline by weight, a 500 mg dose of citicoline provides approximately 90 mg of choline. However, total cognitive benefit should not be judged on choline delivery alone, given the uridine contribution.

For either supplement, it is sensible to account for dietary choline intake when calculating total choline status. If you eat two to three eggs daily, you are already getting 300 mg or more of choline from food, and a moderate supplement dose of either alpha-GPC or citicoline is likely sufficient to optimize brain choline availability. See our choline article for food source details and daily intake targets.

Safety and Side Effects

Both alpha-GPC and citicoline have strong safety profiles in clinical trials. Adverse event rates in most studies have been comparable to placebo. Common side effects, when they occur, tend to be mild and gastrointestinal — nausea, diarrhea, or stomach discomfort — and are more likely at higher doses.

Alpha-GPC: The TMAO Concern

The most important safety distinction between the two supplements involves trimethylamine N-oxide (TMAO). Alpha-GPC, like other sources of free choline, can be metabolized by gut bacteria into trimethylamine (TMA), which is subsequently oxidized in the liver to TMAO. Elevated circulating TMAO has been associated with increased cardiovascular risk in several large observational studies (Wang et al., 2011; Tang et al., 2013).

A 2021 retrospective cohort study by Zheng et al., published in JAMA Internal Medicine and analyzing data from over 12,000 participants in the UK Biobank, found that regular use of alpha-GPC supplements was associated with an increased risk of stroke and major adverse cardiovascular events over a 10-year follow-up period. This study generated considerable attention, and while it has important limitations (observational design, potential confounding, self-reported supplement use), it raised a genuine signal that warrants caution.

It is important to put this in perspective. The TMAO concern is not unique to alpha-GPC — any source of choline, including eggs, red meat, and choline bitartrate, can contribute to TMAO production. The concern is dose-dependent, and moderate alpha-GPC supplementation (300–600 mg/day) likely produces much less TMAO than the high doses (1200 mg/day) used in some clinical settings. Nevertheless, individuals with existing cardiovascular disease or elevated cardiovascular risk factors should be aware of this issue and may prefer citicoline as a precautionary measure.

Citicoline: Minimal TMAO Risk

Citicoline’s metabolic pathway appears to generate substantially less TMAO than alpha-GPC. Because citicoline is hydrolyzed into choline and cytidine before absorption, and because the choline yield per gram is much lower than alpha-GPC, the TMAO burden from typical citicoline doses is considerably smaller. No comparable cardiovascular signal has emerged in citicoline studies or observational data.

Citicoline’s safety profile is consistently described as excellent in clinical trials. Davalos et al. (2002) reported no significant difference in adverse events between citicoline and placebo across doses ranging from 500 to 2000 mg/day. The Cochrane Review similarly found no major safety concerns.

Interactions to Consider

Both supplements may theoretically interact with cholinesterase inhibitors (donepezil, rivastigmine, galantamine) used in Alzheimer’s treatment, potentially producing additive cholinergic effects. While this combination is sometimes used deliberately under medical supervision, it should not be undertaken without a physician’s guidance. Both supplements may also potentiate the effects of acetylcholine-enhancing nootropics such as racetams, which is relevant for the nootropic community.

Cost Comparison

Alpha-GPC is generally less expensive than citicoline on a per-serving basis, and substantially less expensive when normalized to choline delivery per dollar. As of 2026, typical retail pricing in the United States is approximately:

• Alpha-GPC (600 mg capsules): $0.30–0.60 per serving
• Citicoline (250–500 mg capsules): $0.50–1.00 per serving
• Citicoline as Cognizin (branded): $0.70–1.20 per serving

If your primary goal is maximizing choline delivery to the brain at the lowest cost, alpha-GPC wins. If you value the additional uridine pathway and the cleaner cardiovascular safety profile, citicoline’s premium may be justified.

Choline bitartrate remains the cheapest option by a wide margin ($0.05–0.15 per serving) but, as detailed in our choline article, it does not cross the blood-brain barrier effectively and lacks meaningful cognitive evidence. It is adequate for preventing deficiency-related organ dysfunction but is not a serious option for brain-targeted supplementation.

How They Compare to Choline Bitartrate

Choline bitartrate occupies a fundamentally different tier. It is roughly 41 percent choline by weight — slightly more than alpha-GPC — but its poor blood-brain barrier penetration makes it a suboptimal choice for anyone whose primary goal is cognitive enhancement. Studies that have directly compared plasma choline kinetics show that choline bitartrate effectively raises peripheral choline levels but does not produce the same brain choline or acetylcholine increases seen with alpha-GPC or citicoline.

Choline bitartrate is appropriate as a low-cost nutritional insurance policy: if you are concerned about overall choline intake for liver health, methylation support, or general nutritional adequacy, it will do the job. But if you are spending money on a choline supplement specifically because you want to support memory, attention, or neuroprotection, choline bitartrate is the wrong tool for the job. Both alpha-GPC and citicoline are decisively superior for brain-targeted applications.

Who Should Choose Which

Choose Citicoline If:

• Cognitive optimization is your primary goal. The dual mechanism (choline plus uridine) provides broader neurotrophic support than choline delivery alone.
• You are over 50 or concerned about age-related cognitive decline. The clinical evidence in aging populations is strongest for citicoline.
• You have cardiovascular risk factors. Citicoline avoids the TMAO concern associated with alpha-GPC at high doses.
• You are recovering from stroke or brain injury. The post-stroke cognitive recovery evidence specifically supports citicoline.
• You are already taking omega-3 supplements. Citicoline’s uridine metabolite synergizes with DHA for membrane synthesis, making the combination mechanistically compelling.

Choose Alpha-GPC If:

• You also want physical performance benefits. Alpha-GPC’s evidence for growth hormone release and power output makes it a dual-purpose supplement for athletes.
• You want the most choline per dollar. Alpha-GPC delivers more than twice the choline per gram as citicoline and costs less per serving.
• You prefer a rapid cholinergic effect. Alpha-GPC’s faster peak plasma choline may be preferable for acute, situational use (e.g., before a demanding cognitive task or workout).
• You are stacking with racetams or other cholinergic nootropics. The nootropic community has historically paired alpha-GPC with racetam compounds to provide acetylcholine substrate, and this combination has reasonable mechanistic logic.

Consider Using Both (at Lower Doses of Each) If:

• You want to cover both the direct choline/acetylcholine pathway (alpha-GPC’s strength) and the uridine/membrane synthesis pathway (citicoline’s strength) simultaneously. A combination of 300 mg alpha-GPC and 250 mg citicoline, for example, would provide both rapid choline delivery and uridine-mediated membrane support without excessive doses of either compound.

Practical Takeaway

1. Both alpha-GPC and citicoline are legitimate, evidence-backed choline supplements that outperform choline bitartrate for brain-specific goals. The choice between them is not about whether they work, but about which profile of benefits and risks aligns with your situation.

2. Citicoline is the more conservative and versatile default. Its uridine metabolite provides a mechanism that alpha-GPC cannot match, its cardiovascular safety profile is cleaner, and its evidence base in healthy adults and aging populations is slightly more developed.

3. Alpha-GPC makes sense for athletes and performance-focused users. If you want a choline supplement that also supports growth hormone release and physical power output, alpha-GPC is the better fit.

4. Be aware of the TMAO concern with alpha-GPC at high doses. If you have existing cardiovascular risk factors, this is a meaningful consideration that tips the balance toward citicoline.

5. Do not neglect dietary choline. No supplement replaces a choline-rich diet. Two to three eggs per day provide a strong choline foundation, and supplementation should fill gaps rather than serve as a substitute. See our full guide on choline as a brain nutrient for dietary strategies.

6. Dose appropriately. For general cognitive support, 250–500 mg/day of citicoline or 300–600 mg/day of alpha-GPC is the evidence-supported range. Higher clinical doses (1000+ mg/day) should be reserved for specific medical contexts and ideally supervised by a clinician.

7. If you combine citicoline with omega-3 fish oil, you are leveraging a synergy. Uridine from citicoline and DHA from fish oil work through complementary pathways to support synaptic membrane synthesis — a combination with strong mechanistic rationale even if large-scale human trial data are still pending.

Frequently Asked Questions

Can I take alpha-GPC and citicoline together?

Yes. There is no known adverse interaction between the two, and combining them at moderate doses (e.g., 300 mg alpha-GPC plus 250 mg citicoline) allows you to access both rapid choline delivery and the uridine-mediated membrane synthesis pathway. Be mindful of total choline intake from all sources (food plus supplements) and stay well below the Tolerable Upper Intake Level of 3,500 mg/day.

Which one raises acetylcholine more?

Alpha-GPC likely produces a faster and larger acute spike in brain acetylcholine due to its higher choline content per gram and rapid absorption kinetics. However, citicoline’s effects on acetylcholine are also well documented, and the clinical difference in cholinergic activation between the two at standard supplement doses has not been rigorously quantified in head-to-head human studies.

Is there a head-to-head clinical trial comparing the two?

Direct head-to-head randomized controlled trials comparing alpha-GPC and citicoline on cognitive outcomes in humans are extremely limited. Most of the comparative claims in the supplement industry are inferred from separate trials in similar but not identical populations, which makes definitive “winner” declarations premature. The few comparative studies that exist (mostly Italian, in dementia populations) have generally found similar efficacy, with methodological differences making clean comparisons difficult.

Does citicoline actually raise uridine levels meaningfully?

Yes. Oral citicoline supplementation has been shown to increase plasma uridine levels in human studies. Wurtman et al. (2000) demonstrated that citicoline administration raised plasma uridine significantly, and subsequent animal work showed corresponding increases in brain phospholipid synthesis. The uridine effect is not theoretical — it is a measurable pharmacological reality, and it is the primary reason citicoline is considered more than just a choline source.

Is the TMAO risk from alpha-GPC a reason to avoid it entirely?

Not necessarily. The TMAO concern is dose-dependent and context-dependent. At moderate supplemental doses (300–600 mg/day), the TMAO contribution from alpha-GPC is modest relative to what a diet rich in red meat, eggs, and fish already produces. The Zheng et al. (2021) UK Biobank study raised a legitimate signal, but it was observational and cannot establish causation. For individuals with no cardiovascular risk factors, moderate alpha-GPC use remains reasonable. For those with elevated cardiovascular risk, citicoline is the more prudent choice.

Are there food sources of alpha-GPC or citicoline?

Both compounds occur naturally in small amounts in food, but not in quantities sufficient for supplemental effects. Alpha-GPC is found in dairy products, organ meats, and soy lecithin. Citicoline (as CDP-choline) is present in organ meats and egg yolks. In practice, meaningful doses of either compound require supplementation.

Sources

• De Jesus Moreno Moreno, M. (2003). Cognitive improvement in mild to moderate Alzheimer’s dementia after treatment with the acetylcholine precursor choline alfoscerate: a multicenter, double-blind, randomized, placebo-controlled trial. Clinical Therapeutics, 25(1), 178–193.

• McGlade, E., Locatelli, A., Hardy, J., Kamiya, T., Morita, M., Morishita, K., … & Yurgelun-Todd, D. (2012). Improved attentional performance following citicoline administration in healthy adult women. Food and Nutrition Sciences, 3(6), 769–773.

• Alvarez-Sabin, J., Ortega, G., Jacas, C., Santamarina, E., Maisterra, O., Riba, M. D., … & Roman, G. C. (2013). Long-term treatment with citicoline may improve poststroke vascular cognitive impairment. Cerebrovascular Diseases, 35(2), 146–154.

• Fioravanti, M., & Yanagi, M. (2005). Cytidinediphosphocholine (CDP-choline) for cognitive and behavioural disturbances associated with chronic cerebral disorders in the elderly. Cochrane Database of Systematic Reviews, (2), CD000269.

• Davalos, A., Castillo, J., Alvarez-Sabin, J., Secades, J. J., Mercadal, J., Lopez, S., … & Noya, M. (2002). Oral citicoline in acute ischemic stroke: an individual patient data pooling analysis of clinical trials. Stroke, 33(12), 2850–2857.

• Nakazaki, E., Mah, E., Sanoshy, K., Citrolo, D., & Watanabe, F. (2021). Citicoline and memory function in healthy older adults: a randomized, double-blind, placebo-controlled clinical trial. The Journal of Nutrition, 151(8), 2153–2160.

• Bruce, S. E., Werner, K. B., Preston, B. F., & Baker, L. M. (2014). Improvements in concentration, working memory and sustained attention following consumption of a natural citicoline-caffeine beverage. International Journal of Food Sciences and Nutrition, 65(8), 1003–1007.

• Ziegenfuss, T. N., Landis, J., & Hofheins, J. (2008). Acute supplementation with alpha-glycerylphosphorylcholine augments growth hormone response to, and peak force production during, resistance exercise. Journal of the International Society of Sports Nutrition, 5(Suppl 1), P15.

• Bellar, D., LeBlanc, N. R., & Campbell, B. (2015). The effect of 6 days of alpha glycerylphosphorylcholine on isometric strength. Journal of the International Society of Sports Nutrition, 12, 42.

• Hoffman, J. R., Ratamess, N. A., Gonzalez, A., Beller, N. A., Hoffman, M. W., Olson, M., … & Jager, R. (2010). The effects of acute and prolonged CRAM supplementation on reaction time and subjective measures of focus and alertness in healthy college students. Journal of the International Society of Sports Nutrition, 7, 39.

• Parnetti, L., Mignini, F., Tomassoni, D., Traini, E., & Amenta, F. (2007). Cholinergic precursors in the treatment of cognitive impairment of vascular origin: ineffective approaches or need for re-evaluation? Journal of the Neurological Sciences, 257(1–2), 264–269.

• Wang, Z., Klipfell, E., Bennett, B. J., Koeth, R., Levison, B. S., DuGar, B., … & Hazen, S. L. (2011). Gut flora metabolism of phosphatidylcholine promotes cardiovascular disease. Nature, 472(7341), 57–63.

• Zheng, Y., Li, Y., Bhupathiraju, S. N., Wang, D. D., Rimm, E. B., & Hu, F. B. (2021). Association of alpha-glycerophosphocholine supplement use with incident stroke and cardiovascular events. JAMA Internal Medicine, 181(9), 1209–1211.

• Wurtman, R. J., Regan, M., Ulus, I., & Yu, L. (2000). Effect of oral CDP-choline on plasma choline and uridine levels in humans. Biochemical Pharmacology, 60(7), 989–992.

• Wurtman, R. J., Cansev, M., Sakamoto, T., & Ulus, I. H. (2009). Use of phosphatide precursors to promote synaptogenesis. Annual Review of Nutrition, 29, 59–87.