Meals and cholesterol: what the research has found

Cholesterol is one of the most studied links between food and a lab result. Researchers have tested changes to the fats people eat, added fibre and specific foods, and combined several of these at once. Some of the changes they measured were small; one combination was much larger, under conditions that are hard to repeat at home.

This article reports what those studies found, how big the changes were, and what each study cannot tell you. It is research, not a plan, and it says nothing about your own numbers.

A note on units: LDL cholesterol is reported in mmol/L in most of the world and in mg/dL in the US. 1 mmol/L is about 38.7 mg/dL.

Saturated fat: what long trials found

A Cochrane review, updated in 2020 [1], pooled 15 randomised trials with about 56,700 participants, each lasting at least two years, in which people ate less saturated fat than a comparison group.

Cutting saturated fat was followed by small reductions in total and LDL cholesterol. Across 12 trials, combined cardiovascular events were 17 percent less likely; the reviewers rated this moderate-quality evidence. Trials with larger cuts in saturated fat, and larger falls in cholesterol, tended to show larger effects. In trials of people without heart disease, 56 people would need to eat less saturated fat for about four years for one of them to avoid a cardiovascular event.

The review found little or no effect on deaths from any cause or from heart disease, and little or no effect on HDL cholesterol or triglycerides. Replacing saturated fat with polyunsaturated fat or with carbohydrate looked similar; there was too little data on other replacements.

What it cannot tell you. The trials varied widely, from providing all food to giving advice, and the results differed between them. The effect is on groups over years; it does not predict one person's result.

Soluble fibre and oats

Soluble fibre is one of the most tested food components for cholesterol. The trials below used fibre from oats, psyllium and pectin.

• A 1999 meta-analysis of 67 controlled trials [2] found that each gram of soluble fibre, in the range of 2 to 10 g a day, was linked to an LDL cholesterol about 0.057 mmol/L (about 2 mg/dL) lower. The authors give an example: about 3 g of soluble fibre from oats, roughly three 28 g servings of oatmeal, was linked to about 0.13 mmol/L (about 5 mg/dL) lower total and LDL cholesterol. Their own conclusion is that the effect is small within the amounts people can practically eat.
• A 2016 meta-analysis of 58 trials with 3,974 participants [3] looked at oat beta-glucan, the soluble fibre in oats. At a median of 3.5 g a day, LDL cholesterol was 0.19 mmol/L (about 7 mg/dL) lower than in the comparison groups. The results varied a lot between trials, more than the authors could explain.

What they cannot tell you. These are averages across many small trials of a few weeks or months. They measure cholesterol, not heart disease.

Plant sterols and stanols

Plant sterols and stanols occur naturally in foods of plant origin, such as vegetable oils, nuts and seeds, and some food products are enriched with them [4]. A 2014 meta-analysis of 124 studies [4] found that 0.6 to 3.3 g a day was linked to LDL cholesterol 6 to 12 percent lower on average, with the effect growing up to about 3 g a day. Studies of more than 4 g a day were too few to pool.

What it cannot tell you. Most of these amounts come from fortified products rather than ordinary meals. The analysis measured LDL cholesterol, not heart disease, and two of its three authors were employed by Unilever, which, as the paper's own disclosure says, markets food products enriched with plant sterols.

Combining several foods: the "portfolio" trials

A Canadian research group tested what happens when several of these foods are combined in one way of eating: plant sterols, soy protein, viscous fibre and almonds, on top of a diet low in saturated fat.

The 2003 trial [5] randomly assigned 46 adults with raised cholesterol to one of three diets for one month: a diet very low in saturated fat, the same diet plus the statin lovastatin 20 mg a day, or the combined "portfolio" diet. LDL cholesterol fell by 8.0 percent on the low-saturated-fat diet, 30.9 percent with the statin and 28.6 percent on the portfolio diet; the statin and portfolio results were not significantly different.

The 2011 trial [6] asked a harder question: what happens when people choose and cook their own food for six months, with advice? 351 adults with raised cholesterol at four Canadian centres were randomly assigned to advice on a low-saturated-fat diet or to portfolio advice given at two levels of support. LDL cholesterol fell by about 13 to 14 percent with either level of portfolio advice (about 24 to 26 mg/dL) and by 3 percent with the low-saturated-fat advice. People who followed the portfolio advice more closely tended to have larger falls.

What they cannot tell you. The first trial lasted one month and the research centre supplied the food, which is why its result is so much larger than the second. The second shows what happened with advice over six months: a real but smaller change, and between 18 and 26 percent of participants dropped out. Neither trial measured heart attacks or strokes, and neither shows that diet can replace a medicine someone has been prescribed.

What the research, taken together, does and does not say

• Changes to fats and fibre were followed by measurable changes in LDL cholesterol in trials, usually small for any single food.
• Combining several changes was followed by larger falls, largest when the food was provided and smaller when people chose their own food.
• Over years, eating less saturated fat was followed by fewer combined cardiovascular events in pooled trials, but not by fewer deaths.
• Most of these studies measured cholesterol, not illness, and none can predict what will happen to any one person.

Where a food log fits

The trials above asked people to keep up a pattern of eating for weeks or months, and the 2011 trial found that how closely people followed the advice mattered. A food log is one way to keep a record of what you actually ate. Senumi lets you log meals by photo, barcode, typed description or database search, and keep total, LDL and HDL cholesterol readings next to them, typed in or read from a lab report, so you have the record in one place when you talk to your doctor.

Senumi does not change cholesterol, does not give medical advice, and its food and portion figures are estimates. It is a notebook, not a treatment.

Sources

1. Hooper L, Martin N, Jimoh OF, Kirk C, Foster E, Abdelhamid AS. Reduction in saturated fat intake for cardiovascular disease. Cochrane Database Syst Rev. 2020;8:CD011737.
2. Brown L, Rosner B, Willett WW, Sacks FM. Cholesterol-lowering effects of dietary fiber: a meta-analysis. Am J Clin Nutr. 1999;69(1):30-42.
3. Ho HV, Sievenpiper JL, Zurbau A, et al. The effect of oat β-glucan on LDL-cholesterol, non-HDL-cholesterol and apoB for CVD risk reduction: a systematic review and meta-analysis of randomised-controlled trials. Br J Nutr. 2016;116(8):1369-82.
4. Ras RT, Geleijnse JM, Trautwein EA. LDL-cholesterol-lowering effect of plant sterols and stanols across different dose ranges: a meta-analysis of randomised controlled studies. Br J Nutr. 2014;112(2):214-9.
5. Jenkins DJ, Kendall CW, Marchie A, et al. Effects of a dietary portfolio of cholesterol-lowering foods vs lovastatin on serum lipids and C-reactive protein. JAMA. 2003;290(4):502-10.
6. Jenkins DJ, Jones PJ, Lamarche B, et al. Effect of a dietary portfolio of cholesterol-lowering foods given at 2 levels of intensity of dietary advice on serum lipids in hyperlipidemia: a randomized controlled trial. JAMA. 2011;306(8):831-9.