Groundnut Stew with Sweet Potato and Yogurt

What it is

Roasted peanuts, blended with water into a smooth paste and stirred into a pot of onion, garlic, ginger and tomato, where sweet potato simmers soft and the broth turns creamy and orange. Spinach wilts in at the end, lime wakes it all up, and it goes over white rice with a cool spoon of Greek yogurt, chopped peanuts and coriander.

The idea comes from West Africa. Britannica describes mafé as meat in a peanut or peanut butter sauce over rice or couscous, a dish that started in Mali and spread across the region; some versions are a stew with tomato, onion and garlic. I've kept the peanut sauce, that base and the rice, and left out the meat, because I'm lacto-vegetarian. The sweet potato and spinach are my additions, so this is West African-style, and the name mafé stays with the real thing.

It's Protein Champion number ten, and this time the teammate isn't the rice.

Why you should eat it

Here's the short version, before anyone files peanuts under bar snacks. USDA FoodData Central lists 24.4 g of protein per 100 g of dry-roasted peanuts, plus 8.4 g of fiber in that same 100 g. The honest part: that 100 g also holds 49.7 g of fat, more than half of it monounsaturated (26.2 g) and 7.72 g saturated, and 587 kcal. Peanuts are dense in everything, so each bowl gets about 45 g, not half a jar. Unsalted, they carry 6 mg of sodium per 100 g (same database), so the peanuts add almost none: most of the bowl's sodium comes from the salt you measure and the tinned tomatoes. In this pot the sweet potato matches the peanuts on fiber, and the Greek yogurt adds 10.2 g of protein per 100 g (same database). The card below has the per-bowl numbers. The yogurt's other job comes while it simmers.

Tips

• No high-speed blender? The paste comes out a little grainy, and in a stew nobody minds. Blend a minute longer and scrape the sides once.
• Yogurt goes on in the bowl, never into the pot, so it stays cool and tangy. It's the lysine teammate, so be generous.
• Serve from the middle of the table, toppings and extra chilli flakes in little bowls around the pot, and let everyone finish their own.
• Cook the stew on Sunday and half the week's lunches are sorted. Make the rice fresh each time: it takes 20 minutes.
• Peanuts are one of the nine major food allergens the FDA lists, and this dish is built on them, in the sauce and on top. Reactions can be severe, even life-threatening. If anyone at your table has a peanut allergy, this recipe isn't for them. It also contains milk, in the yogurt.

Substitutions

• Roasted peanuts and a blender: 1/2 cup plus 1 tbsp (145 g) of natural peanut butter, peanuts only (salt is fine), whisked with the 1 cup of water No blender needed. Check the label: USDA's smooth peanut butter record (172470) lists 10.5 g of sugars per 100 g against 4.9 g for dry-roasted peanuts (173806), so many jars carry added sugar. The card is built on dry-roasted peanuts, so it won't match.
• Plain nonfat Greek yogurt: Plain whole-milk yogurt, same weight, gelatin-free (check the label) Softer, less tangy and much lower in protein: USDA lists 3.47 g per 100 g of plain whole-milk yogurt (171284) against 10.2 g for nonfat Greek (170894). The card uses the Greek yogurt.
• Long-grain white rice: Brown rice USA Rice gives whole grain rice 40 to 45 minutes on the stovetop, so start it before the stew. The card is built on white rice.
• Tinned chopped tomatoes: A no-salt-added tin Cuts the sodium: by my sums, the tin on the card (170051) brings about 460 mg of the pot's sodium. Salt at the end, to taste.

Storage

Stew, without the yogurt and toppings: fridge 3 to 4 days, freezer 2 to 3 months (FoodSafety.gov chart, soups and stews). It thickens as it stands, so loosen it with a splash of water when you reheat. Rice: chill leftovers fast, ideally within an hour, in small portions and never cooling in the pan. Keep it in the fridge no more than a day and reheat it once only, until steaming hot all the way through (UK Food Standards Agency).

While it simmers: the missing red stars

Rice quiet under its lid, stew bubbling, a stir every five minutes. That's 18 minutes, so pull up a chair.

First, a name check, because the snack aisle got this one wrong. Britannica files the peanut under legumes, the family of Champion number one's black beans, and says plainly that it isn't a true nut. Its pods even ripen underground, so groundnut, another name Britannica lists, is the more honest label.

Now the big idea. Protein is a chain of smaller pieces called amino acids, and nine of them your body can't make, so food has to bring them. An FAO expert group set how much of each one a gram of protein should carry. Check a food against that list, and the one that falls shortest sets the pace.

For peanuts, that's lysine. In USDA FoodData Central's record for dry-roasted peanuts, lysine is 3.48 g of every 100 g of protein, against the 4.8 g FAO asks for: about 73%. Every other one clears its line.

Picture a nursery craft table making paper crowns, one red star per crown. The box overflows with card and glitter but runs short on red stars, so the class can finish only as many crowns as it has stars. That's peanut protein: plenty of everything, one short supply.

Plot twist against Champion number one. There, rice was the partner, because the beans had lysine to lend. Here the rice is short on red stars too: 3.61 g of lysine per 100 g of its protein (USDA again). So the teammate is the yogurt: 8.09 g per 100 g of protein in USDA's Foundation record for nonfat Greek yogurt, about 169% of what FAO asks. That's the kid who walks in with a whole bag of stars. Across the whole bowl, lysine lands at 5.08 g per 100 g of protein, about 106%.

The picture stops in two places. These are shares of the protein sitting in the food, before digestion has its say, so this isn't an FAO protein score, and FAO notes that processing can turn some lysine into a form the body can't use; these peanuts are roasted. And a body isn't a craft table finishing one crown at a time. Whether two proteins need to share a plate at all is a question Champion number one takes on. Here they share a bowl anyway.

So, in one line: peanut protein runs short on lysine, the rice can't help with that, and the yogurt on top fills the gap.

Case one: a peanut shake for new lifters around 60

Thirty-nine untrained adults in Auburn, Alabama, 17 women and 22 men, average age 58.6, started full-body strength training twice a week. Twenty also drank a daily shake of 75 g of defatted peanut powder, about 30 g of protein; the other 19 drank nothing extra. A 6-week group and a 10-week group were pooled.

Whole-body lean mass changed no differently between the groups, and neither did muscle protein building after the first session. The front thigh was the exception: 1.8 to 2.0 cm thick with the shake, a flat 2.1 cm without it (p = 0.041), a gain the authors call small, just above what their ultrasound can tell apart from noise. In the 10-week group, the strength of the back of the thigh, measured as peak torque, rose from 49.5 to 75.0 newton-metres with the shake, and not significantly without it.

For your plate: in older beginners, a lot of extra peanut protein bought a little extra thigh.

Where it stops: there was no placebo drink, so everyone knew their group, and the shake group started with the thinner thigh. The pandemic cut the second group short. The authors call the results preliminary and say it's still open whether the shake's extra energy did the work. The Peanut Institute Foundation paid for it, with no role in the design or analysis, the paper says.

Case two: the sequel with college beginners

Same lab, same powder, younger crowd: 47 untrained students aged 18 to 30 at Auburn University, 34 women and 13 men, trained twice a week for 10 weeks. The peanut group took the same 75 g a day, 30.1 g of protein, after each workout; the others took nothing.

Everyone got stronger, with no difference between the groups in estimated one-rep maxes. In the women, lean mass rose 1.4 kg with the powder against 0.7 kg without, and front-thigh thickness 0.28 cm against 0.17 cm, but neither gap passed the statistics test (p = 0.088 and 0.099). The authors' own verdict: the peanut protein was largely ineffective at producing better gains than no supplement.

For your plate: the sequel didn't repeat case one's thigh result, and the training did the heavy lifting. One bowl here holds about 11 g of peanut protein, a third of their daily dose.

Where it stops: 10 weeks is short, only 13 men were analysed, and there was no placebo and no whey group. By the authors' testing, essential amino acids are about 30% of this peanut protein, against the roughly 50% they cite for whey. They suspect beginners respond so strongly to training that a supplement is hard to see, or that 30 g was too little. Same funder, again with no role in the design, the paper says.

Case three: a daily handful in Barcelona

Ninety healthy young adults in Barcelona, average age 22.7 and about 70% women, were split three ways for six months: 25 g a day of skin-roasted peanuts, 2 tbsp (32 g) of peanut butter made only of peanuts and sea salt, or 32 g of a control butter built on peanut oil, with no fiber or polyphenols. Sixty-three finished.

Two cholesterol ratios, total to HDL and LDL to HDL, came out lower with the skin-roasted peanuts than with the control butter (p = 0.019 and 0.008). The peanut butter, the nearest thing to the paste in this pot, showed no difference. Weight, blood sugar and blood pressure didn't separate.

The same paper pooled 11 trials, 643 people: peanut products lowered triglycerides, another blood fat, by 0.13 mmol/L (about 11.5 mg/dL), at moderate certainty, with no clear change in LDL, HDL, blood sugar or blood pressure. In people with or at risk of metabolic syndrome, weight crept up 0.97 kg.

For your plate: a small hint that the whole peanut, skin on, did something the peanut-oil butter didn't.

Where it stops: each group held 19 to 23 people. The peanut group started with better ratios, and all three groups' ratios rose, so my own reading is that part of the final gap may be the starting gap. Most pooled results were rated low or very low certainty. The Peanut Institute helped pay, alongside Spanish public grants, and the paper says no funder had a role in the design or writing.

Case four: peanuts inside a weight-loss diet

In Adelaide, Australia, 107 adults, average age 58, 65% women, average BMI 33 and all at moderate or high risk of type 2 diabetes, followed a calorie-restricted diet for six months. About half also ate 35 g of lightly salted dry-roasted peanuts before two main meals, 70 g a day; the others got low-fat advice and a grocery voucher instead. Seventy-six finished.

Both groups lost about the same weight, 6.72 kg with peanuts and 6.60 kg without. Systolic blood pressure, the top number, fell 9.46 mmHg with peanuts and 4.13 without, a gap of 5.33 at six months (p = 0.008), though across all the visits together it fell just short of the statistics line (p = 0.063). Blood sugar markers improved in everyone, equally.

For your plate: in this trial, a measured portion of peanuts sat inside a weight-loss diet without slowing it down. One bowl of this stew holds about 45 g.

Where it stops: these were mostly adults living with obesity, not young lifters, and what they ate was self-reported. More people dropped out of the control group, and the authors note that earlier pooled studies found no peanut effect on systolic pressure. The Peanut Institute funded it. If you're managing blood pressure or blood sugar, take this to your doctor before you change your plate around it.