Are Almonds Poisonous? Different Varieties Explained

Unlike sweet almonds, bitter almonds contain glycoside amygdalin. When ingested, this substance breaks down into hydrogen cyanide, which is a deadly toxin.

Almonds are one of the most popular tree nuts worldwide. They’re nutritious and generally thought to benefit your health.

That said, certain varieties are known to increase the likelihood of food poisoning, digestive troubles, and potentially even your risk of diseases like cancer. Others are, in fact, poisonous and ultimately unfit for human consumption.

This article reviews the different types of almonds, which ones are considered safe to eat, and which ones are best avoided.

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Almonds come in different varieties

Almonds can be divided into two major species that are very similar genetically — bitter almonds and sweet almonds.

Sweet almonds have a slightly nutty flavor and are the ones you typically find on your supermarket shelves or in almond-based products, such as nougat or marzipan.

As their name implies, bitter almonds have a very bitter flavor. This type grows both in the wild and commercial settings and is mainly used to make bitter almond pastes or extracts. They’re not typically found in grocery stores.

Bitter almonds were the most common species grown until a few thousand years ago when a genetic mutation inhibited the almond tree’s ability to make amygdalin — the compound that gives bitter almonds their bitter taste (1).

This mutation is what gave rise to sweet almonds and allowed the domestication of the almond tree that we know today.

Raw bitter almonds are poisonous

Bitter almonds contain a toxin known as glycoside amygdalin. When eaten, this toxin gets broken down into several compounds, including hydrogen cyanide — a toxic compound that can cause death (2, 3).

Case studies suggest that swallowing 6–10 raw bitter almonds is sufficient to cause serious poisoning in the average adult, while ingesting 50 or more can cause death. Smaller numbers are likely to have the same harmful effects in children or young adults (4).

Interestingly, hydrogen cyanide appears to leach out of the almonds during heat processing. For instance, baking, microwaving, and boiling reduces the cyanide content of bitter almonds by 79%, 87%, and 98%, respectively (5).

However, more studies are needed to confirm these findings, as well as to determine the exact amount of heat-processed bitter almonds that’s considered safe to eat.

Until more is known, bitter almonds are best avoided.

Sweet almonds are safe to eat

Although sweet almonds still harbor some amygdalin, their content of this compound is up to 1,000 times lower than that of bitter almonds. Such small amounts of amygdalin are insufficient to produce dangerous amounts of hydrogen cyanide (2).

As a result, sweet almonds are typically considered safe to eat.

Almonds can be sweet or bitter. Bitter almonds contain toxic compounds that may cause poisoning and accidental death. Sweet almonds are considered safe to eat, and more research is needed to confirm the safety of heat-processed bitter almonds.

Sprouted and moldy almonds may also be risky to eat

Sprouting almonds can help your body absorb the nutrients they contain more easily. The downside is that sprouted nuts and seeds bear a much higher risk of becoming contaminated with harmful bacteria, such as Salmonella (6, 7).

Research suggests that nut butters made from sprouted nuts, including sprouted almonds, increase your risk of food poisoning. Therefore, pregnant women and people with compromised immune systems may particularly benefit from avoiding them (7).

Peanuts and tree nuts, such as almonds, walnuts, hazelnuts, cashews, pistachios, and Brazil nuts, also may contain toxic molds (8, 9).

In turn, these molds produce mycotoxins, which are toxic compounds linked to various health problems, including digestive disorders and liver tumors (8, 9, 10).

Mold contamination appears likelier in raw, unsalted nuts, compared with roasted and salted varieties. Researchers believe that the high temperatures used during roasting, as well as the lower moisture content caused by the addition of salt, are to thank for this (9).

The Food and Drug Administration (FDA) and European Food Safety Authority (EFSA) have both set maximum levels of mycotoxins considered safe in foods (11, 12).

If you’re worried about the mold content of almonds, consider checking whether a regulatory body has established safe levels in your part of the world. If not, consider sticking to roasted or salted varieties to reduce your risk.

Sprouted almonds and products derived from them may contain harmful bacteria that increase your risk of food poisoning. Although almonds also risk being contaminated with toxic molds, most countries make sure they do not exceed safe levels.

The bottom line

Almonds can be sweet or bitter.

Sweet almonds are the ones typically found in supermarkets and considered safe to eat. However, pregnant women and people with compromised immune systems may wish to avoid sprouted sweet almonds to minimize their risk of food poisoning.

Bitter almonds are those that naturally contain a toxin that your body breaks down into cyanide — a compound that can cause poisoning and even death. For this reason, raw bitter almonds should not be eaten.

Boiling, roasting, or microwaving bitter almonds may help reduce their toxin content and make them safer to eat. However, more research is needed to confirm this.