Quais São Os Efeitos Colaterais Da Soja?

2024 Autor: Cecilia Ryder | [email protected]. Última modificação: 2023-12-17 14:22

A soja é uma leguminosa amplamente consumida. É um alimento básico da dieta asiática e é usado como ingrediente em diversos alimentos processados. A proteína da soja (proteína de soja) pode substituir as proteínas animais em sua dieta e é obtida após a remoção da casca externa da soja e seus ácidos graxos (1), (2).

Embora a soja seja rica em nutrientes como cálcio, ferro, zinco e aminoácidos, ela pode causar alguns efeitos colaterais (3).

Quando consumidos em excesso, podem interferir na medicação para regulação da tireoide e causar desequilíbrio da testosterona, alergias e proliferação de câncer.

Além disso, o uso a longo prazo de produtos de soja em excesso pode não ser seguro. Neste post, discutimos a soja e seus possíveis efeitos adversos. Continue lendo.

Índice

• Qual é o principal problema com a soja?
• O que acontece quando você consome soja? O que causa os efeitos adversos?
• Quais são os efeitos adversos da soja (proteína de soja)?
• Quais produtos de soja você deve evitar?
• Quanta soja é segura para comer em um dia?
• Comer muita soja é prejudicial?

Qual é o principal problema com a soja?

O principal problema com a soja é seu conteúdo de isoflavonas.

A soja é um reservatório de fitoestrogênios (isoflavonas), que são estrutural e funcionalmente semelhantes ao hormônio estrogênio em seu corpo (3). As isoflavonas são uma classe de fitoestrógenos (também chamados de proteínas de soja) encontrados na soja e nos produtos de soja. A tabela a seguir deve dar uma ideia sobre o conteúdo de isoflavonas em diferentes alimentos à base de soja.

Alimentos de soja não fermentados	Conteúdo de isoflavona (mg)
leite de soja, 1 xícara	6
tofu (coalhada de feijão), macio, 3 onças	20
soja, madura, fervida, ½ xícara	55
soja, torrada a seco, 1 onça	40
edamame, fervido, ½ xícara	16
queijo de soja, 1 onça	2
hambúrguer de soja, 1 hambúrguer	5
Alimentos fermentados de soja	Conteúdo de isoflavona (mg)
missô, 3 onças.	37
natto, 3 onças.	70
tempeh, cozido, 3 onças.	30
molho de soja, 1 colher de sopa	0,02

Fonte: Harvard THChan School of Public Health

Fitoestrogênios de soja têm sido usados para compensar a deficiência do hormônio estrogênio. A proteína de soja é uma parte da terapia de reposição de estrogênio administrada a mulheres que estão na menopausa (3).

Alguns estudos epidemiológicos sugerem que a ingestão alimentar de fitoestrogênios pode reduzir a incidência de doenças cardiovasculares na pós-menopausa, osteoporose e ondas de calor, entre outros sintomas. Dados contrastantes também relataram o potencial dos fitoestrógenos para prevenir o câncer de mama e de próstata (3).

No entanto, os benefícios da soja não são claros. Na verdade, alguns outros estudos também afirmam que a proteína de soja pode causar danos potenciais (3).

O que acontece quando você consome soja? O que causa os efeitos adversos?

Quando você consome soja (proteína de soja) em qualquer forma, as isoflavonas de soja (os fitoestrogênios) se ligam aos receptores de estrogênio em seu corpo. Esses fitoestrogênios competem com o estrogênio natural para se ligarem aos receptores. Isso resulta em uma atividade estrogênica ou antiestrogênica fraca. Em outras palavras, as isoflavonas de soja podem tornar o estrogênio natural em seu corpo menos eficaz (3), (4).

Essas interações podem levar a um desequilíbrio hormonal e causar mudanças relacionadas ao gênero nas meninas. Eles também podem exercer efeitos anti-androgênicos em homens. Os homens podem começar a desenvolver seios (ginecomastia) e experimentar uma queda na concentração de espermatozoides quando fazem uma dieta rica em soja (3).

A overdose de isoflavona por um longo período pode estimular o endométrio (útero) e os seios nas mulheres. Portanto, qualquer pessoa que tenha sido tratada para câncer de mama geralmente deve evitar a proteína de soja (3).

Os fitoestrogênios podem afetar vários processos fisiológicos e patológicos do corpo. Doses elevadas de isolados de soja podem causar efeitos adversos na reprodução, pele, remodelação óssea, sistema cardiovascular, sistema nervoso, sistema imunológico e metabolismo.

Vamos dar uma olhada nos efeitos adversos da soja (proteínas de soja) em detalhes.

Quais são os efeitos adversos da soja (proteína de soja)?

1. Pode interferir na regulação da tireoide

Alimentos à base de soja podem aumentar o risco de desenvolver hipotireoidismo em pessoas com função tireoidiana comprometida. Esses indivíduos podem desenvolver bócio e doença autoimune da tireoide. Esse risco aumenta ainda mais quando a ingestão de iodo do indivíduo é baixa (5).

Descobriu-se que as isoflavonas de soja inibem a atividade de uma enzima chamada peroxidase tireoidiana. Esta enzima é necessária para a síntese do hormônio tireoidiano. É por isso que você pode correr o risco de hipotireoidismo ao comer muita proteína de soja (6).

Os produtos da soja também interferem na absorção da levotiroxina (L-tiroxina), medicamento usado no tratamento da deficiência do hormônio tireoidiano (7). Como as proteínas de soja parecem alterar a disponibilidade dos medicamentos, você pode ser desaconselhado de consumir proteína de soja se tiver um desequilíbrio da tireóide.

No entanto, apenas uma alta ingestão de isoflavonas de soja não parece aumentar o risco de hipotireoidismo, a menos que associada ao consumo inadequado de iodo na dieta. Portanto, a influência da proteína de soja na glândula tireóide é discutível. Mais pesquisas são necessárias a esse respeito.

2. Pode causar desequilíbrio da testosterona

Um estudo foi realizado em 12 indivíduos do sexo masculino que consumiram 56 g de isolado de proteína de soja diariamente durante quatro semanas. Como resultado, seus níveis séricos de testosterona caíram 19% (8). Embora os dados fossem inconsistentes, descobriu-se que a proteína de soja diminuiu os níveis de testosterona sérica em homens saudáveis.

Diz-se que a proteína de soja tem efeitos adversos na função reprodutiva masculina. No entanto, não existem estudos específicos a esse respeito. De fato, alguns estudos em animais afirmam que as isoflavonas de soja não exercem nenhum efeito feminilizante nos homens (9).

Most of the observations are based on lab and animal studies. Hence, the relationship between soy isoflavones and testosterone is inconclusive (10).

3. May Elicit Hypersensitivity (Allergy)

Soy products can cause allergies or hypersensitivity in children and adults. Often, soy allergy starts in infancy, with reaction to soy-Soy products that can cause allergies or hypersensitivity in children and adults. Often, soy allergy starts in infancy with a reaction to soy-based infant formula. However, most children outgrow soy allergy (11).

Generally, soy allergy is uncomfortable but not severe. An allergic reaction to soy is rarely frightening or lethal. Symptoms of soy allergy may include tingling in the mouth, eczema or itchy skin, wheezing, diarrhea, stomach ache, vomiting, and skin redness (flushing) (12).

If you experience any of these symptoms, you may have a soy allergy. Get tested to confirm the allergy. If tested positive, you may be advised against having soy products/isoflavones.

4. May Increase The Risk Of Cancer Proliferation

Soy isoflavones (one of them being genistein) may stimulate the proliferation of cancer cells in your body. This is especially true in the case of estrogen-dependent breast cancer, as soy isoflavones tend to have estrogenic effects (13).

As per animal studies, genistein may deregulate the cell cycle and trigger tumor development. It acts by triggering the estrogen receptors (14).

Contrarily, human studies show an inverse relationship between cancer and isoflavones. Soy intake was also found to reduce the incidence and death rate caused due to breast cancer. This could be because of the anti-estrogenic effect exerted by phytoestrogens (13).

The amount and source of soy isoflavones also greatly impact breast cancer risk (14).

5. May Trigger Alzheimer’s Dementia

Traditionally, soy foods were used in cooking only after fermenting. This two-step routine would destroy most of the anti-nutrients in soy, such as isoflavones (like genistein and daidzein) and DNA-altering enzymes (like topoisomerases) (15).

When you eat unfermented, cooked/uncooked soy foods, these anti-nutrients may affect the vital systems of your body, including your brain (15).

These anti-nutrients in soy could have detrimental effects on many individuals. Soy isoflavones could increase the risk of Alzheimer’s dementia (15).

If you are dealing with dementia or have a family history of this condition, it is safe to reduce your soy consumption (15).

6. May Cause Infant Health Issues

Infant food formulas contain fair amounts of soy protein/isoflavones. Infants who are fed these formulas are exposed to 5.7–11.9 mg isoflavones/kg body weight during the first four months of life (16).

These kids are exposed to 6–11 times higher levels of isoflavones than adults. This could lead to disturbances in the reproductive health and endocrine function in the child. The major isoflavones, daidzein and genistein, preferentially bind to the estrogen receptors in the body (16).

However, these conclusions are based on animal studies. Human studies may give a different picture. Moreover, currently available soy-based formulas show no overt toxicities in healthy infants (16), (17). Hence, check with your pediatrician before giving soy-based formulas to your child.

7. Unsure Osteoprotective Effects

Soy protein has shown to conserve bone mineral density, particularly in postmenopausal women. In perimenopausal women, the soy isoflavones were shown to prevent bone loss from the lumbar spine. These compounds had no significant effect (neither positive nor negative) on bone formation and/or bone resorption (18).

In some cases, the mineral balance could be impaired with soy consumption. Soybeans contain (by weight) about 1–3% phytic acid (also called phytate). Phytic acid is an anti-nutrient that binds to minerals like zinc, iron, and calcium. Along with soy isoflavones, phytic acid also may decrease their bioavailability (18).

However, a major chunk of literature highlights the osteoprotective effect of soy protein. Further research is needed to determine the precise impact of soy protein/foods on bone density and other related diseases (19).

Most of the research on soybeans and soy protein is still unclear. While in some studies they seem to promote health, certain other studies tend to state the potential harm they may cause. However, this does not mean you have to totally be off soy. There are a few specific soy products you may want to avoid.

Which Soy Products Should You Avoid?

Moderation is important, and so is eating right. Choosing the right kind of soy products can protect you from the adverse effects mentioned above.

When given a choice between natural soy foods and soy protein isolate, go for the natural options. Avoid industrial soy foods if you have iodine deficiency or thyroid imbalance (15).

Whole soy foods are mostly fermented and cooked in a healthier manner. You can take tofu, edamame, soy milk, tempeh, miso, and natto a few times every week.

How Much Soy Is Safe To Eat In A Day?

According to the US FDA, daily consumption of 25 g of soy seems to be safe. This amount of soy could also help lower cholesterol levels (20).

It also is believed that the intake of 50 g of soy protein per day could help prevent heart disease, diabetes, and estrogen-dependent cancers. However, more research is warranted.

There is limited information on the excess intake of soy protein/soybeans. But we don’t recommend you take more than 25 grams per day.

Is Eating Too Much Soy Harmful?

There is little information about the toxicity of soy protein. In limited doses, soy protein may be helpful for women who are at a high risk of breast cancer (21).

Some studies reported very few drug-related adverse events, which were mild. In very few cases, high levels of soy isoflavones adversely affected blood pressure levels (22).

Hence, it is important you talk to your healthcare provider about a suitable dosage for you.

Conclusion

Soy protein could be the reason Asians have historically had lower rates of cardiovascular disease. Their menopausal symptoms and incidence of breast cancer, diabetes, and obesity are also lower than their Western counterparts (23).

There is substantial yet unclear evidence stating the adverse effects of soybeans and soy protein/foods. Soy isoflavones may disturb the hormonal balance, stimulate cancer proliferation, and trigger allergies.

Hence, choose your soy portions carefully. Pick fermented soy foods over protein or isoflavone isolates. Follow the instructions by your physician/nutritionist and stick to the recommended intake limit.

23 sources

A Stylecraze tem diretrizes rígidas de abastecimento e depende de estudos revisados por pares, instituições de pesquisa acadêmica e associações médicas. Evitamos usar referências terciárias. Você pode aprender mais sobre como garantimos que nosso conteúdo seja preciso e atualizado lendo nossa política editorial.

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